JPWO2013069045A1 - Thin film transistor device manufacturing method, thin film transistor device, and display device - Google Patents

Abstract

The thin film transistor manufacturing method of the present invention includes a step of forming a plurality of gate electrodes on a substrate (S11), a step of forming a gate insulating layer on the plurality of gate electrodes (S12), A step (S13) of forming a crystalline silicon layer, a step (S14) of forming a buffer layer and a light absorption layer on the amorphous silicon layer, and the light using red or near infrared laser light. A step of crystallizing the amorphous silicon layer by heat generated by absorbing the absorption layer to generate a crystalline silicon layer (S15), and a source in a region on the crystalline silicon layer corresponding to each of the plurality of gate electrodes A step of forming an electrode and a drain electrode (S20), and the thickness of the gate insulating layer, the amorphous silicon layer, the thickness of the buffer layer, and the thickness of the light absorption layer satisfy a predetermined conditional expression. Formed.

Description

  The present invention relates to a method for manufacturing a thin film transistor device, a thin film transistor device, and a display device.

  For example, there is a thin film transistor (TFT) constituting a liquid crystal panel or an organic EL panel. The channel portion of the thin film transistor is formed of a-Si which is amorphous silicon or Poly-Si which is crystalline and polycrystalline silicon. For the crystalline silicon layer (Poly-Si layer) in the channel portion of the thin film transistor, generally, after forming an amorphous silicon layer (a-Si layer), laser light such as excimer is applied to the amorphous silicon layer. It is formed by irradiating and instantaneously raising the temperature to crystallize.

  The structure of the thin film transistor includes a bottom gate structure in which the gate metal is disposed on the substrate side when viewed from the x-Si (x is a or poly) of the channel portion, and the gate metal and the source / drain metal of the channel portion. There is a top gate structure arranged in the direction opposite to the substrate as viewed from x-Si. The bottom gate structure is mainly used in an a-Si TFT having a channel portion formed of an amorphous silicon layer, and the top gate structure is a Poly-Si having a channel portion formed of a crystalline silicon layer. Mainly used in TFT. Note that a bottom gate structure is generally used as a structure of a thin film transistor included in a liquid crystal panel or an organic EL panel used in a large-area display device.

  Furthermore, there is a case where a Poly-Si TFT is used in a bottom gate structure, and in that case, there is an advantage that a manufacturing cost can be suppressed. In such a bottom-gate Poly-Si TFT, the amorphous silicon layer is irradiated with a laser and crystallized to form a crystalline silicon layer. In this method (laser annealing crystallization method), the amorphous silicon layer is crystallized by heat based on laser light irradiation.

  As one of laser annealing methods, a silicon oxide layer, for example, is deposited on an amorphous silicon layer as a buffer layer, and a light absorption layer is further deposited on the buffer layer, which is absorbed into the absorption layer and thermally converted. There is a method of indirectly heating amorphous silicon by irradiating a laser beam. Hereinafter, this method is referred to as a laser indirect heating method.

  Further, as the laser used in the laser indirect heating method, it is effective to use red and near infrared fixed lasers capable of increasing the output and having high output time stability. This is because if there is a temporal variation in the intensity of the laser beam, the crystal will not have a uniform temperature distribution and the crystallinity of the crystalline silicon layer formed by crystallization will vary. This is because it is difficult to achieve uniform crystallization due to problems such as variations (temporal variations). In addition, the fixed laser has an advantage in production that the maintenance cost can be reduced as compared with the excimer laser which is a gas laser.

  In addition, the light absorption layer used in the laser indirect heating method has a characteristic that its optical characteristics have a large absorption for light of red and near-infrared wavelengths, specifically, wavelengths of 600 nm to 2000 nm. desirable. It is also desirable to have thermal properties that can withstand laser annealing crystallization processes involving high temperatures.

  As an example of the light absorption layer having such characteristics, there are Mo and Cr which are refractory metals. These refractory metal films generally have a large extinction coefficient k (2 or more), so that they can be stably formed and can withstand heating by laser irradiation (1500 degrees or more) (10 nm or more). Then, the transmittance is 5% or less with respect to the incident laser beam. Therefore, the influence of multiple interference due to the underlying layer structure can be ignored, and the absorption rate of the light absorption layer is constant regardless of the underlying layer structure (for example, the region where the gate electrode exists and the region where it does not exist). become.

  However, since the thin film transistors constituting the organic EL panel are required to have particularly uniform characteristics, inconvenience (problem) occurs when the laser annealing crystallization method is applied to the manufacture of a thin film transistor having a bottom gate structure. . Specifically, in a bottom gate thin film transistor, a gate electrode is first formed of a metal material having a higher thermal conductivity than silicon or an insulating film, and then an insulating layer and an amorphous silicon layer are formed. The Further, after the light absorption layer is formed on the formed amorphous silicon layer, the laser light is irradiated to the upper light absorption layer by the laser indirect heating method, and the amorphous silicon is indirectly indirectly generated by the heat generation. The layer is annealed for crystallization. During the crystallization, heat that should be spent on the crystallization of the amorphous silicon layer is absorbed and propagated by the gate electrode, and the amorphous silicon layer is not sufficiently crystallized. There is a problem that uniformity occurs.

  In contrast, a method is disclosed in which a dummy gate pattern is disposed in the vicinity of the gate electrode, that is, in the vicinity of the channel, thereby reducing the difference in heat capacity between the gate electrode and the amorphous silicon layer above the dummy gate pattern. (For example, Patent Document 1). Also, by extending the gate electrode on the upstream side of the laser beam scan, the pre-annealing effect of the extended gate electrode portion is used before the laser beam reaches the light absorption layer above the gate electrode of the thin film transistor. A method of thermally saturating a gate electrode to reduce absorption of heat generated in a silicon thin film by the gate electrode is disclosed (for example, Patent Document 2).

Japanese Patent Laid-Open No. 10-242052 JP 2007-035964 A

  However, when the conventional method is applied to the laser indirect heating method, there are the following problems. That is, in the methods disclosed in Patent Documents 1 and 2, as a means for thermally saturating the gate electrode before the laser light reaches the light absorption layer above the gate electrode, the gate electrode is contacted with the periphery of the gate electrode and the gate electrode. Electrode material. Therefore, when a higher-definition display device is manufactured using a bottom-gate thin film transistor, there is a problem in that it is difficult to densely arrange gate electrode patterns. Further, the method disclosed in Patent Document 2 has a restriction that the thin film transistor must be arranged so that the channel direction of the thin film transistor is always parallel to the scan direction. This significantly reduces the degree of freedom in designing the circuit pattern in the pixel of the display device, which is a serious problem when a higher-definition display device is manufactured.

  Further, when the crystallization of the amorphous silicon layer is performed using the light absorption layer as described above, that is, continuous oscillation (or quasi-continuous oscillation) in the red (or near infrared) wavelength region in the light absorption layer. ) When the laser is irradiated and scanned, and the heat is indirectly generated, a problem different from the case where the excimer laser is scanned is caused. Specifically, when the above crystallization is performed, the thermal diffusion length in the amorphous silicon layer becomes larger, so that the influence of heat conduction by the gate electrode becomes more remarkable, and the crystallization becomes insufficient. This will be described with reference to FIG. FIG. 1 is a diagram showing crystal unevenness when the laser annealing crystallization method is performed by scanning a solid-state laser in the visible light region.

  As shown in the right diagram of FIG. 1, it can be seen that crystal unevenness occurs on the upstream side of the scan (right direction in the diagram). Here, the left figure of FIG. 1 is a figure which shows the crystallization ratio with respect to the amorphous silicon on one gate metal among the several gate metals of the right figure of FIG. In the left diagram of FIG. 1, for example, the crystallization rate of 80% indicates that the crystalline silicon has a particle size of 30 nm to 40 nm. For example, the crystallization rate of 40% indicates that the crystalline silicon has a particle size of 10 nm to 20 nm. It represents that. Accordingly, as shown in the left diagram of FIG. 1, it can be seen that crystal unevenness occurs when crystallization is insufficient (not uniform).

  As described above, when the amorphous silicon layer is crystallized by the laser indirect heating method, the crystallization becomes insufficient. Therefore, the characteristics of the thin film transistor using the amorphous silicon layer are deteriorated and the characteristics of the individual transistors are not uniform. There is a problem that occurs.

  The present invention has been made in view of the above problems, and a method of manufacturing a thin film transistor device capable of forming a crystalline silicon film having stable crystallinity using a laser in a red or near infrared wavelength region, It is an object to provide a thin film transistor device and a display device using the same.

  In order to achieve the above object, a method of manufacturing a thin film transistor device according to one embodiment of the present invention includes a first step of preparing a substrate, a second step of forming a plurality of gate electrodes on the substrate, and the plurality of the plurality of gate electrodes. A third step of forming a gate insulating layer on the gate electrode; a fourth step of stacking an amorphous silicon layer on the gate insulating layer; and a fifth step of forming a buffer layer on the amorphous silicon layer. And a sixth step of forming a light absorption layer on the buffer layer, and a predetermined laser having a wavelength of 600 nm or more is moved relative to the substrate in a certain direction and irradiated from the predetermined laser. A seventh step of generating a crystalline silicon layer by heating the light absorption layer using laser light and indirectly crystallizing the amorphous silicon layer by heat generated by the heating; and the plurality of gate electrodes An eighth step of forming a source electrode and a drain electrode in a region on the crystalline silicon layer corresponding to each, and a value obtained by integrating the refractive index of the light absorption layer to the film thickness of the light absorption layer A value obtained by dividing the optical film thickness of the light absorbing layer by the wavelength of the laser beam is X, and the optical film thickness of the buffer layer, which is a value obtained by adding the refractive index of the buffer layer to the film thickness of the buffer layer; The film thickness of the amorphous silicon layer and the optical film thickness of the amorphous silicon layer, which is a value obtained by integrating the refractive index of the amorphous silicon layer, the film thickness of the gate insulating layer, and the gate insulating layer The value obtained by summing the optical film thickness of the gate insulating layer obtained by integrating the refractive index of the above is divided by the wavelength of the laser light as Y, and the density of the light absorption layer is ρ and the specific heat is c, The thickness of the gate electrode is dG, the density is ρG, and the specific heat is c. And the maximum value of the absorptance of the gate electrode when the light absorptivity of the light absorption layer above the gate electrode and the light absorption layer not above the gate electrode with respect to the laser light is equal to AG, When the value calculated by the equation of (AG / dG) × (ρ × c) / (ρG × cG) is ΔA ′, the film thickness of the gate insulating layer and the film thickness of the amorphous silicon layer The film thickness of the buffer layer and the film thickness of the light absorption layer are Y ≦ −1.06X−0.22ΔA ′ + 1.07, Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44, Y ≧ 1.06 + 0.33ΔA ′ + 0.89 and Y ≦ 1.29X + −0.97 * ΔA′−0.95 satisfy the X and Y belonging to the range defined by the equation.

  According to the present invention, it is possible to realize a thin film transistor device manufacturing method, a thin film transistor, and a display device using the thin film transistor device capable of forming a crystalline silicon film with stable crystallinity using a red or near infrared laser. it can. Specifically, the silicon thin film, the gate insulating layer, the buffer layer, and the light absorption layer having predetermined optical characteristics with respect to laser light in the red and near-infrared wavelength regions each having a predetermined film thickness. By forming the electrode so as to satisfy the conditions, for example, the crystal shape by the laser indirect heating method using a red or near-infrared laser without changing the structure of the thin film transistor device, such as the pattern shape of the gate electrode. Thin film transistor device manufacturing method, thin film transistor device, and display device using the same can be realized.

FIG. 1 is a diagram showing crystal unevenness when the laser annealing crystallization method is performed by scanning a solid-state laser in the visible light region. FIG. 2 is a cross-sectional view showing the structure of the thin film transistor that constitutes the display device according to the embodiment of the present invention. FIG. 3 is a diagram showing an equivalent circuit of the display device according to the embodiment of the present invention. FIG. 4 is a flowchart showing manufacturing steps of the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5A is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5B is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5C is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5D is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5E is a cross-sectional view for describing the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5F is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5G is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5H is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5I is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5J is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5K is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 5L is a cross-sectional view for explaining the method for manufacturing the thin film transistor of the display device according to the embodiment of the present invention. FIG. 6 is a diagram schematically showing the indirect laser heating method in S15 of FIG. FIG. 7A is a diagram for explaining the amplitude transmittance and the calculation method of the amplitude transmittance. FIG. 7B is a diagram for explaining the amplitude transmittance and the calculation method of the amplitude transmittance. FIG. 8 is a diagram for showing that there are suitable film thickness ranges for the gate insulating layer, the amorphous silicon layer, the buffer layer, and the light absorption layer when the crystalline silicon layer is formed by the laser indirect heating method. . FIG. 9 is a diagram illustrating an example of a value obtained by converting the value on the horizontal axis in FIG. 8 into the film thickness of the light absorption layer. FIG. 10 is a diagram illustrating an example of a value obtained by converting the value on the vertical axis in FIG. 8 into the thickness of the buffer layer. FIG. 11 is a cross-sectional view showing another example of the structure of the thin film transistor constituting the display device according to the embodiment of the present invention. FIG. 12 is a diagram showing a set of film thicknesses when the gate insulating layer of the thin film transistor shown in FIG. 11 is formed of a silicon oxide (SiO) film and a silicon nitride (SiN) film. FIG. 13 is a diagram used for calculating a preferable film thickness range of the buffer layer and the light absorption layer in FIG. 8. FIG. 14 is a diagram illustrating a model used for the simulation. FIG. 15 is a diagram showing the film thickness condition portions implemented in this simulation in FIG. FIG. 16 is a diagram showing a simulation result of the position dependency of the highest temperature reached on the surface of the amorphous silicon layer in the first region and the second region. FIG. 17A is a diagram showing the crystallinity of a crystalline silicon layer when a laser indirect heating crystallization method is performed on the structure of the embodiment of the present invention using laser light in the red and near-infrared wavelength regions. It is. FIG. 17B is a diagram showing the crystallinity of a crystalline silicon layer when a laser indirect heating crystallization method is performed on a conventional structure using laser light in the red and near-infrared wavelength regions. FIG. 18 is a diagram for explaining an effect in the embodiment of the present invention. FIG. 19 shows an example of a display device using the thin film transistor of the present invention.

  In the method of manufacturing the thin film transistor device according to the first aspect, a first step of preparing a substrate, a second step of forming a plurality of gate electrodes on the substrate, and forming a gate insulating layer on the plurality of gate electrodes. A third step, a fourth step of laminating an amorphous silicon layer on the gate insulating layer, a fifth step of forming a buffer layer on the amorphous silicon layer, and a light absorbing layer on the buffer layer And a sixth step of forming a light source, a predetermined laser having a wavelength of 600 nm or more is moved relative to the substrate in a predetermined direction, and the light absorption layer is formed using laser light emitted from the predetermined laser. A seventh step of heating and indirectly crystallizing the amorphous silicon layer by heat generated by the heating to generate a crystalline silicon layer; and the crystalline silicon corresponding to each of the plurality of gate electrodes An eighth step of forming a source electrode and a drain electrode in the upper region, and an optical film thickness of the light absorption layer, which is a value obtained by integrating a refractive index of the light absorption layer to a film thickness of the light absorption layer. The value obtained by dividing the wavelength of the laser beam by X is the optical film thickness of the buffer layer, which is a value obtained by adding the refractive index of the buffer layer to the film thickness of the buffer layer, and the film of the amorphous silicon layer. The gate insulation obtained by integrating the optical thickness of the amorphous silicon layer, which is a value obtained by integrating the thickness and the refractive index of the amorphous silicon layer, and the thickness of the gate insulating layer and the refractive index of the gate insulating layer. A value obtained by adding the optical film thickness of the layer divided by the wavelength of the laser beam is Y, and the density of the light absorption layer is ρ, the specific heat is c, and the film thickness of the gate electrode is dG, The density is ρG, the specific heat is cG, and the light absorption above the gate electrode is AG is the maximum value of the absorptance of the gate electrode when the light absorptivity of the light absorption layer not above the layer and the gate electrode is equal to the laser light, and (AG / dG) × (ρ × c ) / (ΡG × cG) when the value calculated by ΔA ′ is set to ΔA ′, the thickness of the gate insulating layer, the thickness of the amorphous silicon layer, the thickness of the buffer layer, and The film thickness of the light absorption layer satisfies X and Y belonging to a range defined by the following formulas 1) to 4). Here, Formula 1) Y ≦ −1.06X−0.22ΔA ′ + 1.07, Formula 2) Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44, Formula 3) Y ≧ 1.06X + 0.33ΔA ′ + 0 .89, Formula 4) Y ≦ 1.29X + −0.97 * ΔA′−0.95.

  According to this aspect, the gate insulating film, the amorphous silicon layer serving as the channel layer, the buffer layer, and the light absorption layer having predetermined optical characteristics with respect to laser light in the red and near-infrared wavelength regions. When the film thickness satisfies the above conditions, 1) it is not above the gate electrode (hereinafter referred to as the second region) due to the light absorption rate of the light absorption layer above the gate electrode (hereinafter referred to as the first region). 2) the light absorption rate of the light absorption layer is set to be large, and 2) the heat generation temperature of the silicon layer above the gate electrode is set to be larger than the melting point of the amorphous silicon layer. It becomes possible.

  Therefore, first, due to the effect of 1), the heat generation of the amorphous silicon layer in the second region is larger than the heat generation of the amorphous silicon layer in the first region due to the heat generation of the light absorption layer. Become. As a result, before the laser light emitted from the predetermined laser reaches the start end of the light absorption layer in the first region where the laser light starts to be emitted, it is generated in the light absorption layer above the second region. The heat to be transmitted is propagated to the gate electrode in advance, and the gate electrode is in a state of being thermally saturated.

  As a result, heat generated from the light absorption layer in the first region from the start end portion of the gate electrode where the laser beam starts to be irradiated to the end portion of the gate electrode where the laser beam ends being irradiated is caused by the gate electrode. Since the rate of absorption can be reduced, the heat generation temperature distribution of the amorphous silicon layer in the first region can be controlled almost uniformly. Thereby, the crystal structure generated in the crystalline silicon layer obtained by crystallizing the amorphous silicon layer can be controlled almost uniformly.

  Furthermore, from the effect of 2), when the light absorption rate of the light absorption layer in the second region is excessively larger than the light absorption rate of the light absorption layer in the first region, that is, the light absorption layer in the second region. Even when the heat generation of the first region and the light absorption layer in the first region is extremely larger than that of the first region, the amorphous silicon in the first region and the second region is melted to form molten silicon. The thermal conductivity increases to a value comparable to that of a metal generally used as a gate electrode.

  Therefore, heat generated from the molten silicon layer in the second region propagates to the molten silicon layer in the first region, rather than to the gate electrode through the gate insulating layer. The heat generated from the molten silicon layer in the second region does not excessively propagate to the gate electrode. Therefore, since the distribution of the heat generation temperature of the gate electrode is not deteriorated, the uniformity of the heat generation temperature distribution of the silicon layer in the first region accompanying the deterioration of the heat generation temperature distribution of the gate electrode can be avoided.

  As described above, the uniformity of the crystal structure generated in the crystalline silicon layer obtained by crystallizing the amorphous silicon layer is maintained by the combined effect of the above 1) and 2). The crystal ratio in the crystalline silicon layer from the crystalline silicon layer corresponding to the start end portion of the gate electrode that has started to be irradiated to the crystalline silicon layer corresponding to the end portion of the gate electrode that has been irradiated with the laser light. Thus, a thin film transistor device in which the variation is suppressed can be realized.

  As a method of manufacturing the thin film transistor device according to the second aspect, the light absorption layer is translucent (extinction coefficient k <1) in the wavelength range of the predetermined laser beam.

  The method of manufacturing the thin film transistor device according to the third aspect includes a step of removing at least the light absorption layer after the seventh step and before the eighth step.

  The method of manufacturing the thin film transistor device according to the fourth aspect includes a step of removing the buffer layer and the light absorption layer after the seventh step and before the eighth step.

  As a method of manufacturing a thin film transistor device according to a fifth aspect, in the sixth step, the predetermined laser irradiates the laser beam in an oscillation mode of a continuous oscillation mode or a pseudo continuous oscillation mode.

  As a method of manufacturing the thin film transistor device according to the sixth aspect, the predetermined laser is a solid-state laser device.

  According to a seventh aspect of the thin film transistor device manufacturing method, the predetermined laser is a laser device using a semiconductor laser element.

  As a method of manufacturing the thin film transistor device according to the eighth aspect, in the sixth step, the fluctuation of the irradiation energy density of the laser light on the amorphous silicon layer is less than about 5%.

  In the method of manufacturing the thin film transistor device according to the ninth aspect, the wavelength of the predetermined laser is 600 nm to 2000 nm.

  As a method of manufacturing a thin film transistor device according to a tenth aspect, the second step includes a step of forming an undercoat layer made of silicon oxide on the substrate, and a step of forming a plurality of gate electrodes on the undercoat layer. including.

  A thin film transistor according to an eleventh aspect includes a substrate, a plurality of gate electrodes formed on the substrate, a gate insulating layer formed on the plurality of gate electrodes, and a crystallinity formed on the gate insulating layer. A silicon layer; and a source electrode and a drain electrode formed in a region on the crystalline silicon layer corresponding to each of the plurality of gate electrodes, wherein the crystalline silicon layer is amorphous on the gate insulating layer. After forming the crystalline silicon layer, a buffer layer is formed on the amorphous silicon layer, a light absorption layer having predetermined optical characteristics is formed on the buffer layer, and the wavelength is 600 nm or more and 2000 nm or less. It is generated by moving the laser relative to the substrate in a certain direction and absorbing the laser light in the light absorption layer using the laser light emitted from the predetermined laser. Heat is generated by indirectly annealing and crystallizing the amorphous silicon layer through the buffer layer, and is a value obtained by integrating the refractive index of the light absorption layer to the film thickness of the light absorption layer. The optical film thickness of the light absorbing layer is X divided by the wavelength of the laser beam, and the optical film thickness of the buffer layer, which is a value obtained by adding the refractive index of the buffer layer to the film thickness of the buffer layer, The film thickness of the amorphous silicon layer and the optical film thickness of the amorphous silicon layer, which is a value obtained by integrating the refractive index of the amorphous silicon layer, the film thickness of the gate insulating layer, and the thickness of the gate insulating layer The value obtained by summing the optical film thickness of the gate insulating layer integrated with the refractive index divided by the wavelength of the laser light is Y, and the density of the light absorption layer is ρ, the specific heat is c, The thickness of the gate electrode is dG, the density is ρG, and the specific heat is cG. The maximum value of the absorptance of the gate electrode when the light absorptivity of the light absorbing layer above the gate electrode and the light absorbing layer not above the gate electrode with respect to the laser beam is equal is AG, AG / dG) × (ρ × c) / (ρG × cG) where the value calculated by ΔA ′ is the thickness of the gate insulating layer, the thickness of the amorphous silicon layer, The film thickness of the buffer layer and the film thickness of the light absorption layer satisfy X and Y belonging to the range defined by the following formulas 1) to 4). Here, Formula 1) Y ≦ −1.06X−0.22ΔA ′ + 1.07, Formula 2) Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44, Formula 3) Y ≧ 1.06X + 0.33ΔA ′ + 0 .89, Formula 4) Y ≦ 1.29X + −0.97 * ΔA′−0.95.

  A display device according to a twelfth aspect is a display device including a liquid crystal panel or an EL panel, and the display device includes the thin film transistor according to the eleventh aspect, and the thin film transistor drives the liquid crystal panel or the EL panel. Let

  As a display device according to a thirteenth aspect, the EL panel is an organic EL panel.

  In a thin film transistor device manufacturing method according to a fourteenth aspect, a first step of preparing a substrate, a second step of forming a plurality of gate electrodes on the substrate, and forming a gate insulating layer on the plurality of gate electrodes. A third step, a fourth step of laminating an amorphous silicon layer on the gate insulating layer, a fifth step of forming a buffer layer on the amorphous silicon layer, and a light absorbing layer on the buffer layer And a sixth step of forming a light source, a predetermined laser having a wavelength of 600 nm or more is moved relative to the substrate in a predetermined direction, and the light absorption layer is formed using laser light emitted from the predetermined laser. A seventh step of heating and indirectly crystallizing the amorphous silicon layer with the generated heat to generate a crystalline silicon layer; an eighth step of removing the buffer layer and the light absorption layer; No A ninth step of forming a source electrode and a drain electrode in a region on the crystalline silicon layer corresponding to each of the first electrode, the second step, the third step, the fourth step, and the fifth step In the step and the sixth step, in the seventh step, in the upstream region in the relative movement direction of the predetermined laser outside the gate electrode when the light absorption layer is irradiated using the laser beam. The highest temperature of the light absorption layer is higher than the highest temperature of the amorphous silicon layer in the region on the gate electrode when the light absorption layer is irradiated using the laser beam; and In the region on the gate electrode, the maximum absorption temperature of the light absorption layer when the light absorption layer is irradiated using the predetermined laser beam is substantially constant.

  As a method of manufacturing a thin film transistor device according to a fifteenth aspect, in the third step, the fourth step, the fifth step, the sixth step, and the seventh step, the laser light is used in the eighth step. When the light absorption layer is irradiated, the highest temperature of the light absorption layer in the upstream region in the relative movement direction of the predetermined laser light outside the gate electrode is determined by using the laser light. In the region on the gate electrode, the light absorbing layer is formed by using the predetermined laser beam so that the temperature is higher than the highest temperature of the light absorbing layer in the region on the gate electrode when irradiated. The film thickness of the gate insulating layer, the film thickness of the amorphous silicon layer, the film thickness of the buffer layer, and the light absorption so that the maximum temperature reached by the light absorption layer upon irradiation is substantially constant. Layer thickness is composed .

  A method of manufacturing a thin film transistor device according to a sixteenth aspect includes a first step of preparing a substrate, a second step of forming a gate electrode on the substrate, and a third step of forming a gate insulating layer on the gate electrode. A fourth step of forming a semiconductor material layer including a semiconductor material on the gate insulating layer, a fifth step of forming a buffer layer on the semiconductor material layer, and light having a predetermined optical constant on the buffer layer. A sixth step of forming an absorption layer, and irradiating the light absorption layer with a predetermined laser beam having a wavelength of 600 nm or more and 2000 nm or less, causing the light absorption layer to absorb the laser beam and generating from the light absorption layer A seventh step of generating a crystalline semiconductor layer by indirectly crystallization of the semiconductor material layer through a buffer layer by the heat, and a first region that is a region corresponding to the gate electrode, An eighth step of forming a source electrode and a drain electrode on the semiconductor layer in the second region which is a region not corresponding to the gate electrode, and includes the third step, the fourth step, and the fifth step. In the step and the sixth step, the heat generation amount per unit volume in the second region of the light absorption layer is larger than the heat generation amount per unit volume in the first region of the light absorption layer. By forming the gate insulating layer, the semiconductor material layer, the buffer layer, and the light absorption layer, in the seventh step, the light in the first region generated by irradiation with the predetermined laser light. Heat is transferred from the absorption layer to the gate electrode, and the heat absorbed in the gate electrode is stored in the second region while suppressing thermal diffusion to the semiconductor material layer. Is a, and in the light absorbing layer of the first region that generates heat, to form a portion having an equal temperature distribution, thereby crystallizing the semiconductor material layer.

  As a manufacturing method of a thin film transistor device according to a seventeenth aspect, in the third step, the fourth step, the fifth step, and the sixth step, the heat generation amount per unit volume in the second region of the light absorption layer Is larger than the calorific value per unit volume in the first region of the light absorption layer, the film thickness of the gate insulating layer, the film thickness of the amorphous silicon layer, the film thickness of the buffer layer And the said light absorption layer is comprised.

  As a method of manufacturing a thin film transistor device according to an eighteenth aspect, the second region of the light absorption layer is upstream of the first region in the relative movement direction of the predetermined laser beam with respect to the substrate in the seventh step. It corresponds to the region and the downstream region.

  As a method of manufacturing a thin film transistor device according to a nineteenth aspect, in the third step, the fourth step, the fifth step, and the sixth step, the heat generation amount per unit volume in the second region in the seventh step However, the heat generation amount per unit volume in the first region is larger than the heat generation amount per unit volume of the gate electrode.

  As a method of manufacturing a thin film transistor device according to a twentieth aspect, in the third step, the fourth step, the fifth step, and the sixth step, in the seventh step, the light absorption layer is formed in the first region. The size of the portion having the same temperature distribution is configured to be 0.8 or more and 1.0 or less with respect to the first region.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 2 is a cross-sectional view illustrating a structure of a thin film transistor constituting the organic light emitting display device according to the embodiment of the present invention.

  A thin film transistor 100 illustrated in FIG. 2 is a bottom gate thin film transistor, and includes a substrate 10, an undercoat layer 11, a gate electrode 12, a gate insulating layer 13, a crystalline silicon layer 17, and an amorphous silicon layer 18. And an n + silicon layer 19 and source / drain electrodes 20.

  The substrate 10 is an insulating substrate made of, for example, transparent glass or quartz.

The undercoat layer 11 is formed on the substrate 10 and includes, for example, a silicon nitride (SiN _x ) layer, a silicon oxide (SiO _x ) layer, and a stacked layer thereof. Here, the undercoat layer 11 is preferably composed of silicon oxide (SiO _x ) of 1.5 <x <2.0 and a film thickness of 300 nm or more and 1500 nm or less. A more preferable thickness range of the undercoat layer 11 is 500 nm or more and 1000 nm or less. This is because if the thickness of the undercoat layer 11 is increased, the thermal load on the substrate 10 can be reduced, but if it is too thick, film peeling or cracking occurs.

  The gate electrode 12 is formed on the undercoat layer 11 and is typically made of a metal such as molybdenum (Mo) or a metal such as Mo alloy (for example, MoW (molybdenum / tungsten alloy)). The gate electrode 12 only needs to be a metal that can withstand the melting point temperature of silicon. Therefore, those containing W (tungsten), Ta (tantalum), Nb (niobium), Ni (nickel), Cr (chromium), and Mo. It may be made of an alloy of The film thickness of the gate electrode 12 is preferably 30 nm to 300 nm, and more preferably 50 nm to 100 nm. This is because if the thickness of the gate electrode 12 is small, the transmittance of the gate electrode 12 increases, and the reflection of laser light described below tends to decrease. Further, when the thickness of the gate electrode 12 is large, the coverage of the gate insulating layer 13 described below is lowered. In particular, the gate insulating film is disconnected at the end of the gate electrode, so that the gate electrode 12 and the n + silicon are separated. This is because the characteristics of the thin film transistor 100 are likely to deteriorate, for example, the layer 19 is electrically connected.

  The gate insulating layer 13 is formed so as to cover the gate electrode 12 and has, for example, a single layer structure of a silicon oxide layer or a silicon nitride layer, or a stacked structure of a silicon oxide layer and a silicon nitride layer. The film thickness of the gate insulating layer 13 has a suitable range when the crystalline silicon layer 17 is formed by the laser indirect heating crystallization method in each of the single layer structure and the laminated structure. This preferable range is expressed by a certain relational expression. Details of this fixed relational expression will be described later.

  The crystalline silicon layer 17 is formed on the gate insulating layer 13 and is made of a polycrystalline silicon layer (Poly-Si layer). The crystalline silicon layer 17 is formed as follows. That is, first, an amorphous silicon layer 14 (not shown) made of a-Si is formed on the gate insulating layer 13, and then a buffer layer 15 made of, for example, a silicon oxide film is deposited on the amorphous silicon layer 14. To do. Further, after depositing a light absorption layer 16 (for example, a diamond-like carbon film) that absorbs laser light and generates heat on the buffer layer 15, the light absorption layer is irradiated and heated with the laser light. As described above, the amorphous silicon layer 14 is indirectly heated by the heat of the light absorption layer to make the amorphous silicon layer 14 polycrystalline (including microcrystallization), whereby the crystalline silicon layer 17 is formed. It is formed.

  Here, the term “polycrystal” has a broad meaning including not only a polycrystal in a narrow sense consisting of crystals of 50 nm or more but also a microcrystal in a narrow sense consisting of crystals of 50 nm or less. Hereinafter, polycrystal is described in a broad sense.

  Note that the laser light source used for laser irradiation is a laser having a wavelength in the red or near infrared region of the visible light region. The laser having a wavelength in the red or near infrared region is a laser having a wavelength of 600 nm to 2000 nm, and preferably a laser having a wavelength of 800 nm to 1100 nm.

  The laser in the red or near-infrared wavelength region may be in a continuous oscillation or quasi-continuous oscillation mode. The reason is that when the laser is in a pulse oscillation mode other than the continuous oscillation mode or the pseudo continuous oscillation mode, the laser light is irradiated to the light absorption layer 16 discontinuously in time. The heat generation state of the light absorption layer 16 cannot be continuously maintained over time. For this reason, the amorphous silicon layer 14 cannot always be kept in a molten state. The reason why the quasi-continuous oscillation mode is also included is that the melted state can be maintained by irradiating the light absorption layer 16 with a pulse before the amorphous silicon layer 14 is cooled to below its melting point and reheating it. It is. That is, the preferred mode of the quasi-continuous oscillation mode is that the amorphous silicon layer 14 can be reheated by irradiating the light absorption layer 16 before the amorphous silicon layer 14 is cooled to below its melting point, and the high temperature state can be maintained. Is. The laser in the red or near-infrared wavelength region may be a solid-state laser device or a laser device using a semiconductor laser element. In any case, it is preferable because laser light can be accurately controlled. Further, in order to form the crystalline silicon layer 17 without crystal unevenness, the laser in the red or near-infrared wavelength region when the light absorption layer 16 is irradiated has a variation in irradiation energy density of about 5%. If it is less than, it is preferable. By forming the crystalline silicon layer 17 having no crystal unevenness, the initial design characteristics of the thin film transistor can be achieved, and the characteristics can be made uniform.

  The amorphous silicon layer 18 is formed on the crystalline silicon layer 17. In this manner, the thin film transistor 100 has a channel layer having a structure in which the amorphous silicon layer 18 is stacked on the crystalline silicon layer 17.

  The n + silicon layer 19 is formed so as to cover the amorphous silicon layer 18, the side surfaces of the crystalline silicon layer 17, and the gate insulating layer 13.

  The source / drain electrodes 20 are formed on the n + silicon layer 19 and are, for example, a metal such as Mo or Mo alloy, a metal such as titanium (Ti), aluminum (Al) or Al alloy, copper (Cu) or Cu alloy, etc. Or a metal material such as silver (Ag), chromium (Cr), tantalum (Ta), or tungsten (W).

  As described above, the thin film transistor 100 is configured.

  FIG. 3 is a diagram showing an equivalent circuit of the display device according to the embodiment of the present invention.

  The organic light emitting display device shown in FIG. 3 includes a switching transistor 1, a driving transistor 2, a data line 3, a scanning line 4, a current supply line 5, a capacitance 6, and an organic EL element 7.

  The switching transistor 1 is connected to the data line 3, the scanning line 4, and the capacitance 6.

  The drive transistor 2 corresponds to, for example, the thin film transistor 100 shown in FIG. 2 and is connected to the current supply line 5, the capacitance 6, and the organic EL element 7.

  The data line 3 is a wiring through which data (the magnitude of the voltage value) that determines the brightness of the pixel of the organic EL element 7 is transmitted to the pixel of the organic EL element 7.

  The scanning line 4 is a wiring through which data for determining the switch (ON / OFF) of the pixel of the organic EL element 7 is transmitted to the pixel of the organic EL element 7.

  The current supply line 5 is a wiring for supplying a large current to the drive transistor 2.

  The capacitance 6 holds a voltage value (charge) for a certain time.

  The organic light emitting display device is configured as described above.

  Next, a method for manufacturing the above-described thin film transistor 100 will be described.

  FIG. 4 is a flowchart showing a manufacturing process of a thin film transistor of the organic light emitting display device according to the embodiment of the present invention. A plurality of the thin film transistors 100 are manufactured at the same time, but in the following, in order to simplify the description, a method for manufacturing one thin film transistor will be described. 5A to 5L are views for explaining a method of manufacturing a thin film transistor of the organic light emitting display device according to the embodiment of the present invention. FIG. 6 is a diagram schematically showing the indirect laser heating method in S15 of FIG.

  First, the substrate 10 is prepared, the undercoat layer 11 is formed on the substrate 10 (S10), and then the gate electrode is formed on the undercoat layer 11 (S11).

  Specifically, an undercoat layer 11 is formed on the substrate 10 by plasma CVD (Chemical Vapor Deposition), and then a metal film to be a gate electrode is deposited by sputtering, and photolithography is performed. Then, the gate electrode 12 in the thin film transistor 100 is formed by etching (FIG. 5A). Here, the gate electrode 12 is typically formed of a metal material such as Mo or an Mo alloy (for example, MoW (molybdenum / tungsten alloy)).

  Next, the gate insulating layer 13 is formed on the gate electrode 12 (S12). Then, an amorphous silicon layer 14 is formed on the gate insulating layer 13 (S13).

  Specifically, a gate insulating layer 13 is formed on the gate electrode 12 so as to cover the undercoat layer 11 and the gate electrode 12 by plasma CVD (FIG. 5B), and the formed gate insulating layer is formed. An amorphous silicon layer 14 is continuously formed on the substrate 13 (FIG. 5C).

  Next, the buffer layer 15 is deposited on the amorphous silicon layer 14, and the light absorption layer 16 is deposited on the deposited buffer layer 15 (S14).

  Here, the buffer layer 15 is preferably a substance that does not react with silicon even in a temperature region (1400 ° C. or more) where the amorphous silicon layer 14 is annealed and crystallized. Examples of such a substance include silicon oxide and silicon nitride. The buffer layer 15 is preferably deposited continuously by plasma CVD without depositing the gate insulating layer 13 and the amorphous silicon layer 14 and then opening the deposition chamber to the atmosphere. Moreover, the thickness of the buffer layer 15 is 5 nm-500 nm, for example, Preferably it is 30 nm-400 nm. The reason is that a film thickness of 5 nm or less has poor controllability and is inconvenient in production. Further, when the film thickness is 500 nm or more, the heat transfer from the light absorption layer heated by the laser irradiation deteriorates, and the light energy required for crystallization of the amorphous silicon layer becomes excessive.

  The light absorption layer 16 has predetermined optical characteristics, and is preferably formed to be translucent (extinction coefficient k <1) in the laser light wavelength range of the red or near infrared region. . The light absorption layer 16 is formed using a vacuum evaporation method or a sputtering method. For example, when the sputtering method is used, a carbon target is used, and Ar or the like is used as a sputtering gas. Here, the thickness of the light absorption layer 16 is, for example, 10 nm to 500 nm, and preferably 20 nm to 200 nm. The reason is that when the film thickness is 10 nm, the transmission of laser light is large, energy absorbed in the light absorption layer is reduced, and heat generation of the light absorption layer becomes insufficient. In addition, when the film thickness is 500 nm, the probability of occurrence of cracks increases due to the increase in stress of the film itself, and when laser irradiation is performed on the light-absorbing layer where cracks occur, ablation tends to occur. It is not suitable.

  Since the light absorption layer 16 has the predetermined optical characteristics, a certain proportion of the incident laser light is transmitted to the lower layer, and multiple interference occurs in the lower layer film. As a result, the absorption rate of the light absorption layer 16 differs between the region where the gate electrode is present and the region where the gate electrode is not present. In other words, by using the light absorption layer 16 having the predetermined optical characteristics, it is possible to control the absorptance between the region where the gate electrode is present and the region where the gate electrode is not present in the light absorption layer 16. Note that the light absorption layer 16 having such predetermined optical characteristics is formed of, for example, a diamond-like carbon film.

  Hereinafter, the thickness of the gate insulating layer 13, the thickness of the amorphous silicon layer 14, the thickness of the buffer layer 15, and the thickness of the light absorption layer 16 will be described.

  The film thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 satisfy X and Y belonging to the range defined by the following (Expression 1) to (Expression 4). It is preferable to be formed as follows.

Y ≦ −1.06X−0.22ΔA ′ + 1.07 (Formula 1)
Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44 (Formula 2)
Y ≧ 1.06X + 0.33ΔA ′ + 0.89 (Formula 3)
Y ≦ 1.29X + −0.97 * ΔA′−0.95 (Formula 4)

  Here, X represents a value obtained by dividing the optical film thickness of the light absorption layer 16 obtained by multiplying the refractive index of the light absorption layer 16 by the film thickness of the light absorption layer 16 by the wavelength of the predetermined laser beam. On the other hand, Y is the optical film thickness of the gate insulating layer 13 obtained by multiplying the refractive index of the gate insulating layer 13 by the film thickness of the gate insulating layer 13, and the refractive index of the amorphous silicon layer 14 is the film of the amorphous silicon layer 14. A value obtained by adding the optical film thickness of the amorphous silicon layer 14 multiplied by the thickness and the optical film thickness of the buffer layer 15 multiplied by the refractive index of the buffer layer 15 and the film thickness of the buffer layer 15 is a predetermined laser beam. Represents the value divided by the wavelength of.

More specifically, the absorption rate of the light absorption layer 16 above the region where the gate electrode 12 is formed (hereinafter referred to as the first region) is A ₁ and the absorption rate A ₁ is the light absorption. The product obtained by the division (division) by the film thickness d ₁ of the layer 16 is defined as a converted absorption rate A ₁ ′. The light absorption rate of the light absorption layer 16 above the region where the gate electrode 12 is not formed (hereinafter referred to as the second region) is A ₂ , and the absorption rate A ₂ is the film thickness of the light absorption layer 16. The product obtained by dividing by d ₂ is defined as a converted absorption rate A ₂ ′. At that time, the difference A ₁ ′ −A ₂ ′ is equal to or smaller than a value −ΔA ′ defined in the description below. That is, in S12, S13, and S14, the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 having a film thickness that satisfies the relational expression (Formula 5) are formed.

A ₁ ′ −A ₂ ′ ≦ −ΔA ′ (Formula 5)

  In addition, although description is omitted here for details, the absorption rate of the light absorption layer 16 is the film thickness and optical constant of the light absorption layer 16, the film thickness and optical constant of the buffer layer 15, and amorphous. Multiplexing of laser light using as parameters the film thickness and optical constant of the silicon layer 14, the configuration, film thickness and optical constant of the gate insulating layer 13, and the optical constant of the metal material forming the underlying gate electrode 12 and the optical constant of the substrate. Derived by optical calculation considering interference. Hereinafter, it returns to description of a manufacturing process again.

  Next, the light absorption layer 16 is irradiated and heated with a laser in the red or near-infrared wavelength region, and the amorphous silicon layer 14 is annealed by the generated heat to form the crystalline silicon layer 17 (S15). .

  Specifically, a laser having a wavelength of 600 nm or more and 2000 nm or less is moved relative to the substrate 10 in a certain direction, and the light absorption layer 16 is heated using laser light emitted from the laser, whereby the buffer layer The amorphous silicon layer 14 is annealed indirectly through 15 and crystallized to produce a crystalline silicon layer 17. More specifically, first, a dehydrogenation process is performed on the formed amorphous silicon layer 14. For example, there is a method of carrying out in a nitrogen atmosphere at 500 ° C. for 20 minutes. Thereafter, the amorphous silicon layer 14 is made polycrystalline (including microcrystals) by a laser indirect heating method to form a crystalline silicon layer 17 (FIG. 5D).

  Here, in the laser annealing method, as described above, the laser light source used for laser irradiation is a laser in a red or near-infrared wavelength region. That is, a laser having a wavelength of about 600 nm to 2000 nm, preferably a laser having a wavelength of 800 nm to 1100 nm. The laser in the red or near infrared wavelength region may be in a continuous oscillation or quasi-continuous oscillation mode. Further, the laser in this wavelength region may be constituted by a solid-state laser device, or may be constituted by a laser device using a semiconductor laser element. Further, in the laser in this wavelength region, the fluctuation of the irradiation energy density when irradiated on the amorphous silicon layer 14 is less than about 5%.

  In the step of S15, that is, the steps of FIG. 5D to FIG. 5E, the crystalline silicon layer 17 is irradiated by irradiating the amorphous silicon layer 14 with linearly focused laser light as shown in FIG. Is generated. Specifically, there are two methods for irradiating the amorphous silicon layer 14 with laser light. One is a method in which the irradiation position of the linearly focused laser beam is fixed and the substrate 10 on which the amorphous silicon layer 14 is formed is placed on the stage, and the stage moves. The other is a method in which the stage is fixed and the irradiation position of the laser beam moves. In any method, the laser beam is irradiated while moving relative to the light absorption layer 16. The light absorption layer 16 irradiated with the laser beam by such a method absorbs the energy of the laser beam and rises in temperature. Then, the heat propagates to the amorphous silicon layer 14 through the buffer layer 15, and the amorphous silicon layer 14 is annealed and crystallized. In this way, the amorphous silicon layer becomes the crystalline silicon layer 17.

  Next, the light absorption layer 16 and the buffer layer 15 are removed by etching. Specifically, it is removed by dry etching or wet etching. The light absorbing layer 16 and the buffer layer 15 are not necessarily removed. The light absorption layer 16 and the buffer layer 15 may be used as a channel etching stopper (CES), or only the light absorption layer may be etched and the buffer layer may be used as a CES.

  Next, a second amorphous silicon layer 18 is formed (S17), and the silicon layer in the channel region of the thin film transistor 100 is patterned (S18).

  Specifically, a second amorphous silicon layer 18 is formed on the gate insulating layer 13 by plasma CVD (FIG. 5G). Then, the silicon layer film layer (the crystalline silicon layer 17 and the second amorphous silicon layer 18) is patterned so that the channel region of the thin film transistor 100 remains, and the amorphous silicon layer 18 and the crystal to be removed are crystallized. The quality silicon layer 17 is removed by etching (FIG. 5H). Accordingly, a desired channel layer can be formed in the thin film transistor 100.

  Next, an n + silicon layer 19 and source / drain electrodes 20 are formed (S19).

  Specifically, an n + silicon layer 19 is formed by plasma CVD so as to cover the second amorphous silicon layer 18, the side surfaces of the crystalline silicon layer 17, and the gate insulating layer 13 (FIG. 5I). . Then, a metal to be the source / drain electrode 20 is deposited on the deposited n + silicon layer 19 by sputtering (FIG. 5J). Here, the source / drain electrodes are a metal such as Mo or Mo alloy, a metal such as titanium (Ti), aluminum (Al) or Al alloy, a metal such as copper (Cu) or Cu alloy, or silver (Ag). , Chromium (Cr), tantalum (Ta), or tungsten (W).

  Next, the source / drain electrode 20 is patterned (S20). Then, the n + silicon layer 19 is etched (S21), and in the process, the second amorphous silicon layer 18 is partially etched (S22).

  Specifically, the source / drain electrodes 20 are formed by photolithography and etching (FIG. 5K). Further, the n + silicon layer 19 is etched, and the amorphous silicon layer 18 in the channel region of the thin film transistor 100 is partially etched (FIG. 5L). In other words, the amorphous silicon layer 18 is channel etched so as to leave a part of the amorphous silicon layer 18 in the channel region of the thin film transistor 100.

  In this way, the thin film transistor 100 is manufactured.

  As described above, the thin film transistor 100 in this embodiment is formed as a Poly-Si TFT having a bottom gate structure. In manufacturing the thin film transistor 100, the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 are formed so as to have film thicknesses that satisfy the above-described relational expression. Then, the amorphous silicon layer 14 made of an a-Si film is crystallized by annealing with heat generated by irradiating / scanning the light absorption layer 16 with laser light, thereby crystallizing the amorphous silicon layer 14. To a crystalline silicon layer 17 made of Poly-Si. At this time, the gate electrode 12 can be thermally saturated before the laser light reaches the light absorption layer 16 above the channel region (region on the gate electrode) where the thin film transistor 100 is formed, Crystallization of the crystalline silicon layer 17 corresponding to the finally obtained channel region can be performed uniformly.

  In other words, the film thickness of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 has a preferable range when the crystalline silicon layer 17 is formed by laser annealing crystallization. That is.

  Hereinafter, this mechanism will be described.

  Generally, when an amorphous silicon layer is annealed by heating, there is a correlation between the temperature reached and the crystallinity of the crystalline silicon layer after crystallization. The higher the temperature reached, the higher the crystallinity of the crystalline silicon layer formed after crystallization. Therefore, in order to sufficiently and uniformly crystallize the amorphous silicon layer in the first region of the thin film transistor (above the region where the gate electrode is formed), the arrival of the amorphous silicon layer in the first region of the thin film transistor is reached. It is necessary to make the temperature distribution uniform.

  However, in a bottom-gate thin film transistor, a gate electrode exists under the amorphous silicon layer with the gate insulating layer interposed therebetween, and the thermal conductivity of the metal constituting the gate electrode is the thermal conductivity of the gate insulating layer. Bigger than Therefore, in the laser indirect heating method, the heat of the light absorption layer generated by irradiating the light absorption layer formed above the amorphous silicon layer via the buffer layer with the laser light is applied to the amorphous silicon layer. Heat. At the same time, the heat instantly propagates to the gate electrode through the gate insulating layer. As a result, a region where heat generation is insufficient occurs in the amorphous silicon layer above the region where the gate electrode is formed, and the temperature reached is nonuniform. For this reason, unevenness in crystallinity (crystal unevenness) of the crystalline silicon layer after crystallization as shown in FIG. 1 occurs.

  Therefore, in order to avoid the phenomenon that the crystal unevenness occurs, the gate electrode is thermally saturated as described later before the laser beam reaches the light absorption layer above the first region of the thin film transistor. It is desirable to be in a state. Therefore, in this embodiment, the thin film transistor 100 is manufactured so as to have the above-described structure. That is, the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer, and the light absorption layer are formed so as to satisfy the above-described X and Y. Accordingly, the heat generation of the light absorption layer 16 above the region where the gate electrode 12 is not formed (second region) is larger than the heat generation of the light absorption layer 16 above the region where the gate electrode 12 is formed (first region). can do.

  In other words, the film thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer, and the amorphous silicon layer film that constitute the thin film transistor 100 according to this embodiment satisfy the above X and Y. To form. Thereby, first, the heat generated in the light absorption layer 16 above the region where the gate electrode 12 is not formed (second region) by the laser light irradiation is above the region where the gate electrode 12 is formed (first region). Before the laser beam reaches the light absorption layer 16), the temperature of the gate electrode 12 is raised by being transmitted to the gate electrode 12 through the buffer layer 15, the amorphous silicon layer 14, and the gate insulating layer 13. That is, the gate electrode 12 is first preheated before the laser beam reaches. This is because, when the light absorption layer 16 in the second region is irradiated with laser light and heat is generated, the temperature of the second region is absorbed by light above the first region where the laser light has not yet reached due to the above configuration. Since the temperature is higher than the temperature of the layer 16, the heat propagated to the amorphous silicon layer 14 in the second region is further propagated to the gate electrode 12 through the gate insulating film to raise the temperature of the gate electrode 12. It is. Next, when the laser light reaches the light absorption layer 16 above the first region, the light absorption layer 16 above the first region generates heat, and the heat propagates to the amorphous silicon layer 14. Further, heat corresponding to the heat generation amount of the light absorption layer 16 in the first region is transmitted to the gate electrode 12 (heating by laser light). The gate electrode 12 is heated by both the heating by the laser beam and the preliminary heating, so that the gate electrode 12 is thermally saturated. Here, thermally saturating the gate electrode 12 means that the temperature of the gate electrode 12 is made uniform in the plane of the gate electrode 12.

  Thus, according to the configuration of the thin film transistor according to the present embodiment, the gate electrode 12 can be thermally saturated when the amorphous silicon layer 14 is crystallized. Thereby, the heat generation of the light absorption layer due to the laser light irradiation for crystallizing the amorphous silicon layer 14 is used to form the crystalline silicon layer 17 without being absorbed by the gate electrode 12, There is an effect that the crystalline silicon layer 17 without crystal unevenness can be generated.

  Next, a method for calculating ΔA ′ will be described. As described above, the equivalent absorptance with respect to laser light of the light absorption layer 16 above the region where the gate electrode 12 is formed (first region) and above the region where the gate electrode 12 is not formed (second region). When the difference between the two becomes −ΔA ′ or less, the effect according to the present embodiment is obtained.

Here, it is assumed that 100% of the light absorption energy of the laser light absorbed by the light absorption layer 16 contributes to the heat generation of the light absorption layer, and the energy per unit area of the laser light is defined as energy density E. Hereinafter, the light absorption layer 16 above the region where the gate electrode 12 is formed (first region) is referred to as the light absorption layer 16 of the first region, and above the region where the gate electrode 12 is not formed (second region). The light absorption layer 16 is referred to as a second region light absorption layer 16. In addition, the absorption rate of the light absorption layer 16 in the first region with respect to the wavelength of the laser light is A ₁ , and the heat generation amount (per unit area) of the light absorption layer 16 due to the absorption of the laser light is Q ₁ . The absorption rate of the light absorption layer 16 in the second region with respect to the wavelength of the laser light is A ₂ , and the heat generation amount (per unit area) of the light absorption layer 16 due to the absorption of the laser light is Q ₂ . Further, in this configuration in which a gate insulating layer 13 is formed on the gate electrode 12, an amorphous silicon layer is further formed thereon, and a buffer layer is further formed thereon, the gate electrode 12 is formed. A _G is the laser light absorption rate, and Q _G is the calorific value (per unit area) of the gate electrode 12 due to the absorption of the laser light.

Next, by setting the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 to a predetermined thickness, the absorptance of the light absorption layer 16 in the first region with respect to the wavelength of the laser light. And the second region of the light absorption layer 16 have the same absorption rate with respect to the wavelength of the laser light. That is, consider the case where A ₁ = A ₂ holds. In that case, Q ₁ = Q ₂ holds. However, in actuality, the light transmitted through the light absorption layer 16 is also absorbed by the gate electrode 12 and the gate electrode also generates heat (Q _G > 0). Therefore, the heat generation temperature of the amorphous silicon layer 14 in the first region is higher than the heat generation temperature of the amorphous silicon layer 14 in the second region.

  In view of the above, if the heat generation amount of the light absorption layer 16 in the second region is equal to or greater than the sum of the heat generation amount of the light absorption layer 16 in the first region and the heat generation amount of the gate electrode, amorphous silicon in the second region It is considered that the heat generation temperature of the layer 14 is equal to or higher than the heat generation temperature of the amorphous silicon layer 14 in the first region. This relationship can be expressed by (Equation 6).

Q ₁ + Q _G ≦ Q ₂ (Formula 6)

  And if this (Formula 6) is deformed, it can be expressed as (Formula 7).

Q ₁ −Q ₂ ≦ −Q _G (Formula 7)

Here, when the film thickness, density, and specific heat of the light absorption layer 16 are defined as d, ρ, and c, respectively, and the film thickness, density, and specific heat of the gate electrode are defined as d _G , ρ _G , and c _G , respectively. The heat generation amount of the absorption layer 16, the heat generation amount of the light absorption layer 16 in the second region, and the heat generation amount of the gate electrode can be expressed as follows.

Q ₁ = E × A ₁ / (d × ρ × c)
Q ₂ = E × A ₂ / (d × ρ × c)
Q _G = E × A _G / (d _G × ρ _G × c _G )

  Next, when these equations are substituted into (Equation 7) and rearranged, (Equation 8) is obtained.

(A ₁ −A ₂ ) / d ≦ − (A _G / d _G ) × (ρ × c) / (ρ _G × c _G ) (Formula 8)

Here, the absorption rate divided by the film thickness is defined as a converted absorption rate, and is described below as A ₁ / d = A ₁ ′ and A ₂ / d = A ₂ ′. Further, the right side of (Equation 8) is defined as −ΔA ′. Then, (Expression 7) becomes A ₁ ′ −A ₂ ′ ≦ −ΔA ′, and (Expression 5) is derived.

  (Formula 5) shows the following. That is, the gate insulation is satisfied so that the difference between the converted absorption rate of the light absorption layer 16 in the first region and the converted absorption rate of the light absorption layer 16 in the second region is less than or equal to the value defined by −ΔA ′. When the thicknesses of the layer 13, the amorphous silicon layer 14, the buffer layer, and the light absorption layer are configured, the heat generation temperature of the amorphous silicon layer 14 in the second region is the heat generation of the amorphous silicon layer 14 in the first region. Over temperature. That is, when the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer, and the light absorption layer satisfying this condition are formed, the upper layer of the amorphous silicon layer is formed by, for example, a red wavelength region laser. When the amorphous silicon layer is annealed indirectly by heat generated by irradiating and scanning the light absorption layer formed through the buffer layer, the heat absorption and propagation of the crystallization by the gate electrode 12 is prevented. The influence can be reduced. Therefore, it is possible to make uniform the temperature distribution due to the heat generation of the amorphous silicon layer 14 in the first region of the thin film transistor.

  In order to produce this effect, it is necessary that the absorptance of the light absorption layer 16 changes due to changes in the layer structure (the presence or absence of the gate electrode 12) and the layer thickness. This requires that the light absorption layer 16 is translucent, that is, extinction coefficient k <1, in the wavelength region of the laser beam of the predetermined (red or near infrared wavelength region). Due to this optical characteristic, the laser light incident on the light absorption layer is transmitted to the lower layer, and multiple interference occurs in the lower layer film. Therefore, since the multiple interference effect becomes stronger and weaker due to changes in the layer structure and the layer thickness, by utilizing this phenomenon, the absorption rate of the light absorption layer 16 on the gate electrode and the absorption of the light absorption layer outside the gate electrode 12 are obtained. The difference in rate can be controlled.

  On the contrary, the light absorption layer that has been widely used in the conventional laser indirect heating method is a high melting point metal such as Mo or Cr. Since these refractory metals have a large extinction coefficient k of 2 or more, the incident laser beam hardly transmits to the lower layer film, and multiple interference cannot occur in the lower layer film (or very small). In other words, the absorptance of the light absorption layer is constant regardless of the change in the layer structure or the layer thickness, so that the effect of the present invention cannot be produced.

  As described above, the laser light having the predetermined wavelength region has an optical characteristic that the light absorption layer 16 is translucent, which is different from the conventional technique in producing the effect of the present invention.

  As described above, by forming the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 so as to satisfy the above-described conditions, laser light having various wavelengths, gates are formed. Even if it is the material and film thickness of an electrode, the crystalline silicon layer 17 without a crystal nonuniformity can be produced | generated. That is, for example, the variation in crystallinity of the crystalline silicon layer 17 formed on the gate electrode 12 can be reduced without changing the pattern shape of the gate electrode 12 or the like, in particular, the structure of the thin film transistor 100, and stable. Crystallization is possible. Accordingly, it is possible to suppress variation in characteristics of the thin film transistor 100 using the thin film transistor 100 and to improve display quality even when high definition is advanced in a display device such as an LCD or an OLED.

  In the above description, an example in which the amorphous silicon layer 14 is crystallized using a laser beam condensed linearly is shown. However, in the present application, other spot shapes (circular or elliptical) are used. (Including other shapes) may also be used. In that case, it is preferable to carry out laser light by a scanning method suitable for crystallization.

  As described above, according to the method for manufacturing the thin film transistor 100 in this embodiment, the thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 satisfy the above-described conditions. Thus, the distribution of the temperature reached by the heat generation of the amorphous silicon layer 14 in the first region can be made uniform, and the amorphous silicon layer 14 in the first region can be crystallized sufficiently and uniformly.

  Hereinafter, conditions that the film thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 should satisfy will be described in detail in Examples.

(Example)
First, the calculation method of the absorptance with respect to the laser beam wavelength of a light absorption layer is demonstrated.

  7A and 7B are diagrams for explaining the amplitude transmittance and the method for calculating the amplitude transmittance.

7A and 7B show a model structure of a multilayer structure in which the structure of the thin film transistor 100 shown in FIG. 2 is modeled. Model structure shown in Figure 7A, a layer 401 made of complex refractive index _{N 1,} a layer 402 made of complex refractive index _{N 2,} a layer 403 made of complex refractive index _{N 3,} consisting of complex refractive index _{N 4} layer 404 comprising the, a layer 405 made of complex refractive index _{N 5,} and a substrate layer 406 made of complex refractive index _{N 6.} In this model structure, a layer 405, a layer 404, a layer 403, a layer 402, and a layer 401 are stacked on the substrate layer 406 in this order. Note that the model structure illustrated in FIG. 7B is a model structure in the case where the layer 405 illustrated in FIG. 7A is not provided. Further, the region of the complex refractive index N ₀ shown in the figure is outside the model structure and indicates the side on which the laser light is incident on the model structure. This region is, for example, air. In this case, the refractive index is 1 and the extinction coefficient is 0.

The substrate layer 406 is an insulating substrate made of, for example, transparent glass or quartz, and has a refractive index of 1.46, for example, and corresponds to the substrate 10 shown in FIG. 5A. The layer 405 has, for example, a refractive index of 3.55, an extinction coefficient of 3.86, is made of MoW having a thickness of 50 nm, and corresponds to the gate electrode 12 shown in FIG. 5A. The layer 404 is made of, for example, silicon oxide (SiO _x ) having a refractive index of 1.46 and an extinction coefficient of 0, and corresponds to the gate insulating film 13 shown in FIG. 5B. The layer 403 is made of, for example, a-Si having a refractive index of 4.19 and an extinction coefficient of 0, and corresponds to the amorphous silicon layer 14 shown in FIG. 5C. The layer 402 is made of a transparent film having a refractive index of 1.46 and an extinction coefficient of 0, for example, and corresponds to the buffer layer 15 shown in FIG. 5D. The layer 401 is a diamond-like carbon film having a refractive index of 1.9 and an extinction coefficient of 0.6, for example, and corresponds to the light absorption layer 16 in FIG. 5D.

  In this model structure, the layer corresponding to the undercoat layer 11 shown in FIG. 5A is omitted. This is because if the undercoat layer 11 is a transparent layer and does not absorb laser light, its film thickness does not affect the calculation result. Therefore, hereinafter, the calculation proceeds with a model structure in which the layer corresponding to the undercoat layer 11 is omitted.

As shown in FIGS. 7A and 7B, the amplitude reflection coefficient for light incident on the layer 401 from the outside is r ₀₁ , the amplitude reflection coefficient for light incident from the layer 401 to the layer 402 is r ₁₂ , and the layer 402 to layer 403 The amplitude reflection coefficient for light incident on the layer is r ₂₃ , the amplitude reflection coefficient for light incident on the layer 404 from the layer 403 is r ₃₄ , the amplitude reflection coefficient for light incident on the layer 404 from the layer 403 is r ₃₄ , and the layer The amplitude reflection coefficient for light incident from 404 to the layer 405 is r ₄₅ , and the amplitude reflection coefficient for light incident from the layer 404 to the substrate layer 406 is r ₄₆ . Further, the amplitude transmission coefficient for light incident on the layer 401 from the outside is t ₀₁ , the amplitude transmission coefficient for light incident on the layer 402 from the layer 401 is t ₁₂ , and the amplitude transmission for light incident on the layer 402 from the layer 402. The coefficient is t ₂₃ , the amplitude transmission coefficient for light incident on the layer 404 from the layer 403 is t ₃₄ , and the amplitude transmission coefficient for light incident on the substrate layer 406 from the layer 404 is t ₄₆ .

The amplitude reflection coefficients of the entire layers above the region where the layer 405 corresponding to the gate electrode 12 is formed (corresponding to the first region) are r ₀₁₂₃₄₅ (R1), r ₁₂₃₄₅ (R2), and r ₂₃₄₅ (R3), respectively. R ₃₄₅ (R4). Specifically, the amplitude reflection coefficient when the layers 405 and 404 are regarded as one layer is r ₃₄₅ (R4). Similarly, the amplitude reflection coefficient when the layers 405, 404, and 403 are regarded as one layer is r ₂₃₄₅ (R3), and the amplitude when the layers 405, 404, 403, and 402 are regarded as one layer. The reflection coefficient is r ₁₂₃₄₅ (R2), and the amplitude reflection coefficient when the layers 405, 404, 403, 402, and 401 are regarded as one layer is r ₀₁₂₃₄₅ (R1). In addition, the amplitude transmission coefficients of the entire layers in the first region are t ₀₁₂₃₄₅ (T1), t ₁₂₃₄₅ (T2), t ₂₃₄₅ (T3), and t ₃₄₅ (T4), respectively. Specifically, the amplitude transmission coefficient when the layers 405 and 404 are regarded as one layer is t ₃₄₅ (T4). Similarly, the amplitude transmission coefficient when the layers 405, 404, and 403 are regarded as one layer is t ₂₃₄₅ (T3), and the amplitude when the layers 405, 404, 403, and 402 are regarded as one layer. The transmission coefficient is t ₁₂₃₄₅ (T2), and the amplitude transmission coefficient when the layers 405, 404, 403, 402, and 401 are regarded as one layer is t ₀₁₂₃₄₅ (T1).

Next, as shown in FIG. 7B, the amplitude reflection coefficients of the entire layers (in the second region) above the region where the layer 405 corresponding to the gate electrode is not formed are respectively r ₀₁₂₃₄₆ (R1 ′) and r ₁₂₃₄₆ (R2 '), R ₂₃₄₆ (R3'), r ₃₄₆ (R4 '). Specifically, the amplitude reflection coefficient when the substrate layer 406 and the layer 404 are regarded as one layer is r ₃₄₆ (R4 ′). Similarly, the amplitude reflection coefficient when the substrate layer 406, the layer 404, and the layer 403 are regarded as one layer is r ₂₃₄₆ (R3 ′), and the substrate layer 406, the layer 404, the layer 403, and the layer 402 are regarded as one layer. The amplitude reflection coefficient is r ₁₂₃₄₆ (R2 ′), and the amplitude reflection coefficient when the substrate layer 406, the layer 404, the layer 403, the layer 402, and the layer 401 are regarded as one layer is r ₀₁₂₃₄₆ (R1 ′). In addition, the amplitude transmission coefficients of the entire layers of the second region are t ₀₁₂₃₄₆ (T1 ′), t ₁₂₃₄₆ (T2 ′), t ₂₃₄₆ (T3 ′), and t ₃₄₆ (T4 ′), respectively. Specifically, the amplitude transmission coefficient when the substrate layer 406 and the layer 403 are regarded as one layer is t ₃₄₆ (T4 ′). Similarly, the amplitude transmission coefficient when the substrate layer 406, the layer 404, and the layer 403 are regarded as one layer is t ₂₃₄₆ (T3 ′), and the substrate layer 406, the layer 404, the layer 403, and the layer 402 are regarded as one layer. The amplitude transmission coefficient is t ₁₂₃₄₆ (T2 ′), and the amplitude transmission coefficient when the substrate layer 406, the layer 404, the layer 403, the layer 402, and the layer 401 are regarded as one layer is t ₀₁₂₃₄₆ (T1 ′).

  Then, the amplitude reflection coefficient and amplitude transmission coefficient of each layer in the first region can be expressed by the following (Expression 9) to (Expression 16).

  Further, the amplitude reflection coefficient and amplitude transmission coefficient of each layer in the second region can be expressed by the following (Expression 17) to (Expression 24).

であり、ｄは各層の膜厚、θは各層での入射角・透過角、λはレーザー光の波長である。here,

Where d is the film thickness of each layer, θ is the incident angle / transmission angle in each layer, and λ is the wavelength of the laser beam.

  Further, θ can be calculated as shown below from Snell's law of the following equation.

The amplitude reflection coefficients r ₀₁ , r ₁₂ , r ₂₃ , r ₃₄ , r ₃₅ and the amplitude transmission coefficients t ₀₁ , t ₁₂ , t ₁₂ , t ₃₄ , t _{35 of each layer} are expressed by the following (formula 25) to (formula). 36).

  Here, the laser beam is a monochromatic laser beam, and its polarization is assumed to be P-polarized light.

Next, using the above equations, the amplitude reflection coefficient and amplitude transmission coefficient of the entire layer in the first region are calculated as follows. That is, first, r ₃₄₅ is calculated by substituting (Equation 28) and (Equation 29) into (Equation 12). Next, r ₂₃₄₅ is calculated by substituting (Equation 27) and r ₃₄₅ into (Equation 11). Next, r ₁₂₃₄₅ is calculated by substituting (Equation 26) and r ₂₃₄₅ into (Equation 10). Next, r ₀₁₂₃₄₅ is calculated by substituting (Equation 25) and r ₁₂₃₄₅ into (Equation 9). Next, t ₃₄₅ is calculated by substituting (Expression 28), (Expression 29), (Expression 34), and (Expression 35) into (Expression 16). Next, t ₂₃₄₅ is calculated by substituting (Equation 27), (Equation 33), r ₃₄₅ and t ₃₄₅ into (Equation 15). Next, t ₁₂₃₄₅ is calculated by substituting (Equation 26), (Equation 32), r ₂₃₄₅ and t ₂₃₄₅ into (Equation 14). Next, t ₀₁₂₃₄₅ is calculated by substituting (Equation 25), (Equation 31), r _12345, and t ₁₂₃₄₅ into (Equation 13).

Further, the amplitude reflection coefficient and the amplitude transmission coefficient of the entire layers in the second region are calculated as follows. That is, first, r ₃₄₆ is calculated by substituting (Equation 28) and (Equation 30) into (Equation 20). Next, r ₂₃₄₆ is calculated by substituting (Equation 27) and r ₃₄₆ into (Equation 19). Next, r ₁₂₃₄₆ is calculated by substituting (Equation 26) and r ₂₃₄₆ into (Equation 18). _Then, the _{r 012346,} is calculated by substituting the equation (25) and _{r 12346} in (Equation 17). Next, t ₃₄₆ is calculated by substituting (Equation 28), (Equation 30), (Equation 34), and (Equation 36) into (Equation 24). Next, t ₂₃₄₆ is calculated by substituting (Equation 27), (Equation 33), r ₃₄₆ and t ₃₄₆ into (Equation 23). Next, t ₁₂₃₄₆ is calculated by substituting (Equation 26), (Equation 32), r ₂₃₄₆ and t ₂₃₄₆ into (Equation 22).

_Then the _{t 012346,} in (Equation 21) (Equation 25) is calculated by substituting the equation _{(31), r 12346} and _{t 12346.}

  Next, the reflectances R1, R2, R3, and R4 and the transmittances T1, T2, T3, and T4 in each layer in the first region are calculated by (Expression 37) to (Expression 44).

  Further, the reflectances R1 ', R2', R3 ', and R4' and the transmittances T1 ', T2', T3 ', and T4' in each layer in the second region are calculated by (Expression 45) to (Expression 52).

Finally, it is possible to calculate the light absorption rate A ₁ of the (formula 53), the light-absorbing layer in the first region.

Further, by (Equation 54), it is possible to calculate the light absorptivity A ₂ of the light-absorbing layer in the second region.

From the above, using the film thickness d of the light absorption layer, the converted absorption rate of the light absorption layer in the second region from the conversion rate A ₁ ′ (A ₁ ′ = A ₁ / d) of the light absorption layer in the first region. A value ΔA ′ = A ₁ ′ −A ₂ ′ (converted absorption rate difference) obtained by subtracting A ₂ ′ (A ₂ ′ = A ₂ / d) can be calculated.

Next, using the calculation method described above, the wavelength is perpendicular to the model structure shown in FIGS. 7A and 7B, that is, at an incident angle θ ₀ in a range in which θ ₀ = 0 or sin θ ₀ = 0 approximately holds. When a laser beam of λ (600 nm ≦ λ ≦ 2000 nm) (red or near-infrared wavelength region laser light) is incident, the calculated absorption rate for the laser light of the light absorption layers in the first region and the second region is calculated. The difference was calculated. In this case, the calculation result is the same even if the polarization of the laser beam is S polarization.

FIG. 8 is a diagram for showing that there are suitable film thickness ranges for the gate insulating layer, the amorphous silicon layer, the buffer layer, and the light absorption layer when the crystalline silicon layer is formed by the laser indirect heating method. . Specifically, in FIG. 8, the thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 are changed using the model structure shown in FIGS. 7A and 7B. cases, is a contour diagram showing the calculation results of the conversion absorptance difference between the first region and the second region of the light absorbing layer _{16 ΔA '= a 1' -A} 2 '.

  Here, the horizontal axis (X) represents a value obtained by dividing the optical film thickness of the light absorption layer 16 obtained by multiplying the refractive index of the light absorption layer 16 by the film thickness of the light absorption layer 16 by the wavelength of a predetermined laser beam. . The vertical axis (Y) indicates the optical film thickness of the gate insulating film 13 obtained by multiplying the refractive index of the gate insulating layer 13 by the film thickness of the gate insulating layer 13, and the refractive index of the amorphous silicon layer 14 is amorphous. The sum of the optical thickness of the amorphous silicon layer 14 multiplied by the thickness of the silicon layer 14 and the optical thickness of the buffer layer 15 multiplied by the refractive index of the buffer layer 15 and the thickness of the buffer layer 15. Is divided by the wavelength of the predetermined laser beam.

  For example, when the refractive index of the light absorption layer 16 when λ = 808 nm is used, the value on the horizontal axis in FIG. 8 can be converted into the film thickness of the light absorption layer. For example, FIG. 9 is a diagram illustrating a value obtained by converting the value on the horizontal axis in FIG. 8 into the film thickness of the light absorption layer. FIG. 9 shows values obtained by converting the values on the horizontal axis of FIG. 8 into the film thickness of the amorphous silicon layer when λ = 808 nm and λ = 1064 nm.

  For example, when λ = 808 nm, the values on the vertical axis in FIG. 8 can be converted into the film thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, and the buffer layer 15. FIG. 10 shows, for example, when the thickness of the gate insulating layer (silicon oxide film) is 125 nm and the thickness of the amorphous silicon layer is 100 nm, when λ = 808 nm and λ = 1064 nm, the vertical axis of FIG. Is a value obtained by converting the above value into the thickness of the buffer layer. As described above, the vertical axis of FIG. 8 can be converted into the thickness of the buffer layer 15 by using the thickness and optical constant of the gate insulating layer and the thickness and optical constant of the amorphous silicon layer.

  As described above, the vertical axis X and the horizontal axis Y in FIG. 8 can be obtained even when the film thickness, optical characteristics, and the configuration of the gate insulating layer change. By converting this value, it is possible to calculate a preferable film thickness range of the gate insulating layer, the amorphous silicon layer, the buffer layer, and the light absorption layer when the crystalline silicon layer is formed by the laser indirect heating method.

  For example, even in the case where the gate insulating layer 13 has a laminated structure, the value obtained by adding the product of the refractive index and the film thickness (optical film thickness) of each insulating film constituting the laminated film is the same as above. By using it as the optical film thickness of the film, the vertical axis in FIG. 8 can be converted to the film thickness of the buffer layer 15.

  FIG. 11 is a cross-sectional view showing another example of the structure of the thin film transistor constituting the display device according to the embodiment of the present invention. FIG. 12 is a diagram showing pairs of film thicknesses when the gate insulating layer of the thin film transistor shown in FIG. 11 is formed of a silicon oxide film and a silicon nitride film.

  In the thin film transistor 200 shown in FIG. 11, the gate insulating layer 23 is composed of an upper insulating film 23a and a lower insulating film 23b. Here, for example, the upper insulating film 23a is a silicon oxide (SiO) film having a refractive index of 1.46, and the lower insulating film 23b is a silicon nitride (SiN) film having a refractive index of 1.92. At this time, the upper layer in the case where the gate insulating layer 23 having a laminated structure of these insulating films has an optical constant equal to that of the gate insulating layer 13 formed of, for example, a 125 nm-thick silicon oxide film. A set of the thickness of the silicon oxide film of the insulating layer 23a and the thickness of the silicon nitride film of the lower insulating layer 23b is as shown in FIG. 12 (with a laser light wavelength λ in the range of 600 nm to 2000 nm).

  Note that including a SiN film in the gate insulating film can block impurities such as an alkali metal from glass, which is an insulating substrate, and thus is effective as a means that does not affect TFT characteristics and reliability.

In FIG. 8, on the contour line represented by −ΔA ′ and in the inner region, the converted absorptance difference A ₁ ′ −A ₂ ′ of the light absorption layer 16 in the first region and the second region is −ΔA ′ or less. Indicates that this is an area. In other words, the curve indicated by the dotted line in FIG. 8 shows a contour line having a converted absorption rate difference of −0.00018. That is, the converted absorption difference between the curve and the inner region is −0.00018 or less. This region is calculated by the above-described equation (calculation method) from the film thicknesses of the amorphous silicon layer 14 and the gate insulating layer 13, their optical constants, and the optical constants of the gate electrode 12 and the substrate 10. . When the calculated absorptivity difference A ₁ ′ −A ₂ ′ of the amorphous silicon layer 14 in the first region and the second region satisfies the condition that −ΔA ′ or less, the first region of the thin film transistor 100 The temperature distribution due to heat generation of the light absorption layer 16 can be made uniform. As a result, the amorphous silicon layer 14 in the first region is sufficiently and uniformly crystallized into a crystalline silicon layer 17.

  FIG. 13 is a diagram used for calculating the preferable film thickness ranges of the gate insulating layer, the amorphous silicon layer, the buffer layer, and the light absorption layer in FIG.

で表すことができる。なお、Ｌ１〜Ｌ４は、以下のように表すことができるが、これらはそれぞれ上述した（式１）〜（式４）に相当する。In FIG. 13, X is the optical thickness of the light absorption layer 16 calculated by the wavelength of the laser beam, the optical thickness of the gate insulating layer 13, the optical thickness of the amorphous silicon layer, and the optical thickness of the buffer layer. Y is the product of the sum of the above and the wavelength of the laser beam. These X and Y are the same as described above. Then, using these X and Y, the contour line on the contour line represented by −ΔA ′ and the inner region are approximated by a mathematical expression. That is, the product of the sets indicated by L1 to L4

Can be expressed as In addition, although L1-L4 can be expressed as follows, these correspond to the above-described (Formula 1) to (Formula 4), respectively.

L1: Y ≦ −1.06X−0.22ΔA ′ + 1.07
L2: Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44
L3: Y ≧ 1.06X + 0.33ΔA ′ + 0.89
L4: Y ≦ 1.29X + −0.97 * ΔA′−0.95

Note that ΔA ′ is represented by ΔA ′ = (A _G / d _G ) × (ρ × c) / (ρ _G × c _G ) as described above. Here, ρ and c are the density and specific heat of the light absorption layer 16 respectively, and d _G , ρ _G and c _G are the film thickness, density and specific heat of the gate electrode, respectively.

で表す範囲が決定される。Next, as a specific example, consider a case where red laser light having a wavelength of 808 nm is vertically irradiated from above the model structure of FIGS. 7A and 7B. Here, the density of the light absorption layer 16 is 1800 (kg / m 3), and the specific heat is 970 (J / (kg · K)). Further, the gate electrode 12 is made of MoW having a film thickness of 50 nm, its density is 11720 (kg / m 3), and its specific heat is 226.4 (J / (kg · K)). At this time, the absorptance of the light absorption layer 16 in the first region with respect to the wavelength of the laser light is equal to the absorptance of the light absorption layer in the second region with respect to the wavelength of the laser light, ie, A ₁ = A ₂ To do. Then, using the film thicknesses of the gate insulating layer, the amorphous silicon layer, the buffer layer, and the light absorption layer when A ₁ = A ₂ is established, and the optical calculation formulas (Formula 9) to (Formula 54) described above. The maximum value _AG of the absorption rate of the gate electrode is calculated. As a result, _AG is calculated as 0.25, and ΔA ′ is calculated as 0.00018 therefrom. Note that A _G is calculated from the relational expression of A _G = T1 × T2 × T3 × T4 × (1-R _G ). Here, R _G is the reflectance of the gate electrode 12 when a silicon oxide film is used as a medium, and R _G = {(n _SiO −n _G ) ² + k _G ² } / {(n _SiO + n _G ) ² + k _G ² }. Further, the refractive index n _{SiO of} silicon oxide, the refractive index n _{G of} the gate electrode, and the extinction coefficient k _G of the gate electrode are used. As described above, ΔA ′ is calculated as 0.00018. Using this value, the product of the set indicated by L1 to L4 above

The range represented by is determined.

  Next, when the model shown in FIGS. 7A and 7B is irradiated with a red laser beam of λ = 808 nm perpendicularly and scanned, the temperature is increased by receiving heat generated from the light absorption layer. A simulation of the position dependence of the maximum temperature reached on the surface of the silicon layer 14 was performed. FIG. 14 shows a model used for the simulation. As shown in FIG. 14, the model includes a substrate layer 406, a corresponding layer 405 corresponding to the gate electrode 12, a layer 404 corresponding to the gate insulating layer 13, a layer 403 corresponding to the amorphous silicon layer 14, and a buffer. A layer 402 corresponding to the layer 15 and a layer 401 corresponding to the light absorption layer 16 are configured. In this model, the length of the layer 405 corresponding to the gate electrode 12 in the laser scanning direction is 30 μm, and the physical properties of the layer 401 corresponding to the light absorption layer 16 and the layer 405 corresponding to the gate electrode 12 are the values described above. Using.

FIG. 15 is a diagram showing the film thickness condition portions implemented in this simulation in FIG. Here, the vertical axis (X) and the horizontal axis (Y) are converted from the vertical axis (X) and the horizontal axis (Y) shown in FIG. 8 using the optical constants of the respective films when λ = 808 nm. is there. In the model used in this simulation, it was assumed that the gate insulating layer 13 was a silicon oxide (SiO) film and the film thickness was 125 nm. The film thickness of the amorphous silicon layer 14 was assumed to be 100 nm. The locations of points 1 to 8 (star 1 to star 8) marked with a star (☆) shown in FIG. 15 indicate the film thickness conditions of the buffer layer 15 and the light absorption layer 16 implemented in this simulation. Also, the converted absorption rate difference A ₁ '-A ₂ ' for star 1, star 2, star 3, and star 4 is smaller than -ΔA '(= -0.00018), and star 5, star 6, star 7, star 8 The difference in the converted absorption rate in A ₁ is larger than −ΔA ′ in A ₁ ′ −A ₂ ′. That is, star 1, star 2, star 3, and star 4 are present in the dotted line inner region of FIG.

  FIG. 16 is a diagram showing a simulation result of the position dependency of the highest temperature reached on the surface of the amorphous silicon layer in the first region and the second region. The horizontal axis represents position coordinates, and the vertical axis represents the highest temperature reached on the surface of the amorphous silicon layer 14. The amorphous silicon layer 14 receives heat from the light absorption layer that has generated heat by absorbing the laser light, and the temperature rises. Moreover, FIG. 16 has shown the simulation result of the film thickness conditions in the location of the stars 1-8 shown in FIG. As shown in FIG. 16, under the film thickness conditions at the locations of stars 1 to 4, the curve indicating the highest temperature reached on the surface of the amorphous silicon layer 14 is flat in the first region on the gate electrode 12. On the other hand, under the film thickness conditions at the locations of stars 5 to 8, the curve indicating the highest temperature reached on the surface of the amorphous silicon layer 14 is not flat in the first region on the gate electrode 12.

According to the above simulation results, the equivalent absorption difference A ₁ ′ −A ₂ ′ of the amorphous silicon layer 14 in the first region and the second region on the contour line represented by −ΔA ′ and in the region inside the contour line. When the film thickness of the amorphous silicon layer 14 and the film thickness of the gate insulating layer 13 are satisfied, it can be seen that the temperature distribution due to heat generation of the amorphous silicon layer 14 in the first region of the thin film transistor 100 can be made uniform. Thereby, it is possible to generate a crystalline silicon layer 17 in which the amorphous silicon layer 14 in the first region of the thin film transistor 100 is sufficiently and uniformly crystallized.

In summary, a buffer layer and a light absorption layer are formed on the amorphous silicon layer, and the light absorption layer is irradiated with laser light to heat the light absorption layer, and indirectly by the generated heat through the buffer layer. There is a laser indirect heating crystallization process to crystallize the amorphous silicon layer. Normally, in this laser indirect heating crystallization process, when a gate electrode exists under the amorphous silicon layer through a gate insulating layer, the amorphous material above the gate electrode is affected by the heat absorption and heat propagation of the gate electrode. The heat generation of the crystalline silicon layer becomes insufficient and non-uniform, and the crystallinity of the formed crystalline silicon layer varies. On the other hand, when the gate insulating layer, amorphous silicon layer, buffer layer, and light absorption layer are formed in the above-mentioned film thickness range, the influence of heat absorption and heat propagation of the gate electrode is suppressed in the laser indirect heating crystallization process. Thus, crystallization can be performed. Therefore, a thin film transistor (TFT) including an amorphous silicon layer and a gate insulating layer that is a base film thereof can realize uniform thin film transistor characteristics. FIG. 17A is a diagram showing the crystallinity of a crystalline silicon layer when a laser indirect heating crystallization method is performed on the structure of the embodiment of the present invention using laser light in the red and near-infrared wavelength regions. It is. FIG. 17B is a diagram showing the crystallinity of a crystalline silicon layer when a laser indirect heating crystallization method is performed on a conventional structure using laser light in the red and near infrared wavelength regions for comparison. . 17A and 17B show an example in which the laser beam energy density is 100 KW / cm ² per unit time and the laser scanning speed is 600 mm / s. The conventional structure is divided into a region crystallized with a crystal grain size of 50 nm and a region crystallized with a crystal grain size of less than 50 nm, that is, the crystallinity is uneven. On the other hand, it can be seen that the structure according to the embodiment of the present invention is uniformly crystallized with a crystal grain size of 50 nm. The unevenness in crystallinity shown in FIG. 17B represents unevenness in the maximum temperature reached of the amorphous silicon layer on the gate electrode. When the laser indirect heating crystallization process is performed on the structure of this embodiment, the arrival temperature of the amorphous silicon layer on the gate electrode can be made uniform in the plane, and the crystallinity of the obtained crystalline silicon layer is also improved. It becomes uniform.

  FIG. 18 is a diagram for explaining an effect in the embodiment of the present invention. That is, FIG. 18 focuses on a region other than the gate electrode 12 as a means for thermally saturating the gate electrode 12, and utilizes the heat generation of the light absorption layer 16 (in the second region) not above the gate electrode 12. It shows that. Specifically, by setting the film thicknesses of the gate insulating layer 13, the amorphous silicon layer 14, the buffer layer 15, and the light absorption layer 16 within appropriate ranges, the difference in the light interference effect due to the presence or absence of the gate electrode 12 can be reduced. 1) The light absorption rate of the light absorption layer 16 not above the gate electrode 12 is larger than the light absorption rate of the light absorption layer 16 above the gate electrode 12, that is, when laser annealing is performed, the gate The heat absorption of the light absorption layer 16 not above the gate electrode 12 (second region) can be set larger than the heat generation of the light absorption layer 16 above the electrode 12 (first region), and 2) the gate electrode 12 The heating temperature of the upper (first region) amorphous silicon layer 14 can be set to be equal to or higher than the melting point of silicon.

  1), the heat generated from the light absorption layer 16 in the second region is absorbed and propagated to the gate electrode 12 through the buffer layer 15, the amorphous silicon layer 14, and the gate insulating layer 13. be able to. Accordingly, the gate electrode 12 can be thermally saturated in advance before the laser light irradiates the light absorption layer 16 on the gate electrode 12 (first region). In the crystallization of the amorphous silicon layer 14, the influence of heat absorption / propagation of the gate electrode 12 can be reduced. Further, by being able to set 2), when the light absorption rate of the light absorption layer (in the second region) not above the gate electrode 12 is transiently larger than the light absorption rate of the light absorption layer 16 above the gate electrode 12, that is, Even when the heat generation of the light absorption layer 16 (in the second region) not above the gate electrode 12 is extremely larger than the heat generation of the light absorption layer 16 (in the first region) above the gate electrode 12, the gate electrode The amorphous silicon layer 14 in both regions of the light absorption layer 16 above the first electrode 12 (in the first region) and the light absorption layer 16 above the gate electrode 12 (in the second region) is melted to melt the molten silicon layer. Thus, the thermal conductivity increases to a value similar to the thermal conductivity of a metal generally used as the gate electrode 12.

  Therefore, heat conducted to the molten silicon layer (in the second region) that is not above the gate electrode 12 mainly propagates to the molten silicon layer (in the first region) above the gate electrode 12, so that the gate insulation There is no excessive propagation to the gate electrode 12 through the layer 13. Therefore, the temperature distribution of the gate electrode 12 is not deteriorated, and the heat generation temperature distribution of the amorphous silicon layer 14 (in the first region) thereabove is not affected.

  Accordingly, the temperature distribution of the amorphous silicon layer 14 (in the first region) above the gate electrode 12 can be maintained uniformly by the combined effects of 1) and 2) above, and crystalline silicon obtained at that time can be maintained. The uniformity of the crystal structure generated in the layer 17 can be maintained.

  As described above, according to the present invention, a method of manufacturing a thin film transistor device capable of forming a crystalline silicon film with stable crystallinity using laser beams in the red and near-infrared wavelength regions, a thin film transistor, and a display using the same An apparatus can be realized. Specifically, by forming the gate insulating layer, the amorphous silicon layer, the buffer layer, and the light absorption layer so that each film thickness satisfies a predetermined condition, for example, the pattern shape of the gate electrode, etc. A method of manufacturing a thin film transistor device capable of forming a crystalline silicon layer having stable crystallinity using laser light in the red and near-infrared wavelength regions without changing the structure of the thin film transistor, and the thin film transistor The display device that was used can be realized.

  Further, when the thin film transistor of the present invention is used for the display device shown in FIG. 19, a high-quality display device having uniform TFT characteristics can be realized. Further, the yield can be improved and the cost can be reduced by improving the display quality.

  In addition, according to the present invention, for example, the effect can be realized only by taking the film thickness condition within the above range without changing the structure of the thin film transistor, for example, the pattern shape of the gate electrode. Even when a higher-definition display device is manufactured, it can be said that it is superior to the conventional technique in that the design flexibility can be maintained.

  As described above, the method for manufacturing a thin film transistor device, the thin film transistor, and the display device using the thin film transistor device according to the present invention have been described based on the embodiment. However, the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to this embodiment, and the structure constructed | assembled combining the component in different embodiment is also contained in the scope of the present invention. .

  INDUSTRIAL APPLICABILITY The present invention can be used for a manufacturing method of a thin film transistor device, a thin film transistor, a liquid crystal panel using the thin film transistor, or a display device including an EL panel such as an organic EL panel. In the case where the gate electrode is present through the gate insulating film, the effect of heat absorption and heat propagation of the gate electrode can be suppressed and stable crystallization can be performed, so that a high-quality liquid crystal panel having homogeneous TFT characteristics or It can be used for manufacturing a display device including an EL panel such as an organic EL panel.

DESCRIPTION OF SYMBOLS 1 Switching transistor 2 Drive transistor 3 Data line 4 Scan line 5 Current supply line 6 Capacitance 7 Organic EL element 10 Substrate 11 Undercoat layer 12 Gate electrode 13, 23 Gate insulating layer 23a Silicon oxide layer 23b Silicon nitride layer 14, 18 Amorphous Crystalline silicon layer 15 Buffer layer 16 Light absorption layer 17 Crystalline silicon layer 19 n + silicon layer 20 Source / drain electrode 100, 200 Thin film transistor 401, 402, 403, 404, 405 layer 406 Substrate layer

Claims (20)

A first step of preparing a substrate;
A second step of forming a plurality of gate electrodes on the substrate;
A third step of forming a gate insulating layer on the plurality of gate electrodes;
A fourth step of laminating an amorphous silicon layer on the gate insulating layer;
A fifth step of forming a buffer layer on the amorphous silicon layer;
A sixth step of forming a light absorption layer on the buffer layer;
Heat generated by heating by moving a predetermined laser having a wavelength of 600 nm or more relative to the substrate in a certain direction to heat the light absorption layer using laser light emitted from the predetermined laser. A seventh step of indirectly crystallizing the amorphous silicon layer to generate a crystalline silicon layer;
An eighth step of forming a source electrode and a drain electrode in a region on the crystalline silicon layer corresponding to each of the plurality of gate electrodes,
A value obtained by dividing the optical film thickness of the light absorption layer, which is a value obtained by integrating the refractive index of the light absorption layer with the film thickness of the light absorption layer, is X,
The optical film thickness of the buffer layer, which is a value obtained by integrating the refractive index of the buffer layer to the film thickness of the buffer layer, the film thickness of the amorphous silicon layer, and the refractive index of the amorphous silicon layer are integrated. A value obtained by adding together the optical film thickness of the amorphous silicon layer, the film thickness of the gate insulating layer, and the optical film thickness of the gate insulating layer obtained by integrating the refractive index of the gate insulating layer. The value divided by the wavelength of light is Y,
Furthermore, the density of the light absorption layer is ρ, the specific heat is c, the thickness of the gate electrode is dG, the density is ρG, and the specific heat is cG.
The maximum value of the absorptance of the gate electrode when the light absorptivity of the light absorption layer above the gate electrode and the light absorption layer not above the gate electrode with respect to the laser light is equal is AG,
When a value calculated by the formula of (AG / dG) × (ρ × c) / (ρG × cG) is set as ΔA ′,
The film thickness of the gate insulating layer, the film thickness of the amorphous silicon layer, the film thickness of the buffer layer, and the film thickness of the light absorption layer are defined by the following equations 1) to 4). Satisfy X and Y belonging to a range;
A method for manufacturing a thin film transistor device.
Formula 1) Y ≦ −1.06X−0.22ΔA ′ + 1.07
Formula 2) Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44
Formula 3) Y ≧ 1.06X + 0.33ΔA ′ + 0.89
Formula 4) Y ≦ 1.29X + −0.97 * ΔA′−0.95 The light absorption layer is translucent (extinction coefficient k <1) in the wavelength range of the predetermined laser beam.
A method for manufacturing the thin film transistor device according to claim 1. After the seventh step and before the eighth step,
Removing at least the light absorption layer,
A method for manufacturing a thin film transistor device according to claim 1. After the seventh step and before the eighth step,
Removing the buffer layer and the light absorbing layer.
A method for manufacturing a thin film transistor device according to claim 1. In the sixth step, the predetermined laser irradiates the laser light in an oscillation mode of continuous oscillation or pseudo continuous oscillation mode.
The manufacturing method of the thin-film transistor device of any one of Claims 1-4. The predetermined laser is composed of a solid-state laser device.
The manufacturing method of the thin-film transistor device of any one of Claims 1-4. The predetermined laser is composed of a laser device using a semiconductor laser element,
The manufacturing method of the thin-film transistor device of any one of Claims 1-4. In the sixth step, the fluctuation of the irradiation energy density of the laser light on the amorphous silicon layer is less than about 5%.
The manufacturing method of the thin-film transistor device of any one of Claims 1-7. The wavelength of the predetermined laser is 600 nm to 2000 nm.
The manufacturing method of the thin-film transistor device of any one of Claims 1-8. The second step includes a step of forming an undercoat layer made of silicon oxide on the substrate and a step of forming a plurality of gate electrodes on the undercoat layer.
The manufacturing method of the thin-film transistor device of any one of Claims 1-9. A substrate,
A plurality of gate electrodes formed on the substrate;
A gate insulating layer formed on the plurality of gate electrodes;
A crystalline silicon layer formed on the gate insulating layer;
A source electrode and a drain electrode formed in a region on the crystalline silicon layer corresponding to each of the plurality of gate electrodes,
The crystalline silicon layer is
After forming an amorphous silicon layer on the gate insulating layer, a buffer layer is formed on the amorphous silicon layer, a light absorption layer having predetermined optical characteristics is formed on the buffer layer, and the wavelength is Heat generated by moving a predetermined laser having a wavelength of 600 nm or more and 2000 nm or less relative to the substrate in a certain direction and absorbing the laser light in the light absorption layer using laser light emitted from the predetermined laser. Is generated by indirectly annealing and crystallizing the amorphous silicon layer through the buffer layer,
A value obtained by dividing the optical film thickness of the light absorption layer by the film thickness of the light absorption layer by the film thickness of the light absorption layer, divided by the wavelength of the laser beam, is X, and the film thickness of the buffer layer In addition, the optical film thickness of the buffer layer, which is a value obtained by integrating the refractive index of the buffer layer, and the amorphous film, which is a value obtained by integrating the film thickness of the amorphous silicon layer and the refractive index of the amorphous silicon layer. The sum of the optical thickness of the silicon layer, the thickness of the gate insulating layer, and the optical thickness of the gate insulating layer obtained by integrating the refractive index of the gate insulating layer was divided by the wavelength of the laser beam. The value is Y, and the density of the light absorption layer is ρ, the specific heat is c, the film thickness of the gate electrode is dG, the density is ρG, the specific heat is cG, and the light absorption layer above the gate electrode A light absorption layer not above the gate electrode is applied to the laser beam. The maximum value of the absorptance of the gate electrode when the respective optical absorptances are equal is AG, and the value calculated by the formula of (AG / dG) × (ρ × c) / (ρG × cG) Is ΔA ',
The film thickness of the gate insulating layer, the film thickness of the amorphous silicon layer, the film thickness of the buffer layer, and the film thickness of the light absorption layer are defined by the following equations 1) to 4). Satisfy X and Y belonging to a range;
Thin film transistor device.
Formula 1) Y ≦ −1.06X−0.22ΔA ′ + 1.07
Formula 2) Y ≧ 1.29X + 1.61 * ΔA ′ + 1.44
Formula 3) Y ≧ 1.06X + 0.33ΔA ′ + 0.89
Formula 4) Y ≦ 1.29X + −0.97 * ΔA′−0.95 A display device including a liquid crystal panel or an EL panel,
The display device includes the thin film transistor device according to claim 11.
The thin film transistor device drives the liquid crystal panel or the EL panel.
Display device. The EL panel is an organic EL panel.
The display device according to claim 12. A first step of preparing a substrate;
A second step of forming a plurality of gate electrodes on the substrate;
A third step of forming a gate insulating layer on the plurality of gate electrodes;
A fourth step of laminating an amorphous silicon layer on the gate insulating layer;
A fifth step of forming a buffer layer on the amorphous silicon layer;
A sixth step of forming a light absorption layer on the buffer layer;
Heat generated by heating by moving a predetermined laser having a wavelength of 600 nm or more relative to the substrate in a certain direction to heat the light absorption layer using laser light emitted from the predetermined laser. A seventh step of indirectly crystallizing the amorphous silicon layer to generate a crystalline silicon layer;
An eighth step of forming a source electrode and a drain electrode in a region on the crystalline silicon layer corresponding to each of the plurality of gate electrodes,
In the second step, the third step, the fourth step, the fifth step, and the sixth step, in the seventh step, when the light absorption layer is irradiated using the laser beam, The highest temperature reached by the light absorption layer in the upstream region in the relative movement direction of the predetermined laser outside the gate electrode is the region on the gate electrode when the light absorption layer is irradiated using the laser light. In the region on the gate electrode so as to be higher than the highest temperature reached of the amorphous silicon layer, the light absorption layer is irradiated when the light absorption layer is irradiated using the predetermined laser beam. Configured so that the maximum temperature reached is approximately constant,
A method for manufacturing a thin film transistor device. In the third step, the fourth step, the fifth step, the sixth step and the seventh step,
In the eighth step, when the light absorption layer is irradiated using the laser light, the highest temperature of the light absorption layer in the upstream region in the relative movement direction of the predetermined laser light outside the gate electrode is , Higher than the highest temperature of the light absorption layer in the region on the gate electrode when the light absorption layer is irradiated using the laser beam, and in the region on the gate electrode, In order that the maximum temperature reached by the light absorbing layer when the light absorbing layer is irradiated using a predetermined laser beam is substantially constant,
The gate insulating layer thickness, the amorphous silicon layer thickness, the buffer layer thickness, and the light absorption layer thickness are configured,
The method for manufacturing the thin film transistor device according to claim 14. A first step of preparing a substrate;
A second step of forming a gate electrode on the substrate;
A third step of forming a gate insulating layer on the gate electrode;
A fourth step of forming a semiconductor material layer containing a semiconductor material on the gate insulating layer;
A fifth step of forming a buffer layer on the semiconductor material layer;
A sixth step of forming a light absorbing layer having a predetermined optical constant on the buffer layer;
Irradiating the light absorption layer with a predetermined laser beam having a wavelength of 600 nm or more and 2000 nm or less, causing the light absorption layer to absorb the laser beam, and indirectly through the buffer layer by heat generated from the light absorption layer. A seventh step of crystallizing the semiconductor material layer to produce a crystalline semiconductor layer;
And an eighth step of forming a source electrode and a drain electrode on the semiconductor layer in a second region which is a region not corresponding to the gate electrode, which is different from the first region which is a region corresponding to the gate electrode. ,
In the third step, the fourth step, the fifth step, and the sixth step, the heat generation amount per unit volume in the second region of the light absorption layer is in the first region of the light absorption layer. In the seventh step, the predetermined laser light is irradiated by forming the gate insulating layer, the semiconductor material layer, the buffer layer, and the light absorption layer so as to be larger than the calorific value per unit volume of The heat absorbed from the light absorption layer in the first region to the gate electrode is absorbed, and the heat absorbed in the gate electrode is transferred to the semiconductor material layer in the second region. The semiconductor material layer is crystallized by forming a portion having the same temperature distribution in the light absorption layer of the first region where heat is generated by suppressing thermal diffusion and storing heat. Make
A method for manufacturing a thin film transistor device. In the third step, the fourth step, the fifth step and the sixth step,
The heat generation amount per unit volume in the second region of the light absorption layer is larger than the heat generation amount per unit volume in the first region of the light absorption layer.
The thickness of the gate insulating layer, the thickness of the amorphous silicon layer, the thickness of the buffer layer, and the light absorption layer are configured.
The method for manufacturing the thin film transistor device according to claim 16. The second region of the light absorption layer corresponds to an upstream region and a downstream region with respect to the first region in a relative movement direction of the predetermined laser light with respect to the substrate in the seventh step.
The method for manufacturing the thin film transistor device according to claim 16. In the third step, the fourth step, the fifth step and the sixth step,
In the seventh step, the heat generation amount per unit volume in the second region of the semiconductor material layer is larger than the heat generation amount per unit volume in the first region of the semiconductor material layer. Configured to be greater than the amount of heat generated per unit,
The method for manufacturing the thin film transistor device according to claim 16. In the third step, the fourth step, the fifth step and the sixth step,
In the seventh step, the size of the light absorption layer at the portion having the same temperature distribution formed in the first region is 0.8 or more and 1.0 or less with respect to the first region. Composed,
The method for manufacturing the thin film transistor device according to claim 16.

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