JPS63100777A - Pattern forming method of transparent electrode - Google Patents

Abstract

PURPOSE:To obtain a transparent electrode pattern, through which breakdown and a defective contact are not generated, by a method wherein a substrate is kept at 200 deg.C or more, the film formation of an InSn oxide is started through an ion plating method, the film of the oxide is formed, while lowering the temperature of the substrate gradually, and a predetermined electrode pattern is shaped through photoetching. CONSTITUTION:An ITO film 2 is formed onto a glass substrate 1 through an ion plating method, while lowering the temperature of the substrate 1 gradually from a temperature of 200 deg.C or more. The ITO film 2 is etched, using a resist pattern 3 as a mask, and the resist pattern 3 is removed. A drain electrode 2-1 and a source electrode 2-2 consisting of the ITO film are shaped, and an a-Si film 4, an SiN film 5 and a gate electrode 6 are formed, thus acquiring a thin-film Tr.

Description

[Detailed Description of the Invention] [Summary] In a method for forming patterns of transparent electrodes used in thin film transistors that drive liquid crystal display elements, indium, which becomes the transparent electrode, is added to the substrate in order to prevent short circuits between electrodes and poor connections between the electrodes. When forming a tin oxide film by ion plating, the temperature of the substrate is gradually lowered from 200° C. or higher to form a tapered edge-shaped transparent electrode pattern.

[Industrial application field]

The present invention relates to a method for forming patterns of transparent electrodes of thin film transistors that drive liquid crystal display elements.

The thin film transistor of the liquid crystal display element drives the liquid crystal display element arranged in a matrix. Therefore, the transparent electrodes of the thin film transistor intersect in large numbers on the substrate. If even one of these intersection points is short-circuited, the wiring passing through the intersection becomes line defective. In addition, if the connection (contact) between the transparent electrode and the active semiconductor is poor, a point defect occurs.

Therefore, there is a need for a transparent electrode pattern forming method that does not generate line defects or point defects.

[Conventional technology]

FIG. 4 is a diagram showing a conventional transparent electrode pattern forming process.

Figure 4 (In the step of al, the glass substrate l is
While maintaining the temperature at 0° C., an indium tin oxide film (hereinafter referred to as 1i1TO film) 20 is formed.

In the next step shown in FIG. 4('b), the resist pattern 3 is ITOIl! to form the drain and source electrodes. 2
Formed on 0. After this, as shown in Figure 4 (in step C1)
The film 20 is etched based on the resist pattern 3 to form a drain electrode 20-1 and a source electrode 20-2, and the resist pattern 3 is peeled off.

In the next step of FIG. 4 (dl), an active semiconductor layer 4 made of amorphous silicon (a-3i), a gate insulating layer 5 made of silicon nitride (SiN), and a gate electrode 6 are sequentially formed on these electrodes. At this time, the source electrode 20-2
is connected to the display electrode.

[Problem that the invention seeks to solve]

Although thin film transistors are formed as described above,
In order to make the electrodes made of ITO film, that is, the drain electrode 20-1 and the source electrode 20-2, have low resistance, the film thickness is set to 2.
It is necessary to make the film as thick as 000 or more, and due to this thick film, this a-SiJ'i
j grows abnormally, resulting in dielectric breakdown at the ITO film pattern edge, that is, a short circuit between the gate electrode 6 and the source electrode 2o-2 or the drain electrode 20-1, and a-5i layer 4 and the ITO layer.
There was a problem in that poor film connection (contact) occurred.

The object of the present invention is to provide a transparent electrode pattern forming method that does not cause dielectric breakdown or poor contact in view of the above-mentioned conventional situation.

[Means for solving problems]

ITOy on the substrate using ion plating method! When forming the film, film formation is started while keeping the substrate at 200° C. or higher, and as the film formation progresses, the substrate temperature is gradually lowered to below zoo'c.

[Effect]

ITO film formation is carried out while gradually lowering the temperature, so when the next ITO II pattern is formed by etching, the etching rate changes and the etched ITO II pattern is formed by etching.
The edges of the TO[9] pattern have a tapered shape, and as a result, abnormal growth does not occur near the edges when forming the next a-Si layer, thereby preventing dielectric breakdown and contact failure.

〔Example〕

FIG. 1 is a process diagram showing a method for forming a pattern of a transparent electrode of a thin film transistor according to the present invention. First, in the step shown in FIG. 1(a), the ITO film 2 is formed on the substrate by the ion plating method while the glass substrate Fi1 is gradually heated from a temperature of 200'C or higher to a temperature of 200C or lower. The relationship between the time required for film formation and the substrate temperature is shown in FIG.

The following process in Figure 1 ('b) is the same as the conventional process, and the ITO
After etching the film 2 using the resist pattern 3 as a mask, when the resist pattern 3 is removed, I↑0 model 2 has a cross-sectional shape as shown in Figure 1 (C1).At this time, the etching rate is is changing, and ITO
The edges of the film 2 are etched into a tapered shape with an open surface.

This is based on the experimental data of substrate temperature or annealing temperature and etching rate shown in FIG. The solid line shows the case where a hydrofluoric acid-based etching solution is used, and the dashed line shows the case where a mixed solution of ferric chloride and hydrochloric acid is used.

The etching solution used in this example was a mixed solution of ferric chloride and hydrochloric acid. Erasing gray at point A after patterning) 1) For an ITO film having an etching rate of 00 n/min, the etching rate increases to 500 n++/min or more by lowering the substrate temperature to 200° C. or less. Taking note of this experimental result, we are gradually lowering the substrate temperature.

That is, the ITO film formed first during the film forming time shown in FIG. 2 has a low etching rate, so there is little side etching, and the rTO film formed later is, for example, at point B, and has a high etching rate, so side etching is small. The etching is also large. Therefore, a desired tapered shape can be obtained.

A transparent electrode, that is, a drain electrode 12 made of this ITO film
After forming a pattern of -1 and source electrode 2-2,
In the process of Fig. 1+d), the a-5i layer 4 and Si
N layer 5 and gate electrode 6 are formed in sequence.

〔effect〕

As is clear from the above description, according to the present invention, patterned ITOll1j! having a tapered shape!
can be used as the source and drain electrodes, preventing short circuits and improving the contact condition, which is effective in producing a high-quality one-mock transistor.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing the transparent electrode pattern forming method according to the present invention, Fig. 2 is a substrate temperature state diagram during ITO film formation of the present invention, and Fig. 3
The figure is a diagram showing the relationship between the etching rate and temperature of an ITO film produced by the ion plating method, and FIG. 4 is a process diagram of conventional transparent electrode pattern formation. In the figure, 1 is a glass substrate, 2 is an ITO film, and 3 is a resist pattern. A (Li Koming l two islands Ω to B month electric failure Qn Tsuma turn pull to Kem E Hou j 〔D light 1 Fig. 2 I>fL-ra 1-゛, 5-te-1-i bottom; Gilet T; 1-cho Omeko/Nonani) JAmeh ball No. 33

Claims (3)

[Claims] (1) When forming an electrode pattern of indium tin oxide on a substrate, keep the substrate at 200°C or higher and start forming the indium tin oxide film using the ion plating method, and gradually lower the temperature of the substrate. 1. A transparent electrode pattern forming method, characterized in that the indium tin oxide film is formed into a predetermined electrode pattern by photo-etching. (2) The transparent electrode pattern forming method according to claim 1, wherein the substrate on which the electrode pattern is formed is heat-treated at 200° C. or higher. (3) The method for forming a transparent electrode pattern according to claims 1 and 2, wherein the indium tin oxide electrode is a source/drain electrode of a thin film transistor.