JPS635379A - Tft active matrix substrate - 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 TFT active matrix substrate used, for example, in flat display devices such as liquid crystal televisions.

[Conventional technology]

In recent years, liquid crystal display devices using active matrix substrates equipped with TFTs (thin film transistors) have been attracting attention as a means of realizing liquid crystal televisions that can provide highly clear color images (Nikkei Electronics 1984).
(September 10th issue, P211).

The active matrix substrate has TFTs for controlling each pixel arranged in a matrix on an insulating substrate, and the gate electrode and one of the source/drain electrodes of each TFT are commonly connected in the X direction and the Y direction, respectively. is terminated to the terminal. The other source/drain electrode is connected to the pixel electrode.

FIG. 5 shows a conventionally used liquid crystal display device of this type. The figure shows only one pixel, and the TFT includes a gate electrode GT, an island-shaped non-quality silicon film AS formed thereon, and first and second source/drain electrodes SDI.
, SD2.

The gate electrode GT is
The first source/drain electrode SDI is commonly connected to the gate electrodes of adjacent TFTs arranged in the Y direction, and the first source/drain electrode SDI is connected to the gate electrodes of adjacent TFTs arranged in the Y direction by an integrally formed signal line SG.
It is commonly connected to the source and drain electrodes of the FT.

The second source/drain pole SD2 is the pixel electrode I
Connected to TOI.

[Problem that the invention seeks to solve]

In the above configuration, the first source/drain electrode SDI and the signal line SG are connected vertically through the island-shaped non-quality silicon AS.
is arranged, but this source/drainfflf4sD
1 and the signal line SG by etching,
As shown in FIG. 6 (corresponding to the Vl-ITII cross-sectional view in FIG. 5), along the non-quality silicon film AS at the part that goes over the edge of the non-quality silicon AS (portions A and B in FIG. 5), Etching solution seeps in. As is clear from FIG. 5, the source/drain electrode SDI and the signal line SG cross over the amorphous silicon film AS over their entire width in this part, and therefore the enoting liquid soaks into the entire width. , the signal line may be disconnected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a TFT active matrix substrate that can prevent signal lines from being disconnected due to penetration of etching solution into the edge portions of island-shaped semiconductor films constituting TFTs.

[Means for solving problems]

The above problem can be solved by making the length of the portion where the source/drain electrodes and the signal line cross over the island-like semiconductor film larger than the line width of the source/drain electrode and the signal line.

[Effect]

The path through which the etching solution penetrates becomes longer, reducing the probability of wire breakage.

〔Example〕

FIG. 1 is a plan view showing an embodiment in which the present invention is applied to a liquid crystal display device, and FIG. 2 is a cross-sectional view taken along line 1--2.

In the figure, SUB1 is a glass substrate having a thickness of about 1.1 (mm), and GT is a gate electrode made of Cr or the like. AS is an island-shaped non-quality silicon film, and there is a film G that acts as a gate insulating film of a field effect transistor (FET) between the gate GT and the glass substrate SUBl.
I is formed. SD1 and SD2 are a pair of source/drain electrodes, which are formed on the silicon film As with a gap between them, and the gate electrode GT straddles them. The pair of source/drain electrodes SD is called the source/drain voltage tl because the operational source and drain switch when the bias polarity of the circuit changes, that is, they are bidirectional like a normal FET.

The source/drain electrodes SD of ε are made of amorphous Si. It has a three-layer structure of Cr and An. The N+-SL electrode layer is used to reduce the contact resistance with the non-quality silicon film, and the Or'I1i electrode layer is used to prevent the Al1 electrode layer from reacting with the Si layer. P.S.
v is a protective film that protects the FET from moisture, etc., and is made of highly transparent and moisture-resistant Si○2 film, Si,N. Formed by a membrane.

ITO is a transparent conductive film connected to one of the source and drain electrodes SD (SD2), and acts as one electrode of the liquid crystal display device. The other source/drain electrode SDI
is also used as a wiring running in the Y direction, that is, a signal line SG. Further, in the X direction, a gate electrode GT runs also as a wiring, that is, a scanning line SC. LS has FE external light
This is a light shielding film to prevent the light from entering the gate region, which is the heart of the T, and is made of Cr material or the like. This FE
For T, if the gate electrode is biased positively with respect to the source electrode, the resistance between the source and drain becomes small, and if the gate bias is made close to zero, the resistance becomes large.

The liquid crystal LC is sealed between the upper and lower glass substrates SUB1 and SUB2, and the orientation of the liquid crystal molecules is determined by the upper and lower alignment films ORI2 and oRI1. PSV2 is a protective film made of acrylic resin.

FIL is a color filter. ITO2 is a common transparent electrode facing the plurality of arranged pixel electrodes IT○1.

Such a display device is assembled by separately laminating the substrates SUB1 and SUB2, and then filling them with liquid crystal.

Here, in the conventional example shown in FIG. 5, the source/drain electrode SDI and the signal line SG were structured to cross over the edge of the island-shaped non-quality silicon film AS only in the width portions indicated by A and B. On the other hand, in this embodiment, as shown in FIG. 1, even in the portion C running in the Y direction, there is a sliding structure that goes over the edge of the non-quality silicon film As. For this reason, the etching solution infiltrates along the interface with the edge of such poor quality silicon film AS, and the path it must pass through until it infiltrates the entire width of the source/drain electrode SD1 and signal line SG is extremely long. The probability of it penetrating to that extent and causing a disconnection is extremely low.

In this example, the islands of the non-quality silicon film AS are
As shown by D or E in the figure, the etching solution has a step-like shape to further lengthen the path through which the etching solution penetrates.

In the example shown in Figure 1, one pixel plane pattern PIXI is designed so that the vertical and horizontal arrangement pitches are almost the same, and in the case of monochromatic display where the dot size is the same vertically and horizontally. can be arranged in rows and columns in the same pattern.

In the case of color display, when red, green, blue, etc. color filters are arranged horizontally alternately, that is, in a vertical stripe arrangement, one pixel pattern is vertically elongated as shown in FIG. 3A (PIX2), In the opposite arrangement of horizontal stripes, the stripes are horizontally elongated as shown in Figure 3B (PIX
3).

FIG. 4 shows a liquid crystal display device (L
This figure shows an equivalent circuit of a CD panel (PNL) and its peripheral drive circuit. LVS is an LCD vertical scanning circuit, which applies a scanning switching signal to the gate electrode of the TFT. LHS is an LCD horizontal scanning circuit, which sequentially and selectively applies video signals to the source/drain electrodes SDI of the TFTs.

Above, we have explained an example of application to a liquid crystal display device.
The invention is not limited thereto and can be applied to other flat display devices as well.

〔Effect of the invention〕

According to the present invention, disconnection of signal lines due to etching can be prevented, and manufacturing yield can be improved.

It is especially useful for large, high-definition active matrix substrates.

[Brief explanation of drawings]

Figure 1 is a plan view showing one embodiment of the present invention, Figure 2 is
-■ Cross-sectional view, FIG. 3 is a plan view showing another example of horizontal formation of pixel electrodes, FIG. 4 is a circuit diagram of a liquid crystal display device and peripheral drive circuit, FIG. 5 is a plan view showing a conventional example, and FIG. The diagram is the VI
- VI sectional view. AS...non-quality silicon film, SDI...FIG. 1 AS...non-quality silicon film 501--... drain electrode SG... signal line FIG.

Claims (1)

[Claims] 1. Multiple TFs consisting of a gate electrode and source/drain electrodes stacked on an insulating substrate via an island-shaped semiconductor film
In an active matrix substrate in which T is arranged in a matrix, gate electrodes are commonly connected in the X direction by scanning lines, and source/drain electrodes are commonly connected in the Y direction by signal lines, the source/drain electrodes and the signal lines are A TFT active matrix substrate characterized in that the length of the portion that goes over the edge of the island-shaped semiconductor film is larger than the line width of the source/drain electrodes and the signal line.