JPH05257161A - Active matrix substrate - Google Patents

Abstract

PURPOSE:To improve a yield and characteristics by forming additive capacity parts to an inner side without protruding from the angle parts of the front end faces of insulating films. CONSTITUTION:The additive capacity electrode 18 is so formed that the end face parts of the insulating film 21 do not overlap. Namely, the additive capacity electrode 18 is formed on the side inner by a prescribed distance or above without protruding from the angle parts of the insulating film 21 and at a size at which a sufficient capacity is obtainable. This electrode is satisfactory if its position is on the side inner than the angle parts of the top end face of the insulating film 21 formed by oxidation of the metal of a scanning line 12 in such a case. The additive capacity electrode 18 and a picture element electrode 14 are bridged by a connecting part 18a so as not to pose a problem in electric resistance. The formation of an additive capacity line between the scanning lines 12 and 12 and the formation of the additive capacity electrode 18 on this additive capacity line are equally well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an active matrix substrate, and more particularly, it uses a thin film transistor as an address element and has an additional capacitance portion,
The present invention relates to a structure of an active matrix substrate which enables improvement of characteristics and yield.

[0002]

2. Description of the Related Art Liquid crystal display devices, which have the features of thinness and low power consumption, have been attracting attention as display devices that replace CRTs. Among them, an active matrix drive type liquid crystal display device using a thin film transistor (hereinafter abbreviated as TFT) as a switching element has advantages such as high response speed of liquid crystal and high display quality. It is being appreciated.

FIG. 4 shows a conventional example of an active matrix substrate having an additional capacitance section. In addition, FIG. 5 is BB of FIG.
The arrow sectional drawing in a line is shown. The active matrix substrate 100 of this conventional example shows one in which a pixel electrode 114 and an additional capacitance electrode 118 are bridged by a connecting portion 118a having a width of about 5 μm. The active matrix substrate 100 has a scanning line 112 and a signal line 113 arranged in a grid pattern on a glass substrate 111, which is an insulating substrate, and a picture arranged in a region surrounded by the scanning line 112 and the signal line 113. The pixel electrode 114 and the thin film transistor 120 as a switching element electrically connected to the scanning line 112, the signal line 113, and the pixel electrode 114 are included.

The TFT 120 is formed at a corner of the pixel electrode 114, and has a source electrode 116 branched from the signal line 113 toward the pixel electrode 114 and a drain branched from the pixel electrode 114 toward the source electrode 116. The electrodes 117 are arranged to face each other. Further, below the source electrode 116 and the drain electrode 117, there is a gate electrode 115 branched toward the pixel electrode 114.

FIG. 6 shows a conventional example of an active matrix substrate 100 having an additional capacitance section. FIG. 7 is a sectional view taken along the line CC of FIG. In the conventional active matrix substrate 100, the scanning line 112 and the additional capacitance line 119 are separated, and the pixel electrode 114 is added to the additional capacitance line 11.
It covers the entire end of 9. In any of these structures, the pixel electrode 114 overlaps the end face of the insulating film 121 entirely or only in the upper portion.

In order to avoid a defect caused by foreign matter adhering to the end face after forming an insulating film by anodic oxidation, there has been a conventional one in which the pixel electrode 114 is formed slightly smaller than the insulating film 121.

[0007]

However, the conventional active matrix substrate 100 described above has the following problems. In the conventional active matrix substrate 100, a margin at the time of forming the gate metal, that is, a minus amount from the design value of the bus line due to the etching shift and a margin in patterning the pixel electrode 114,
That is, the pixel electrode 1
It was impossible to completely separate 14 from the end surface of the insulating film 121.

In this insulating film 121, the insulating property of the end face portion is worse than that of the flat part as a characteristic, and the insulating property is further deteriorated by applying an electric field to the end face portion. It was a cause of defects in the.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to improve yield and characteristics in an active matrix substrate having an additional capacitance section.

[0010]

An active matrix substrate of the present invention is arranged on an insulating substrate in a grid pattern by scanning lines and signal lines and arranged in each region surrounded by the scanning lines and the signal lines. The pixel electrode, the scanning line, the signal line, and a switching element electrically connected to the pixel electrode, and the insulating film formed in the lowermost layer by oxidation of the metal of the scanning line, and the scanning is performed. An active matrix substrate having a scanning line adjacent to a line and a portion of the pixel electrode, the additional capacitance portion being overlapped between the scanning line and the pixel electrode; It is formed on the inner side without protruding so that the above object is achieved.

Preferably, the additional capacitance section is located on the additional capacitance line formed between the scanning lines, and is predetermined from a corner of the upper end surface of the insulating film formed by oxidation of the metal of the additional capacitance line. It is formed inside more than the distance.

[0012]

In the active matrix substrate of the present invention, the additional capacitance portion is formed so that the upper pixel electrode does not overlap the end face portion of the upper end face of the insulating film. The additional capacitance electrode of the pixel electrode is formed inside a corner portion of the insulating film by a predetermined distance or more and has a size capable of obtaining a sufficient capacitance. The predetermined distance is 0 μm or more inside the corner of the upper end surface of the insulating film formed by the oxidation of the metal of the scanning line, as shown by the inside of the arrowed line a to a in FIG. good. The additional capacitance electrode and the pixel electrode are bridged by a connecting portion having a width of about 5 μm so as not to cause a problem in electrical resistance.

As a result, it is possible to suppress the occurrence of a short circuit between the upper end surface of the insulating film of the additional capacitance electrode and the pixel electrode, and to provide a display device with few display defects.

[0014]

FIG. 1 shows an embodiment of the active matrix substrate of the present invention. 2 is a sectional view taken along line AA of FIG. The active matrix substrate 10 includes scanning lines 12 arranged in a grid on an electrically insulating glass substrate 11.
A signal line 13, a scanning line 12 and a pixel electrode 14 arranged in a region surrounded by the signal line 13, a scanning line 12,
The thin film transistor 20 as a switching element electrically connected to the signal line 13 and the pixel electrode 14 is provided.

The TFT 20 is formed at a corner of the pixel electrode 14, and has a source electrode 16 branched from the signal line 13 toward the pixel electrode 14 and a drain branched from the pixel electrode 14 toward the source electrode 16. The electrodes 17 are arranged so as to face each other. Further, below the source electrode 16 and the drain electrode 17, there is a gate electrode 15 branched toward the pixel electrode 14. In this embodiment, an amorphous silicon TFT is used as the TFT 20. The TFT 20 can be formed on the scanning line 12. The scanning line 12 adjacent to the scanning line 12 is superimposed on the other end of the pixel electrode 14 with respect to the TFT 20, and the additional capacitance electrode 18 is formed on the overlapping portion.

The additional capacitance electrode 18 is formed so that the end face portions of the insulating film 21 do not overlap. That is, the additional capacitance electrode 18 is formed inside a predetermined distance or more without protruding from the corner portion of the insulating film 21, and has a size capable of obtaining a sufficient capacitance. The predetermined distance is 0 μm or more inside the corner of the upper end surface of the insulating film 21 formed by the oxidation of the metal of the scanning line 12, as indicated by the inside of the arrowed line a to a in FIG. I wish I had it. The additional capacitance electrode 18 and the pixel electrode 14 are bridged by a connecting portion 18a having a width of about 5 μm so that there is no problem in terms of electrical resistance.

FIG. 3 shows another embodiment of the active matrix substrate of the present invention. This active matrix substrate 10
Forms an additional capacitance line 19 between the scanning lines 12 and 12,
The additional capacitance electrode 18 is formed on the additional capacitance line 19. It is shown that such a structure is also possible.

The manufacturing procedure of the active matrix substrate 10 will be described below in sequence. First, the glass substrate 11
Then, tantalum is formed to a thickness of 300 nm by sputtering. Next, the scanning line 12 having the additional capacitance portion is patterned by the photolithography method, or the scanning line 12 and the additional capacitance line 19 separated from the scanning line 12 (hereinafter, both are collectively referred to as the scanning line 12). Form. At this time, the gate electrode 15 is simultaneously formed. A structure in which an insulating film such as tantalum pentoxide is formed under the scanning line 12 by sputtering is also possible.

Next, an insulating film 21 of 300 nm is formed on the scanning line 12 and the gate electrode 15 by an anodic oxidation method, a thermal oxidation method or the like.
Formed with a thickness of. The active matrix substrate 10 of this embodiment is manufactured by using the anodic oxidation method. Next, the nitride insulating film 22 made of silicon nitride is formed by the plasma CVD method.
Are formed to a thickness of 300 nm. In this way, the oxide insulating film 21 and the nitride insulating film 22 form a two-layer structure for the gate insulating film, thereby enhancing the electrical insulating property.

Next, amorphous silicon having a thickness of 30 nm is formed as a semiconductor layer and silicon nitride having a thickness of 200 nm as an etching stopper layer is formed continuously on the nitride insulating film 22 by a plasma CVD method. And
The etching stopper layer is patterned by photolithography to form an etching stopper.
(Neither is shown.) Then, a contact layer of phosphorus-doped n + type amorphous silicon is stacked to a thickness of 50 nm by plasma CVD. Next, the contact layer and the semiconductor layer are simultaneously patterned by the photolithography method. (Not shown) As a material for the signal line, a metal film of Ti, Al, Cr, Mo or the like is formed by a sputtering method, and patterning is performed by a photolithography method to obtain the signal line 13 and the TFT 20.
The source electrode 16 and the drain electrode 17 are formed. The TFT 20 of this embodiment uses Ti as a material.

Next, a transparent electrode film containing indium oxide as a main component is formed to a thickness of 100 nm by sputtering, and this transparent electrode film is formed on the pixel electrode 14 and the additional capacitance electrode 18 by the photolithography method. At this time, the end of the transparent electrode film in the additional capacitance electrode 18 is formed so as to be inside by 1 μm or more from the end of the nitride insulating film 22. The pixel electrode 14 and the additional capacitance electrode 18 have a connecting portion 18a having a width of about 5 μm so as not to cause a problem in electrical resistance.
Bridged by.

When the picture element electrode 14 and the additional capacitance electrode 18 are formed as described above, a protective film (not shown) is formed on the pixel electrode 14 and the additional capacitance electrode 18, whereby the active matrix substrate 10 is formed. The protective film may have a window structure for removing the central portion of the pixel electrode 14.

[0023]

According to the active matrix substrate of the present invention, the additional capacitance electrode of the pixel electrode is located inside a predetermined distance or more without protruding from the corner of the upper end surface of the insulating film formed by the oxidation of the metal of the scanning line. It is formed. By eliminating the overlap between the end face of the insulating film and the pixel electrode in the additional capacitance electrode, an active matrix substrate with few short circuits between the end face of the insulating film of the additional capacitance electrode and the pixel electrode can be realized.
Therefore, using this active matrix substrate,
A display device with few display defects can be provided.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an active matrix substrate of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a plan view showing another embodiment of the active matrix substrate of the present invention.

FIG. 4 is a plan view showing an example of a conventional active matrix substrate.

5 is a sectional view taken along line BB of FIG.

FIG. 6 is a plan view showing another example of a conventional active matrix substrate.

7 is a sectional view taken along the line CC of FIG.

[Explanation of symbols]

 10 Active Matrix Substrate 11 Insulating Substrate 12 Scanning Line 13 Signal Line 14 Picture Element Electrode 15 Gate Electrode 16 Source Electrode 17 Drain Electrode 18 Additional Capacitance Electrode 18a Contact 19 Additional Capacitance Line 20 TFT 21 Oxide Insulating Film 22 Nitride Insulating Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Manabu Takahama 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Takayoshi Nagayasu 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within the corporation

Claims (2)

[Claims] 1. A pixel electrode arranged in a grid pattern on an insulating substrate by scanning lines and signal lines and arranged in each region surrounded by the scanning lines and the signal lines, the scanning lines, and the signals. A line and a switching element electrically connected to the pixel electrode, and a scan line adjacent to the scan line and the pixel electrode with an insulating film formed in the lowermost layer formed by oxidation of the metal of the scan line. An active matrix substrate having an additional capacitance portion overlapped with a part thereof, wherein the additional capacitance portion is formed inside without protruding from a corner portion of an upper end surface of the insulating film. 2. The additional capacitance section is on the additional capacitance line formed between the scanning lines, and a predetermined distance from a corner of an upper end surface of an insulating film formed by oxidation of the metal of the additional capacitance line. The active matrix substrate according to claim 1, wherein the active matrix substrate is formed inside a distance or more.