JP2011077532A - Method for preparing wiring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dry-etching method whose selection ratio for the ground is large and which forms wirings of tapered shapes. <P>SOLUTION: A film composed of a conductive material is formed on a substrate, and the film composed of the conductive material is dry-etched by using an ICP etching device, thereby the wiring of a taper angle not larger than 60° is formed. Moreover, the film composed of the conductive material is formed on a substrate, the film composed of the conductive material is dry-etched by using an ICP etching device, thereby the gate wiring of a taper angle not larger than 60° is formed; a gate insulating film is formed on the gate wiring; and an active layer is formed on the gate insulating film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a semiconductor device having a circuit formed of a thin film transistor (hereinafter referred to as TFT) and a method for manufacturing the semiconductor device. For example, the present invention relates to an electro-optical device typified by a liquid crystal display panel and an electronic apparatus in which such an electro-optical device is mounted as a component. In particular, the present invention relates to a dry etching method for etching a metal thin film, and a semiconductor device including a tapered wiring obtained by the dry etching method.

Note that in this specification, a semiconductor device refers to all devices that can function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic device are all semiconductor devices.

In recent years, a technique for forming a thin film transistor (TFT) using a semiconductor thin film (having a thickness of about several to several hundred nm) formed on a substrate having an insulating surface has attracted attention. Thin film transistors are widely applied to electronic devices such as ICs and electro-optical devices, and development of switching devices for image display devices is urgently required.

Conventionally, Al is often used as a TFT wiring material because of its ease of processing, electrical resistivity, chemical resistance, and the like. However, when Al is used for the wiring of the TFT, the operation of the TFT and the deterioration of the TFT characteristics are caused by the formation of protrusions such as hillocks and whiskers and the diffusion of aluminum atoms into the channel formation region by heat treatment. Therefore, as a wiring material other than Al, tungsten (W) having a relatively low bulk specific resistance of 5.5 μΩ · cm and a high heat resistance is preferable.

In recent years, the demand for microfabrication technology has become increasingly severe. In particular, liquid crystal displays are required to have a very strict control of the line width as well as a high selection ratio in the wiring processing step as the definition and screen size increase.

In general, the wiring can be processed by wet etching using a solution or dry etching using a gas. However, since wet etching is disadvantageous when considering miniaturization of wiring, ensuring reproducibility, reduction of waste, and reduction of cost, wiring processing is considered to be directed to dry etching.

When processing tungsten (W) by a dry etching method, a mixed gas of SF ₆ and Cl ₂ is generally used as an etching gas. When this mixed gas is used, the etching rate is high and fine processing can be performed in a short time. On the other hand, it is difficult to obtain a desired tapered shape. In order to improve the coverage of the laminated film formed on the wiring, the cross section of the wiring may be intentionally tapered forward depending on the device structure.

Accordingly, an object of the present invention is to provide a dry etching method for patterning a layer to be etched made of tungsten (W) or a tungsten compound so that the cross section thereof has a forward tapered shape. In addition, a method for controlling an arbitrary taper angle with a uniform taper angle regardless of the location of the layer to be etched is provided.
In addition, a semiconductor device using a wiring having an arbitrary taper angle obtained by the above method and a manufacturing method thereof are provided.

The configuration of the invention related to the wiring disclosed in the present specification includes a tungsten film, a metal compound film containing a tungsten compound as a main component, or a metal alloy film containing a tungsten alloy as a main component, and has a taper angle α of 5 ° to 85 °. It is the wiring characterized by being in the range.

Further, the configuration of another invention related to wiring has a laminated structure in which a thin film selected from a tungsten film, a metal compound film containing a tungsten compound as a main component, or a metal alloy film containing a tungsten alloy as a main component is laminated, The wiring has a taper angle α in the range of 5 ° to 85 °.

In each of the above configurations, the metal alloy film includes Ta, Ti, Mo, Cr, Nb, and Si.
It is characterized by being an alloy film of one kind of element selected from the above or a plurality of kinds of elements and tungsten.

In each of the above structures, the metal compound film is a tungsten nitride film.

In each of the above structures, a conductive silicon film (for example, a phosphorus-doped silicon film or a boron-doped silicon film) may be provided in the lowermost layer in order to improve adhesion.

In addition, the configuration of the invention relating to the semiconductor device includes a tungsten film, a metal compound film mainly containing a tungsten compound, or a metal alloy film mainly containing a tungsten alloy, and the taper angle α is in the range of 5 ° to 85 °. A semiconductor device provided with a certain wiring.

In addition, another configuration of the invention relating to the semiconductor device has a stacked structure in which a thin film selected from a tungsten film, a metal compound film containing a tungsten compound as a main component, or a metal alloy film containing a tungsten alloy as a main component is stacked. The semiconductor device includes a wiring having a taper angle α in the range of 5 ° to 85 °.

In each of the structures related to the semiconductor device, the wiring is a gate wiring of a TFT.

In addition, the configuration of the invention related to the method for manufacturing the wiring includes a step of forming a metal thin film on the base film,
A method of manufacturing a wiring, comprising: forming a resist pattern on the metal thin film; and etching the metal thin film having the resist pattern to form a wiring having a taper angle α controlled according to a bias power density It is.

In addition, another configuration of the invention relating to a method for manufacturing a wiring includes a step of forming a metal thin film on a base film, a step of forming a resist pattern on the metal thin film, and etching the metal thin film having the resist pattern. Forming a wiring having a taper angle α controlled in accordance with the flow rate of the reactive gas containing fluorine.

Further, in each configuration relating to the wiring manufacturing method, the etching uses an etching gas which is a mixed gas of a first reaction gas containing fluorine and a second reaction gas containing chlorine, and the base film in the etching gas The selection ratio with the metal thin film is greater than 2.5.

Further, in each configuration related to the method for manufacturing the wiring, the metal thin film is a thin film selected from a tungsten film, a metal compound film containing a tungsten compound as a main component, or a metal alloy film containing a tungsten alloy as a main component, or those It is characterized by being a laminated film.

Further, according to the structure of the invention relating to the dry etching method, a desired portion of a thin film selected from a tungsten film, a metal compound film containing a tungsten compound as a main component, or a metal alloy film containing a tungsten alloy as a main component is removed by an etching gas. In the dry etching method, the etching gas is a mixed gas of a first reaction gas containing fluorine and a second reaction gas containing chlorine.

In the configuration of the invention relating to the dry etching method, the first reaction gas may be
It is characterized by being a gas selected from CF ₄ , C ₂ F ₆ , or C ₄ F ₈ .

In the configuration of the invention relating to the dry etching method, the second reaction gas may be
It is characterized by being a gas selected from Cl ₂ , SiCl ₄ , or BCl ₃ .

Further, in the structure of the invention related to the dry etching method, dry etching is performed using an ICP etching apparatus. .

In the structure of the invention relating to the dry etching method, the taper angle α is controlled by adjusting the bias power density of the ICP etching apparatus.

Another invention relating to the dry etching method is a dry etching method characterized in that the taper angle of the inner side walls of holes, grooves and the like formed by etching is controlled in accordance with the bias power density.

Another aspect of the invention relating to the dry etching method is a dry etching method characterized in that the taper angle of the inner side walls of holes, grooves and the like formed by etching is controlled in accordance with the gas flow rate ratio.

According to the present invention, a desired taper angle α can be obtained while setting a high selection ratio with respect to the substrate by appropriately setting conditions under which the taper angle α of the wiring can be controlled, bias power, and gas flow ratio.
Can be obtained. As a result, the coverage of the film formed on the wiring is improved, so that occurrence of defects such as chipping, disconnection, and short-circuiting of the wiring can be reduced.

  In addition, etching can be performed with good in-plane distribution, and a uniform wiring shape can be obtained.

  Further, the present invention can also be applied to an opening process such as a contact hole.

It is the figure which showed the bias power dependence of taper angle (alpha). It is the figure which showed the flow rate ratio dependence of taper angle (alpha) and CF4. It is the figure which showed taper angle (alpha) and (W / resist) selection ratio dependence. It is the figure which showed the plasma production | generation mechanism of the ICP etching apparatus. It is the figure which showed the ICP etching apparatus of a multi spiral coil system. It is explanatory drawing of taper angle (alpha) and (beta). It is a cross-sectional SEM photograph figure of wiring. It is a cross-sectional SEM photograph figure of wiring. It is the figure which showed the bias power dependence of an etching rate and (W / resist) selection ratio. It is the figure which showed the CF4 flow ratio dependence of an etching rate and (W / resist) selection ratio. It is the figure which showed the ICP power dependence of an etching rate and (W / resist) selection ratio. FIG. 6 is a cross-sectional structure diagram of an active matrix liquid crystal display device. FIG. 6 is a cross-sectional structure diagram of an active matrix liquid crystal display device. FIG. 6 is a cross-sectional structure diagram of an active matrix liquid crystal display device. The cross-section figure of wiring. FIG. 11 illustrates a structure of an active matrix EL display device. The figure which shows the external appearance of AM-LCD. FIG. 14 illustrates an example of an electronic device. FIG. 14 illustrates an example of an electronic device.

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

In the present invention, an ICP (Inductively Coupled Plasma) etching apparatus using high-density plasma is used. Briefly, the ICP etching apparatus achieves a plasma density of 10 ¹¹ atoms / cm ³ or more by inductively coupling RF power into the plasma at a low pressure, and has a high selectivity and a high etching rate. Processing is performed.

First, the ICP dry etching apparatus plasma generation mechanism will be described in detail with reference to FIG.

FIG. 4 shows a simplified structural diagram of the etching chamber. An antenna coil 12 is disposed on the quartz plate 11 at the upper part of the chamber, and is connected to an RF power source 14 via a matching box 13. Further, an RF power source 17 is connected to the lower electrode 15 on the substrate side arranged opposite to the substrate via a matching box 16.

When an RF current is applied to the antenna coil 12 above the substrate, an RF current is applied to the antenna coil 12.
A current J flows in the θ direction, and a magnetic field B is generated in the Z direction.

  In accordance with Faraday's law of electromagnetic induction, an induced electric field E is generated in the θ direction.

Electrons are accelerated in the θ direction by this induced electric field E, collide with gas molecules, and plasma is generated.
Since the direction of the induced electric field is the θ direction, the probability that the charged particles collide with the etching chamber wall or the substrate and lose the charge is reduced. Therefore, high-density plasma can be generated even at a low pressure of about 1 Pa. Further, since there is almost no magnetic field B downstream, a high-density plasma region spreading in a sheet shape is obtained.

The plasma density and the self-bias voltage are independently controlled by adjusting the RF power applied to each of the antenna coil 12 (ICP power is applied) and the lower electrode 15 on the substrate side (bias power is applied). Is possible. In addition, it is possible to vary the frequency of the RF power to be applied according to the material of the object to be processed.

In order to obtain high-density plasma with an ICP etching apparatus, it is necessary to flow the RF current J flowing through the antenna coil 12 with low loss. To increase the area, the inductance of the antenna coil 12 must be reduced. For this purpose, as shown in FIG. 5, an ICP etching apparatus for the multi-spiral coil 22 in which the antenna is divided has been developed. 21 in FIG.
Is a quartz plate, 23 and 26 are matching boxes, and 24 and 27 are RF power supplies. In addition, a lower electrode 25 that holds the substrate 28 is provided via an insulator 29 at the bottom of the chamber. When an etching apparatus using ICP to which such a multi-spiral coil is applied is used, the heat-resistant conductive material can be satisfactorily etched.

The present inventors performed several experiments by changing the etching conditions using this multi-spiral coil ICP etching apparatus (Matsushita Electric Industrial Co., Ltd .: E645).

First, an etching sample used in the experiment will be described. Insulating substrate (1737 substrate)
A base film (200 nm) made of a silicon nitride oxide film was formed thereon, and a metal laminated film was formed thereon by sputtering. Here, a tungsten target having a purity of 6N or more was used. Sputtering gases include argon (Ar), krypton (Kr), and xenon (Xe).
Etc.) or a mixed gas thereof may be used. The practitioner may appropriately control film forming conditions such as sputtering power, gas pressure, and substrate temperature.

This metal laminated film is formed of a tungsten nitride film (Wnx (where 0 <x <1))
The film thickness is 30 nm, and the upper layer is a tungsten film (370 nm).

The metal laminated film thus obtained contains almost no impurity elements, and particularly the oxygen content can be 30 ppm or less, and the electric resistivity is 20 μΩ · cm or less, typically 6 μ to 15 μΩ · cm. Moreover, the stress of the film is −5 × 10 ^{9 to} 5 × 1.
It can be 0 ⁹ dyn / cm ² .

Note that in this specification, a silicon nitride oxide film is an insulating film expressed by SiOxNy and indicates an insulating film containing silicon, oxygen, and nitrogen at a predetermined ratio.

This etching sample was subjected to a patterning experiment of a metal laminated film using a multi-spiral coil type ICP etching apparatus. Needless to say, when dry etching is performed, a resist mask pattern (film thickness: 1.5 μm) patterned in a desired shape using a resist is formed.

A schematic cross-sectional view of an etching sample before the etching treatment is shown in FIG. 6A, reference numeral 601 denotes a substrate, 602 denotes a base film, 603a and 603b denote metal laminated films (film thickness X = 400 n).
m), 604a and 604b are resist mask patterns (film thickness Y = 1.5 μm). FIG. 6B shows a state after the etching process.
It is.

Note that in this specification, the taper angle refers to an angle α formed by the taper portion (inclined portion) of the cross-sectional shape of the wiring 603 and the surface of the base film 602 as illustrated in FIG. The taper angle can be defined as tan α = X / Z using the width Z of the taper portion and the film thickness X.

  The present inventors have observed various cross-sectional shapes of wiring under various dry etching conditions.

Experiment 1)
FIG. 1 is a diagram showing the bias power dependence of the taper angle α. The bias power of 13.56 MHz is 20 W, 30 W, 40 W, 60 W, 100 W, that is, the bias power density (W / cm ² ) is 0.128, 0.192, 0.256, 0.384, 0.64. The experiment was conducted. The lower electrode is 12.5 cm × 12.5 cm. The resist film thickness is 1.5 μm, the gas pressure is 1.0 Pa, and the gas composition is CF ₄ / Cl ₂ = 30/30 sccm.
(Where sccm represents the volume flow rate (cm ³ / min) in the standard state). Also,
The ICP power is 500 W, that is, the ICP power density is 1.02 W / cm ² . In this specification, the value obtained by dividing the ICP power by the IPC area (diameter 25 cm) is I
CP power density (W / cm ² ).

As can be seen from FIG. 1, the higher the bias power density, the smaller the taper angle α of the wiring. Further, by simply adjusting the bias power density, a desired taper angle α = 5 ° ˜
85 ° (preferably in the range of 20 ° to 70 °) can be formed.

The bias power is 20 W (bias power density; 0.128 W / cm ² )
FIG. 7A shows a cross-sectional SEM photograph with the bias power set to 30 W (bias power density; 0.192 W / cm ² ), and FIG. 7B shows a cross-sectional SEM photograph with the bias power set to 4
0 W (bias power density; 0.256W / cm ²⁾ the cross-sectional SEM photograph of when to FIG. 7 (
C), a cross-sectional SEM photograph when the bias power is 60 W (bias power density; 0.384 W / cm ² ) is shown in FIG. 8A, and the bias power is 100 W (bias power density;
A cross-sectional SEM photograph at 64 W / cm ² ) is shown in FIG. It can be observed from the SEM photographs shown in FIGS. 7 and 8 that the taper angle α is formed in the range of 20 ° to 70 °, and the taper angle α can be controlled by changing the bias power density. .

This is presumably because the selectivity between tungsten and the resist becomes small, and a resist receding phenomenon occurs.

Experiment 2)
FIG. 2 is a graph showing the dependency of the taper angle α and CF _{4 on} the flow rate ratio. Gas composition ratio is C
The experiment was conducted with F ₄ / Cl ₂ = 20/40 sccm, 30/30 sccm, and 40/20 sccm. Gas pressure is 1.0 Pa, bias power density is 0.128 W / cm ² , resist film thickness is 1.5 μm, ICP power is 500 W (ICP power density; 1.02 W / cm ² )
It is.

It can be seen from FIG. 2 that as the flow rate ratio of CF ₄ increases, the selectivity between tungsten and resist increases and the taper angle α of the wiring increases. In addition, the roughness of the base is reduced. It is considered that the roughening of the base is caused by the fact that the etching anisotropy is weakened by increasing the flow rate ratio of CF ₄ (decreasing the flow rate ratio of Cl ₂ ). Further, the desired taper angle α = 5 ° to 85 ° (preferably in the range of 60 ° to 80 °) can be formed simply by adjusting the flow rate ratio of CF ₄ .

Experiment 3)
Also, 13.56MHz ICP power is 400W, 500W, 600W, that is, ICP
Experiments were performed at power densities of 0.82, 1.02, and 1.22. Bias power is 20
W (bias power density; 0.128 W / cm ² ), resist film thickness is 1.5 μm, gas pressure is 1.0 Pa, and gas composition is CF ₄ / Cl ₂ = 30/30 sccm.

As the ICP power density increases, the tungsten etch rate increases,
Etching rate distribution becomes worse. Further, no particular change in taper angle was observed.

Experiment 4)
The experiment was conducted with gas pressures of 1.0 Pa and 2.0 Pa. ICP power is 500W
(ICP power density; 1.02 W / cm ² ), gas composition is CF ₄ / Cl ₂ = 30/30 sc
cm, the bias power is 20 W (bias power density; 0.128 W / cm ² ), and the resist film thickness is 1.5 μm.

As the vacuum is increased, the etching rate of tungsten becomes faster and the anisotropy becomes stronger. Moreover, it became a reverse taper shape at 2.0 Pa.

Experiment 5)
The experiment was conducted with the total flow rate of the etching gas set to 60 sccm and 120 sccm.
Gas pressure is 1.0 Pa, ICP power is 500 W (ICP power density; 1.02 W / cm ²
), The gas composition is _{CF 4 / Cl 2 = 30 /} 30sccm, the bias power is 20W (bias power density; 0.128W / cm ^2), the resist film thickness of 1.5 [mu] m.

  The rate increased slightly as the total flow rate of the etching gas increased.

From the above experimental results, it is considered that the taper angle depends mainly on the bias power density condition and therefore depends on the selection ratio of tungsten and resist. FIG. 3 shows the dependence of the selectivity between tungsten and resist and the taper angle.

The change in the bias power density has a greater effect on the tungsten / resist selectivity than the tungsten etching rate, and the tungsten / resist selectivity tends to decrease as the bias power density is increased. FIG. 9A shows the bias power density dependence of the etching rate of tungsten and resist, and FIG. 9B shows the bias power density dependence of the selection ratio between tungsten and resist.

That is, as shown in FIGS. 6A and 6B, since the resist is etched at the same time as the tungsten is etched, the taper angle increases when the tungsten-resist selection ratio is large, and the tungsten and the resist are selected. When the ratio is small, the taper angle becomes small.

Similarly, when the CF ₄ gas flow ratio is reduced, the selectivity between tungsten and resist tends to decrease. FIG. 10A shows the etching rate of CF ₄ for tungsten and resist.
FIG. 10B shows the dependency of the selectivity ratio of tungsten to resist on the CF ₄ gas flow rate.

FIG. 11A shows the dependency of the etching rate of tungsten and resist on the ICP power density, and FIG. 11B shows the dependency of the selectivity ratio of tungsten and resist on the ICP power density.

In each of the above experiments, as an etching sample, a base film (200 nm) made of a silicon nitride oxide film is formed on an insulating substrate, and a metal laminated film (a laminated film of a tungsten nitride film and a tungsten film) is formed thereon. In the present invention, a thin film selected from a tungsten film, a metal compound film containing a tungsten compound as a main component, or a metal alloy film containing a tungsten alloy as a main component, or a laminate of these thin films is used. Any laminated structure can be applied. However, the case where the selection ratio with the base film is 2.5 or less or the case where the etching rate is extremely small are excluded. For example, a W—Mo alloy film (having a weight percentage ratio of W: Mo = 52: 48) has a selectivity with respect to the base film (SiOxNy) of about 1.5 or less, and an etching rate of about 5
Since it is as small as 0 nm / min, it is not suitable from the viewpoint of workability.

Here, the W film is shown as an example, but a generally known heat-resistant conductive material (Ta, T
If an ICP etching apparatus is used for i, Mo, Cr, Nb, Si, etc., the end of the pattern can be easily processed into a tapered shape. For example, a Ta film etching rate of 140 to 160 nm / min and a selection ratio of 6 to 8 are selected, and a W film etching rate of 70 is selected.
It is an excellent value for up to 90 nm / min and a selection ratio of 2 to 4. Therefore, a Ta film is also suitable from the viewpoint of workability, but the Ta film has a resistivity of 20 to 30 μΩcm and a W film has a resistivity of 10 to 16 μΩcm as values not shown in the table. A slightly higher point becomes a difficult point.

Further, CF ₄ (carbon tetrafluoride gas) is used as an etching gas for the dry etching.
A mixed gas of C ₂ and Cl ₂ gas was used, but there is no particular limitation, and for example, C ₂ F ₆ or C ₄ F ₈
It is also possible to use a mixed gas of a reaction gas containing fluorine selected from the above and a gas containing chlorine selected from Cl ₂ , SiCl ₄ , or BCl ₃ .

The etching conditions of the present invention are not particularly limited. For example, when an ICP etching device (Matsushita Electric Industrial Co., Ltd .: E645) is used and carbon tetrafluoride gas (CF ₄ ) and chlorine (Cl ₂ ) are used. If present, etching gas total flow rate: 60 to 120 sccm Etching gas flow rate ratio: C
F ₄ / Cl ₂ = 30/30 sccm to 50/10 sccm gas pressure (pressure in the etching gas atmosphere): 1.0 Pa to 2.0 Pa ICP power density: 0.61 W / cm ^{2 to} 2.04 W /
cm ² (ICP power: 300 W to 1000 W), frequency is 13 MHz to 60 MHz Bias power density: 0.064 W / cm ^{2 to} 3.2 W / cm ² (Bias power: 10 W to
500 W), the frequency is 100 kHz to 60 MHz, preferably 6 MHz to 29 MHz, substrate temperature: 0 ° C. to 80 ° C., preferably 70 ° C. ± 10 ° C., and the practitioner may determine the etching conditions as appropriate within this range. .

Note that in this specification, an “electrode” is a part of “wiring” and refers to a portion where electrical connection with another wiring is made or a portion intersecting with a semiconductor layer. Therefore, for convenience of explanation, “wiring” and “electrode” are used properly, but “wiring” is always included in the term “electrode”.

The present invention having the above-described configuration will be described in more detail with the following examples.

An embodiment of the present invention will be described with reference to FIGS. Here, the pixel TFT in the pixel section
An active matrix substrate in which a storage capacitor and a TFT of a driver circuit provided around the pixel portion are manufactured at the same time will be described.

As shown in FIG. 12, the structure of this example is a TFT on a substrate 101 having an insulating surface.
have. As the substrate 101, it is desirable to use a glass substrate or a quartz substrate. In addition, a substrate in which an insulating film is formed on the surface of a silicon substrate, a metal substrate, or a stainless steel substrate may be used. If heat resistance permits, a plastic substrate can be used.

An insulating film containing silicon (silicon) is provided on the surface of the substrate 101 where a TFT is formed (in this specification, a generic name of a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film)
The base film 102 is made of. For example, SiH ₄ , NH ₃ , N ₂ by plasma CVD method
The silicon oxynitride film 102a formed from O is 10 to 200 nm (preferably 50 to 1).
00 nm), and similarly, a silicon oxynitride silicon film 10 made of SiH ₄ , N ₂ O, and H ₂
2b was laminated to a thickness of 50 to 200 nm (preferably 100 to 150 nm). Although the base film 102 is shown here as a two-layer structure, it may be formed by laminating a single layer film or two or more layers of the insulating film.

Further, an active layer of TFT is provided on the base film 102. As the active layer, a crystalline semiconductor film obtained by crystallizing a semiconductor film having an amorphous structure was used. As a crystallization method, a known technique such as laser annealing method, thermal annealing method (solid phase growth method), rapid thermal annealing method (RTA method), or JP-A-7-1306 is used.
According to the technique disclosed in Japanese Patent No. 52, a crystallization method using a catalytic element may be applied. Note that the semiconductor film having an amorphous structure includes an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be applied.

The gate insulating film 130 covering the active layer of the TFT is formed of an insulating film containing silicon with a film thickness of 40 to 150 nm using a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film is formed with a thickness of 120 nm. In addition, a silicon oxynitride film manufactured by adding O ₂ to SiH ₄ and N ₂ O is a preferable material for this application because the fixed charge density in the film is reduced. Needless to say, the gate insulating film is not limited to such a silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure.

The gate electrodes 118 to 122 and the capacitor electrode 123 formed on the gate insulating film are made of a heat-resistant conductive material, and a conductive layer (A) made of a conductive nitride metal film and a conductive layer made of a metal film ( B) is laminated. The conductive layer (B) may be formed of an element selected from Ta, Ti, and W, an alloy containing the element as a component, or an alloy film combining the elements. In this embodiment, Ar gas and nitrogen (N ₂ ) gas are introduced by sputtering using a W target having a purity of 6N, and the conductive layer (A) is formed with a WN film to a thickness of 50 nm. layer(
B) is formed by patterning the conductive laminated film formed with the W film to a thickness of 250 nm to form the gate electrode 11
8 to 122 and the capacitor electrode 123 were completed. Note that etching is performed so that tapered portions are formed at end portions of the gate electrodes 118 to 123. This etching process is performed by an ICP etching apparatus. Details of the technology are as shown in the embodiment of the invention. In this embodiment, a mixed gas of CF ₄ and Cl ₂ is used as an etching gas, the flow rate thereof is 30 sccm, the ICP power density is 3.2 W / cm ² (frequency: 13.56 MHz), and the bias power density is 0.00. Etching was performed at 224 W / cm ² (frequency: 13.56 MHz) and a gas pressure of 1.0 Pa. By setting such etching conditions, the gate electrode 11
8 to 122 and the end of the capacitor electrode 123 are formed with a tapered portion that gradually increases in thickness from the end toward the inside, and the angle can be set to 25 to 35 °, preferably 30 °. It was.

In addition, when the gate electrodes 118 to 122 having the tapered shape and the capacitor electrode 123 are formed, in order to perform etching without leaving a residue, overetching is performed to increase the etching time at a rate of about 10 to 20%. The gate insulating film 130 has a substantially thinned portion.

Further, in this embodiment, in order to form a desired LDD region, an impurity element that imparts n-type or p-type in a self-aligning manner with a gate electrode 118 to 122 having a tapered portion as a mask is formed by ion doping. Added to the active layer. Further, in order to form a desired LDD region, an impurity element imparting n-type or p-type is added to the active layer by ion doping using a resist pattern as a mask.

Thus, in the first p-channel TFT (A) 200a of the driver circuit, the channel formation region 206 in the active layer, the LDD region 207 overlapping with the gate electrode, the source region 208 composed of the high-concentration p-type impurity region, the drain region 209 It has a structure with. The first n-channel TFT (A) 201a includes a channel formation region 210 in the active layer, an LDD region 211 formed by a low-concentration n-type impurity region and overlapping the gate electrode 119, and a source formed by a high-concentration n-type impurity region. A region 212 and a drain region 213 are included. For a channel length of 3 to 7 μm, the LDD region overlapping with the gate electrode 119 is Lov, and the length in the channel length direction is 0.1.
˜1.5 μm, preferably 0.3 to 0.8 μm. The length of this Lov is the gate electrode 11
It controls from the thickness of 9 and the angle of a taper part.

Similarly, the second p-channel TFT (A) 202a of the driver circuit similarly has a channel formation region 214 in the active layer, an LDD region 215 overlapping the gate electrode 120, and a source region 216 formed of a high-concentration p-type impurity region. The drain region 217 has a structure. The second n-channel TFT (A) 203a includes a channel formation region 218 in the active layer, an LDD region 219 overlapping with the gate electrode 121, a source region 220 formed with a high-concentration n-type impurity region,
A drain region 221 is provided.
The LDD region 219 has the same configuration as the LDD region 211. In the pixel TFT 204, channel formation regions 222a and 222b in the active layer, LDD regions 223a and 223b formed with low-concentration n-type impurity regions, and source or drain regions 225 formed with high-concentration n-type impurity regions.
~ 227. The LDD regions 223a and 223b have the same configuration as the LDD region 211. Further, a storage capacitor 205 is formed from the capacitor wiring 123, the gate insulating film, and the semiconductor layers 228 and 229 connected to the drain region 227 of the pixel TFT 204. FIG.
2, the n-channel TFT and the p-channel TFT of the driving circuit have a single gate structure in which one gate electrode is provided between a pair of source and drain, and the pixel TFT has a double gate structure. Either of them may have a single gate structure or a multi-gate structure in which a plurality of gate electrodes are provided between a pair of source and drain.

Further, a protective insulating film 142 is provided so as to cover the gate electrode and the gate insulating film 130. The protective insulating film may be formed using a silicon oxide film, a silicon oxynitride film, a silicon nitride film, or a stacked film including a combination thereof.

Further, an interlayer insulating film 143 made of an organic insulating material is provided so as to cover the protective insulating film 142. Organic resin materials include polyimide, acrylic, polyamide, polyimide amide, BC
B (benzocyclobutene) or the like can be used.

In addition, a source wiring or a drain wiring that is in contact with a source region or a drain region formed in each active layer through a contact hole is provided over the interlayer insulating film 143. Note that the source wiring or the drain wiring has a laminated structure of a laminated film of Ti and aluminum indicated by 144a to 154a and a transparent conductive film indicated by 144b to 154b. The drain wirings 153a and 153b function as pixel electrodes. Indium oxide zinc oxide alloy (In ₂ O ₃ —ZnO) and zinc oxide (ZnO) are also suitable materials for the transparent conductive film,
Furthermore, zinc oxide (Z) added with gallium (Ga) to increase the transmittance and conductivity of visible light
nO: Ga) and the like can be preferably used.

The configuration as described above makes it possible to optimize the structure of the TFT constituting each circuit according to the specifications required by the pixel TFT and the drive circuit, and to improve the operation performance and reliability of the semiconductor device. Furthermore, LDD is formed by forming the gate electrode from a heat-resistant conductive material.
The activation of the region, the source region, and the drain region is facilitated.

Further, when forming the LDD region overlapping the gate electrode through the gate insulating film, the impurity element added for the purpose of controlling the conductivity type is provided with a concentration gradient to form the LDD region, particularly in the vicinity of the drain region. It can be expected that the electric field relaxation effect will increase.

Further, the active matrix substrate shown in FIG. 12 can be applied to a reflective liquid crystal display device as it is.

Next, an active matrix liquid crystal display device to which the active matrix substrate shown in FIG. 12 is applied will be described with reference to FIG.

First, columnar spacers 405a to 405e and 406 obtained by patterning a resin film on an active matrix substrate are formed. Further, the arrangement of the spacers may be determined arbitrarily. The spacer may be provided by dispersing particles of several μm.

Next, an alignment film 407 made of polyimide resin or the like is provided in the pixel portion of the active matrix substrate in order to align the liquid crystal. After the alignment film was formed, rubbing treatment was performed so that the liquid crystal molecules were aligned with a certain pretilt angle.

A light shielding film 402, a transparent conductive film 403, and an alignment film 404 are formed on the counter substrate 401 on the opposite side. As the light shielding film 402, a Ti film, a Cr film, an Al film, or the like is formed with a thickness of 150 to 300 nm. Then, the active matrix substrate on which the pixel portion and the driver circuit are formed and the counter substrate are bonded together with a sealant 408.

Thereafter, a liquid crystal material 409 is injected between both substrates. A known liquid crystal material may be used as the liquid crystal material. For example, in addition to the TN liquid crystal, a thresholdless antiferroelectric mixed liquid crystal exhibiting electro-optical response in which the transmittance continuously changes with respect to the electric field can be used. Some thresholdless antiferroelectric mixed liquid crystals exhibit V-shaped electro-optic response characteristics. In this way, FIG.
The reflective active matrix liquid crystal display device shown in FIG.

On the other hand, in the case of a transmissive liquid crystal display device, a pixel electrode provided in each pixel of the pixel portion may be formed using a transparent electrode.

This embodiment shows an example in which a display device using a bottom gate type TFT different from the above example (top gate type TFT) is manufactured with reference to FIG.

First, a metal laminated film is formed on the insulating substrate 1801 by sputtering. This metal laminated film has a tungsten nitride film in the lower layer and a tungsten film in the upper layer. Note that a base film such as a silicon nitride oxide film represented by SiOxNy may be formed in contact with the substrate. Next, a resist mask for obtaining a desired gate wiring pattern is formed by photolithography.

In the bottom gate TFT, it is necessary to form a gate insulating film, a channel formation region, and the like on the gate wiring. In order to improve the TFT characteristics of the bottom gate structure, the coverage of the film formed on the gate wiring, and the breakdown voltage of the gate insulating film, the gate wirings 1802-1805 are provided.
The taper angle is desirably 60 ° or less, preferably 40 ° or less.

Next, using an ICP etching apparatus, the bias power or the gas flow rate ratio is appropriately selected as shown in the embodiment of the invention, and the taper angle of the gate wiring 1802 to 1805 is 60 ° or less, preferably 40 ° or less. did. For the subsequent steps, a known technique may be used.
There is no particular limitation.

In FIG. 21, 1814 is a CMOS circuit, 1815 is an n-channel TFT, 1816
Is a pixel TFT, 1817 is an interlayer insulating film, 1818a is a pixel electrode, and 1818b is an ITO film. The ITO film 1818b is provided for connection to an external terminal such as an FPC. Also,
Reference numeral 1819 denotes a liquid crystal material, and 1820 denotes a counter electrode. Reference numeral 1801 denotes a first substrate, 180
Reference numeral 8 denotes a sealing region, 1807 and 1809 to 1812 denote columnar spacers, and 1821 denotes a second substrate.

  Note that this embodiment can be freely combined with Embodiment 1.

FIG. 15 shows an example of various wiring structures formed on an insulating surface using the present invention. FIG.
FIG. 5A shows a cross-sectional view of a wiring having a single layer structure made of a material 1501 containing tungsten as a main component over a film (or substrate) 1500 having an insulating surface. This wiring is formed by patterning a film formed by using a target having a purity of 6N and using a single gas of argon (Ar) as a sputtering gas. The stress is controlled by setting the substrate temperature to 300 ° C. or less and the sputtering gas pressure to 1.0 Pa or more, and other conditions (sputtering power, etc.) may be appropriately determined by the practitioner.

In the patterning, the taper angle α is controlled according to the method described in the embodiment of the invention, for example, the bias power density.

The cross-sectional shape of the wiring 1501 thus obtained has a desired taper angle α. Also,
The impurity element is hardly contained, and the oxygen content can be 30 ppm or less, and the electrical resistivity can be 20 μΩ · cm or less, typically 6 μ to 15 μΩ · cm. The stress of the film can be −5 × 10 ^{10 to} 5 × 10 ¹⁰ dyn / cm ² .

FIG. 15B shows a two-layer structure similar to that of the gate electrode of Example 1. Note that tungsten nitride (WNx) is the lower layer and tungsten is the upper layer.
Note that the tungsten nitride film 1502 may be 10 to 50 nm (preferably 10 to 30 nm), and the tungsten film 1503 may be 200 to 400 nm (preferably 250 to 350 nm). In this example, the layers were continuously formed using a sputtering method without being exposed to the atmosphere.

FIG. 15C illustrates an example in which a wiring 1504 formed using a material containing tungsten as its main component and formed over a film (or substrate) 1500 having an insulating surface is covered with an insulating film 1505. The insulating film 1505 is a silicon nitride film, a silicon oxide film, a silicon oxynitride film SiOxNy (where 0 <x
, Y <1) or a laminated film combining them.

15D illustrates the surface of the wiring 1506 formed of a material containing tungsten as a main component formed over the film (or substrate) 1500 having an insulating surface.
This is an example covered with 7. Note that when the wiring in the state of FIG. 15A is subjected to nitriding treatment such as plasma nitriding, the structure of FIG. 15D is obtained.

FIG. 15E illustrates a wiring 1509 made of a material containing tungsten as a main component formed over a film (or substrate) 1500 having an insulating surface.
This is an example surrounded by 508. Note that the structure shown in FIG. 15E can be obtained by performing nitriding treatment such as plasma nitriding on the wiring in the state shown in FIG.

FIG. 15F illustrates an example in which the state of FIG. 15E is formed and then covered with an insulating film 1511. The insulating film 1511 may be formed using a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or a stacked film including a combination thereof.

Thus, the present invention can be applied to various wiring structures. Further, this embodiment can be freely combined with Embodiment 1 or Embodiment 2.

In this embodiment, the case where the present invention is applied to a reflective liquid crystal display device manufactured on a silicon substrate will be described. In the present embodiment, an impurity element imparting n-type or p-type is directly added to a silicon substrate (silicon wafer) instead of the active layer made of a crystalline silicon film in the first embodiment, thereby realizing a TFT structure. Just do it. Further, since it is a reflection type, a metal film having high reflectance (for example, aluminum, silver, or an alloy thereof (Al—Ag alloy)) or the like may be used as the pixel electrode.

In addition, the structure of a present Example can be freely combined with any structure of Examples 1-3.

The present invention can also be used when an interlayer insulating film is formed on a conventional MOSFET and a TFT is formed thereon. That is, it is possible to realize a three-dimensional semiconductor device.
In addition, SIMOX, Smart-Cut (registered trademark of SOITEC), ELTRA as substrates
It is also possible to use an SOI substrate such as N (registered trademark of Canon Inc.).

In addition, the structure of a present Example can be freely combined with any structure of Examples 1-4.

The present invention can also be applied to an active matrix EL display. An example is shown in FIG.

FIG. 16 is a circuit diagram of an active matrix EL display. Reference numeral 81 denotes a pixel circuit, and an X direction driving circuit 82 and a Y direction driving circuit 83 are provided around the pixel circuit.
Each pixel of the pixel circuit 81 includes a switching TFT 84, a capacitor 85, and a current control T.
An FT 86 and an organic EL element 87 are included, and an X direction signal line 88a (or 88b) and a Y direction signal line 89a (or 89b, 89c) are connected to the switching TFT 84. Further, power supply lines 90 a and 90 b are connected to the current control TFT 86.

In the active matrix EL display of this embodiment, the TFTs used for the X-direction drive circuit 82, the Y-direction drive circuit 83 or the current control TFT 86 are the p-channel TFT 200 or 202 of FIG. Type TFT 201 or 203
Are formed in combination. Further, the TFT of the switching TFT 84 is formed by the n-channel TFT 204 of FIG.

In addition, you may combine any structure of Examples 1-5 with respect to the active matrix type EL display of a present Example.

The configuration of the active matrix liquid crystal display device shown in FIG. 13 of Embodiment 1 will be described with reference to the perspective view of FIG. The active matrix substrate (first substrate) is a glass substrate 80.
1, a pixel portion 802, a gate side driver circuit 803, and a source side driver circuit 80 formed on
It is composed of four. A pixel TFT 805 (corresponding to the pixel TFT 204 in FIG. 13) in the pixel portion is an n-channel TFT, and includes a pixel electrode 806 and a storage capacitor 807 (the storage capacitor 20 in FIG. 13).
5).

Further, the drive circuit provided in the periphery is configured based on a CMOS circuit. The gate side driver circuit 803 and the source side driver circuit 804 are connected to the pixel portion 802 through a gate wiring 808 and a source wiring 809, respectively. Input / output wirings (connection wirings) 812 and 813 for transmitting signals to the drive circuit are connected to the external input / output terminal 811 to which the FPC 810 is connected.
Is provided. Reference numeral 814 denotes a counter substrate (second substrate).

Note that in this specification, the semiconductor device shown in FIG. 17 is called an active matrix liquid crystal display device, but a liquid crystal panel mounted up to an FPC as shown in FIG. 17 is generally called a liquid crystal module. . Therefore, the active matrix liquid crystal display device in this embodiment may be called a liquid crystal module.

A TFT formed by implementing the present invention can be used in various electro-optical devices. That is, the present invention can be implemented in all electronic devices in which these electro-optical devices are incorporated as display media.

Examples of such an electronic device include a video camera, a digital camera, a head mounted display (goggles type display), a wearable display, a car navigation system, a personal computer, a personal digital assistant (mobile computer, mobile phone, electronic book, etc.), and the like. . An example of these is shown in FIG.

FIG. 18A illustrates a personal computer, which includes a main body 2001, an image input unit 2002,
A display device 2003 and a keyboard 2004 are included. The present invention is applied to an image input unit 2002,
The present invention can be applied to the display device 2003 and other signal driving circuits.

FIG. 18B illustrates a video camera, which includes a main body 2101, a display device 2102, and an audio input unit 2.
103, an operation switch 2104, a battery 2105, and an image receiving unit 2106. The present invention can be applied to the display device 2102, the audio input unit 2103, and other signal driving circuits.

FIG. 18C shows a mobile computer, which is a main body 2201.
, A camera unit 2202, an image receiving unit 2203, an operation switch 2204, and a display device 2205. The present invention can be applied to the display device 2205 and other signal driving circuits.

FIG. 18D illustrates a goggle type display which includes a main body 2301, a display device 2302, and an arm portion 2303. The present invention can be applied to the display device 2302 and other signal driving circuits.

FIG. 18E shows a player using a recording medium (hereinafter referred to as a recording medium) on which a program is recorded. The main body 2401, the display device 2402, the speaker unit 2403, and the recording medium 240.
4 and operation switch 2405. This apparatus uses a DVD (Di as a recording medium).
gial Versatile Disc), CD, etc. can be used for music appreciation, movie appreciation, games, and the Internet.
The present invention can be applied to the display device 2402 and other signal driving circuits.

FIG. 18F illustrates a digital camera, which includes a main body 2501, a display device 2502, and an eyepiece unit 25.
03, an operation switch 2504, and an image receiving unit (not shown). The present invention can be applied to the display device 2502 and other signal driving circuits.

As described above, the application range of the present invention is extremely wide and can be applied to electronic devices in various fields. Moreover, the electronic apparatus of a present Example is realizable even if it uses the structure which consists of what combination of Examples 1-7.

A TFT formed by implementing the present invention can be used in various electro-optical devices. That is, the present invention can be implemented in all electronic devices in which these electro-optical devices are incorporated as display media.

Examples of such an electronic device include a projector (rear type or front type). An example of these is shown in FIG.

FIG. 19A shows a front projector, which includes a display device 2601 and a screen 26.
02. The present invention can be applied to display devices and other signal driving circuits.

FIG. 19B shows a rear projector, which includes a main body 2701, a display device 2702, a mirror 2703, and a screen 2704. The present invention can be applied to display devices and other signal driving circuits.

Note that FIG. 19C illustrates the display device 2601 in FIGS. 19A and 19B.
2 is a diagram illustrating an example of a structure 2702. FIG. The display devices 2601 and 2702 are the light source optical system 2.
801, mirrors 2802, 2804 to 2806, dichroic mirror 2803, prism 2807, liquid crystal display device 2808, phase difference plate 2809, and projection optical system 2810. Projection optical system 2810 includes an optical system including a projection lens. Although the present embodiment shows a three-plate type example, it is not particularly limited, and for example, a single-plate type may be used. In addition, in the optical path indicated by the arrow in FIG.
You may provide optical systems, such as a film for adjusting a phase difference, and an IR film.

FIG. 19D shows an example of the structure of the light source optical system 2801 in FIG. In this embodiment, the light source optical system 2801 includes a reflector 2811 and a light source 28.
12, 2813, 2814, polarization conversion element 2815, and condenser lens 2816.
Note that the light source optical system illustrated in FIG. 19D is an example and is not particularly limited. For example, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the light source optical system.

As described above, the application range of the present invention is extremely wide and can be applied to electronic devices in various fields. Further, the electronic apparatus of the present embodiment can be realized by using any combination of the first to third embodiments and the seventh embodiment. However, it goes without saying that the projector in this embodiment is a transmissive liquid crystal display device and is not applicable to a reflective liquid crystal display device.

Claims (1)

Forming a metal thin film on the underlying film;
Forming a resist pattern on the metal thin film;
Etching the metal thin film having the resist pattern, and forming a wiring having a taper angle α controlled in accordance with a bias power density.

Images