JPS60239015A - Formation of amorphous silicon film - Google Patents

Abstract

PURPOSE:To contrive to suppress generation of powder and to enhance the depositing speed of an amorphous Si film at formation of the amorphous silicon film by a method wherein plasma intensity in glow discharge space is dispersed. CONSTITUTION:Raw material gas 9 is introduced into a reaction chamber 8. Gas 9 flows in discharge space, and deposited on a substrate 5. Discharge space is divided into two spaces of discharge space W formed by electrodes 1, 2, and discharge space S formed by the electrode 2 and an electrode 4 by equipping the electrode 2 between the electrodes 1, 4. At this case, weak discharge is generated in space W, and moreover strong discharge is generated in space S. An inclination of plasma intensity is provided to discharge space like this, and by flowing raw material gas to the strong part from the weak part of plasma intensity, the decomposition process of raw material gas, and other excitation, diffusion and surface reaction processes are made to be performed in different plasma intensity regions. Accordingly, the respective processes from decomposition of raw material gas to a surface reaction are advanced smoothly, and as a result, suppression of generation of powder, and enhancement of the depositing speed of an amorphous Si film can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming an amorphous silicon film (hereinafter referred to as an A-8T film) which dramatically improves the film formation rate.

Relationship with conventional technology A-8i film has recently been used in solar cells, optical sensors, and FETs.

It is an electronic material that is attracting attention as it is being widely put into practical use in electrophotographic photoreceptors and the like. A method for forming such an a-8T film is a method of sputtering in a silicon target atmosphere of activated hydrogen, or SiH, SiF.

A method of decomposing gas using glow discharge is known.

It is difficult to obtain a good quality A-8T film obtained by the above sputtering method because it is difficult to control the hydrogen content, which greatly affects the film properties.

On the other hand, with the glow discharge method, a film with few defects such as dangling bonds and voids can be obtained (therefore, when used as a photoconductor, a film with very high sensitivity can be obtained).
The glow discharge method is a
-8i film formation has become mainstream.

However, even this glow discharge method has inherent problems that need to be solved. For example, attempts have been made to improve the deposition rate and stacking rate. For example, increasing the supply amount of SiH, SiF, and Kasa raw material gas, or increasing the discharge power, etc., but this is at most about 3 to 4 μ/hour. In this case, if the deposition rate is further increased, the physical properties of the film will deteriorate significantly. Furthermore, together with the deterioration of the film properties, a large amount of powder is generated during molding of the A-8T film, which is incorporated into the film, resulting in the formation of defects in the film.

The purpose of the invention is that the inventors of the present invention have conducted intensive studies on a method for forming an a-8t film that does not cause the same reduction in film physical properties and also increases the overall film deposition rate. The present inventors have discovered that all of the drawbacks of the prior art can be overcome by providing a complete distribution of .

Components of the Invention Namely, the present invention is characterized in that the discharge intensity in the discharge space is distributed when it is produced using an amorphous silicon film whole glow discharge whose matrix is silicon containing at least one of hydrogen or halogen. It is.

The method of the present invention will be explained below with reference to the drawings.

FIG. 1 shows the case of a capacitively coupled glow discharge device in which the entire discharge space is divided into two to give a distribution of discharge intensity.The discharge space is evacuated to a level of torr and then introduced into the reaction chamber 8. H! is added to these raw material gases 9, 5IHI, S i Fa, and S i xHa as a diluent gas. , He % A, r, etc., mixed with a doping gas as necessary, flows through the discharge space and is deposited on the substrate 5 . The discharge space is divided into two with all the electrodes 2 installed between the electrodes 1 and 40. That is, there is a discharge space (W) formed by electrodes 1 and 2, and a discharge space (S) formed by electrodes 2 and 4.

In the case of FIG. 1, one iRF power source 6 (high frequency power source) is divided into two. In this case, a weak discharge occurs in the discharge space (W), and a strong discharge occurs in the discharge space (S).

In general, an a-8t film is produced by decomposing and exciting a raw material gas by discharge energy, and causing all of the decomposed active species to diffuse and move in the electric space, thereby depositing a solid phase film on a substrate. Therefore, in order to fully realize high-speed film formation, it is necessary to decompose the source gas, increase the efficiency of excitation, increase the speed of diffusion and movement of the active species, and increase the speed of the surface solid phase reaction on the substrate. However, in reality, it is extremely difficult to control each of the above elementary processes completely independently.

By the way, as in the present invention, by creating a complete plasma intensity gradient in the discharge space and flowing the raw material gas from a region where the plasma intensity is weak to a region where the plasma intensity is strong, the decomposition process of the raw material gas (which occurs in the weak region) and other excitation, diffusion, The surface reaction process (occurs in the strong part) is carried out in a different plasma intensity range, so each process from the decomposition of the raw material gas to the surface reaction proceeds smoothly, and as a result, the generation of powder is suppressed and a
- It was possible to improve the deposition rate of the Si film.

When all of the above processes are carried out under the same discharge intensity as in the past (Figure 2), no powder is generated and the deposition rate is reduced, but this is because the generation of powder is caused by the formation of solids due to gas phase reactions. This is because the surface reaction is not promoted since the activated species are consumed before they reach the substrate.

In FIG. 1, electrodes 1 and/or electrodes 2 having openings that allow ventilation are employed. Also, the substrate 5 has electrodes 1.4
It can be installed on either side, but when installing it on electrode 1,
．． It is preferred that the plasma intensity between electrodes 2.2 is stronger than that between electrodes 2.4.

FIG. 1 shows a case where the discharge space is divided into two by electrodes, but the present invention can even form a gradient in the plasma intensity, so there is no need to equally limit the number of divisions. The number of divisions can be determined by appropriately using RF and/or DC (direct current power) as a power source.

Here, the distribution of discharge intensity will be explained. The distribution of the discharge intensity is determined by measuring the emission spectrum from the glow discharge plasma of the source gas using an emission spectrometer. For example, if the raw material gas is SiH+ gas, the wavelength of 414 nm is [
By observing the emission intensity of SiH, :], the intensity (gradient) of the discharge is determined.

FIG. 3 shows the complete formation of the A-8T film using open DC discharge between electrodes 1 and 2 and RF discharge between electrodes 3 and 46. The electrodes 1, 2, and 3 are all ventilated and have openings. A weak discharge intensity is formed between electrodes 1 and 2, and a strong discharge intensity is formed between electrodes 3 and 4.

FIG. 4 shows an example in which two RF power sources 6 are used to divide the discharge space. Electrodes 1, 2, and 3 each have an opening that allows ventilation.

A weak discharge intensity is formed between electrodes 1 and 2, and a strong discharge intensity is formed between electrodes 3 and 4.

Although the embodiments described above are all related to a joint type glow discharge, FIG. 5 shows an example of an inductively coupled type glow discharge. In FIG. 5, an induction coil 11 is wound around a glass tube 8 and two RF power sources 6 are used to form a weak discharge intensity section A and a strong discharge intensity section B't-. Incidentally, it is advantageous to employ the above-mentioned capacitive coupling type device for large-scale production and for producing a large-area film having uniform film characteristics.

Effects of the Invention According to the method of the present invention as described above, a significant improvement in the deposition rate of the a-8i film was achieved, and at the same time, the generation of powder in the reaction vessel could be almost completely suppressed. The elimination of powder generation is also advantageous in terms of safety. Furthermore, the film properties of the obtained film were extremely good despite the fact that a significant improvement in the deposition period was achieved. A-8T membrane solar cell, optical sensor, obtained by the method of the present invention,
FET.

It is suitable for applications such as electrophotographic photoreceptors. It is particularly promising for electrophotographic photoreceptors that require a large film thickness.

EXAMPLES All examples of the present invention will be described below, but the same limitations will not apply to the examples according to the present invention.Comparative Example 1 A device without division of discharge space as shown in FIG. 2? Film formation was carried out using the following method. The distance between the electrodes 1.4 was 50 cm, and a high frequency voltage of 500 W was applied using a high frequency power source of 13.56 MeHz.
Introduced at iH, 100% at a flow rate of 400 CC/cm, substrate temperature 250°C, gas pressure 0.5 Torr.

When the entire film was formed, a deposition rate of 3.5 u/hr k was obtained, but a very large amount of powder was generated, and the physical properties of the obtained film were not good as shown in the physical property values in Table 1.

Example 1 In Fig. 1, 1.2 is an electrode with a full opening;
The distance relationship was 25 + im between 2.4 m and 2.4 m, and using a 13.56 MeHz RF constant power source, a full high frequency voltage was applied at a power of 500 W, and S was used as the raw material gas in step 9.
Introducing iH, 100qb at a flow rate of 400cc/IItRo, and performing film formation at a substrate temperature of 250°C and a gas pressure of 0-5 Torr, a deposition rate of $25 It/Hr was obtained, and various good gases as shown in Table 1 were obtained. Physical property values were obtained.

Example 2 Film formation was carried out in the same manner as in Example 1 using SiF+ gas as the raw material gas, and a deposition rate of 28 μ/Hr k was obtained.
EXAMPLE 3 In which good physical properties as shown in Table 1 were obtained, f) an a-8i film was produced by DC discharge between electrodes 1.2 and RF discharge between electrodes 1.2 and 3.4 as shown in FIG. Electrodes 1.2, -〇- 3 are electrodes with 5 mesh openings, and the distance relationship is 25 m between electrodes 1.2 and 25 m between 3 and 4, and 1.
．． DC discharge of 2'e30w, between 3.4 f 13 , 56
Using MeHz high-frequency power source sound, the full high-frequency voltage was applied at a power of 500 W, and 5iHa k was used as the raw material gas in step 9.
When the entire film was formed in the same manner as in Example 1, the deposition rate was 24.
μ/Hr and satisfactory physical property values as shown in Table 1 were obtained.

Example 4 As shown in Fig. 4, the discharge space is completely divided using two high-frequency power sources, and the spacing between electrodes 1.2 is 25 m, the spacing between electrodes 3.4 is 25 m, and 2.
．． 3 shows the distance relationship with an interval of 3m, 60W between 1.2,
3. Apply a high frequency voltage with a power of 500W between S
When a film was formed in the same manner as in Example 1 using iH, 100% gas as the raw material gas, a deposition rate of 23μ〆Hr'lH was obtained, and good physical properties as shown in Table 1 were obtained.

Example 5 FIG. 5 shows an example of an inductively coupled glow discharge.

10- Using a high frequency power source 6 with two full windings of induction coils in a Pyrex glass tube 8 with an outer diameter of 8 crn, generate a weak discharge part and a strong discharge part. SIH*100%T with raw materials and 1~
Introduced from 9 at 150CC/m, gas pressure 0.5Torr
All film formation was carried out at a substrate temperature of 250°C.

■Apply a high frequency voltage with a total discharge power of 30w and ■a total leaving power of 200w. Luminescent species (
From the observation of SiH), the strength of ■ [Yes], the strength of 0 parts ■
As a result, IO/I■=0.1. At this time, a deposition rate of 20 μ/Hr was achieved, and satisfactory physical property values as shown in Table 1 were obtained.

Table 1 *1 Dark conductivity...a- on Corning 7059 glass
8iJtWk was deposited, and a gap electrode made of aluminum was completely formed on top of it. This was used as the sample for all measurements. The conductivity was set at full open at room temperature and in the dark. *2 Photoconductivity...In the case of dark conductivity All conductivity measurements were made on the same sample under irradiation with light at 600 nm and 50 μw/ca at room temperature.

[Brief explanation of the drawing]

1 and 3 to 5 show embodiments of the method of the present invention, and FIG. 2 shows an embodiment of the method other than the method of the present invention. 1 Electrode 9 Raw material gas 2 Electrode 10 Exhaust system 3 Electrode 11 Induction coil 4 to pole 5 Substrate 6 Power supply 7 Matching box 8 Reaction vessel Patent applicant Toyobo Co., Ltd. 13- 1st @ 3rd! Q 51st! l

Claims (1)

[Claims] 1. Glow discharge of an amorphous silicon film whose base material is silicon containing at least one of hydrogen or halogen? 1. A method for forming an amorphous silicon film characterized by providing a distribution of discharge intensity in a discharge space. 2. The forming method according to claim 1, wherein the raw material gas flows from a portion where the total discharge intensity is small to a portion where it is large.