JPH06112487A - Manufacture of insulating film and thin film transistor element provided therewith - Google Patents

Abstract

PURPOSE:To obtain an anodized film dense and with no film defect when a substrate of a large area is anodized. CONSTITUTION:An Al:Ta film is deposited on a glass substrate 1, and a gate electrode 2 is formed as thick as 3000Angstrom through photolithography and etching (figure a). The surface of the electrode 2 is thermally treated at a temperature of 400 deg.C for 15 minutes to form a thermal oxide film as thick as 2000Angstrom (figure b). An Al2O3 film 4 is formed as thick as 2000Angstrom through an anodizing process (figure c). A second SiNX gate insulating film 5, an a-Si semiconductor layer 6, and a channel stopper layer SiNX film 7 are consecutively formed as thick as 2000Angstrom , 500Angstrom , and 1000Angstrom respectively through a P-CVD method (figure d). The channel stopper layer SiNX film 7 is selectively etched to serve as a channel stopper layer (figure e). Al is deposited through a sputtering process and turned into a source electrode 8 by photolithography and etching (figure f).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an insulating film which can be used in a liquid crystal display device and the like, and to a thin film transistor element using the same and a switching element suitable for preventing a short circuit between a gate electrode and a source electrode.

[0002]

2. Description of the Related Art An amorphous silicon thin film transistor (hereinafter abbreviated as a-SiTFT) is a gate electrode made of Al on an insulating substrate such as glass or quartz, and an Al on the gate electrode.
A gate insulating film formed by anodizing
It was composed of a SiNx gate insulating film formed by P-CVD, an a-Si semiconductor layer, a SiNx layer provided on the semiconductor layer, and a source electrode made of Al.

[0003]

[Problems to be Solved by the Invention]
When a gate insulating film is formed on a large-area substrate of inches or more by anodic oxidation, there are the following problems. That is, in the case of a large area, the anodizing current becomes very large, so that electric field concentration occurs in the non-uniform portion of the anodized electrode surface. As a result, a defect was generated in the anodic oxide film, which became a defect in the gate insulating film, and finally resulted in a short circuit between the gate electrode and the source electrode.

It is an object of the present invention to provide an a-Si TFT element in which a short circuit between a gate electrode and a source electrode does not occur by eliminating defects in an anodized film on a large area substrate.

[0005]

In order to achieve this object, the switching element of the present invention is characterized in that a thermal oxide film is formed on the surface of the gate electrode before the anodization of the gate insulating film. The method is to heat-treat the electrode surface before anodic oxidation in an oxygen or nitrogen atmosphere, and then to form a gate insulating film by anodic oxidation. Moreover, the thermal oxide film needs to be 100 Å or more.
About Å is enough.

[0006]

According to the present invention, when an electrode is formed on a glass substrate having a large area, and subsequently, an insulating film is anodized, a thermal oxide film is previously formed on the surface of the electrode and then anodized. Defects on the electrode surface can be repaired, and defects on the insulating film serving as the anodic oxide film can be eliminated. As a result, it is possible to prevent a short circuit phenomenon between the gate electrode and the source electrode in the thin film transistor element manufactured by the method for manufacturing a gate insulating film of the present invention.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) A first embodiment will be described with reference to FIG.

An Al: Si film is deposited on the glass substrate 1 by a sputtering method, and an electrode 2 is formed by photolithography and etching (FIG. 1a).

The electrode is heat-treated at 400 ° C. for 15 minutes in an oxygen atmosphere to form a surface oxide film 3 of about 300 Å (FIG. 1b).

An insulating film Al ₂ O ₃ film 4 having a thickness of 2000 Å is formed by anodizing using citric acid (see FIG. 1).
c).

The effect of heat treatment according to the embodiment of the present invention is shown in (Table 1).

[0013]

[Table 1]

The evaluation is performed by a pinhole check by a plating method. ○ pinhole density
Less than 0.001 pieces / mm ² , △: 0.1 to 0.01 pieces / mm ² , ×: 1 piece / mm ²
That is all.

Incidentally, when a sample under the oxidation condition, which was evaluated as ◯, was observed by SEM, it was found that a thermal oxide film of 200 Å or more was formed.

(Second Embodiment) A second embodiment of the present invention will be described with reference to (FIG. 2).

An Al: Ta film 2 is deposited on the glass substrate 1 and a gate electrode is formed by photolithography and etching (FIG. 2a).

A thermal oxide film 3 of about 200 Å is formed by heat treatment in a nitrogen atmosphere at 250 ° C. for 60 minutes (FIG. 2).
b).

A 2000 Å gate insulating film Al ₂ O ₃ film 4 is formed by anodic oxidation (FIG. 2c).

The second SiNx gate insulating film 5 is formed by the P-CVD method.
Then, the a-Si semiconductor layer 6 and the channel stopper layer SiNx film 7 provided thereon are continuously formed (FIG. 2d).

The SiNx film 7 is selectively etched to form a channel stopper layer (FIG. 2e). After forming Al8 by the sputtering method, the source electrode is formed by photolithography and etching (FIG. 2f).

Since the gate electrode 2 made of Al is apt to generate hillocks at high temperatures, a material mixed with impurities is used, and the mixed amount is preferably 1.5 wt% or more.

Comparing the switching element of the present invention with the switching element manufactured by the conventional method, the conventional method generated a short circuit between the gate and the source in 5 of 10 samples. Then, the short-circuit phenomenon did not occur.

[0024]

As described above, according to the present invention, a dense anodic oxide film having no film defects can be obtained when anodizing a large-area substrate. As a result, the yield of the switching element can be improved without causing a short circuit between the gate electrode and the source electrode due to the defect in the gate insulating film.

[Brief description of drawings]

FIG. 1 is a process chart showing a method of manufacturing an insulating film according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method of manufacturing a thin film transistor element according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Glass Substrate 2 Electrode 3 Thermal Oxide Film 4 Insulating Film 5 Second Gate Insulating Film 6 Semiconductor Layer 7 Channel Stopper Layer 8 Source Electrode

Claims (3)

[Claims] 1. A thermal oxide film or a nitride film is formed on the electrode by 100.
Å A method for manufacturing an insulating film, which comprises forming the insulating film by an anodic oxidation method after forming it to a thickness of Å or more. 2. The method for producing an insulating film according to claim 1, wherein the insulating film contains Al as a main component. 3. A thin film transistor element, wherein a gate insulating film is formed by using the anodic oxidation method according to claim 1.