JPH02264927A - Thin film transistor array - Google Patents

Abstract

PURPOSE:To execute a display of a high duty ratio and to suppress a defect caused by the influence of dust and a pin hole by forming a gate electrode and a conductive layer on the same plane. CONSTITUTION:On a glass substrate 21, a gate electrode 24 is formed into a pattern, and a transparent conductive film 23 is brought to pattern formation. Both of them are on the same plane, and do not intersect with each other. Subsequently, an insulating film 22 and a semiconductor layer 26 are formed, and formed into a pattern. Next, a picture element electrode 25 is formed. In a part in which a wiring of a transparent conductive film 42 is extended to the outside peripheral part of a thin film transistor array, an insulating film opening part 43 is provided, a source electrode 28, a drain electrode 27 and a wiring part are made, and simultaneously, a transparent conductive film outside take-out electrode 44 is formed. As a result, the film 42 can be connected to the outside. By constituting a thin film capacitor of the picture element electrode 25, the insulating film 22 and the transparent conductive film 23, a holding characteristic of a voltage is improved. Thereafter, a counter electrode 29 is formed on the substrate 30, and a liquid crystal 31 is enclosed between the transistor array and the substrate 30.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to the structure and manufacturing method of a thin film transistor array used, for example, as a display driving element of a liquid crystal display device.

<Technical Background of the Invention> Liquid crystal display elements (hereinafter referred to as LCDs) have excellent features such as thinness, light weight, and low driving voltage.
2. Description of the Related Art Displays for office automation equipment such as word processors and even small televisions have been put into practical use, and the scope of their applications is expanding, whether for consumer use or industrial use. Currently, active development is underway to achieve higher density, larger screens, higher image quality, and lower costs. In particular, it is known that an LCD using an amorphous silicon thin film transistor (hereinafter referred to as a-5i TPT) as a display driving element can perform matrix display by selecting picture elements arranged in a matrix.

In LCDs using a-3 ITFT, effective driving methods for achieving high display contrast characteristics and large-capacity display include TPT, which operates as a switching element for each pixel, as well as TPT for charge retention. 'iiJ
This is a method that adds a II9 capacitor. This thin film capacitor can improve the display signal voltage retention characteristics and provide design margin for variations in TPT characteristics.

<Invention tries to solve! Problem 1> However, since the LCD using this A-3J TPT has to have O defects in a large area, it is necessary to simplify the process as much as possible, and even when adding a 'III film capacitor, the structure The structure and process of a conventional a-3i TFT with an mtl* capacitor, which must be taken into account, will be explained with reference to FIG. First, on a glass substrate 1, a transparent conductive material such as ITO is deposited and patterned using a zero-order P-CVD method, etc.
A first insulating film 2 of Nx, S10, etc. is formed. Subsequently, the gate electrode 5 is formed using Cr, etc., by P-CVD.
A second insulating film 3 such as SiNx and an a-S+ semiconductor layer 7 are successively deposited by a method. Thereafter, the semiconductor layer 7 is patterned into an island shape, and the pixel electrode 6 is formed using a transparent conductive film such as ITO. A thin film capacitor is formed by this pixel electrode 6, the first insulating film 2, the second insulating film 3, and the transparent conductive film 4. Next, a drain electrode 8 and a source electrode 9 are formed by a conductive film such as Ai. In this way, an a-3i TFT array is produced.

When such a process is used, dust and pinholes, especially when the first insulating film 2 is deposited by the P-CVD method, etc.
This tends to cause defects during the formation of the gate electrode 5, and the process becomes long because the thin film is deposited twice for the first and second insulating films.

Means for Solving the Problems> The present invention provides a pixel electrode connected to a thin film transistor and to which a display driving voltage is applied, a conductive film layer facing each other with an insulating film interposed therebetween, thereby imparting a charge retention function. 'is film transistor array, the gate electrode of the thin film transistor and the conductive II! This thin film transistor array is characterized in that the conductive film layers are formed on the same plane, and that the conductive film layer is connected to the outside through an insulating film opening at the outer periphery of the thin film transistor array.

<Embodiments of the invention> Thin according to the invention 11! Figure 2 shows an example of a transistor array.
This will be described in detail using FIG. FIG. 2 is a cross-sectional view of the thin film transistor array of the present invention. First, the glass substrate 21
A conductive film such as Cr is used on the gate 71t4fi24.
Next, a transparent conductive film 23 such as 1'rO is formed and patterned. The gate electrode 8i24 and the transparent conductive film 23 are on the same plane and are wired without crossing each other. Then, the insulating film 22 and the semiconductor layer 26 were formed by the P-CVD method. The insulation film 22 is 5k
The semiconductor layer 26 and the insulators 11 and 22 are dry-etched in the form of islands using butter. I did a ning. Insulating film 2
The film thickness of 2 can be varied by this dry etching.
A pixel type 8i25 was formed and patterned using a transparent conductive film such as [TO].

Thereafter, as shown in FIG. 3, an insulating film opening 43 is formed by dry etching at a portion where the wiring of the transparent conductor 11142 extends to the outer periphery of the thin film transistor array.
Subsequently, when the source electrode fi 28, the drain electrode 27, and the wiring portion were made of a conductive film such as Af, the transparent conductive TL film external extraction electrode 44 was also formed at the same time. This results in
The transparent conductive IIfi42 can now be connected to the outside.

In addition, by forming a thin film capacitor with the pixel electrode 25, the insulating film 22, and the transparent conductive film 23, the signal and voltage holding characteristics during one field period during driving are improved, and variations in TPT characteristics are improved by design. was given the freedom of Furthermore, by wiring the transparent conductive film 23 to the outside, the capacitance of this thin film capacitor can be adjusted.

After producing the thin film transistor array as described above, the counter electrode 29 was patterned on the glass substrate 30, liquid crystal 31 was sealed between the thin film transistor array and the glass substrate 30, and a thin film transistor panel was produced.

In the thin film transistor display, the pixel electrodes are regularly arranged in a matrix on the glass substrate 21 over the entire display surface, and the TPTs are also arranged in a matrix corresponding to this. The gate electrode 24 and source electrode 28 of the TPT are commonly connected in the row and column direction and connected to an external driving circuit.

A signal voltage is applied to the source electrode 28, a switching voltage is applied to the gate electrode 24 to selectively turn on and off the TPT, a voltage is applied to the pixel electrode 25 via the source electrode 28, and a voltage is applied to the pixel electrode 25 and the counter electrode 29. The liquid crystal exhibits electro-optical characteristics due to the electric field applied between the two, and arbitrary pixel display is performed.

Function> When a voltage is applied to the pixel electrode 25, charge is accumulated in the thin film capacitor formed between the pixel 1Xfi and the transparent conductor 11g23. This charge is released when T P T is turned off, but Fjl I11! Since the charge is retained in the capacitor, an electric field is applied for a certain period of time even after the OFF operation.
The on state of TPT is connected and the liquid crystal maintains its electro-optical properties. Therefore, high contrast display is possible.

In addition, the process is simplified and there is no need to pattern the gate electrode after a process such as the P-CVD method, so there is no defect in the gate electrode, there are few defects in other wiring, etc., and the circuit has capacitance. It has become possible to fabricate a thin film transistor array with element functions. <Effects of the Invention> As described above, the thin film transistor array of the present invention has a charge retention function and can drive a display at a high duty ratio, and also solves the problems that existed in the past. Increase in the number of processes, P-C
Defects caused by dust such as VD deposits and holes can be suppressed as much as possible, making it possible to display pixels on a liquid crystal panel with very few defects.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a conventional thin film transistor array having a charge retention function, and FIG. 2 is a cross-sectional view of an example of a thin film transistor array according to the present invention.
III! FIG. 3 is a cross-sectional view of the transistor array, and FIG. 3 is a plan view illustrating the outer periphery of the thin film transistor array of the present invention. 1.11...Glass substrate 2...First @edge film 3
...Second insulating film 4...Transparent conductive film 5...
Gate electrode 6... Pixel electrode 7... Semiconductor layer 9... Source electrode 12... Liquid crystal 22... Insulating film 24... Gate electrode 26... Semiconductor layer 28... Source electrode 31 ...Liquid crystal 41...Pixel electrode 43...Insulating film opening 8...Drain electrode IO...Counter electrode 2130...Glass base 1 23...Transparent conductor 11 25... Pixel electrode 27...Drain electrode 29...Counter electrode 42...Transparent conductive film 44...Removal: i-pole Figure 1 Patent letterpress representative edition Printer's application printing Suzuto style

Claims (2)

[Claims] (1) In a thin film transistor array that has a charge retention function by providing a conductive film layer facing the pixel electrode connected to the thin film transistor and to which a display driving voltage is applied via an insulating film, the gate electrode and the conductive film A thin film transistor array characterized in that layers are formed on the same plane. (2) The thin film transistor array according to claim 1, wherein the conductive film layer is connected to the outside through an opening in the insulating film at the outer periphery of the thin film transistor array.