JPH0282616A - Formation of amorphous semiconductor thin film - Google Patents

Abstract

PURPOSE:To enhance the quality of a thin film by controlling the energy of irradiation beam from an electron gun or an ion gun, decomposing stock gas, and forming a thin amorphous semiconductor film on a substrate by the reaction of generated film radical. CONSTITUTION:The energy of an electron beam Eb is controlled under the control of an accelerating voltage of an electron gun 8, and raw gas to be supplied toward a substrate 4 from diffusing holes of a diffuser 6 by the energy of the beam Eb is decomposed. Thus, film radical is generated, and a thin film is formed on the substrate 4. Since the energy of the beam Eb can be accurately controlled, the generation of the film radical for causing the distur bance of forming a thin film of high quality us suppressed, and the generation of the film radical which contributes to the formation of the thin film of high quality can be promoted. Thus, the quality of the film can be controlled, and an amorphous semiconductor thin film of high quality can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming an amorphous semiconductor thin film on a substrate by decomposing a source gas.

[Conventional technology]

In general, chemical vapor deposition (CVD) is a method of decomposing a raw material gas containing the elemental element of the material desired to form a thin film fζ and forming a thin film on a substrate. As described on pages 141 to 149 of , plasma CVD, MCVD, and optical CVD are broadly classified depending on the method of applying energy to decompose the source gas.

By the way, in plasma CVD, a raw material gas is turned into plasma by high-frequency glow discharge or microwave discharge, and the raw material gas is decomposed by the energy of electrons in the plasma to generate active radicals and ions, and a thin film is formed on a substrate at a low temperature. This is the way to do it.

Next, thermal CVD is a method in which a substrate is heated to a high temperature using resistance heating, high-frequency induction heating, etc., raw material gas is decomposed by thermal energy, and a thin film is formed on the substrate through a chemical reaction on the substrate surface. CVD uses a low-pressure mercury lamp, excimer laser, etc. as a light source, and uses the energy of the light irradiated by these light sources to excite gas molecules such as H and Ar to generate excited volatiles, and the energy of these excited species decomposes the source gas. However, this is a method of forming a thin film on a substrate through a chemical reaction on the substrate surface.

[Problem to be solved by the invention]

Among the methods described in the conventional technology, in the case of plasma CVD, the energy of electrons in the plasma has a wide distribution ranging from 0 to several 1 Oev, so there are many types of film-forming radicals generated by decomposition of the raw material gas. When SiH4 as a gas is decomposed, 5i)(a).

Film-forming radicals of SiH2, SrH, and Si are generated,
When forming a thin film of amorphous Si:H (hereinafter referred to as a-3i:H), the film formation process of fζ, a-5i:H becomes complicated, and it is difficult to control the film quality of the formed thin film and achieve high quality. The problem is that it is extremely difficult to

On the other hand, in the case of thermal CVD, the thermal energy is 0 to about toev
Because of the distribution of
There are similar problems as in the case of

In addition, in the case of photoCVD, the energy of the excited species that decomposes the source gas is uniquely determined by excitation 1, so the film-forming radicals generated by selecting the excited species are uniquely determined, and the energy of the excited species that decomposes the source gas is uniquely determined. It is extremely difficult to accurately control the energy of
It is impossible to easily improve quality.

Therefore, the present invention was made with the above-mentioned points in mind, and the energy of the irradiation beam consisting of an electron beam or an ion beam is
Accurate control by controlling the acceleration voltage of the electron gun or ion gun promotes the generation of film-forming radicals that contribute to the formation of high-quality thin films, making it possible to control film quality and improve the quality of the formed amorphous semiconductor thin film. The purpose is to make it easier to achieve Eζ.

[Means to solve the problem]

In order to achieve the above object, in the method for forming an amorphous semiconductor thin film of the present invention, a substrate is disposed in a reaction chamber, a raw material gas is supplied to the reaction chamber in the direction of the substrate, and an electron gun is provided in the reaction chamber. An irradiation beam consisting of an electron beam or an ion beam from an ion gun is irradiated, the energy of the irradiation beam is controlled by controlling the acceleration voltage of the electron gun or the ion gun, and the energy of the irradiation beam is is decomposed to generate film-forming radicals, and the generated film-forming radicals react on the surface of the substrate to form an amorphous semiconductor thin film on the substrate.

[Effect]

With the above configuration, the energy of the irradiation beam consisting of a 9-element beam or an ion beam is accurately controlled by controlling the accelerating voltage of the 9-element gun or ion gun,
This irradiation beam decomposes the source gas and promotes the generation of film-forming radicals that contribute to the formation of a high-quality thin film, making it possible to control film quality and obtain a high-quality amorphous semiconductor thin film.

〔Example〕

Examples will be described with reference to the drawings.

(Example I) First, FIG. 1F showing the first embodiment will be explained.

In FIG. 1 showing the forming apparatus, (1) is a vacuum container, (
2) is a reaction chamber formed in the container (1), (3) is a substrate heating means installed on the upper surface of the container (υ), (4) is a substrate held in the heating means (3), (5) is a raw material gas supply pipe whose tip end is introduced into the lower part of the reaction chamber (2);
6) is a raw material gas blowing part attached to the tip of the supply pipe (5) and has a plurality of blowing holes, (7) is a gas outlet formed on the bottom surface of the container, and (8) is an electron gun. is provided outside the container (1), and irradiates the reaction chamber (2) with an electron beam (Eb), which is an irradiation beam, through an irradiation hole (9).

At this time, the energy of the electron beam (Eb) decomposes the source gas supplied toward the electron gun substrate (4).

When a thin film of a-3+2H is formed using the above-mentioned apparatus, SiH4 gas is used as the source gas ζ
From ζ, SiH is formed by the energy of the electron beam (Eb).
4 gas is decomposed, film-forming radicals containing Si are generated, and a thin film of a-3i:H is formed on the substrate (4).

At this time, due to the energy of the electron beam (Eb), S
The production process of film-forming radicals by decomposition of iH4 gas is as follows: @ e+5iH4-3iH2+H2+e (a
t t, 9ev) e+5iH4-3iHa-1-H
−) −e (at 8.9ev) @ e″″−+−
3iH4→Si+2Hz+e (at 4.2
eV) and the process C is not necessary, by reducing the energy of the electron beam (Eb) to less than 4.2 eV, the process of generating film-forming radicals excluding the process O is realized. can. Note that e represents an electron.

By the way, using the apparatus shown in FIG. 1, the substrate temperature was set to 150
'C, reaction pressure lx 103Torr, 5iH4u
Let the flow rate be IQsccM, i Baby A (Eb) (
y) x energy 'e L9eV, electron current density 0.1
7) E
SR[Electron 5pin Re5onanc
e] As a result of measuring the spin density, the conventional I
``cm'' d > 5 cut d'cm, and this a
-3i: The conversion efficiency of the pin type solar cell using the Hfei layer was improved by about 10% compared to the conventional one.

By controlling the energy of the electron beam (Eb) to 3, geV tζ by controlling the acceleration voltage of the electron gun (8), the decomposition of the 5iHa gas, which is the raw material gas, becomes a factor that inhibits the formation of a high-quality thin film. Highly excited state S
As shown in the above-mentioned 0,O process, the film-forming radicals of SiH2,5iHa, which contribute to the formation of a high-quality thin film, were generated, while the film-forming radicals of i and SiH were not generated. A thin film of 5i:H was obtained.

Therefore, according to Example 1, the energy of the electron beam (Eb) can be precisely controlled by controlling the accelerating voltage of the electron gun (8), so that formation radicals, which are a factor that inhibits the formation of a high-quality thin film, are generated. At the same time as suppressing
When the obtained thin film is applied to, for example, a solar cell, the conversion efficiency can be significantly improved fζ compared to the conventional method.

(Example 2) For now, let us explain with reference to FIG. 2f, which shows the second embodiment.

In the 22nd box showing the forming device, the same symbols as in Figure @1 indicate the same or equivalent ones, and αQ is the reaction chamber (2).
an ion gun installed at the bottom of the substrate (4) for irradiating the substrate (4) with an Ar ion beam (Ib) at ±;
01) is a DC power supply for bias, which applies a positive bias to the substrate (4) fζ, and the ion beam (Ib) is directly applied to the substrate (4).
).

At this time, control of the acceleration voltage of the ion gun QO [therefore,
The energy of the ion beam (Ib) is controlled in the same manner as in the first embodiment.

Then, using the above-mentioned apparatus, SiH4 is used as the raw material gas.
Using gas and CH4 gas, the substrate temperature is aooc.

The reaction pressure was 0.2 Torr, and the SiH4 gas flow rate was t.
ooSCCM, CH4 gas flow rate 11005CC, Ar
When a thin film of a-5iC:H was formed using the energy of the Hanawa ion beam (Ib) as LOOeV, the ion current density as 1 mA/cm, and the bias voltage of the substrate (4) as +100V, the resulting aSiC:H4 film The bandgap was 2.3 eV and the photoconductivity was >109 cm, which is about two orders of magnitude higher than that of the conventional method.

This is because in conventional plasma CVD, the energy of most of the electrons in the plasma is below toeV, which inhibits the formation of ions. (I
By controlling the energy in b) to a high value of tooev, 20 to 30% of CH4 gas is decomposed into CH or C, and by the generation of these CH and C film-forming radicals, a dense 5i-C regular tetrahedron is formed. Since a physical network was formed, a high-quality a-3iC:H thin film with high photoconductivity was obtained.

+ Also, since a positive bias was applied to the substrate (4) to prevent the Ar ion beam (tb) from directly hitting the substrate (4), damage to the film surface due to the ion beam (Ib) was prevented, and film quality deterioration was prevented. Prevented.

Therefore, according to the second embodiment, the energy of the Ar ion beam (Ib) can be precisely controlled by controlling the acceleration + voltage of the ion gun GO, so that, as in the case of the first embodiment, a high-quality thin film can be formed. High-quality a-3iC:
An amorphous semiconductor thin film such as H can be formed.

(Example 3) Furthermore, FIG. 3 showing Example 3 will be explained.

In FIG. 3 showing the formation device, the same symbols as in FIG. The head of the ion gun that irradiates is a neutralizer installed near the ion beam irradiation port of the ion gun (2), which neutralizes the H ion beam to create a neutral H atom particle beam ( cb), and the source gas is decomposed by the energy of this neutral particle beam (cb).

At this time, the energy of the H ion beam is controlled and the energy of the particle beam (cb) is controlled by controlling the accelerating voltage of the ion gun (2) in accordance with the first embodiment described above.
．． It is the same as 2.

Then, using the above-mentioned apparatus, SiH4 is used as the raw material gas.
Using gas, the substrate temperature was 200C, and the reaction pressure was 10
Torr, SiH4 gas flow rate IO5ccM, H ion beam energy from ion gun (2)+ leV, ion current density Kwo0, 1mA/cm to form a-5i:H thin film. As a result of measuring the ESR spin density of the a-3i:H thin film, it was 8X10 an,
The conversion efficiency of the pin type solar cell used in this a-5i:H1ei layer was improved by about 15% compared to the conventional one.

This is done by controlling the energy of the ion beam of H0 to leV by controlling the acceleration voltage of the ion gun (2).

By controlling the energy of the particle beam (CB),
The SiH4+H-+5iHa-1-H+ process selectively generates 5iHa film-forming radicals, and these 5iHa film-forming radicals contribute to the formation of a high-quality thin film, resulting in a high-quality a-3i:H thin film. This is what was obtained.

Therefore, according to the embodiment 3f, by controlling the accelerator voltage of the ion gun @, the energy of the H ion beam can be controlled and the energy of the neutral particle beam (cb) can be controlled. As in the case, the generation of film-forming radicals that contribute to the formation of a high-quality thin film can be selectively promoted, and a high-quality amorphous semiconductor thin film such as a-3i:H can be formed.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

The energy of the irradiation beam consisting of an electron beam or ion beam can be precisely controlled by controlling the acceleration voltage of the electron gun or ion gun, so the energy of the irradiation beam decomposes the source gas, contributing to the formation of high-quality thin films. It is possible to promote the production of film-forming radicals, to control film quality, and to form high-quality amorphous semiconductor thin films, such as amorphous silicon solar cells Cζ
This is extremely advantageous in terms of improving conversion efficiency.

[Brief explanation of the drawing]

The drawings show an embodiment of the method for forming an amorphous semiconductor thin film of the present invention, and FIGS. 1 to 3 are schematic diagrams of I forming apparatuses of embodiment 1 to practical example 3, respectively. (2)...Reaction chamber, (4)...Substrate, (8)...
Electron gun, QO, Q2...Ion gun, (Eb)...Electron beam, (tb)...Ion beam.

Claims (1)

[Claims] (1) disposing a substrate in a reaction chamber, supplying raw material gas to the reaction chamber in the direction of the substrate, and irradiating the reaction chamber with an irradiation beam consisting of an electron beam from an electron gun or an ion beam from an ion gun; The energy of the irradiation beam is controlled by controlling the accelerating voltage of the electron gun or the ion gun, and the raw material gas is decomposed by the energy of the irradiation beam to generate film-forming radicals. A method for forming an amorphous semiconductor thin film, comprising forming an amorphous semiconductor thin film on the substrate by a reaction on the surface of the substrate.