JPH03240027A - Display device - Google Patents

Abstract

PURPOSE:To improve DC cutting performance and its reliability and to reduce the cost by oxidizing the surfaces of a source electrode, an electric conductor, and a drain electrode by an anode oxidizing method and covering them with insulators Al2O3. CONSTITUTION:On a transparent insulating substrate 1, a picture element electrode 2, a gate electrode, the electric conductor 3, a gate insulating film 4, a semiconductor layer 5, an etching stopper 6, an ohmic contact layer 7, the source electrode, the electric conductor 8, and the drain electrode 9 are formed to obtain a TFT array substrate, whose source electrode, electric conductor 8, and drain electrode 8 have their surfaces oxidized by the anode oxidizing method and covered completely with insulating films. Even if signals inputted to the source electrode, electric conductor 8, and drain electrode 9 contain DC components, they are absorbed by the Al2O3 of the films, so liquid crystal does not deteriorate. A DC cutting film is therefore not necessary and a DC leak is eliminated, so the display quality and manufacture yield can be expected to be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the reliability of a TFT array substrate and a display device using the TFT array substrate.

[Prior Art] A liquid crystal display device is usually constructed by a method in which a display material such as a liquid crystal is sandwiched between two opposing substrates, and a voltage is applied to the display material. At this time, pixel electrodes arranged in a matrix are provided on at least one of the substrates, and in order to selectively operate these pixels, an active element having nonlinear characteristics such as a TFT is provided for each pixel.

Conventionally, there are devices of this type as shown in FIGS. 3 and 4. FIG. 3 is a partial plan view of the conventional device, and FIG. 4 is a partial plan view of the conventional device.
The figure is a B-BIFi plane view of FIG. 3.

First, I to
(Indium Tin Oxide) is formed into a film. This is processed into a desired pattern by photoetching or the like to form a pixel electrode (2), an electrode terminal, etc. Second, a film of high melting point metal such as Cr or Mo is formed by sputtering or the like, and patterned in the same manner to form gate electrodes, wiring, etc. (3). Thirdly, SiO2 or SiN is used as the gate insulating film (4), and 1-a- is used as the semiconductor layer (5).
Si:H, poli-Si, and SiN or SiO2 as an etching stopper (6) are continuously exposed to plasma carbon.
A film is formed using a VD method or the like. Fourth, contact holes for source and drain contacts are formed in the etching stopper, and after pretreatment, a film of n-a-3i:H is formed as an ohmic contact layer (7) for the source and drain by plasma CVD or the like. . Fifth, a contact hole is formed to connect the pixel electrode and the drain electrode (9). Sixth, a film of Al/Cr, Al/MO, etc. is formed by sputtering or the like, and patterned to form a source electrode/wiring (8) and a drain electrode (9). At this time, depending on the pattern or process, A l ((
8-1) and (9-1)) and Cr(orMo)
The film formation or pattern processing ((8-2) and (9-2)) may be divided into two steps.

Thereafter, na-Si:H remaining between the source electrode and the drain electrode is removed. Finally, an insulating film such as SiN or Si02 is formed as a TFT insulator (10) by plasma CVD or the like and patterned.

The following TFT array substrate is constructed. Opposed to this TFT array substrate is a counter-type Pi substrate provided with transparent electrodes, color filters, etc., and a liquid crystal flat display is constructed by sandwiching a liquid crystal or the like between the two.

[Problems to be Solved by the Invention] When forming the TFT array substrate as described above, the protective film (10) formed last is designed to cut the DC component of the signal input to the source electrode/wiring and drain electrode. There is also a role to play. However, when Al used for the source electrode, wiring, and drain electrode, hillocks (12) grow when SiN or Si02 is formed or by heating (WaX approximately 300°C) during other processes, and this YaSi
In order to cover with 02 etc., a considerable film thickness (1.5 μm) or more is required (normally, it cannot be covered as shown in FIG. 4). However, with such a thick film, the signal entering the pixel electrode is attenuated, causing no voltage to be applied to the liquid crystal, or requiring the development of pattern processing and etching techniques to prevent this.

The present invention has been made to solve the above problems, and involves oxidizing the surfaces of the source electrode, wiring, and drain electrode by anodizing, and covering the surfaces of the source electrode, wiring, and drain electrode with an insulator, Al2O3. The purpose of this invention is to improve DC cut performance and its reliability, and to reduce costs by eliminating the expensive protective film formation process in the above-mentioned TFT array substrate formation process.

[Means for Solving the Problems] A display device according to the present invention oxidizes the Al surface of the source electrode/wiring and drain electrode by an anodic oxidation method using an ammonium tartrate solution or the like. It has a structure in which AI is covered with an insulator Al2O.

[Function] In the display device of the present invention, the Al surfaces of the source electrode, wiring, and drain electrode are oxidized by an anodic oxidation method using an ammonium tartrate solution, etc., so that the Al of the source electrode, wiring, and drain electrode becomes an insulator Al2O3. The covered structure not only eliminates the need for the DC cut film used in the conventional method, but also completely eliminates DC leakage. The structure of a liquid crystal flat display using this will be explained.

1 and 2 are diagrams showing the configuration of the present invention. FIG. 1 is a partial plan view of the TFT array substrate of the present invention, and FIG.
It is an A-Alyt side view of a figure.

First, approximately 1,000 people deposit ITO on a transparent insulating substrate (1) using the EBi deposition method or sputtering method, and pattern this using photoetching methods to form pixel electrodes (2), electrode terminals, etc. do. Second, about 2000 people deposited a high-melting point metal such as Cr by sputtering, patterned it, and connected the gate electrode/wiring (3), gate and source terminal wiring, and the outer periphery of the TFT array. Short ring.

Then, an anodic oxidation pad connected to the short ring is formed. Third, Si07 or SiN as the gate insulating film (4) is deposited by 1,000 to 5,000 layers, and the semiconductor layer (
5) as 1-a-3i:H or poli-Si as 1
00-2000 people, and etching stopper (6)
A film of 2,000 to 3,000 SiN or SiO2 is continuously formed using a plasma CVD method or the like. Fourth, contact holes for source and drain contacts are formed in the etching stopper, and after pretreatment, a film of n-a-3i:H is formed as a source and drain contact layer (7) by plasma CVD or the like. Fifth, a contact hole is formed to connect the pixel electrode (2) and the drain electrode pi (9). sixth, A l /Cr and A l /
A film of Mo or the like is formed by a sputtering method or the like, and patterned by a photoetching method or the like to form a source electrode/wiring (8) and a drain electrode (9). At this time, Al((8
-1) and (9-1)) and Cr (Mo) ((
8-2) and (9-2)) may be formed and processed separately. In addition, the film thickness of Cr(Mo) is 1000 to 20
00 people, and Al about 5,000 to 10,000 people. Seventh, an oxide film (11) of approximately 500 to 5,000 layers is formed on the Al surface of the source/drain electrode by an anodic oxidation method using an ammonium tartrate solution, an oxalic acid solution, or the like. Finally, the remaining n-
a-Si:H etc. are removed by etching.

The TFT array substrate of the present invention is constructed as described above. A counter electrode substrate provided with transparent electrodes, color filters, etc. is provided opposite to this TFT array substrate, and a display material such as liquid crystal is sandwiched between the two, thereby constructing the liquid crystal flat display of the present invention.

[Effects of the Invention] As described above, according to the present invention, Al of the source electrode/wiring and drain electrode is completely covered with Al2O (insulating film), so that Al2O is input to the source electrode/wiring and the drain electrode. Even if a DC component occurs in the signal, this Al
Since it is absorbed by 2O3, it does not deteriorate the liquid crystal.

This Al2O film is formed by an anodic oxidation method using a solution, so a uniform film without pinholes can be formed.
Before starting this anodic oxidation process, it is assumed that hillocks (12
) occurs, in the case of anodic oxidation, Al2O is formed to cover the entire hillock, so coverage defects that occur when another insulating film is deposited on the hillock will not occur. DC leakage at the level of point defects does not occur.

Therefore, if the structure of the present invention is used to create a TFT array substrate and a flat liquid crystal display, the DC
Not only does a cut film become unnecessary, but also DC leakage can be completely eliminated, so improvements in display quality and manufacturing yield can be expected.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the main parts of a TFT array substrate used in a liquid crystal display device δ according to an embodiment of the present invention. Fig. 2 is an A-Alti plane view in Fig. 1, Fig. 3 is a plan view showing the main parts of a TFT array substrate used in a conventional liquid crystal display device, and Fig. 4 is a sectional view taken along B-B in Fig. 3. It is. In the figure, (1) is a transparent insulating substrate, (2) is a pixel electrode,
(3) is the gate electrode/wiring, (4) is the gate insulating film, (
5) is a semiconductor layer, (6) is an etching stopper (7)
is an ohmic contact layer, (8 is a source electrode/wiring,
(8-1) is Al, (8-2) is Cr orMo
, (9) is the drain electrode, (10) is the ys retention film, (11
) is an anodic oxide film Al2O3, and (12) is a hillock. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] At least ITO (Ind.
A pixel electrode formed of a transparent conductive film such as (Ium Tin Oxide), a gate electrode formed of a high melting point metal such as Cr or Mo, a gate insulating film formed of an insulator such as SiN or SiO_2, ia- Si:H or po
Semiconductor layer formed of li-Si etc., SiN and SiO_
Etching stopper formed of a second grade insulating film, n-
A thin film transistor (hereinafter referred to as TFT) array substrate having source and drain contact layers formed of a-Si:H etc., and lease electrodes and drain electrodes formed of Al/Mo, Al/Cr etc., and the above TFT
In a matrix display device in which a display material such as a liquid crystal is sandwiched between an array substrate and a counter electrode substrate having transparent electrodes, color filters, etc., source electrodes, wiring, and drain electrodes are formed by anodizing using an ammonium tartrate solution, etc. A TFT array substrate and a matrix type display device characterized in that the Al surface of the substrate is oxidized and the Al of the source electrode, wiring, and drain electrode is covered with an insulator Al_2O_3.