JPS61290712A - Manufacture of amorphous semiconductor film - Google Patents

Abstract

PURPOSE:To manufacture a good-quality amorphous silicon film by controlling the quantity of a remaining surfactant on the surface of the substrate by carrying out a later treatment after a washing process. CONSTITUTION:The washed surface of a substrate is exposed in the atmosphere of glow discharge of a selected gas and a remaining impurity (especially nitrogen) on the surface of the substrate is removed by a post-treatment. In this case, the selected gas means, e.g., oxygen or hydrogen. The later treatment is done for approx. several minutes. Further, an amorphous silicon film is formed to the first thickness by glow discharge as the first stage and then an impurity such as oxygen or nitrogen mixed in the first thickness amorphous silicon film is removed by introducing a gas of CF4+O2 into a reaction chamber. Then, the amorphous silicon film is formed to a desired thickness without removing the vacuum in the reaction chamber. This enables to obtain a good-quality amorphous silicon film on the substrate.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a method for manufacturing an amorphous semiconductor film on an insulating substrate, and more specifically, a method for manufacturing amorphous silicon on a substrate such as quartz or alumina. It's about how to do it.

BACKGROUND OF THE INVENTION It is required to manufacture amorphous silicon films having a relatively large area for use in various devices such as life-size optical sensors, thin film transistors, and solar cells. For this purpose, an amorphous silicon film is manufactured on an insulating substrate such as quartz or alumina by a glow discharge method or the like.In this case, as shown in FIG. A residual impurity layer 2 mainly containing nitrogen is formed interposed between the amorphous silicon film 3 and the amorphous silicon film 3 to be manufactured. The electrical characteristics are also deteriorated.

Dry etching, which is exposed in a normal CF4+02 glow discharge atmosphere, is not suitable for insulating substrates, especially quartz and alumina.
It is difficult to etch the surface of the substrate and therefore it is impossible to remove residual material from the substrate surface. Also, CF4+H2
When exposed to a glow discharge atmosphere of 5iO20
Although the surface can be etched and residual impurities can be removed from the surface, problems with adhesion and electrical properties with films formed on the surface are inevitable because the surface is exposed. be.

Purpose The present invention has been made in view of the above points, and provides a method for manufacturing an amorphous semiconductor film that can eliminate the drawbacks of the prior art as described above and improve adhesion strength and electrical properties. The purpose is to provide.

Structure As a result of extensive research, the inventor of the present invention found that the reason for the deterioration and dispersion in the adhesion strength of amorphous silicon films formed on insulating substrates is mainly due to the amount of nitrogen present on the substrate surface, especially the amino groups. , and found that it is dominated by surfactants such as ammonia ions. Such surfactants are used in a cleaning process to clean the surface of an amorphous silicon film before forming an amorphous silicon film on a substrate such as quartz or alumina. The present invention provides a method for manufacturing a high-quality amorphous silicon film on a substrate by controlling the amount of surfactant remaining on the surface of the substrate through treatment.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

When forming an amorphous silicon film on an insulating substrate such as quartz or alumina, the substrate is usually placed in a reaction chamber, a prescribed reaction gas is introduced into the reaction chamber, a glow discharge is generated, and the film is deposited on the substrate. Amorphous silicon is deposited. In this case, the surface of one substrate is cleaned with a surfactant and then an amorphous silicon film is formed by glow discharge. In the present invention, after the cleaning process, instead of forming an amorphous silicon film immediately, the cleaned substrate surface is exposed to a glow discharge atmosphere of a selected gas for post-treatment to eliminate impurities remaining on the substrate surface. In particular, nitrogen) is removed. The selected gas in this case is preferably oxygen or hydrogen, for example.

Also, this post-processing lasts for about several minutes.

Furthermore, in a preferred embodiment, after performing the above-mentioned post-treatment, as a first step, an amorphous silicon film is formed to a first thickness of about 500× by a glow discharge method, and then a CF4+02 (about 500×) film is formed. 5 cm) of gas is introduced into the reaction chamber to remove impurities such as oxygen and nitrogen mixed into the amorphous silicon film of the first thickness. Next, without releasing the vacuum in the reaction chamber, an amorphous silicon film is again formed to a desired thickness. With such gloss, it becomes possible to further improve the adhesion strength between the amorphous silicon film and the substrate.

The table in Figure 2 compares the elemental analysis results and film properties of amorphous silicon films manufactured according to the present invention (Example 1 and Example 2) with those manufactured by the conventional method (Example 3). This is shown below. Note that ESCA is electron spectrochemical analysis. As is clear from the results shown in the table of FIG. 2, the peel strength of the conventional example (Example 3) has a lower level of peel strength than that of the present invention (Examples 1 and 2). Also, the optical response time (rise time) is about three times as long.

In addition, the definition of photoresponse time is 3rd v! It is shown at the voltage rise time shown in ta3 figure (b) when a photonoise pulse as shown in J (a) is irradiated, and tr is from 'min to Vt=V
It is the time to rise to min + O* 9 (Vmaz-vrrlin).

The reason why the performance of conventional products is inferior in this way is thought to be mainly due to nitrogen as an impurity remaining on the substrate surface, which diffuses into the amorphous silicon film and enters the semiconductor film. This seems to be to create a donor level in the . Excitation of electrons from the valence band to the conduction band by light is less likely to occur due to donor level drag or buttrap. Therefore, carriers are difficult to generate in the conduction band, photocurrent does not flow immediately, and the response time tr increases.

Effects As described in detail above, according to the present invention, it is possible to increase the adhesion strength between the insulating substrate and the amorphous silicon film, and it is also possible to shorten the photoresponse time. Furthermore,
It is possible to reduce irregularities in characteristics.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an amorphous silicon film manufactured by the conventional technique, FIG. 2 is an explanatory diagram showing a table comparing the present invention and the conventional technique, and FIGS. b) is an explanatory diagram showing the definition of photoresponse time. (Explanation of symbols) 1: Insulating substrate 2: Residual impurity film 3: Amorphous silicon film

Claims (1)

[Claims] 1. In a method for manufacturing an amorphous semiconductor film on an insulating substrate, the surface of the substrate is cleaned and then exposed to a glow discharge of a selected gas for a predetermined period of time to form a glow on the surface. A method characterized by manufacturing an amorphous semiconductor film by a discharge method. 2. The method according to item 1 above, wherein the amorphous semiconductor film is an amorphous silicon film, and the substrate is made of quartz or alumina. 3. The method according to item 1 or 2 above, wherein the selected gas is oxygen or hydrogen. 4. In the above item 3, after forming the amorphous silicon film to a predetermined first thickness, CF_4+O_2 (5%)
A method characterized in that impurities mixed into the film of the first thickness are removed by exposing the film to a mixed gas of: 5. The method of item 4 above, wherein the first thickness is about 500 Å. 6. In the above item 4 or 5, after the step of removing impurities, an amorphous silicon film of a second thickness is formed again on the film of the first thickness without releasing the vacuum in the reaction chamber. A method characterized by forming a film.