JP5159558B2 - Manufacturing method of display device - Google Patents

Description

  The present invention relates to a method for manufacturing a display device (thin electronic display device) represented by a liquid crystal display, an organic electroluminescence (EL) display, or the like. Specifically, the present invention relates to a method for manufacturing a display device having a structure in which an oxide transparent conductive film and an Al alloy film for a reflective electrode are directly connected, and alkaline corrosion during patterning of the Al alloy film. Can be effectively suppressed. In the following, a liquid crystal display will be described as a representative example, but the present invention is not limited to this.

  A liquid crystal display includes a transmissive display device that uses light from a lighting device (backlight) installed behind a liquid crystal panel as a light source, a reflective display device that includes ambient light, and a transmissive and reflective type. And a transflective display device having both types.

  Of these, the transflective display device has both the function of transmitting the light of the backlight and the function of reflecting the incident light (ambient light) from the surface of the display device with the reflective electrode. Power can be saved by using light, and display in the transmissive mode and in the reflective mode can be performed according to the usage environment, such as using a backlight when necessary indoors or at night.

  With reference to FIG. 1, the configuration and operation principle of a typical transflective liquid crystal display device will be described. FIG. 1 corresponds to FIG. 2 disclosed in Patent Document 2 described later.

  As shown in FIG. 1, a transflective liquid crystal display device 11 includes a thin film transistor (hereinafter referred to as “TFT”) substrate 21, a counter substrate 15 disposed to face the TFT substrate 21, and a TFT A liquid crystal layer 23 is provided between the substrate 21 and the counter substrate 15 and functions as a light modulation layer. The counter substrate 15 includes a color filter (not shown), and a transparent common electrode 13 is formed on the color filter. On the other hand, the TFT substrate 21 has a pixel electrode 19 and a wiring portion (not shown) including switching elements and scanning line signal lines.

  As shown in FIG. 1, the pixel region P of the pixel electrode 19 is composed of a transmissive region A and a reflective region C. The transmissive region A includes a transparent pixel electrode (oxide transparent conductive film) 19a and a reflective region C. Comprises a transparent pixel electrode 19a and a reflective electrode 19b. In the transmissive mode, the light F of the backlight 41 disposed below the TFT substrate 21 is used as a light source. The light emitted from the backlight 41 enters the liquid crystal layer 23 through the transparent pixel electrode 19a and the transmission region A, and the liquid crystal in the liquid crystal layer 23 is generated by an electric field formed between the transparent pixel electrode 19a and the common electrode 13. It is a mechanism to control the molecular orientation. On the other hand, in the reflection mode, external natural light or artificial light (ambient light) B is used as a light source. Ambient light B incident on the counter substrate 15 is reflected by the reflective electrode 19b, and the arrangement direction of the liquid crystal molecules in the liquid crystal layer 23 is controlled by the electric field formed between the reflective electrode 19b and the common electrode 13. It has become.

The transparent pixel electrode 19a is formed of an oxide transparent conductive film having high transparency in the visible light region, and typically, 10% by mass of tin oxide (SnO) in indium oxide (In ₂ O ₃ ). It is formed from an oxide transparent conductive film such as indium tin oxide (ITO) contained to a certain extent and indium zinc oxide (IZO) containing about 10% by mass of zinc oxide in indium oxide.

  The reflective electrode 19b is made of a metal material having a high reflectance. Considering only the reflectance, Ag (silver) is an ideal material. However, in thin electronic display devices, it is possible to reduce material costs from the viewpoint of suppressing abnormal oxidation due to moisture adsorption or atmospheric exposure in the manufacturing process. From the viewpoint, Al alloys such as pure Al and Al—Ni alloys (hereinafter collectively referred to as “Al-based alloys”) are used as typical materials. Al-based alloys are extremely useful as wiring materials because of their low electrical resistivity.

  However, after laminating the oxide transparent conductive film and the Al-based alloy film for the reflective electrode in this order, the Al-based alloy film is immersed in tetramethylammonium hydroxide aqueous solution (TMAH), which is an alkaline developer of photoresist, in order to pattern the Al-based alloy film. It was found that corrosion occurred. In particular, it has been found that this corrosion tends to be remarkable at the pattern edge of the oxide transparent conductive film.

  The above corrosion is caused by the TMAH aqueous solution, which is an electrolyte solution, penetrating into the interface with the oxide transparent conductive film along the pinholes and penetrating grain boundaries generated in the Al-based alloy film and electrically contacting the oxide transparent This is so-called galvanic corrosion in which an Al-based alloy film having a low electrode potential is corroded and eluted out of the conductive film and the Al-based alloy film, and the oxide transparent conductive film is blackened.

  Galvanic corrosion is said to occur when the electrode potential difference between dissimilar metals is large, such as an oxide transparent conductive film such as the ITO film and an Al alloy film. As shown in Table 1 below, the electrode potential for the Ag / AgCl standard electrode in the TMAH aqueous solution is about -0.17 V for amorphous-ITO (a-ITO) and about -0.19 V for poly-ITO (p-ITO). On the other hand, pure Al is very low at about -1.93V.

  When the galvanic corrosion as described above occurs in the display device, various defects such as blackening of the oxide transparent conductive film, resulting in blackening of the pixels, pattern formation defects such as wiring thinning and disconnection, and Al-based alloy film An increase in contact resistance with the oxide transparent conductive film, resulting in display (lighting) failure, and the like.

  Therefore, in the conventional display device, as shown in FIG. 1, between the Al-based alloy film constituting the reflective electrode 19b and the oxide transparent conductive film such as the ITO film and the IZO film constituting the transparent pixel electrode 19a. As shown in Table 1, a barrier metal layer 51 made of Mo or the like having an electrode potential difference with the ITO film smaller than that of the Al-based alloy film is formed. For example, in Patent Document 1 and Patent Document 2, a barrier metal layer 51 such as Mo or Cr is interposed between an Al-based alloy film and an oxide transparent conductive film. However, the method of interposing the barrier metal layer has problems such as a complicated manufacturing process and an increase in production cost.

  In view of this, a “direct contact technique” in which the formation of the barrier metal layer can be omitted and the Al-based alloy film can be brought into direct contact with the transparent pixel electrode has been studied. The direct contact technology is required to have a low contact resistance between the Al-based alloy film, which is an electrode material, and the transparent pixel electrode, and to have excellent heat resistance so that a display device with high display quality can be obtained.

  The applicant of the present application is not intended for a display device having a structure in which an oxide transparent conductive film and an Al alloy film for a reflective electrode are directly connected as in the present invention. 3 is proposed. Patent Document 3 discloses an Al alloy film wiring material containing 0.1 to 6 atomic% of at least one alloy element selected from the group consisting of Au, Ag, Zn, Cu, Ni, Sr, Ge, Sm, and Bi. Is disclosed.

  If the Al alloy film is used, a conductive alloy element-containing precipitate is formed at the interface between the Al alloy film and the transparent pixel electrode, and generation of an insulating material such as aluminum oxide is suppressed. Can be reduced. Moreover, if the addition amount of the alloy element is within the above range, the electrical resistivity of the Al alloy itself can be kept low. Furthermore, if at least one alloy element of Nd, Y, Fe, Co is further added to the Al alloy film, generation of hillocks (cove-like projections) can be suppressed, and heat resistance can be improved. The alloy element precipitate is formed by forming an Al alloy film on the substrate by sputtering or the like, and then heating (annealing) at 150 to 400 ° C. (preferably 200 to 350 ° C.) for 15 minutes to 1 hour. Obtained by.

If an Al alloy film having such a component composition is adopted for the reflective electrode, as shown in Table 1, the electrode potential difference with the ITO film is smaller than that of the pure Al film, but the electrode potential difference is still smaller than that of Mo or the like. It is large and it is difficult to sufficiently suppress galvanic corrosion. Therefore, as a manufacturing method for display devices with a structure in which the oxide transparent conductive film and the Al alloy film for the reflective electrode are directly connected, a unique method has been established to sufficiently suppress corrosion in the corrosive environment during the manufacturing process. I think it is necessary to do.
JP 2004-144826 A JP 2005-196172 A JP 2004-214606 A

  An object of the present invention is to manufacture a display device (for example, a liquid crystal display or an organic EL display) having a structure in which an Al alloy film for a reflective electrode is directly connected to an oxide transparent conductive film (for example, an ITO film). The present invention provides a method of manufacturing a display device capable of effectively suppressing corrosion of the Al alloy film when exposed to an alkaline developer such as a TMAH aqueous solution. Another object of the present invention is to provide a method for manufacturing a display device including a reflective electrode that exhibits a reflectance equivalent to that of pure aluminum and also exhibits high heat resistance.

  The method for manufacturing a display device according to the present invention is a method for manufacturing a display device having a structure in which an Al alloy film for a reflective electrode is directly connected on an oxide transparent conductive film. A first step of forming an oxide transparent conductive film, a second step of heating the oxide transparent conductive film to 150 ° C. or more for 5 minutes or longer to form a crystalline state, and the oxide transparent conductive film on the oxide transparent conductive film And a third step of forming an Al alloy film, wherein the Al alloy film is characterized by being made of an Al alloy containing 0.1 to 4 atomic% of Ni.

  The Al alloy film further includes La, Mg, Cr, Mn, Ru, Rh, Pt, Pd, Ir, Ce, Pr, Gd, Tb, Dy, Nd, Ti, Zr, Nb, Mo, Hf, Ta, Made of an Al alloy containing 0.1 to 2 atomic% in total of at least one element selected from the group consisting of W, Y, Fe, Co, Sm, Eu, Ho, Er, Tm, Yb, and Lu It may be.

  Further, the fourth step includes a step of patterning the Al alloy film, and when the patterning is performed using an aqueous tetramethylammonium hydroxide solution, the effects of the present invention are fully exhibited.

  The present invention is a display device manufactured by the above method, comprising a structure in which an Al alloy film for a reflective electrode is directly connected on an oxide transparent conductive film, and the oxide transparent conductive film comprises A display device characterized by being crystalline is also included.

  According to the present invention, during patterning of an Al alloy film for a reflective electrode formed on an oxide transparent conductive film (for example, an ITO film) in the manufacturing process of a display device, the Al alloy film is made of a TMAH aqueous solution or the like. Corrosion is suppressed even when exposed to an alkali developer, and as a result, reduction in contact resistance between the oxide transparent conductive film and the Al alloy film constituting the reflective electrode can be achieved. In addition, the display device of the present invention includes a reflective electrode exhibiting the same reflectance and high heat resistance as pure aluminum. Therefore, it is possible to provide a liquid crystal display or an organic EL display having higher performance than conventional display devices.

  The present inventors have manufactured a display device in which the reflective electrode is made of an Al alloy film containing Al as a main component (composition ratio of 94 atomic% or more) and directly connected on the oxide transparent conductive film. In this study, the inventors have conducted extensive research to effectively suppress the corrosion (galvanic corrosion) of the Al alloy film caused by the alkaline developer of the photoresist (TMAH aqueous solution or the like) during the patterning of the Al alloy film for the reflective electrode. The applicant of the present invention has already heated the substrate under predetermined conditions when forming the Al alloy film for the reflective electrode, or after heating the Al alloy film, heated the Al alloy film under the predetermined conditions. Therefore, a technique for suppressing galvanic corrosion has been proposed (Japanese Patent Application No. 2007-33004). In the above technique, the Al alloy film for the reflective electrode is made of a multi-component Al alloy material centering on Al-Ni, so that the conductivity and reflectivity comparable to the pure Al film and the pure Al film can be expected. It also shows that it can combine excellent heat resistance.

  In addition to proposing such a technique, the present inventors further studied another means for reliably suppressing the corrosion. As described above, the galvanic corrosion occurs when the TMAH aqueous solution penetrates to the interface between the oxide transparent conductive film and the reflective electrode through pinholes and through grain boundaries formed in the Al alloy film for the reflective electrode. Therefore, the idea of suppressing galvanic corrosion by suppressing pinholes and through-grain boundaries generated in the reflective electrode and preventing the TMAH aqueous solution from entering the interface between the transparent oxide conductive film and the reflective electrode. As a result of studying the means for achieving the above, if the oxide transparent conductive film which becomes the substrate when forming the Al alloy film is made crystalline, the Al alloy film formed on the oxide conductive film becomes dense (specifically In other words, it was found that the crystal grains became fine or pinholeless).

  This will be described with reference to FIG. FIG. 2A is a schematic cross-sectional view of an amorphous oxide transparent conductive film and an Al alloy film (reflecting electrode) formed thereon. As shown in FIG. 2 (a), when the oxide transparent conductive film is amorphous, the growth nuclei of sputtered particles are not formed so much during the initial film formation process of the Al alloy film. Since the density is reduced, the formed Al alloy film has a porous film quality, and it is considered that pinholes and through grain boundaries are easily formed. On the other hand, FIG. 2B is a schematic cross-sectional view of a crystalline oxide transparent conductive film and an Al alloy film (reflecting electrode) formed thereon, which is shown in FIG. 2B. As described above, when the oxide transparent conductive film is crystalline, many of the growth nuclei are formed in the initial process of forming the Al alloy film, and the density of the growth nuclei is increased. It is considered that the holes and through grain boundaries are suppressed and become dense. Note that the dotted line in the oxide transparent conductive film in FIG. 2A is in an amorphous state, and the dotted line in the oxide transparent conductive film in FIG. 2B is visually in a polycrystalline state. It is expressed in

  Thus, by forming an Al alloy film with suppressed pinholes and through grain boundaries for the reflective electrode, galvanic corrosion of the Al alloy film during resist development by TMAH in the patterning process of the Al alloy film. Can be suppressed. In addition, as described above, by crystallizing the oxide transparent conductive film, the surface potential of the oxide transparent conductive film fluctuates and the work function increases [= the electrode potential difference with the reflective electrode (Al alloy film) decreases. Therefore, it was also found that the effect of suppressing the galvanic corrosion can be obtained.

  The degree of crystallization can be determined as crystalline / amorphous based on diffraction patterns in X-ray diffraction and electron beam diffraction. Specifically, as shown in the examples to be described later, for example, in the case of an ITO film, it is determined that a crystal having a peak at diffraction angles of 30 ° and 35 ° is crystalline, and peaks at diffraction angles of 30 ° and 35 ° Although not confirmed, those having a broad peak around a diffraction angle of 32 ° were judged to be amorphous.

And, in order to embody the above crystallization of the oxide transparent conductive film, further examination, in the manufacturing method of the display device,
A first step of forming the oxide transparent conductive film on a substrate;
A second step in which the transparent oxide conductive film is heated to 150 ° C. or higher for 5 minutes or longer to be crystalline;
A third step of forming the Al alloy film on the oxide transparent conductive film;
It was found that it should be included. As described above, the method of the present invention is characterized in that after the oxide transparent conductive film is heated to 150 ° C. or higher for 5 minutes or longer to be crystalline, an Al alloy film is formed on the oxide transparent conductive film. The heating is preferably performed at 200 ° C. or higher. On the other hand, even if the heating temperature is too high, the flat film in the lower layer is deteriorated and damaged. Therefore, the heating temperature is preferably 400 ° C. or lower. More preferably, it is 350 degrees C or less.

  In addition, even if the heating time at the above temperature is too short, sufficient crystallization cannot be achieved. Therefore, the heating time at the above temperature is set to 5 minutes or more (preferably 10 minutes or more). On the other hand, if the heating time is too long, the manufacturing time increases and the throughput is lowered. Therefore, the heating time at the above temperature is preferably 60 minutes or less (more preferably 30 minutes or less).

The heating atmosphere may be a vacuum (for example, a degree of vacuum ≦ 3 × 10 ⁻⁴ Pa), a nitrogen atmosphere, or the like.

  There are several types of oxide transparent conductive films such as ITO film, IZO film, ITZO film, etc., but the method of the present invention is characterized in that the oxide transparent conductive film is crystallized by heating under the above conditions. Therefore, it is preferable that the oxide transparent conductive film has a characteristic that crystallization is promoted by heating under the above conditions. From such a viewpoint, an ITO film or an ITZO film in which crystallization by heating is more sufficiently promoted than the IZO film is preferable.

  The second step may be heating performed for the purpose of improving the crystallinity of the oxide transparent conductive film, or heating performed for another purpose may satisfy the above temperature and time. As heating performed for other purposes, after patterning the oxide transparent conductive film, as the reflective electrode, for example, heating may be performed in a part of a process of manufacturing a liquid crystal cell internal diffuse reflective film.

  Here, the liquid crystal cell internal diffuse reflection film will be described. Conventionally, a specular reflective film made of a conductive metal has been used as a reflective electrode, and this specular reflective film has both a function as a reflector and a function as an electrode, but the surface of the reflective film is not a mirror surface. In some cases, the reflection function is further enhanced by providing irregularities and the function of diffuse reflection. If a reflective electrode having an uneven surface is used in this way, a front scattering plate, a transmission type diffusion hologram, or the like can be eliminated. As a result, it is possible to avoid parallax due to the presence of the glass substrate between the front scattering plate and the reflection film, and a decrease in contrast due to back scattering of incident light, which becomes a problem when the front scattering plate is used together.

As a method of forming irregularities on the surface of the reflective electrode, for example,
(1) A method of roughening the surface of a metal thin film by heating or sun blasting,
(2) A method of obtaining fine irregularities (wrinkles) by forming a metal thin film while heating an organic thin film having a different thermal expansion coefficient from that of the metal,
(3) A method of forming a metal thin film thereon by subjecting an inorganic thin film such as SiO ₂ to taper etching on the unevenness,
(4) An insulating layer having a concavo-convex shape is prepared using a photosensitive resin and the like, and a method of forming a metal thin film on the insulating layer, and the method (4) is practically used.

  Specific methods of (4) include the following methods. First, a photosensitive resin is spin-coated, and exposure and development are performed using a photomask having a circular pattern hole to form an insulating layer having a circular convex pattern. Thereafter, the upper corner portion of the pattern is heated to soften and round. Further, the same photosensitive resin is spin-coated on the circular convex pattern, exposed and developed, and then a contact hole is formed on the drain electrode. An oxide transparent conductive film and a reflective electrode (Al alloy film) are formed thereon. ) Are sequentially formed to obtain a liquid crystal cell internal diffuse reflection film.

  In this case, as a case where heating is performed for the other purpose, when the reflective electrode (Al alloy film) is formed on the oxide transparent conductive film, the stage (oxide transparent conductive film) is heated in the state. For example, an Al alloy film is formed.

  In the present invention, after forming an oxide transparent conductive film as described above, the oxide transparent conductive film is heated under the above conditions to be crystalline, and then an Al alloy film is formed on the oxide transparent conductive film. There is the greatest feature and other conditions in the second step are not particularly limited. Moreover, what is necessary is just to select and employ | adopt a well-known method appropriately for the 1st process of forming an oxide transparent conductive film, and the 3rd process of forming an Al alloy film on an oxide transparent conductive film.

  In the third step, as proposed in Japanese Patent Application No. 2007-33004 mentioned above, the substrate is heated at the time of forming the Al alloy film under a predetermined condition, or after the third step, that is, After the Al alloy film is formed, the galvanic corrosion can be more reliably suppressed by heating the Al alloy film under predetermined conditions.

  The present invention includes the first step, the second step, and the third step. For example, the oxide transparent conductive film formed in the first step is patterned by a known method. As a second step, the patterned oxide transparent conductive film is heated under the above conditions, and then an Al alloy film is formed as in the third step, and then the formed Al alloy film is patterned. The method of giving is mentioned.

  About processes other than the said 1st-3rd process, a normal method can be employ | adopted regardless of especially.

  In the present invention, after the Al alloy film for the reflective electrode is formed (that is, after the oxide transparent conductive film and the Al alloy film are directly connected), the Al alloy film is patterned as the fourth step. When exposed to an aqueous solution of TMAH in order to perform the treatment, the effect is fully exhibited. For other patterning conditions (resist type, etching method, etc.), a normal method may be employed.

  In the present invention, the Al alloy film for the reflective electrode is made of an Al alloy containing 0.1 to 4 atomic% of Ni. Ni has an effect of reducing contact resistance with the oxide transparent conductive film, and also has an effect of improving heat resistance. The reason why the contact resistance with the oxide transparent conductive film is reduced by adding Ni to the Al alloy film is that Al diffusion can be prevented at the interface (contact interface) between the Al alloy film and the oxide transparent conductive film. This is probably because Ni-containing precipitates are formed.

  The Ni content is set to 0.1 atomic% or more in order to effectively exhibit the above-described contact resistance reducing effect and heat resistance improving effect. On the other hand, if the Ni content exceeds 4 atomic%, the reflectance and electrical resistivity of the Al alloy film are lowered and cannot be put to practical use. Therefore, the Ni content in the Al alloy film is determined to be 0.1 atomic% or more (preferably 0.2 atomic% or more) and 4 atomic% or less (preferably 2.0 atomic% or less). In the present invention, the balance of the Al alloy film is made of Al and inevitable impurities.

  Furthermore, La, Mg, Cr, Mn, Ru, Rh, Pt, Pd, Ir, Ce, Pr, Gd, Tb, Dy, Nd, Ti, Zr, Nb, Mo, Hf, Ta, W, Y, Fe , Co, Sm, Eu, Ho, Er, Tm, Yb, and at least one element selected from the group consisting of Lu (group X) (third element) is contained in a total amount of 0.1 to 2 atomic%. An Al alloy film may be used.

  The group X element is an element that contributes to improving the heat resistance of the Al alloy film (heat resistance improving element). Specifically, the inclusion of at least one of group X can effectively prevent the formation of hillocks (cove-like projections) on the surface of the Al alloy film during heating. These elements may be used alone or in combination of two or more.

  In order to sufficiently exhibit such heat resistance improving effect, the total content of elements belonging to Group X is preferably 0.1 atomic% or more, more preferably 0.2 atomic% or more in total. is there. However, when the content of elements belonging to group X becomes excessive, the electrical resistivity of the Al alloy film itself increases. Therefore, the total content of elements belonging to Group X is preferably 2 atomic percent or less, and more preferably 0.8 atomic percent or less.

  In consideration of realizing high heat resistance and low electrical resistivity together, among the elements belonging to Group X, La, Gd, Tb and Mn are preferable, and La is more preferable.

A typical method for forming the Al alloy film is a sputtering method using a sputtering target. In the sputtering method, a plasma discharge is formed between a substrate and a sputtering target (target material) made of the same material as the thin film to be formed, and a gas ionized by the plasma discharge is caused to collide with the target material. In this method, atoms of the target material are knocked out and stacked on a substrate to produce a thin film. Unlike the vacuum vapor deposition method and the arc ion plating (AIP) method, the sputtering method has an advantage that a thin film having the same composition as the target material can be formed. In particular, an Al alloy film formed by a sputtering method has an advantage that it can dissolve an alloy element such as Nd that cannot be dissolved in an equilibrium state, and exhibits excellent performance as a thin film. However, the gist of the present invention is not limited to the above, and a method usually used for a method of forming an Al alloy film can be appropriately employed.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the above and the following purposes. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

(Experimental example 1)
An ITO film (thickness: about 50 nm) containing about 10% by mass of SnO is sputtered on a substrate (non-alkali glass plate, thickness 0.7 mm, 4 inch size) as an oxide transparent conductive film (transparent pixel electrode). Formed by law. The sputtering conditions at this time were set to a pressure of about 3 mTorr under an argon atmosphere. Next, photolithography and etching were sequentially performed to pattern the ITO film.

  Next, a heated sample and a non-heated sample were prepared for the patterned ITO film. When heating was performed, heating was performed at 200 ° C. for 1 hour. The heating atmosphere was a nitrogen atmosphere.

  A pure Al film or an Al-2 atomic% Ni-0.35 atomic% La alloy film (hereinafter referred to as “Al-2Ni-0.35 La film”) is formed as a reflective electrode on the ITO film by a sputtering method. Formed. The film thickness was about 100 nm in all cases. The sputtering conditions were a substrate temperature: room temperature, an argon atmosphere, and a pressure: about 2 mTorr.

  Next, after applying a resist to a pure Al film or an Al-2Ni-0.35La film and exposing it, a 2.38 mass% tetramethylammonium hydroxide aqueous solution (TMAH, developer manufactured by Tokyo Ohka Kogyo Co., Ltd .: NMD-W) ) Was developed for 1 minute, and the resist in the exposed portion was removed by etching. Then, the pattern was observed with an optical microscope to observe the occurrence of galvanic corrosion. The galvanic corrosion rate is determined by measuring the area ratio of the corroded portion (black part) of any five visual fields (size of one visual field: 200 μm × 200 μm) on three substrates (area: 10 cm × 10 cm), and calculating the average value (galvanic corrosion). Rate).

  And when the galvanic corrosion rate was 3 area% or less, it evaluated that corrosion was suppressed.

  The result is shown in FIG. FIG. 3 is a graph showing the galvanic corrosion rate of a pure Al film or an Al—Ni—La alloy film according to the presence or absence of heating. From FIG. 3, when a pure Al film is formed, galvanic corrosion is remarkable regardless of the presence or absence of heating, whereas when an Al-2Ni-0.35La film is formed, corrosion is suppressed. It can be seen that when the Al-2Ni-0.35La film is formed after heating the ITO film, there are almost no black spots.

  When the Al-2Ni-0.35La film is formed, optical micrographs when the ITO film (oxide transparent conductive film) is heated and not heated are shown in FIGS. Shown as (b). From the photograph of FIG. 4, it can be seen that black spots exist when the ITO film is not heated, whereas the black spots are almost completely eliminated by heating the ITO film under the above conditions.

  FIG. 5 shows transmission electron micrographs of the cross sections of (a) an unheated amorphous ITO film and (b) a crystalline ITO film obtained by heating. 5A and 5B, a streak-like grain boundary can be confirmed in the cross section of the crystalline ITO film in FIG. 5B, whereas the amorphous structure in FIG. The streak-like grain boundary cannot be confirmed in the cross section of the ITO film.

  The distinction between crystalline and amorphous was made from the ratio of the peak intensity of the pure crystalline phase and the amorphous phase by X-ray diffraction. X-ray diffraction was performed using a RINT 1500 X-ray diffractometer manufactured by Rigaku under conditions of a measurement range of 10 to 90 °. As a result, in the crystalline ITO film as shown in FIG. 5B, peaks were observed at diffraction angles of 30 ° and 35 °, whereas in the amorphous ITO film as shown in FIG. No peaks were observed at diffraction angles of 30 ° and 35 °, and broad peaks were observed at a diffraction angle of 32 °.

(Experimental example 2)
A sample was prepared in the same manner as in Experimental Example 1 except that the transparent oxide conductive film (ITO film) was heated in four patterns of 100 ° C., 150 ° C., 200 ° C., and 250 ° C. The galvanic corrosion rate was obtained. FIG. 6 shows the results when heating the oxide transparent conductive film (ITO film) at 150 ° C., 200 ° C., and 250 ° C. FIG. 6 is a graph showing the galvanic corrosion rate of a pure Al film or an Al-2Ni-0.35La alloy film according to heating temperature. From FIG. 6, the galvanic corrosion rate is remarkable regardless of the heating temperature in the case of the pure Al film, whereas in the case of the Al-2Ni-0.35La film, the galvanic corrosion rate is 2.0 when the heating temperature is 150 ° C. When the heating temperature is 200 ° C. and 250 ° C., it can be seen that both are 0.0%. When the heating temperature was 100 ° C., the galvanic corrosion rate exceeded 60% in the pure Al film, and the galvanic corrosion rate increased to about 5% even in the case of the Al-2Ni-0.35La film. .

(Experimental example 3)
As an oxide transparent conductive film, a sample was prepared in the same manner as in Experimental Example 1 except that an indium zinc oxide (IZO) film containing about 10% by mass of zinc oxide in indium oxide was formed instead of the ITO film. The galvanic corrosion rate was determined in the same manner as in Experimental Example 1. The result is shown in FIG.

  FIG. 7 is a graph showing the galvanic corrosion rate of a pure Al film or an Al-2Ni-0.35La alloy film according to the presence or absence of heating. From FIG. 7, when an IZO film is used as the transparent oxide conductive film instead of the ITO film, the reduction rate of the corrosion rate of the Al-2Ni-0.35La film due to heating of the transparent oxide conductive film (IZO film) is reduced. It can be seen that it is smaller than the case of the ITO film of FIG. From this, it can be seen that the use of the ITO film as the oxide transparent conductive film serving as the substrate when forming the Al alloy film exhibits the effect of the present invention more sufficiently.

  In addition, when the IZO film is formed, the corrosion rate decreases from 4.0% to 2.7% by heating, but this is because the surface of the IZO film is heated. This is probably because the electrode potential difference from the reflective electrode (Al alloy film) has decreased as a result of changes in the surface state of the IZO film, such as the unevenness being reduced or being oxidized.

FIG. 1 is a diagram schematically showing a cross section of a typical transflective liquid crystal display device. 2A is a schematic cross-sectional view showing the state of each Al alloy film when the oxide transparent conductive film is amorphous, and FIG. 2B is a state where each of the oxide transparent conductive films is crystalline. It is. FIG. 3 is a graph showing the galvanic corrosion rate by immersion in TMAH for each pure Al film or Al-2Ni-0.35La film with or without heating of the ITO film. 4A and 4B are optical micrographs of the sample after being immersed in the TMAH aqueous solution. FIG. 4A shows the case where the ITO film is heated, and FIG. 4B shows the case where the ITO film is not heated. FIG. 5A shows a transmission electron micrograph of the cross section of the amorphous ITO film, and FIG. 5B shows the cross section of the crystalline ITO film. FIG. 6 is a graph showing the galvanic corrosion rate by immersion in TMAH according to the heating temperature of the ITO film for a pure Al film or an Al-2Ni-0.35La film. FIG. 7 is a graph showing the galvanic corrosion rate by immersion in TMAH according to whether the IZO film is heated for a pure Al film or an Al-2Ni-0.35La film.

Explanation of symbols

11 transflective liquid crystal display device 13 common electrode 15 counter substrate 19 pixel electrode 19a transparent pixel electrode (oxide transparent conductive film)
19b Reflective electrode 21 TFT substrate 23 Liquid crystal layer 41 Backlight 51 Barrier metal layer P Pixel region A Transmission region B Ambient light (natural light or artificial light)
C Reflection area F Light from backlight

Claims (3)

A manufacturing method of a display device having a structure in which an Al alloy film for a reflective electrode is directly connected on an oxide transparent conductive film,
A first step of forming the oxide transparent conductive film on a substrate;
A second step of heating the oxide transparent conductive film to 150 ° C. or more for 5 minutes or more to form a crystalline state;
A third step of forming the Al alloy film in the transparent conductive oxide film,
Furthermore, the fourth step includes a step of patterning the Al alloy film ,
The patterning is performed using an aqueous tetramethylammonium hydroxide solution, and the Al alloy film is made of an Al alloy containing 0.1 to 4 atomic% of Ni.   The Al alloy film further includes La, Mg, Cr, Mn, Ru, Rh, Pt, Pd, Ir, Ce, Pr, Gd, Tb, Dy, Nd, Ti, Zr, Nb, Mo, Hf, Ta, Claims comprising an Al alloy containing in total 0.1 to 2 atom% of at least one element selected from the group consisting of W, Y, Fe, Co, Sm, Eu, Ho, Er, Tm, Yb, and Lu. Item 2. The manufacturing method according to Item 1. A display device manufactured by the method according to claim 1 or 2 ,
A display device comprising a structure in which an Al alloy film for a reflective electrode is directly connected on an oxide transparent conductive film, and the oxide transparent conductive film is crystalline.