JP2003015145A - Electrode forming method and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode forming method by which production costs are reduced, and a liquid crystal display device to which the electrode forming method is applied. SOLUTION: After a transparent electrode film 10 and a reflecting electrode film 11 are formed, a resist film 12 is formed, the resist film 12 is removed so that a groove 12a and a thin part 12b can be formed on the resist film 12, and the reflecting electrode film 11 and the transparent electrode film 10 are etched with the resist film 12 on which the groove 12a and the thin part 12b are formed, as a mask. Afterwards, the thin part 12b is removed by ashing the resist film 12, and a reflecting electrode 110 is etched by the resist film 12 from which the thin part 12b is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode forming method and a liquid crystal display device for forming a transparent electrode and a reflective electrode in a predetermined region on a substrate.

[0002]

2. Description of the Related Art In recent years, so-called transflective liquid crystal display devices having both transmissive and reflective functions have become widespread. In this semi-transmissive liquid crystal display device, a transparent electrode and a reflective electrode are formed in each pixel so that both the transmissive and reflective functions can be exhibited.

[0003]

The manufacturing process of a semi-transmissive liquid crystal display device requires a lithography process for forming a transparent electrode and a lithography process for forming a reflective electrode. There is a problem that the number increases and the manufacturing cost increases.

In view of the above circumstances, it is an object of the present invention to provide an electrode forming method in which the manufacturing cost is reduced, and a liquid crystal display device to which the electrode forming method is applied.

[0005]

The electrode forming method of the present invention for achieving the above object is an electrode forming method for forming a transparent electrode and a reflective electrode in a predetermined region on a substrate, wherein the transparent electrode is formed on the substrate. A first step of forming a first film for electrodes,
A second step of forming a second film for the reflective electrode on the first film, a third step of forming a third film on the second film, and the third film Of the third film such that the portion corresponding to the predetermined region has a relatively thin portion and a thick portion, and the portion of the third film corresponding to the periphery of the predetermined region is removed. A fourth step of processing the film, a fifth step of etching the first film and the second film using the processed third film as a mask, and the third step.
And a seventh step of removing the thin film portion of the film, and a seventh step of etching the second film using the third film from which the thin film portion has been removed as a mask. It is characterized by

In the electrode forming method of the present invention, in the fourth step, the portion of the third film corresponding to the periphery of the predetermined region is removed, and the film thickness is relatively increased in the portion corresponding to the predetermined region. The third film is processed so that a thin portion and a thick portion are formed. In the fifth step, the first film for the transparent electrode and the second film for the reflective electrode are etched using the thus processed third film as a mask, so that the first film for the transparent electrode is etched. And the second film for the reflective electrode can be left only in the predetermined region. In the sixth step, the thin portion of the third film is removed. Therefore, in the seventh step, it is possible to etch the second film for the reflective electrode by using the third film from which the thin portion is removed as a mask. As described above, in the electrode forming method of the present invention, after etching both the first film for the transparent electrode and the second film for the reflective electrode in the fifth step,
In the sixth step, the thin film portion of the third film is removed, and in the seventh step, the second film is etched using the third film from which the thin film portion is removed as a mask. . That is, by removing the thin portion of the third film in the sixth step, the first film for the transparent electrode and the second film for the reflective electrode can be patterned into different shapes. . Therefore, even if a mask for etching only the first film for the transparent electrode and a mask for etching only the second film for the reflective electrode are not separately formed, the first mask for the transparent electrode is not formed. The film and the second film for the reflective electrode can be patterned into different shapes, and the number of manufacturing steps and the manufacturing cost can be reduced.

Here, in the electrode forming method of the present invention, the third film is a photosensitive film, and in the fourth step, different exposure energies are applied depending on the portion of the photosensitive film. Preferably, the method further comprises an exposing step of exposing the photosensitive film and a developing step of developing the exposed photosensitive film.

By performing the above steps, the portion of the photosensitive film corresponding to the predetermined region has a relatively thin portion and a thick portion, and the predetermined region of the photosensitive film. It is possible to remove the portion corresponding to the periphery of.

Further, the electrode forming method of the present invention preferably comprises an eighth step of forming a fourth film having concave portions or convex portions on the substrate before the execution of the first step. .

By forming the fourth film having the concave portion or the convex portion before the first step is performed, the concave portion or the convex portion can be formed in the reflective electrode.

Further, the liquid crystal display device of the present invention comprises:
It has a reflective electrode and a transparent electrode formed by using the electrode forming method described in any one of 1 to 3.

Here, the liquid crystal display device of the present invention is characterized in that the reflective electrode is formed directly on the transparent electrode.

Further, in the liquid crystal display device of the present invention, the transparent electrode or the reflective electrode may have a laminated structure.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a partial cross-sectional view of a transflective liquid crystal display device having a transparent electrode and a reflective electrode formed by using an embodiment of the electrode forming method of the present invention.

This liquid crystal display device has a TFT substrate 51 on which a TFT 50, a transparent electrode 100, a reflective electrode 110 and the like are formed, and a color filter substrate 52 on which a color filter and the like are formed. The structure of the color filter substrate 52 is irrelevant to the characteristic part of the present embodiment, and therefore is illustrated in a simplified manner in FIG. 1. A liquid crystal layer 53 exists between the TFT substrate 51 and the color filter substrate 52. A backlight 54 is provided on the back surface of the TFT substrate 51.
Is provided.

Hereinafter, the TFT substrate 5 on which the transparent electrode 100 and the reflective electrode 110, which are the characteristic parts of this embodiment, are formed.
The manufacturing method of No. 1 will be described.

FIG. 2 is a plan view showing a state immediately after the TFT 50 is formed on the glass substrate 1 of the TFT substrate 51 shown in FIG. 1, and FIG. 3 is a sectional view seen from the direction I--I of FIG. is there.

First, as shown in FIG. 3, a gate electrode 2 and a gate insulating film 3 are formed on a glass substrate 1. Then, a semiconductor layer 4 such as a-Si: H, an ohmic contact layer 5 such as n + a-Si: H, a source electrode 6 and a drain electrode 7 are formed on the gate insulating film 3 to form each pixel. The TFT 50 is formed in the area.
As shown in FIG. 2, the gate electrodes 2 of the TFTs 50 arranged in the row direction are electrically connected to each other by the gate bus 20, and the source electrodes 6 of the TFTs 50 arranged in the column direction are electrically connected to each other by the source bus 60. ing. TFT
After forming 50, an insulating film and a flattening film are formed on the glass substrate 1 (see FIG. 4).

FIG. 4 is a sectional view of a glass substrate on which an insulating film and a flattening film are formed.

As shown in FIG. 4, an insulating film 8 is formed on the glass substrate 1 so as to cover the TFT 50. Then, a photosensitive material is applied to the entire surface of the insulating film 8 to form a flattening film 9. After the flattening film 9 is formed, the flattening film 9 is exposed and developed (see FIG. 5).

FIG. 5 is a sectional view showing a state after the flattening film 9 is exposed and developed.

By exposing and developing the flattening film 9,
In this flattening film 9, a large number of recesses 9a and the flattening film 9 are formed.
And a through hole 9b penetrating therethrough is formed. The through hole 9b is formed right above the drain electrode 7 of each TFT 50. In order to form the recesses 9a and the through holes 9b as shown in FIG. 5, the amount of exposure energy absorbed in the portion of the flattening film 9 where the recesses 9a are formed when the flattening film 9 is exposed. , The amount of exposure energy absorbed at the portion where the through hole 9b is formed may be different. Thus, when the exposed flattening film 9 is developed, the depth of removal of the flattening film 9 can be adjusted according to the amount of the absorbed exposure energy, and the recess 9a and the through hole 9b can be formed. Can be formed. After forming the recess 9a and the through hole 9b in the flattening film 9, the insulating film 8 is etched using the flattening film 9 as a mask (see FIG. 6).

FIG. 6 is a sectional view showing a state where the insulating film 8 is etched.

Through holes 9b formed in the flattening film 9
Is formed right above the drain electrode 7, so that when the insulating film 8 is etched using the flattening film 9 as a mask, a through hole 8a exposing the drain electrode 7 is formed in the insulating film 8. After the insulating film 8 is etched, a transparent electrode and a reflective electrode are formed by the method shown in FIGS. Hereinafter, FIGS. 7 to 13 will be described.

FIG. 7 shows a transparent electrode film 10 and a reflective electrode film 11.
FIG. 3 is a cross-sectional view of a glass substrate on which a resist film 12 is formed.

After etching the insulating film 8 (see FIG. 6), the transparent electrode material and the reflective electrode material are sequentially deposited to form the transparent electrode film 10 and the reflective electrode film 11, as shown in FIG. . For example, ITO or the like can be used as the material of the transparent electrode film 10, and Al alloy, Ag alloy, or the like can be used as the material of the reflective electrode film 11. Since the flattening film 9 formed under the transparent electrode film 10 has a recess 9a (see FIG. 6),
The recesses 10a and 11a are formed in the transparent electrode film 10 and the reflective electrode film 11 following the shape of the recess 9a of the flattening film 9. After forming the transparent electrode film 10 and the reflective electrode film 11,
A resist is applied to the entire surface of the reflective electrode film 11 to form a resist film 12. After forming the resist film 12, a part of the resist film 12 is removed as follows.

FIG. 8 is a plan view showing a state after a part of the resist film 12 is removed, and FIG. 9 is a sectional view taken along the line II-II of FIG.

After the resist film 12 is formed (see FIG. 7), the resist film 12 is exposed and developed to form a groove 12a for separating the resist film 12 into pixel regions as shown in FIG. And a thin portion 12b having a thin film thickness
And are formed. Due to the groove 12a, the resist film 12
From the resist film separated for each pixel area (hereinafter,
A "separation resist film" 12c is formed. Figure 8
In the figure, the separation resist film 12c is indicated by diagonal lines, and the thin portion 12b formed in the separation resist film 12c is indicated by mesh hatching. The groove 12a is the gate bus 20.
Further, the reflective electrode film 11 is formed so as to be exposed along the source bus 60, and therefore the separation resist film 1 is formed.
The material of the resist film 12 is removed from the periphery of 2c. On the other hand, since the thin portion 12b is formed so as to have a small film thickness, each separation resist film 12c has a relatively thick film portion and a relatively thin film portion, as shown in FIG. There is. Therefore, the reflective electrode film 11 is exposed in the groove 12a, while the reflective electrode film 11 is not exposed in the thin portion 12b. Groove 12 as shown in FIG.
In order to form a and the thin portion 12b, the resist film 1
2 is exposed, the amount of exposure energy absorbed in the portion where the groove 12a of the resist film 12 is formed and the amount of exposure energy absorbed in the portion where the thin portion 12b is formed may be different. . Thereby, when the flattening film 9 after exposure is developed, the depth of the resist film 12 to be removed can be adjusted according to the amount of absorbed exposure energy, and the groove 12a and the thin portion 12b are formed. can do. After forming the groove 12a and the thin portion 12b in the resist film 12, the reflective electrode film 11 and the transparent electrode film 10 are etched by using the separation resist film 12c as a mask (FIG. 1).
0).

FIG. 10 is a sectional view showing a state where the reflective electrode film 11 and the transparent electrode film 10 are etched.

When an Al alloy or an Ag alloy is used as the material of the reflective electrode film 11, a mixed solution of phosphoric acid, nitric acid, acetic acid and water can be used as an etching solution. When ITO is used as the material of the transparent electrode film 10, a mixed solution of hydrochloric acid and water can be used as an etching solution. The reflective electrode film 1 using the separation resist film 12c as a mask
By etching 1 and the transparent electrode film 10, the reflective electrode film 11 and the transparent electrode film 10 are separated for each pixel region, and the transparent electrode 100 and the reflective electrode 110 are provided in each pixel region.
Is formed. Through the above steps, the transparent electrode 100 and the reflective electrode 110 are formed in each pixel area. However, in FIG. 10, the reflective electrode 110 is laminated on the transparent electrode 100 so as to cover the entire surface of the transparent electrode 100. Therefore, when the reflective electrode 110 covers the entire surface of the transparent electrode 100, the light of the backlight 54 (see FIG. 1) is blocked by the reflective electrode 110 when the liquid crystal display device is used in the transmissive mode. Therefore, the light of the backlight 54 cannot enter the liquid crystal layer 53. Therefore, in the manner shown in FIGS. 11 and 13 below,
A passage window for allowing the light of the backlight 54 to pass through is formed in the reflective electrode 110.

First, the reflective electrode film 11 and the transparent electrode film 10
After etching (see FIG. 10), the isolation resist film 12c is ashed as shown in FIG.

FIG. 11 is a sectional view showing a state where the separation resist film 12c is ashed.

As the separation resist film 12c is ashed, the film thickness of the separation resist film 12c becomes thinner as a whole, but the thin portion 12b is formed in the separation resist film 12c (see FIG. 10). ), As shown in FIG. 11, the region A corresponding to the thin portion 12b of the reflective electrode 110 is exposed first. When the area A is exposed, the ashing is finished. After the ashing is completed, the reflective electrode 110 is etched using the ashed separation resist film 12c as a mask (see FIGS. 12 and 13).

FIG. 12 is a plan view showing a state after the reflective electrode 110 is etched, and FIG. 13 is a III-I line of FIG.
It is the sectional view seen from the II direction.

By etching the reflection electrode 110, the area A (see FIG. 11) of the reflection electrode 110 is removed, and a passage window 110a for passing the light of the backlight 54 is formed in the reflection electrode 110. . As a result, the transparent electrode 100 is exposed. By exposing the transparent electrode 100 in this manner, when the liquid crystal display device is used in the transmissive mode, it is possible to secure a region in which the light of the backlight 54 is incident on the liquid crystal layer 53.

After etching the reflective electrode, the separation resist film 12c is peeled off. Then, the alignment film 13 (see FIG. 1) is printed and a rubbing process is performed. In this way, T
The FT substrate 51 is formed.

In this embodiment, a resist film 12 is formed on the transparent electrode film 10 and the reflective electrode film 11, and the resist film 12 is exposed and developed to form the resist film 12 into the shape shown in FIG. It is being processed. Reflective electrode film 11
Since the transparent electrode film 10 and the transparent electrode film 10 are etched by using the separation resist film 12c having the shape shown in FIG. 9 as a mask, the transparent electrode film 10 is separated for each pixel region, and as shown in FIG. 100 is formed. After that, the separation resist film 12c is ashed and processed into the shape shown in FIG. 11, and the reflective electrode 110 is etched by using the separation resist film 12c having the shape shown in FIG. And FIG. 13) are formed. As described above, in the present embodiment, by changing the shape of the resist film 12 in two steps shown in FIGS. 9 and 11, both the reflective electrode film 11 and the transparent electrode film 10 are patterned into desired shapes. is doing. Therefore, in order to pattern the reflective electrode film 11 and the transparent electrode film 10 into desired shapes, the resist film for patterning only the reflective electrode film 11 and the transparent electrode film 1
It is not necessary to separately form a resist film for patterning only 0, and the number of manufacturing steps and the manufacturing cost can be reduced.

Further, in this embodiment, since a large number of recesses 9a are formed in the flattening film 9 formed under the reflective electrode 110, the reflective electrode 110 also has a large number of recesses 11a.
Is formed. By providing the reflective electrode 110 with the concave portion 11a, the reflective electrode 110 can have a desired light reflection characteristic. In the present embodiment, the reflective electrode 11
In order to give 0 a desired light reflection characteristic, the reflection electrode 11
Although the concave portion 11a is formed at 0, the reflecting electrode 110 can have a desired light reflection characteristic even if the reflecting electrode 110 has a convex portion instead of the concave portion 11a.
In order to provide the reflective electrode 110 with a convex portion, the flattening film 9
It suffices to change the exposure pattern when exposing the. By changing the exposure pattern of the flattening film 9, the flattening film 9 can have convex portions instead of concave portions, so that the reflective electrode 110 can also have convex portions. Although it is not always necessary to form the concave portion or the convex portion on the reflective electrode 110, it is necessary to form the concave portion or the convex portion on the reflective electrode 110 in order to give the reflective electrode 110 a desired light reflection characteristic. preferable.

Further, although the insulating film 8 is formed under the flattening film 9 in this embodiment, the insulating film 8 may be omitted. Further, in this embodiment, the concave portion 11 is formed in the reflective electrode 110.
In order to form a, the flattening film 9 having a large number of recesses 9a is formed. However, by forming the recesses in the insulating film 8, for example, the flattening film 9 is not formed in the reflective electrode 110. Can be formed.

In the present embodiment, both the transparent electrode 100 and the reflective electrode 110 have a single layer structure, but each of the transparent electrode 100 and the reflective electrode 110 may have a laminated structure composed of two or more layers. Good. For example, the reflective electrode 1
In order to form 10 into a laminated structure, another reflective electrode film may be formed in addition to the reflective electrode film 11 before forming the resist film 12. By forming a plurality of reflective electrode films in this way and etching the plurality of reflective electrode films using the separation resist film 12c as a mask, the reflective electrode 110 can have a laminated structure. Similarly, the transparent electrode 100 may have a laminated structure. Therefore, for example, in order to make both the transparent electrode and the reflective electrode have a two-layer structure, it is sufficient to form two transparent electrode films and two reflective electrode films. in this case,
The transparent electrode film and the reflective electrode film are combined to form a four-layer film. By deforming the resist film 12, the four-layer film can be patterned into a desired shape.

Finally, the electrode forming method of this embodiment will be briefly described in comparison with the conventional electrode forming method.

FIG. 14 is a sectional view of a substrate on which a transparent electrode and a reflective electrode are formed by using an example of a conventional electrode forming method.

Conventionally, after forming the transparent electrode 30, for example, the insulating film 31, the first planarizing film 32 and the second planarizing film 33 are formed, and then the reflective electrode 34 is formed. . Therefore, in order to form the transparent electrode 30 and the reflective electrode 34, a resist film for patterning only the transparent electrode film and a resist film for patterning only the reflective electrode film are required. On the other hand, in the electrode forming method of the present embodiment, as described above, the shape of the resist film 12 is deformed in two steps to pattern both the transparent electrode film 10 and the reflective electrode film 11. You can Therefore, it can be seen that the number of manufacturing steps and the manufacturing cost can be reduced as compared with the conventional method.

[0045]

As described above, according to the present invention,
Provided are an electrode forming method which can reduce manufacturing cost, and a liquid crystal display device to which the electrode forming method is applied.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a semi-transmissive liquid crystal display device having a transparent electrode and a reflective electrode formed by using an embodiment of an electrode forming method of the present invention.

FIG. 2 is a plan view showing a state immediately after a TFT 50 is formed on the glass substrate 1 of the TFT substrate 51 shown in FIG.

3 is a cross-sectional view as seen from the direction I-I in FIG.

FIG. 4 is a cross-sectional view of a glass substrate on which an insulating film and a flattening film are formed.

FIG. 5 is a cross-sectional view showing a state after the flattening film 9 is exposed and developed.

FIG. 6 is a cross-sectional view showing a state where the insulating film 8 is etched.

FIG. 7 is a cross-sectional view of a glass substrate on which a transparent electrode film 10, a reflective electrode film 11 and a resist film 12 are formed.

FIG. 8 is a plan view showing a state after a part of the resist film 12 is removed.

9 is a cross-sectional view seen from the direction II-II in FIG.

FIG. 10 is a cross-sectional view showing how the reflective electrode film 11 and the transparent electrode film 10 are etched.

FIG. 11 is a cross-sectional view showing how the resist film 12 is ashed.

FIG. 12 is a plan view showing a state after the reflective electrode 110 is etched.

13 is a cross-sectional view seen from the direction III-III in FIG.

FIG. 14 is a cross-sectional view of a substrate on which a transparent electrode and a reflective electrode are formed by using an example of a conventional electrode forming method.

[Explanation of symbols]

1 glass substrate 2 Gate electrode 3 Gate insulation film 4 semiconductor layers 5 Ohmic contact layer 6 Source electrode 7 Drain electrode 8 insulating film 8a through hole 9 Flattening film 9a, 10a, 11a Recess 9b through hole 10 Transparent electrode film 11 Reflective electrode film 12 Resist film 12a groove 12b Thin part 13 Alignment film 50 TFT 51 TFT substrate 52 Color filter substrate 53 Liquid crystal layer 54 Backlight 100 transparent electrode 110 reflective electrode 110a passage window

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sadazo Yukawa             4-3-1 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo             Philips mobile display system             Within Kobe Co., Ltd. (72) Inventor Tomihisa Sunada             4-3-1 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo             Philips mobile display system             Within Kobe Co., Ltd. F-term (reference) 2H092 GA13 GA17 GA19 JA26 JB07                       JB08 JB58 MA15 MA16 MA18                       MA19 NA27 PA12                 5C094 AA22 AA43 AA44 BA03 BA43                       CA19 CA24 DA13 EA04 EA05                       EA06 EB02 ED03 ED11 ED13                       FA01 FB01 FB02 FB12 FB15                       GB10

Claims (6)

[Claims] 1. An electrode forming method for forming a transparent electrode and a reflective electrode in a predetermined region on a substrate, wherein a first film for the transparent electrode is formed on the substrate.
A second step of forming a second film for the reflective electrode on the first film, a third step of forming a third film on the second film, and The portion of the third film corresponding to the predetermined region has a relatively thin portion and a thick portion, and the portion of the third film corresponding to the periphery of the predetermined region is removed. A fourth step of processing the third film, a fifth step of etching the first film and the second film by using the processed third film as a mask, and the third step of A sixth step of removing a thin film portion of the film; and a seventh step of etching the second film using the third film from which the thin film portion is removed as a mask And a method for forming an electrode. 2. The third film is a photosensitive film, and in the fourth step, the photosensitive film is exposed so that different exposure energy is applied depending on a site of the photosensitive film. The electrode formation according to claim 1, further comprising an exposure step and a development step of developing the exposed photosensitive film, wherein the sixth step ashes the developed photosensitive film. Method. 3. The method according to claim 1, further comprising an eighth step of forming a fourth film having concave portions or convex portions on the substrate before the execution of the first step. The described electrode forming method. 4. A liquid crystal display device comprising a reflective electrode and a transparent electrode formed by using the electrode forming method according to claim 1. 5. The liquid crystal display device according to claim 5, wherein the reflective electrode is directly formed on the transparent electrode. 6. The liquid crystal display device according to claim 4, wherein the transparent electrode or the reflective electrode has a laminated structure.