JP2002090726A - Liquid crystal display device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which a reflective electrode having ruggedness, can be formed so as to have a substantially high aperture ratio while suppressing the generation of cross talk and to provide a manufacturing method by which a photograph process to form the ruggedness and a contact hole can be simplified and production efficiency is improved. SOLUTION: An active element array substrate 1 provided with active elements for drive 2a, 6a and 7 has a first film 8 formed by coating the channel parts of active elements, a passive layer 20 formed on the first film, and a pixel electrode 11 formed on the upper part of the passive layer. A contact hole 21 and the ruggedness 22 are formed into a laminated film consisting of the passive layer and the first film. The pixel electrode is formed on the ruggedness and electrically connected with the electrodes of active elements through the contact hole. The ruggedness has such a shape that it has a smooth protruded structure and a recessed structure in which the diameter narrower than that of the contact hole and the bottom part is not flat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device used for a display section of an image display application device such as an information processing terminal or a video device, and a method of manufacturing the same. More specifically, the present invention relates to a reflection type liquid crystal display device that performs display by reflecting incident light, or a transflective type liquid crystal display device that uses both incident light and transmitted light, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, with the personalization of information, information terminal equipment which emphasizes portability has been rapidly developed as seen in higher performance of mobile phones. For long-time operation and battery thinning and weight reduction which are the key points of these portability,
Attention has been focused on a reflection type liquid crystal display device which can display without a backlight by reflecting incident light from a use environment. As a reflection type liquid crystal display device and a method of manufacturing the same, one described in Japanese Patent No. 2756206 is known.

FIG. 4 is a plan view showing a conventional reflection type liquid crystal display device. FIG. 5 is a cross-sectional view showing the AA cross section in FIG. 4 for each process for explaining the method of manufacturing the liquid crystal display device of FIG.

In FIG. 4, on a substrate (not shown),
A gate electrode 2a, a channel layer 4, a source electrode 6a, and a drain electrode 7 constituting a thin film transistor (hereinafter, abbreviated as TFT) are formed.
Reference numeral 2 denotes a gate wiring integrated with the gate electrode 2a, and reference numeral 6 denotes a source wiring integrated with the source electrode 6a. 8a is a first uneven portion, 10a is a second contact hole, and 11 is a pixel electrode.

[0005] As shown in FIG. 5 (a), first, C
A plurality of gate wirings 2 (see FIG. 4) having branched gate electrodes 2a made of r, Ta or the like are formed. Next, after a gate insulating film 3 made of silicon nitride (hereinafter abbreviated as SiNx) is formed on the entire surface, a channel layer made of amorphous silicon (hereinafter abbreviated as a-Si) is formed on the gate insulating film 3 on the gate electrode 2a. 4 is formed. Next, on both ends of the channel layer 4, a contact layer 5 made of low-resistance a-Si and a source electrode 6a and a drain electrode 7 made of Ti, Al or the like are formed so as to overlap. Here, the source electrode 6a is formed so as to be branched from the source wiring 6. Next, a first film 8 made of SiNx is formed on the entire surface as a protective film of the channel layer 4 to obtain a TFT array.

After forming the TFT as described above, a resist 9 is patterned on the first film 8 as shown in FIG. Next, as shown in FIG. 5C, the first film 8 is processed using the resist 9 as a mask, and a number of fine first uneven portions 8a are formed on the reflection electrode forming portion, and the first After forming one contact hole 8b, the resist 9 is removed. Next, as shown in FIG. 5D, an acrylic resin is applied to the entire surface to form a second contact hole 10a having a second contact hole 10a.
Is formed. Next, as shown in FIG.
a pixel electrode 11 made of a metal having a high light reflectance such as l, Ag, etc.
Is formed on the second film 10 having projections and depressions and the drain electrode 7 through the second contact hole 10a, whereby an active element array substrate is obtained. Further, although not shown, a color filter and a substrate having a transparent electrode are attached to face the active element array substrate, and a liquid crystal is sealed therebetween to complete a liquid crystal display device.

As described above, the first film 10 is formed by using the second film 10.
By forming irregularities having a curved surface state on the first uneven portion 8a having many planar states composed of the film 8 of the above, and forming the pixel electrode 11 thereon, the regular reflection component (reflection by a plane) by the pixel electrode 11 is formed. (Indicating a mirror surface state). Therefore, a pixel electrode that is close to a scattering surface state rather than a mirror surface state is obtained, and the reflection of peripheral light is suppressed, and the reflection efficiency is improved by condensing the reflected light by controlling the unevenness of the curved surface state. A high liquid crystal display device can be obtained.

[0008]

In the conventional liquid crystal display device and the method of manufacturing the same, the reflection characteristic with respect to incident light is roughly determined by the shape of the first uneven portion 8a made of SiNx as a protective film. The second film 10 is formed by coating for the purpose of reducing the regular reflection component. Therefore, the second film 10 needs to be formed thin enough to make the flat portion of the first uneven portion 8a a curved surface, for example, about 0.5 μm. If the thickness of the second film 10 is larger than 0.5 μm, for example, 1 μm or more, the first uneven portion 8a is buried, and the entire surface becomes a flat mirror surface state. Therefore, when the aperture ratio is increased to obtain the brightness of the liquid crystal display device, that is, when the pixel electrode 11 is increased, the pixel electrode 11 is closer to the source wiring 6 and the gate wiring 2 and the parasitic capacitance therebetween is increased. There is concern that crosstalk will occur.

One of the features of the reflection type liquid crystal display device is that the pixel electrode 11 is formed on the uppermost layer of the active element array substrate. There is no need to do this. Although it is a reflection type that is originally suitable for high aperture ratio,
In the above-described conventional liquid crystal display device and the method of manufacturing the same, it is necessary to sacrifice the aperture ratio due to concern about the occurrence of crosstalk. Here, it is conceivable to increase the thickness of SiNx, which is the first film 8, but in that case, the time for forming the SiNx and the time for forming and processing the first uneven portion 8a and the first contact hole 8b become longer. There is a concern that productivity problems may occur, such as breakage of the substrate due to warpage of the substrate due to an increase in stress due to thickening. Furthermore, since the unevenness is formed by two steps of forming the first uneven portion 8a and applying and forming the second film 10, the production efficiency is reduced.

The present invention has been made in view of the above problems, and it is possible to form a reflective electrode having irregularities so as to obtain an original high aperture ratio while suppressing occurrence of crosstalk, and to improve production efficiency. It is an object of the present invention to obtain a liquid crystal display device and a method for manufacturing the same, which can perform the following.

[0011]

According to the present invention, there is provided a liquid crystal display device which displays an image by driving a liquid crystal sandwiched between two substrates constituting a liquid crystal display panel through a plurality of pixel electrodes. In the display device, an active element array substrate provided with a driving active element, which is one of the two substrates, has the following configuration. That is, in order to solve the above problem, the active element array substrate includes a first film formed by covering a channel portion of the active element, an insulating film formed on the first film, and an insulating film. A contact electrode and an unevenness are formed in a laminated film composed of an insulating film and a first film, and the pixel electrode is formed on the unevenness and activated through the contact hole. The concavo-convex structure is electrically connected to the electrodes of the element, and the concavo-convex shape has a smooth convex structure and a concave structure having a smaller bottom than the diameter of the contact hole and an uneven bottom.

According to this structure, the unevenness for reducing the regular reflection component by the pixel electrode can be formed by using the thick interlayer insulating film, so that the original high aperture ratio can be reduced while suppressing the occurrence of crosstalk. It is possible to get. In addition, since this configuration can be obtained by simultaneously forming the contact hole and the unevenness in the insulating film and the first film,
The conventional process of forming an insulating film after forming a contact hole and unevenness in the first film is simplified, and the production efficiency can be improved.

[0013] Similar effects can be obtained by modifying the above structure and forming a structure in which a contact hole is formed in a laminated film composed of an insulating film and a first film and irregularities are formed in the insulating film.

According to a method of manufacturing a liquid crystal display device of the present invention, a liquid crystal device sandwiched between two substrates constituting a liquid crystal display panel is driven through a plurality of pixel electrodes to display an image. In the manufacturing method, an active element array substrate provided with a driving active element, which is one of the two substrates, is manufactured by the following steps. That is, a step of forming active elements in an array on a substrate, a step of forming a first film for protecting the channels of the active elements over the entire surface, and a step of applying an insulating film on the first film and comparing the resolution with the resolution. Using a photomask having a sufficiently large hole-shaped contact hole pattern and a concavo-convex formation pattern with the diameter of the concave portion as the resolution limit, developing after exposure, forming a contact hole portion and a concavo-convex portion in the insulating film; Hardening while smoothing the square shape of the insulating film, and the first step using the insulating film as a mask.
By dry-etching the film, at least the drain electrode of the active element immediately below the contact hole is exposed to form a contact hole, and a portion of the protrusion of the uneven portion is removed, and the smooth protrusion and the bottom are flattened. Forming a pixel electrode that is electrically connected to the drain electrode through a contact hole and covers the unevenness.

According to the manufacturing method having this configuration, a reflective or transflective active element array substrate having a high aperture ratio can be obtained while improving production efficiency.

In the liquid crystal display device of any one of the above structures or the method of manufacturing a liquid crystal display device, a thick interlayer insulating film can be easily formed by using an organic film as the insulating film.

Further, the number of steps can be reduced by using, as the first film, a silicon nitride film processed and formed using an insulating film as a mask.

Further, by forming the pixel electrode of a reflective or semi-transmissive type which is a high light reflective metal, the thickness of the high light reflective metal can be controlled to obtain a bright reflective or semi-transmissive liquid crystal display device. Can be.

Further, by forming the pixel electrode of a semi-transmissive type composed of a high-reflection metal part and a transparent electrode part, the brightness as a reflective type when the use environment is bright and the transmission when the use environment is dark are reduced. It can also have the brightness as a mold.

Further, in the above structure, the high light reflecting metal or the high light reflecting metal portion is made of Al, Al alloy, Ag and A.
By using a metal selected from g alloy,
By controlling the film thickness, a bright reflective or transflective liquid crystal display device can be obtained.

Further, by forming the transparent electrode portion using indium tin oxide, a transflective liquid crystal display device which is bright in transmissive display can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a sectional structure of a pixel portion on an active element array substrate of a liquid crystal display device, and FIG. 2 is a plan view of the pixel portion similarly. FIG. 1 is a cross section taken along line BB of FIG. FIG. 3 shows each step of the manufacturing method,
Are shown in cross section.

In FIGS. 1, 2 and 3, the same elements as those of the conventional example shown in FIGS.
The same reference numerals are given and the description is omitted. The present embodiment is different from the conventional example in that the insulating film 20 and the contact hole 2
1 and irregularities 22.

First, as shown in FIG. 3A, a Ti / Al / Ti layer is formed on a glass substrate 1 by sputtering using Ar gas at a thickness of 100/200/100 nm, and then branched. A plurality of gate wires 2 (see FIG. 2) having the gate electrodes 2a thus formed are formed. Next, SiNx and a-S are formed by plasma enhanced chemical vapor deposition (hereinafter abbreviated as p-CVD).
i, after forming three layers of low-resistance a-Si, a-Si and low-resistance a-Si other than the TFT region are removed by etching to form island-like channel layers 4 and contact layers 5 and a gate insulating film over the entire surface. Form 3 Next, a Ti / Al / Ti layer is again stacked by 100/200/100 nm by a sputtering method using Ar gas to form a film.
(Refer to FIG. 2), and processed into a pattern of a source electrode 6a and a drain electrode 7 of a TFT branched therefrom. At this time, the contact layer 5 is formed separately in the source and drain regions. Next, a first film 8 made of SiNx is formed on the entire surface as a protective film of the channel layer 4 by a p-CVD method, and a TFT array is obtained.

As described above, after forming a TFT array in the same manner as in the conventional example, a photosensitive acrylic resin (JS
R Company PC305) is applied about 3 μm. Next, an elliptical contact hole pattern whose short side is about 8 μm, which is sufficiently larger than the resolution,
Using a photomask having a concavo-convex pattern having a size of μm, development is performed after exposure by an exposure machine (MA3000 manufactured by CANON). As a result, as shown in FIG. 3B, the contact hole portion 20a where the underlying first film 8 is sufficiently exposed is formed.
Then, an insulating film 20 having an uneven portion 20b in which the underlying first film 8 is exposed with a diameter of about 1 μ or less is formed.

Next, as shown in FIG. 3C, a heat treatment at 220 ° C. is performed to harden the insulating film 20 while softening the square shape by softening with a rise in temperature. Further, at least the drain electrode 7 immediately below the contact hole portion 20a is exposed by dry etching using chlorine-based gas plasma to form a contact hole 21 and to form the uneven portion 2
By removing a part of the convex portion of Ob, unevenness 22 having a smoother convex portion and a concave portion whose bottom is not flat is formed. Next, as shown in FIG. 3D, an Al film is formed on the entire surface, and then the pixel electrode 11 is processed and formed. That is, it has a shape that covers the irregularities 22, is electrically connected to the drain electrode 7 through the contact hole 21, and extends to partially overlap the gate wiring 2 and the source wiring 6 (see FIG. 2). Thus, an active element array substrate is obtained. Further, similarly to the conventional example, a substrate having a color filter and a transparent electrode is attached to face the active element array substrate, and a liquid crystal is sealed therebetween to complete a liquid crystal display device.

According to the above embodiment, the thick insulating film 2
With 0, the pixel electrode 11 can be formed in the vicinity of the source wiring 6 and the gate wiring 2 with reduced concern about occurrence of crosstalk. The unevenness 22 and the contact hole 21
Can be reduced to one photo step. Further, by forming the pixel electrode 11 on the unevenness 22 having a smooth convex portion and a concave portion whose bottom is not flat, the reflection of the peripheral light is reduced with a small specular reflection component, and the convex portion having a curved surface state is formed. By controlling, the reflection efficiency can be increased, that is, brightened.

The unevenness 2 having a concave portion whose bottom is not flat
2 is a method of dry-etching the first film 8 using the insulating film 20 having the irregularities 20b in which the underlying first film 8 is exposed with a diameter of about 1 μ or less as a mask, as in the above method. Instead, the following method can be used. That is, the formation of the concave portion in the concave and convex portion 20b of the insulating film 20 is performed by exposure and development using a photomask having a concave and convex forming pattern in which the diameter of the concave portion is equal to or less than the resolution limit, for example, about 3 μm. Thereby, the underlying first film 8
Is formed without forming a concave / convex portion 20b which does not expose the drain electrode 7, and even after the dry etching for exposing the drain electrode 7, the concave / convex portion 22 having a concave portion whose bottom is not flat, that is, a smooth concave portion is formed without exposing the underlying first film 8. I do.

The material of the pixel electrode 11 is not limited to Al, but may be any material as long as it is electrically connected to the drain electrode 7 and has a high reflectance. For example, Al alloy, AlTi, A
lTa, AlW, AlNd, AlZr, etc., or Ag or Ag alloy AgCu, AgPdCu, AgTi
A material made of Cu or the like may be used.

Further, although the active elements are made of TFTs, they may be non-linear two-terminal elements such as MIM.

[0032]

According to the present invention, the fear of occurrence of crosstalk is reduced by a thick insulating film, and a pixel electrode is formed in the vicinity of a source wiring and a gate wiring. A transmissive liquid crystal display device is obtained. In addition, by reducing the number of photo steps for forming irregularities and contact holes to one,
A significant increase in productivity results.

Further, by forming a pixel electrode on unevenness having a smooth convex portion and a concave portion whose bottom is not flat,
By suppressing the reflection of the ambient light with a small amount of the regular reflection component and controlling the convex portion having the curved surface state, it is possible to obtain a liquid crystal display device of high reflection efficiency, that is, a bright reflective or transflective liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a liquid crystal display device according to one embodiment of the present invention.

FIGS. 3A to 3C are cross-sectional views illustrating a method for manufacturing a liquid crystal display device according to an embodiment of the present invention in cross sections in respective steps.

FIG. 4 is a plan view showing a conventional liquid crystal display device.

FIG. 5 is a sectional view showing each step in a conventional method for manufacturing a liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate wiring 2a Gate electrode 3 Gate insulating film 4 Channel layer 5 Contact layer 6 Source wiring 6a Source electrode 7 Drain electrode 8 First film 8a First uneven part 8b First contact hole 9 Resist 10 Second Film 10a Second contact hole 11 Pixel electrode 20a Contact hole 20b Uneven part 21 Contact hole 22 Uneven

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/30 349 G02F 1/136 500 (72) Inventor Junji Boshita 1006 Odakazuma Kadoma, Kadoma City, Osaka Matsushita Inside Electric Industrial Co., Ltd. (72) Inventor Yoshinari Sakurai 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Gohisa Asano 1006 Okadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. 72) Inventor Masato Tanabe 1006 Kadoma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Mitsuhiro Uno 1006 Kadoma Kadoma, Kadoma-shi, Osaka Pref. FC10 FC26 FC29 FC30 FD04 FD23 GA13 2H092 HA05 JA26 JA29 JA38 JA42 JA44 JB13 JB23 JB32 JB33 JB38 JB57 KA05 KA07 KA16 KA18 KB14 K B24 MA05 MA08 MA14 MA15 MA16 MA18 MA19 MA20 MA27 MA35 MA37 MA41 NA25 NA27 PA04 PA12 QA06 5C094 AA09 AA10 AA43 BA03 BA43 CA18 CA24

Claims (16)

[Claims] 1. A liquid crystal display device which displays an image by driving a liquid crystal sandwiched between two substrates constituting a liquid crystal display panel through a plurality of pixel electrodes, wherein one of the two substrates is provided. An active element array substrate provided with the driving active elements, a first film formed by covering a channel portion of the active element, and an insulating film formed on the first film. A pixel electrode formed on the insulating film, a contact hole and unevenness are formed in a laminated film including the insulating film and the first film, and the pixel electrode is formed on the unevenness Electrically connected to the electrode of the active element through the contact hole, the unevenness has a smooth convex structure and a concave structure having a smaller diameter than the contact hole and a flat bottom. The liquid crystal display device which is a convex shape. 2. A liquid crystal display device which displays an image by driving a liquid crystal sandwiched between two substrates constituting a liquid crystal display panel through a plurality of pixel electrodes, wherein one of the two substrates is provided. An active element array substrate provided with the driving active elements, a first film formed by covering a channel portion of the active element, and an insulating film formed on the first film. A pixel electrode formed on the insulating film, a contact hole is formed in a laminated film including the insulating film and the first film, and irregularities are formed in the insulating film;
The pixel electrode is formed on the unevenness and is electrically connected to the electrode of the active element through the contact hole. The unevenness has a smooth convex structure and a concave portion having a smaller diameter than the diameter of the contact hole and an uneven bottom. A liquid crystal display device having an uneven shape having a structure. 3. The method according to claim 1, wherein the insulating film is an organic film.
The liquid crystal display device according to the above. 4. The liquid crystal display device according to claim 1, wherein the first film is a silicon nitride film formed by using an insulating film as a mask. 5. The liquid crystal display device according to claim 1, wherein the pixel electrode is of a reflective or semi-transmissive type made of a highly light-reflective metal. 6. The liquid crystal display device according to claim 1, wherein the pixel electrode is configured as a semi-transmissive type including a high light reflection metal portion and a transparent electrode portion. 7. The high light reflection metal or the high light reflection metal portion,
7. The liquid crystal display device according to claim 5, wherein the liquid crystal display device is formed using a metal selected from Al, an Al alloy, Ag, and an Ag alloy. 8. The liquid crystal display device according to claim 6, wherein the transparent electrode portion is formed using indium tin oxide. 9. A manufacturing method of a liquid crystal display device for displaying an image by driving a liquid crystal sandwiched between two substrates constituting a liquid crystal display panel through a plurality of pixel electrodes, wherein the driving active A step of manufacturing the active element array substrate provided with the elements, a step of forming the active elements in an array on the substrate, a step of forming a first film for protecting a channel of the active element over the entire surface, After applying an insulating film on the first film, the film is exposed and developed using a photomask having a contact hole pattern having a hole shape sufficiently larger than the resolution and a concavo-convex forming pattern with the diameter of the concave portion as the resolution limit, and developing the insulating film A step of forming a contact hole portion and an uneven portion in the film; a step of hardening while smoothing the square shape of the insulating film by heat treatment; The first film is dry-etched to form a contact hole by exposing at least the drain electrode of the active element immediately below the contact hole portion, and removing a part of the convex portion of the uneven portion. A step of forming irregularities having a smooth convex portion and a concave structure in which the bottom is not flat, and a step of forming a pixel electrode electrically connected to the drain electrode through the contact hole and covering the irregularities. A method for manufacturing a liquid crystal display device, comprising: 10. The method according to claim 9, wherein the insulating film is an organic film. 11. The method according to claim 9, wherein the first film is a silicon nitride film. 12. The method for manufacturing a liquid crystal display device according to claim 9, wherein the pixel electrode is of a reflective type or a semi-transmissive type, which is made of a highly light reflective metal. 13. The method of manufacturing a liquid crystal display device according to claim 9, wherein the pixel electrode is configured as a transflective type including a high light reflective metal portion and a transparent electrode portion. 14. The method for manufacturing a liquid crystal display device according to claim 12, wherein the high light reflection metal or the high light reflection metal portion is formed using a metal selected from Al, an Al alloy, Ag, and an Ag alloy. 15. The method according to claim 13, wherein the transparent electrode portion is formed using indium tin oxide. 16. An image display application device using the liquid crystal display device according to claim 1 for a display unit.