JPH0645258A - Manufacture of amorphous semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain an amorphous semiconductor thin film having high quality at a high temperature by incorporating a short wavelength light source in an electrode, and applying optical energy to a deposited surface of the film. CONSTITUTION:An electric field is applied from a power source to an electrode and substrate holder 15 through an electrode 13. A short wavelength light source 16 such as a low-pressure mercury lamp, etc., is incorporated in the electric field applying electrode 13, and a discharge surface 17 of the electrode 13 is formed of a metal mesh, etc. Thus, a plasma region P between the electrodes 13 and 15 is irradiated with a light generated from the source 16 through the mesh perpendicularly to a substrate 20. Material gas 14 or other gas is introduced from a gas inlet 18 to plasma decompose it, and the substrate is simultaneously irradiated with a light from the source 16 to be deposited with a film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing an amorphous semiconductor thin film. More specifically, it relates to an apparatus for producing an amorphous semiconductor thin film, which uses both plasma chemical vapor decomposition means and photochemical reaction means.

[0002]

2. Description of the Related Art Conventionally, hydrogenated amorphous silicon (a-S
The plasma CVD apparatus used for forming an amorphous semiconductor thin film, represented by i: H), has a configuration as shown in FIG. 41 is evacuated to a vacuum through the exhaust hole 42 in the vacuum chamber. An electric field from the direct current or high frequency power source 43 is applied to the electrode 4.
4, which can be heated by a substrate holder-electrode 4
An electric field is applied between the electrode 5 and the plasma and plasma is generated. Reference numeral 46 is a gas inlet, which is monosilane (SiH ₄ ), disilane (Si
₂ H ₆ ) or other source gas 48 or H ₂ or He or other dilution gas 4
9 is introduced. These gases are decomposed by plasma or promoted plasma decomposition to be deposited and formed on the substrate 47 as an a-Si: H thin film.

[0003]

However, in such a conventional plasma CVD apparatus, the gas pressure for causing plasma decomposition is generally in the range of 0.1 to 5 Torr, whereby the electron energy distribution in the plasma is As a result, for example, monosilane (Si
In the decomposition of H ₄ ), it is considered that neutral radicals composed of high-order hydrogenated silicon such as SiH ₃ and SiH ₂ contribute to most of the deposition as a precursor. Therefore, it is said that the substrate temperature needs to be 200 ° C. or higher. As a result, for example, when forming a semiconductor device such as an amorphous silicon solar cell or an amorphous silicon thin film transistor for a liquid crystal display, for example, diffusion of the interface of the multilayer film structure occurs, or the substrate material itself is weak to heat. When it is, it cannot be used, or diffusion occurs at the interface between the substrate material and the thin film, so there are restrictions on the material used,
There are problems that device design must be devised and that there are many process restrictions.

In order to solve the above-mentioned problems of the prior art, it is an object of the present invention to provide a manufacturing apparatus for forming an amorphous semiconductor thin film at a lower temperature.

[0005]

In order to achieve the above object, an apparatus for producing an amorphous semiconductor thin film of the present invention comprises at least a plasma chemical vapor phase decomposition means by an alternating electric field containing direct current or high frequency, and a substrate surface. Further, in the apparatus for producing an amorphous semiconductor thin film, a light energy supply unit for supplying short-wavelength light is provided on or near the surface of the substrate.

In the above structure, it is preferable to use a light source containing light having a wavelength of at least 150 nm to 350 nm as the short wavelength light source. Further, in the above structure, the short wavelength light source is built in the electrode having the opening for applying the electric field for causing the plasma chemical vapor deposition process, and the irradiation direction from the light source and the electric field application direction are the same direction. It is preferable.

Further, in the above structure, it is preferable that a short wavelength light source is provided in the diluting gas supply passage.

[0008]

According to the above-mentioned constitution of the present invention, by using the plasma chemical vapor decomposition means and the photochemical reaction means in combination,
It becomes possible to form a high quality thin film at a low temperature. That is, first of all, the light energy that replaces the substrate temperature acts on the deposition surface as a chemical reaction on the volume surface,
By irradiating short-wavelength light to a precursor composed of radicals generated by plasma decomposition and contributing to film formation, a chemical reaction action on the surface of the substrate is promoted to contribute to re-decomposition of the precursor. Second, conventional plasma CV
The gas pressure region where plasma can be generated in D is from 0.1 Torr
What was 5 Torr, but because it is excited by light irradiation, it becomes possible to perform plasma decomposition at a relatively high pressure of 100 Torr, and as a result, the impact of ions of equicharged particles on the substrate is reduced and device formation is possible. In this case, good reliability can be realized.

Next, at least 150 as a short wavelength light source.
According to the preferable configuration of using the light source including the light having the wavelength of nm to 350 nm, the photochemical reaction can be performed more efficiently.

Further, it is preferable that the short-wavelength light source is built in an electrode having an opening for applying an electric field for causing the plasma chemical vapor deposition process, and the direction of irradiation from the light source and the direction of application of the electric field are the same. According to the configuration, the photochemical reaction can be selectively performed in the deposition film direction, and rational film formation can be performed.

Further, according to the preferable construction in which the short-wavelength light source is provided in the diluting gas supply passage, in addition to the above-mentioned action, the light source can be prevented from becoming dirty.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Representative embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a light irradiation type plasma C used in the present invention.
It is a schematic diagram of a VD device. A vacuum chamber 11 is evacuated to a vacuum through an exhaust hole 12. An electric field is applied from the power supply to the electrode / substrate holder 15 through the electrode 13.
A short-wavelength light source 16 such as a low-pressure mercury lamp is built in the electric field applying electrode 13, and the electric field applying electrode 13
The discharge surface 17 of is made of metal mesh or the like. As a result, plasma cannot enter the electrode 13 and light generated from the light source 16 can be radiated through the mesh to the plasma region P between the electrodes 13 and 15 and vertically to the surface of the substrate 20. Reference numeral 18 denotes a gas inlet, for example, when forming an amorphous silicon thin film, SiH ₄ , Si ₂ H ₆
Raw material gas 14 such as Reference numeral 19 is a second gas introduction port through which a gas such as H ₂ , He, Ar, etc. or a mixed gas thereof is introduced from the electrode 15 through the light source section, which has a function to prevent film deposition on the light source lamp and a deposition. It has the effect of suppressing the speed and promoting the light irradiation action. In addition, 21 is a heater. A raw material gas and other gases are introduced from these gas introduction ports to cause plasma decomposition, and at the same time, light is irradiated from the short wavelength light source toward the substrate surface to deposit a film.

The high frequency power density for plasma generation is shown in FIG.
0 mW / cm ² , light irradiation amount of 50 mW / cm ² (wavelength: 270
nm), and the formed amorphous silicon (a-Si: when the deposition temperature is changed from room temperature (25 ° C.) to 400 ° C.
H) Dark electrical conductivity of thin film and simulated sunlight (AM 1: 100
The change in photoconductivity under irradiation of mW / cm ² ) is shown.
For comparison, changes in the case where short wavelength light irradiation is not performed are also shown in the figure. Other conditions were as follows. (1) SiH ₄ supply amount: 100 SCCM (2) H ₂ supply amount: 400 SCCM (3) Vacuum degree: 0.5 Torr (List all other necessary conditions in concrete values.) As is clear from FIG. The improvement in photoconductivity at room temperature to 200 ° C. substrate temperature is apparent with and without irradiation.

[0014]

As described above, according to the present invention, a high quality thin film can be formed at a low temperature by using the plasma chemical vapor decomposition means and the photochemical reaction means in combination.

[Brief description of drawings]

FIG. 1 is a schematic view of a plasma CVD apparatus used for forming a thin film in the present invention.

FIG. 2 is a diagram showing the relationship between the substrate temperature and the photoconductivity when the amount of light irradiation is performed and when it is not performed in order to show the effect of the present invention.

FIG. 3 is a schematic view of a conventional plasma CVD apparatus.

[Explanation of symbols]

 11 Vacuum Chamber 12 Exhaust Hole 13 Electric Field Applying Electrode 14 Electric Field Applying Power Supply 15 Electrode / Substrate Holder 16 Short Wavelength Light Source 17 Discharge Surface (Mesh Electrode Surface) 18 Raw Material Gas Inlet 19 Second Gas Inlet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Hirao 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An apparatus for producing an amorphous semiconductor thin film on a substrate surface, which comprises at least plasma chemical vapor phase decomposition means using a direct current or an alternating electric field containing a high frequency, and a short wavelength light on or near the substrate surface. An apparatus for producing an amorphous semiconductor thin film, comprising an energy supply means. 2. A short wavelength light source of at least 150 nm
The apparatus for manufacturing an amorphous semiconductor thin film according to claim 1, wherein a light source including light having a wavelength of ˜350 nm is used. 3. A short-wavelength light source is built in an electrode having an opening for applying an electric field for causing a plasma chemical vapor deposition process, and the direction of irradiation from the light source and the direction of application of the electric field are the same. Item 2. An apparatus for producing an amorphous semiconductor thin film according to item 1. 4. The apparatus for producing an amorphous semiconductor thin film according to claim 1, wherein a short-wavelength light source is provided in a diluting gas supply channel.