JPH0261620A - liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technique that is effective when applied to a liquid crystal display device, particularly a liquid crystal display device configured using an active matrix method.

[Conventional technology]

A plurality of pixels are arranged in a matrix in a liquid crystal display section of an active matrix type liquid crystal display device.

Each pixel is located within an area surrounded by multiple scanning signal lines (gate signal lines) that extend horizontally and multiple video signal lines (drain signal lines) that extend vertically and intersect with these lines. It is located. An external terminal to which a scanning signal is applied is connected to one end of the scanning signal line, and an external terminal to which a video signal is applied is connected to one end of the video signal line.

Each external terminal is arranged around the outer periphery of the liquid crystal display section.

Each pixel is composed of a series circuit of a thin film transistor (TPT) and a transparent pixel electrode. A thin film transistor is constructed by sequentially stacking a gate insulating film, a semiconductor layer (channel forming region), a source electrode, and a drain electrode on a gate electrode. The source electrode is electrically connected to the transparent pixel electrode. The drain electrode is integrally constructed and electrically connected to the video signal line. The gate electrode is integrated with and electrically connected to the scanning signal line.

This type of liquid crystal display device, as described in Japanese Unexamined Patent Publication No. 59-22030, has a part of the video signal line connected to an external terminal that is formed thicker than the width of the video signal line. There is. The wide portion of the video signal line is formed so as to go over a stepped portion formed at the end of the insulating film corresponding to the gate insulating film. In other words,
The video signal line has a feature that it can prevent disconnection due to climbing over the stepped portion and reduce so-called line defects in which a plurality of pixels connected to the video signal line become unusable.

[Problem to be solved by the invention]

The video signal lines of the liquid crystal display device described above are formed using photolithography technology (photo-etching technology).

That is, the video signal line is formed by forming an etching mask with a photoresist film on the conductive film and etching the conductive film in a predetermined planar shape using this etching mask. However, since the step portion of the video signal line has a large width dimension, stress due to the difference in linear expansion coefficient increases at the interface between the step portion of the video signal line and the etching mask, resulting in frequent peeling of the interface. For this reason, there is a problem in that during the etching, the etching liquid infiltrates the peeled interface and the video signal line is disconnected due to side etching.

This disconnection of the video signal line causes a line defect specific to liquid crystal display devices, and reduces the manufacturing yield of the liquid crystal display device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique that can prevent disconnection at a stepped portion of a signal wiring in a liquid crystal display device.

Another object of the present invention is to provide a technique that can prevent line defects peculiar to liquid crystal display devices and reduce manufacturing yield in the liquid crystal display device.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

In a liquid crystal display device, at least a portion of a video signal line (or a scanning signal line) that crosses a stepped portion is branched into a plurality of signal lines.

[For production]

According to the above-mentioned means, the surface area of the portion of the video signal line that crosses over the stepped portion is reduced, and the stress acting on the interface between the video signal line and the photoresist film (etching mask) is reduced. It is possible to prevent disconnection of the video signal line due to peeling of the video signal line.

As a result, line defects specific to liquid crystal display devices can be prevented, so that the manufacturing yield of liquid crystal display devices can be improved.

Hereinafter, the structure of the present invention will be described together with an embodiment in which the present invention is applied to a liquid crystal display device that employs an active matrix method.

In addition, in all the figures for explaining the embodiment, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

〔Example〕

A liquid crystal display section of a liquid crystal display device according to an embodiment of the present invention is shown in FIG. 1 (a plan view of main parts), and FIG. 2 shows a cross section taken along the line 1--2 in FIG.

As shown in FIGS. 1 and 2, the liquid crystal display device includes 1.
Lower transparent glass substrate SU having a thickness of about 1 mm
A thin film transistor T is placed on the inner surface (liquid crystal side) of B1.
Has PT. The thin film transistor TPT is mainly
It is composed of a gate electrode GT, an insulating film GI used as a gate insulating film, an i-type semiconductor layer AS used as a channel formation region, a source electrode (or drain electrode) SDI, and a drain electrode (or source electrode) SD2. .

The gate electrode GT is formed by depositing, for example, a sputtering method.
It is formed of a Cr film with a thickness of about 100 r. The gate electrode GT is formed in the same manufacturing process (same conductive layer) as the scanning signal line (gate signal line or horizontal signal line GL),
It is integrated into the scanning signal line GL. The scanning signal line OL is formed of, for example, a composite film in which an AQ-8i film is laminated on the Cr film. The AQ-8i film is deposited by sputtering and is formed to a thickness of approximately 1000 μm. This AQ-
The 8i film is mainly configured to reduce the resistance value of the scanning signal line GL and increase the transmission speed of the scanning signal. The gate electrode GT is formed integrally with the lower layer Cr film of the scanning signal line GL. The scanning signal lines OL extend horizontally as shown in FIG. 1, and a plurality of scanning signal lines OL are arranged vertically (not shown).

Although not shown, at least one end of the scanning signal line OL is connected to an external terminal GP at the outer periphery of the liquid crystal display section of the liquid crystal display device. A scanning signal is applied to this external terminal GP.

The insulating film GI is formed above the gate electrode GT and the scanning signal line OL, except for the external terminal GP (the same applies to the external terminal DP, which will be described later).

The insulating film GI is formed using, for example, a silicon nitride film deposited by a plasma CVD method, and has a thickness of about 3500 [in].

The i-type soil conductor layer AS is formed in an island shape on the upper layer of the gate insulating film GI. The i-type soil conductor layer AS is formed of an amorphous silicon film or a polycrystalline silicon film deposited by the CVD method, and has a thickness of about 2
The film thickness is approximately that of a human body. The i-type soil conductor layer AS is mainly used as a channel forming region of the thin film transistor TPT.

Each of the source electrode SD1 and the drain electrode SD2 is provided on the i-type semiconductor layer As, separated from each other. The source electrode SDI and the drain electrode SD2 are operationally switched between source and drain when the bias polarity of the circuit changes. In other words, the thin film transistor TPT has a bidirectional structure like the insulated gate field effect transistor FET.

Each of the source electrode soi and drain electrode SD2 is
Although they are formed in the same manufacturing process and do not clearly show the cross-sectional structure, for example, a composite film in which an n+ type thick conductor layer Cr film and an AQ-5i film are sequentially laminated from the lower layer side that contacts the i-type soil conductor layer AS. It is made up of. Formed with n° type half body layer, amorphous silicon film or polycrystalline silicon film, approximately 500 people
It is formed with a film thickness of approximately The n0 type semiconductor layer is configured to reduce the contact resistance value between the i type soil conductor layer AS and the Cr film. The Cr film is deposited by, for example, a sputtering method, and is formed to have a thickness of about 600 [layers]. AQ-5i
The film is deposited by, for example, a sputtering method, and is formed to have a thickness of about 3,500 cm. The Afi-8i film is mainly configured to reduce the resistance value of the video signal 11DL and increase the transmission speed of the video signal.

The video signal line DL, like the source electrode SDI and drain electrode SD2, is formed of a composite film in which a Cr film and an Afl-8i film are sequentially laminated.

The video signal line DL is connected to the scanning signal line GL as shown in FIG.
It extends in the vertical direction that intersects with the , and multiple pieces are arranged in the horizontal direction. The drain electrode SD2 is integrally configured and electrically connected to the video signal line DL, and the drain electrode SD2 can be seen as part of the video signal line DL.

A transparent electrode (transparent pixel electrode) ITOI provided for each pixel is connected to the source electrode SDI. The transparent electrode ITOI constitutes one of the pixel electrodes of the liquid crystal display section.

The transparent electrode ITOI is provided on the insulating film GI. The transparent electrode ITOI is deposited by sputtering, for example, and has a thickness of about 12
00E It is formed with a film thickness of about the same thickness as that of a human body.

As shown in FIGS. 1 and 2, source electrodes SD1. Each of the drain electrodes 5D2 (video signal line DL) is formed so as to go over the stepped portion.

This stepped portion is formed at the end of the i-type soil conductor layer AS, which is the channel formation region of the thin film transistor TPT. Actually, the height of the stepped portion is the sum of the stepped portion formed at the end of the i-type soil conductor layer AS and the stepped portion formed at the end of the gate electrode GT. The step portions of the source electrode SDI and the drain electrode SD2 are located at the first
As shown in the figure, it is branched into a plurality of electrodes (signal wiring). The individual branched electrodes are configured to independently overcome the stepped portion, and the individual branched electrodes are designed to reduce the surface area. In this embodiment, the source electrode SD1 , drain electrode SD2
Although each stepped portion is branched into three electrodes, the present invention is not limited to this number, and may be branched into two or four electrodes in order to reduce the surface area.

The source electrode SDI, drain electrode SD2, and video signal line DL are formed using photolithography. In other words, these electrodes and wirings are formed by forming an etching mask made of a photoresist film on a conductive film made of a Cr film, an AQ-Si film, etc., and using this etching mask, the conductive film is etched. It can be formed by etching in a predetermined planar shape.

The etchant for the Cr film is, for example, a ceric ammonium nitrate solution. The etchant for the A 11-8 i film is, for example, a mixed solution of phosphoric acid, nitric acid and acetic acid.

In this way, the source electrode SDI, the drain electrode SD2 . In a liquid crystal display device in which each of the video signal lines DL overcomes a step formed at an end of an i-type semiconductor layer As, the source electrode SD
By branching the step portions of each of the source electrode SDI, drain electrode SD2, and video signal line DL into a plurality of electrodes and signal lines, the source electrode SDI, drain electrode SD2. The surface area of the portion of the video signal line DL that crosses over each stepped portion is reduced, and the stress acting on the interface between those surfaces and the photoresist film (etching mask) during the photolithography process is reduced, and the stress at the interface is reduced. Since the adhesiveness can be improved, it is possible to prevent the etching solution from entering the interface.

Source electrode SD1, drain electrode SD2. Video signal line D
It is possible to prevent side etching and disconnection of each stepped portion of L. As a result, line defects specific to liquid crystal display devices can be prevented, so that the manufacturing yield of liquid crystal display devices can be improved.

At least one end portion of the video signal line DL is similar to the external terminal GP, as shown in FIG. 3 (a plan view of the main part of the external terminal area).
As shown in the figure, the outer peripheral portion of the liquid crystal display section of the liquid crystal display device is connected to the external terminal DP. This external terminal D
P is configured to be applied with a video signal. A plurality of external terminals DP are arranged on the surface of the lower transparent glass substrate SUB1. The external terminal DP is constructed integrally with the video signal line DL and is formed in substantially the same manufacturing process.

The connection part of this video signal line DL with the external terminal DP (the boundary part between the liquid crystal display section and the external terminal area) is connected to the video signal line DL.
The insulating film GI is configured to cross over a step formed at the end of the insulating film GI formed in the lower layer. The step portion of the video signal line DL is located at the source electrode SD1. Like the drain electrode SD2 and the video signal line DL, it is branched into a plurality of signal lines. In other words, the stepped portion of the video signal line DL is configured to prevent disconnection.

A protective film psvt is provided on the thin film transistor TPT and the transparent electrode IrO2. The protective film PSVI is formed mainly to protect the thin film transistor TPT from moisture, etc., and a film having high transparency and good moisture resistance is used. The protective IEiPSV1 is formed of, for example, a silicon oxide film or a silicon nitride film deposited by a plasma CVD method, and is formed to have a thickness of about 10 mm.

A light shielding film LS is provided above the protective film PSVI on the thin film transistor TFT to prevent external light from entering the i-type semiconductor layer AS used as a channel formation region. The light shielding film LS is made of, for example, an AQ film (or AQ-8i
, An-Cu), Cr[, etc., and is deposited by sputtering to have a film thickness of about 1000 to 4000 [layers].

The liquid crystal LC is defined by a lower alignment film ○RII and an upper alignment film 0RI2, which set the orientation of liquid crystal molecules, and is sealed in an air barrier formed between a lower transparent glass substrate SUB1 and an upper transparent glass substrate 5UB2. ing.

The lower alignment film 0RII is formed on the protective film psvi on the lower transparent glass substrate 5UBl side.

On the inner surface (liquid crystal side) of the upper transparent glass substrate 5UB2, a color filter FIL, a protective film PSv2, a common transparent electrode (common transparent pixel electrode) IrO2, and the upper alignment film 0RI2 are sequentially laminated.

The common transparent electrode ITO2 is connected to the lower transparent glass substrate 5U.
It faces the transparent electrode TOI provided for each pixel on the BI side and is configured integrally with another adjacent common transparent electrode IT○2.

The color filter FIL is formed by dyeing a dyed base material made of a resin material such as acrylic resin with a dye for each pixel. Dyeing is done using photolithography technology.

The protective film PSV2 is provided to prevent the dyes used to dye the color filter FIL into different colors from leaking into the liquid crystal LC. The protective film PSV2 is made of a transparent resin material such as acrylic resin or epoxy resin.

This liquid crystal display device has a lower transparent glass substrate 5UBl side,
Each layer on the upper transparent glass substrate 5UB2 side is formed separately, and then the upper and lower transparent glass substrates SUB1 and 5UB are formed separately.
2 are stacked on top of each other and a liquid crystal LC is sealed between the two.

Lower transparent glass substrate 5UB1. Upper transparent glass substrate 5U
A polarizing plate POL is formed on each outer surface of B2.

As above, the invention made by the present inventor has been specifically explained based on the above embodiments, but the present invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist thereof. Of course.

For example, in the present invention, when the scanning signal line is configured to cross over a stepped portion, the stepped portion of the scanning signal line may be branched into a plurality of signal lines.

Further, in the present invention, the stepped portion of the video signal line that intersects with the scanning signal line may be branched into a plurality of signal lines.

In other words, one aspect of the present invention is to branch a portion where a signal wiring or an electrode breaks when it crosses a step into a plurality of wires,
The present invention can be applied to any part of a liquid crystal display device in which such a structure exists.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

In a liquid crystal display device, disconnection of signal wiring can be prevented.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a plan view of a main part showing a liquid crystal display section of a liquid crystal display device according to an embodiment of the present invention. FIG. A cut sectional view. FIG. 3 is a plan view of a main part showing an external terminal area of the liquid crystal display device shown in FIG. 1. FIG. In the figure, SUB...transparent glass substrate, GL...scanning signal line, DL...video signal line, GI...insulating film, GT...
...Gate electrode, AS...i-type semiconductor layer, SD1 source electrode, SD2...drain electrode, Psv...protective film, LS...light shielding film, LC...liquid crystal, TPT...
- Thin film transistor, GP, DP...external terminals. Figure 1 Third cause

Claims (1)

[Scope of Claims] 1. In a liquid crystal display device in which a video signal line or a scanning signal line formed by photolithography technology overcomes a stepped portion formed at an end of an insulating film, the video signal line or scanning signal line A liquid crystal display device characterized in that the stepped portion is branched into a plurality of signal lines. 2. The video signal line crosses over a step formed at the end of a semiconductor layer used as a channel formation region of a thin film transistor, and a step formed at an end of an insulating film when connecting to an external terminal. 2. The liquid crystal display device according to claim 1, wherein the portion to be overcome is branched into a plurality of signal lines. 3. The video signal line or the scanning signal line is formed by forming an etching mask made of a resist film on the conductive film, and using this etching mask, etching the conductive film into a predetermined planar shape. A liquid crystal display device according to claim 1 or 2, characterized in that: