JP2003140173A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a disconnection, etc., in transparent electrodes having a poor coverage characteristic. SOLUTION: An interlayer insulating film 10 consisting of an organic resin film is deposited and the unnecessary segments of the interlayer insulating film 10, such as drain contact holes 12, are removed by using a photolithographic technique. Next a transparent electrode material is deposited and this transparent electrode material is patterned by using the photolithographic technique, by which transparent electrodes 8 are formed. A reflection electrode material is then deposited and this reflection electrode material is patterned by the photolithographic technique, by which the reflection electrodes 11 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a transmissive electrode and a reflective electrode.

[0002]

2. Description of the Related Art FIG. 5 shows a sectional view of one pixel of an active matrix substrate of a conventional liquid crystal display device. The active matrix substrate includes a gate electrode 2, a gate insulating film 4, a semiconductor layer 5, a semiconductor contact layer 6, a transmissive electrode 8, a source electrode 9b, a drain electrode 9c, an interlayer insulating film 10, a reflective electrode 11, and a contact portion 12. There is.

In a liquid crystal display device, a liquid crystal layer is interposed between a counter substrate (not shown) and the active matrix substrate, and a transparent electrode 8 and a reflective electrode 11 of the active matrix substrate and a counter electrode formed on the counter substrate. Display is performed by applying a voltage to change the alignment state of the liquid crystal.

External light or the like is reflected by the reflective electrode 11 to perform display at the reflective electrode 11, and light from a backlight or the like installed below is provided in the region of the transmissive electrode 8 where the reflective electrode 11 is not formed. It is made transparent and displayed.

Therefore, the liquid crystal display device provided with the active matrix substrate of FIG. 5 can obtain a bright display by utilizing the light of the backlight and the external light.

[0006]

Since the indium oxide-based thin film used for the transmission electrode 8 has poor coverage characteristics, disconnection is likely to occur at the contact portion which is the connection portion with the drain electrode. A voltage for driving the liquid crystal is not applied from the switching element to the transmissive electrode 8 and the reflective electrode 11, resulting in display failure.

Further, when the transmissive electrode 8 is formed on the reflective electrode 11, since the transmissive electrode 8 is formed over the reflective electrode 11 at the end portion of the reflective electrode 11, the transmissive electrode 8 having poor coverage characteristics may be broken. Occurrence and increase in resistance value result in display failure.

[0008]

The present invention provides a liquid crystal display device comprising a switching element formed on an insulating substrate, and a reflective electrode and a transmissive electrode electrically connected to the switching element. A pixel electrode including a reflective electrode and the transmissive electrode is provided, and the reflective electrode is formed so as to be in contact with the liquid crystal layer side of the transmissive electrode.

Further, the transparent electrode is made of a material containing indium oxide as a main component.

The reflective electrode is made of Al, Ag, P.
One of t, Ti, Cr, Mo, W, and Ni, and a material containing these metals as a main component.

Further, the switching is formed via a switching element formed on the insulating substrate, an interlayer insulating film formed on the switching element, and a contact portion of the interlayer insulating film formed on the switching element. In the liquid crystal display device including the reflective electrode and the transmissive electrode electrically connected to the element, the reflective electrode may be formed on the contact portion.

The operation of the present invention will be described below.

Indium oxide-based thin films generally used as transparent electrodes have poor coverage characteristics.

According to the present invention, in the pixel electrode composed of the reflective electrode and the transmissive electrode, since the reflective electrode is formed on the transmissive electrode, a step due to the reflective electrode is not formed in the transmissive electrode having poor coverage characteristics. Cuts at steps are reduced.

Further, by continuously forming the transmissive material and the reflective material, the process can be shortened, and a liquid crystal display device in which the transmissive electrode having poor coverage characteristics does not cause step disconnection due to the reflective electrode can be manufactured.

Further, when the switching element is connected to the picture element electrode composed of the reflective electrode and the transmissive electrode via the contact portion of the interlayer insulating film, the reflection formed of the metal layer having excellent coverage characteristics is formed on the contact portion. By forming the electrodes, the connection reliability between the pixel electrodes and the switching elements can be improved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 shows the structure of one picture element of an active matrix substrate of a transflective liquid crystal display device. FIG. 2 shows an AA cross section of FIG.

A conductive thin film made of Ta is formed on an insulating substrate 1 made of glass, and the conductive thin film is patterned by photolithography to form a gate wiring 3 and a gate electrode 2. . The insulating substrate 1 may be made of another transparent insulating material, and the gate material may be made of another conductive material such as Al, Cr, Mo, W, Cu, or Ti.

Next, SiNx is used as the gate insulating film 4, amorphous Si is used as the semiconductor layer 5, and the semiconductor contact layer 6 is used.
CVD of n + type amorphous Si doped with P as
The film was continuously formed by the method. Then, the semiconductor layer 5 and the semiconductor contact layer 6 are patterned by using the photolithography technique.

Next, a conductive film made of Cr is formed, and the conductive film is patterned by using a photolithography technique to form a source wiring 9a, a source electrode 9b and a drain electrode 9c. Although Cr is used as the conductive film in the present embodiment, other conductive materials such as Al, Mo, Ta, W, Cu, and Ti may be used.

Next, the semiconductor contact layer 6 is etched by using the source electrode 9b and the drain electrode 9c as a mask, and the semiconductor contact layer 6 is divided into a source side 6a and a drain side 6b to form a TFT 7.

Next, the interlayer insulating film 10 made of an organic resin film is formed, and unnecessary portions of the interlayer insulating film 10 such as the drain contact hole 12 are removed by using the photolithography technique. At this time, the concavo-convex portion 14 for scattering the incident light is formed on the interlayer insulating film 10 where the reflective electrode 11 is formed. Although the organic resin film is used for the interlayer insulating film 10 in the present embodiment, the interlayer insulating film 10 may be a laminated film of different materials, and unevenness may not be formed on the surface.

Next, a transparent electrode material is deposited, and the transparent electrode material is patterned by using a photolithography technique to form a transparent electrode 8. In this embodiment, the transparent electrode material is I
TO (In-Sn-0) was used.

Next, a reflective electrode material is deposited, and the reflective electrode material is patterned by a photolithography technique to form the reflective electrode 11. In this embodiment, Al is used for the reflective electrode 11.

As described above, the active matrix substrate of this embodiment is obtained.

In the liquid crystal display device of this embodiment, a transparent electrode 8 of the active matrix substrate is formed by interposing a liquid crystal layer between a counter substrate (not shown) and the active matrix substrate.
Also, a voltage is applied between the reflective electrode 11 and the counter electrode formed on the counter substrate to change the alignment state of the liquid crystal, thereby performing display.

In the reflective electrode 11, external light is reflected by the reflective electrode 11 for display, and in a region of the transmissive electrode 8 where the reflective electrode 11 is not formed, light from a backlight or the like installed below is upward. It is made transparent and displayed.

Therefore, in the liquid crystal display device of this embodiment, a bright display can be obtained by utilizing the light of the backlight and the external light.

By connecting the drain electrode 9c in the drain contact portion 12 with the reflective electrode 11,
Separately, it is possible to form a liquid crystal display device including a transmissive electrode and a reflective electrode with improved reliability of drain connection without forming a metal for connection.

When the transparent electrode 8 is an oxide film made of an ITO film, the surface of the transparent electrode is oxidized if it is a conductive material whose lower layer film is oxidized at the time of film formation. Therefore, the contact between the ITO film and the lower layer film is made by the oxide insulating film. Getting worse. In particular, Al or Ta forming an oxide film having a high insulating property has a large contact resistance.

Further, the reflective electrode 11 covers the transmissive electrode 8,
By forming the transmissive electrode 8 having poor coverage characteristics in the lower layer of the reflective electrode 11, the disconnection of the transmissive electrode 8 is reduced and the electrical connection between the transmissive electrode 8 and the reflective electrode 11 is excellent, and the occurrence of defects such as step disconnection is suppressed. Thus, it is possible to form a transmissive / reflective liquid crystal display device.

(Embodiment 2) FIG. 3 shows an active matrix substrate of Embodiment 2. The same components as those in the first embodiment are designated by the same reference numerals.

A conductive thin film made of Ta is formed on an insulating substrate 1 made of glass, and the conductive thin film is patterned by using a photolithography technique to form a gate wiring 3 and a gate electrode 2. . Other transparent substrates may be used for the insulating substrate 1, and other conductive materials such as Al, Cr, Mo, W, Cu, and Ti may be used as the gate material.

Next, SiNx is used as the gate insulating film 4, amorphous Si is used as the semiconductor layer 5, and the semiconductor contact layer 6 is used.
CVD of n + type amorphous Si doped with P as
The film was continuously formed by the method. Then, the semiconductor layer 5 and the semiconductor contact layer 6 are patterned by using the photolithography technique.

Next, a conductive film made of Cr is formed, and the conductive film is patterned by using the photolithography technique to form the source wiring 9a, the source electrode 9b and the drain electrode 9c.
To form. Although Cr is used as the conductive film in the present embodiment, other conductive materials such as Al, Mo, Ta, W, Cu, and Ti may be used.

Next, the semiconductor contact layer 6 is etched using the source electrode 9b and the drain electrode 9c as a mask to divide the semiconductor contact layer 6 into a source side 6a and a drain side 6b, thereby forming a TFT 7.

Next, the interlayer insulating film 10 made of an organic resin film is formed, and unnecessary portions of the interlayer insulating film 10 such as the drain contact hole 12 are removed by using the photolithography technique. At this time, the concavo-convex portion 14 for scattering the incident light is formed on the interlayer insulating film 10 where the reflective electrode 11 is formed. Although the organic resin film is used for the interlayer insulating film 10 in the present embodiment, the interlayer insulating film 10 may be a laminated film of different materials, and unevenness may not be formed on the surface.

The following steps will be described step by step with reference to FIG.

Next, the transmissive electrode material 15 is deposited, and then the reflective electrode material 16 is deposited continuously. In this embodiment, ITO (In-Sn-0) was used for the transmissive electrode material 15 and Al was used for the reflective electrode material 16 (Fig. 3a).

Next, the transmissive electrode material 15 and the reflective electrode material 16 are continuously patterned into the same shape as the pixel electrode shape including the reflective electrode and the transmissive electrode by using the photolithography technique. In this embodiment, a hydrochloric acid-based etchant is used as the etching solution (FIG. 3b).

Next, by using a photolithography technique, the reflective electrode material 16 covering the transmission region 13 is removed,
The transmissive electrode 8 and the reflective electrode 11 are formed. In the present embodiment, a mixed acid of phosphoric acid mononitric acid monoacetic acid was used as the etching solution (FIG. 3c).

As described above, it is possible to obtain a liquid crystal display device which is excellent in the electrical connection between the transmissive electrode 8 and the reflective electrode 11 and can suppress the occurrence of defects such as step breaks.

Further, since the reflective electrode is formed on the transmissive electrode at the contact portion 12, even if the coverage of the transmissive electrode is poor and the electrical connection between the drain electrode and the transmissive electrode is insufficient, the reflective electrode is used as the drain electrode. Electrical connection is obtained.

(Embodiment 3) FIG. 4 shows an active matrix substrate of Embodiment 3. The same components as those in the first embodiment are designated by the same reference numerals.

A conductive thin film made of Ta is formed on the insulating substrate 1 made of glass, and the conductive thin film is patterned by using a photolithography technique to form the gate wiring 3 and the gate electrode 2. . Other transparent substrates may be used for the insulating substrate 1, and other conductive materials such as Al, Cr, Mo, W, Cu, and Ti may be used as the gate material.

Next, SiNx is used as the gate insulating film 4, amorphous Si is used as the semiconductor layer 5, and the semiconductor contact layer 6 is used.
CVD of n + type amorphous Si doped with P as
The film was continuously formed by the method. Then, the semiconductor layer 5 and the semiconductor contact layer 6 are patterned by using the photolithography technique.

Next, a conductive film made of Cr is formed, and the conductive film is patterned by using the photolithography technique to form the source wiring 9a, the source electrode 9b and the drain electrode 9c.
To form. Although Cr is used as the conductive film in the present embodiment, other conductive materials such as Al, Mo, Ta, W, Cu, and Ti may be used.

Next, the semiconductor contact layer 6 is etched by using the source electrode 9b and the drain electrode 9c as a mask to divide the semiconductor contact layer 6 into a source side 6a and a drain side 6b to form a TFT 7.

Next, an interlayer insulating film 10 made of an organic resin film is formed, and unnecessary portions of the interlayer insulating film 10 such as the drain contact hole 12 are removed by using a photolithography technique. At this time, the concavo-convex portion 14 for scattering the incident light is formed on the interlayer insulating film 10 where the reflective electrode 11 is formed. Although the organic resin film is used for the interlayer insulating film 10 in the present embodiment, the interlayer insulating film 10 may be a laminated film of different materials, and unevenness may not be formed on the surface.

The following steps will be described step by step with reference to FIG.

Next, the transmissive electrode material 15 is deposited, and then the reflective electrode material 16 is deposited continuously. In this embodiment, ITO (In-Sn-0) is used for the transmissive electrode material 15 and Al is used for the reflective electrode material 16 (Fig. 4a).

Next, the reflective electrode material 16 is patterned into the shape of the reflective electrode 11 by using the photolithography technique. In this embodiment, a mixed acid of phosphoric acid mononitric acid monoacetic acid was used as the etching solution (FIG. 4B).

Next, the transparent electrode material 15 is patterned into the shape of the transparent electrode 8 by using the photolithography technique. In this embodiment, a hydrochloric acid-based etchant is used as the etching solution (FIG. 4c).

As described above, it is possible to obtain a liquid crystal display device which is excellent in the electrical connection between the transmissive electrode 8 and the reflective electrode 11 and can suppress the occurrence of defects such as step breakage.

Since the transmissive electrode material 15 is not patterned when the reflective electrode material 16 is patterned, the transmissive electrode material 15 acts as a protective layer of the interlayer insulating film 10, so that the display roughness due to damage due to etching of the interlayer insulating film 10 is caused. And leakage between picture elements can be prevented.

Further, since the reflective electrode is formed on the transmissive electrode in the contact portion 12, even if the coverage of the transmissive electrode is poor and the electrical connection between the drain electrode and the transmissive electrode is inadequate, the reflective electrode forms the drain electrode. Electrical connection is obtained.

[0057]

According to the present invention, in the pixel electrode composed of the reflective electrode and the transmissive electrode, since the reflective electrode is formed on the transmissive electrode, the step due to the reflective electrode is not formed in the transmissive electrode having poor coverage characteristics. Therefore, breakage at a step is reduced.

Further, by continuously forming the transmissive material and the reflective material, the process can be shortened, and a liquid crystal display device in which step breakage due to the reflective electrode does not occur in the transmissive electrode having poor coverage characteristics can be manufactured.

Further, when the switching element is connected to the pixel electrode composed of the reflective electrode and the transmissive electrode via the contact portion of the interlayer insulating film, the reflection formed of the metal layer having excellent coverage characteristics is formed on the contact portion. By forming the electrodes, the connection reliability between the pixel electrodes and the switching elements can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing one picture element of an active matrix substrate of a liquid crystal display device according to a first embodiment.

FIG. 2 is a cross-sectional view of the liquid crystal display device according to the first embodiment taken along the line AA of FIG.

FIG. 3 is a cross-sectional view showing a manufacturing process of the liquid crystal display device of the second embodiment.

FIG. 4 is a cross-sectional view showing the manufacturing process of the liquid crystal display device of the third embodiment.

FIG. 5 is a cross-sectional view of an active matrix substrate of a conventional liquid crystal display device.

[Explanation of symbols]

1 Insulating substrate 2 Gate electrode 3 gate wiring 4 Gate insulation film 5 Semiconductor layer 6a Semiconductor contact layer (source electrode side) 6b Semiconductor contact layer (drain electrode side) 7 TFT section 8 Transparent electrode 9a Source wiring 9b source electrode 9c drain electrode 10 Interlayer insulation film 11 Reflective electrode 12 Contact part 13 Transparent area 14 Reflective electrode irregularities 15 Transparent electrode material 16 Reflective electrode material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yozo Narutaki             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company (72) Inventor Naoyuki Shimada             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F term (reference) 2H091 FA14Y FB08 FC01 FC10                       GA03 GA13 LA01 LA12 LA30                 2H092 HA04 HA05 JA24 KA05 KA18                       KB24 KB25 MA13 MA18 NA15                       NA27 NA29

Claims (3)

[Claims] 1. A liquid crystal display device comprising: a switching element formed on an insulating substrate; and a reflective electrode and a transmissive electrode electrically connected to the switching element, the liquid crystal display device comprising the reflective electrode and the transmissive electrode. A liquid crystal display device comprising a pixel electrode, wherein the reflective electrode is formed so as to be in contact with a liquid crystal layer side of the transmissive electrode. 2. The liquid crystal display device according to claim 1, wherein the transmissive electrode is a material containing indium oxide as a main component. 3. The reflective electrode is made of Al, Ag, Pt, T
The liquid crystal display device according to claim 1 or 2, which is made of any one of i, Cr, Mo, W, and Ni, and a material containing these metals as a main component.