JPS6126772A - Formation of accumulated film - Google Patents

Abstract

PURPOSE:To suppress heating temp. of a carrier itself lower to obtain accumulated film having good film characteristic, by preheating raw material gas for forming accumulated film, then heating, decomposing said gas at decomposition temp. or more, and supplying it on the carrier to form accumulated film. CONSTITUTION:The carrier 6 is arranged on a supporting base 2 in an accumulating chamber 1, and the desired pressure is maintained therein. Raw material gas from a bomb 13 is subjected to controls of pressure, flow rate, etc. at a gas pressure controller 12, a mass flow controller 11, and preheated less than decomposition temp. by a preheater 10 of a nozzle 8. Next, it is heated to said temp. or more by a heater 9 and decomposed, a radical 14 is generated and released toward the carrier 6 from a releasing hole 18, to form accumulated film thereon. In this way, heating of carrier 6 to gas decomposition temp. or more in unnecessary, a water cooling pipe 3 and a heater 4 are controlled by a controller circuit 5 to maintain the carrier 6 to the desired temp.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a deposited film forming method for forming a photoconductive film, a semiconductor film, an insulating film, etc. on a desired carrier.

(2) Prior Art Hereinafter, this type of technology will be described using as an example a case where a deposited film of amorphous silicon (hereinafter abbreviated as a-3i) is formed on a carrier.

Conventionally, methods for forming a-3i deposited films include plasma decomposition using glow discharge and so-called CVD (Chemical
Al Vapor Diposition) method and the like are known. Among them, the a-9i film obtained by plasma decomposition method using glow discharge using monosilane (SiH4) or silicon tetrafluoride (SiF4) has dangling bonds terminated with H or F. Because it has a small number of dangling bonds, has high photoconductivity, and conductivity can be controlled by adding impurities, it has been proposed for applications in solar cells, electrophotographic photoreceptors, optical sensor thin films, transistors, etc. .

However, in such a plasma decomposition method using glow discharge, the deposition film formation conditions such as applied force, degree of vacuum, inflow gas amount, electrode structure, carrier temperature, etc. are correlated with each other. particularly,
When producing something that has a large area and requires a thick film, such as an electrophotographic photoreceptor, various problems arise due to these conditions.

That is, l) it is extremely difficult to generate uniform plasma over such a large area over a long period of time, and 2) a long deposition time is required to increase the film thickness. However, in order to shorten the deposition time, it is necessary to use conditions different from the normal deposited film formation conditions (for example, increase the applied power, increase the amount of gas inflow, etc.), and this may cause deterioration of the film properties. 3) Various ions and radicals are generated in plasma, and some of them have an unfavorable effect on membrane properties, and are decomposed especially as the applied load increases. For example, the variety of things will increase.

On the other hand, in the CVD method, a raw material gas such as monosilane is thermally decomposed to create radicals, which are attached to a carrier to form a-Si.
This is a method for creating deposited films such as That is, for example 5
i) When L gas is applied to a carrier heated to about 500°C, the reaction 5i) (4→ SiH2 + H2 occurs on the carrier surface, generating SiH2 radicals.
iH2 radicals adhere to the carrier surface, and along with this, H2
It is believed that a release reaction occurs and an a-Si film is deposited on the carrier. In this method, the radicals created are limited and there is no generation of ions, which are believed to have a negative effect on membrane properties.

However, since the carrier must be heated to a high temperature of about 500° C., there is a problem in that a carrier with poor heat resistance, such as a carrier such as AI, cannot be used. In addition, when an a-9i film produced by glow discharge decomposition method, which is normally produced at a temperature of about 250 to 300 degrees Celsius, is heated to about 500 degrees Celsius, the H atoms terminating the dangling bonds of Si atoms are removed, and the film properties change. However, CV created by decomposing 5il (, + gas at high temperature)
Even in the a-9i film produced by method D, there is a problem in that the number of dangling bonds in the 5iji molecules increases due to the high temperature, making it impossible to obtain a film with good characteristics.

(3) Disclosure of the Invention The present invention has been made in view of the above-mentioned points, and an object of the present invention is to solve the problems of conventional deposited film forming methods, especially the CVD method, and to achieve a high film deposition rate. It is an object of the present invention to provide a novel method for forming a deposited film which enables the creation of a deposited film having the above properties and excellent film properties.

The above objects of the present invention are achieved by the present invention as follows.

A deposited film is formed on the carrier by introducing a raw material gas which is preheated to a temperature below the decomposition temperature and further heated to a temperature above the decomposition temperature to decompose the carrier into a deposition chamber in which the carrier is disposed. Characteristic deposited film formation method.

As mentioned above, the major problem with the CVD method is that the raw material gas for forming the deposited film is decomposed by heating the carrier to form the film, so the carrier itself must be heated to a high temperature higher than the decomposition temperature of the raw material gas, for example, a-9i. In order to create a film, it is necessary to heat the material to a high temperature of about 500°C, but in the present invention, by using the above-mentioned raw material gas, there is no need to heat the carrier itself to a high temperature, and this problem is solved. At the same time, by preheating the raw material gas, thermal decomposition of the raw material gas is facilitated, and the film deposition rate is increased.

(4) Embodiments of the invention The method of the invention will be explained in detail below with reference to FIG.

FIG. 1 is a schematic diagram of a deposited film forming apparatus for forming a deposited film such as a-srs on a carrier.

Formation of the deposited film takes place inside the deposition chamber l. The deposition chamber 1 can be maintained at a desired pressure by an exhaust system including a rotary pump, a diffusion pump, etc. (not shown). In this example, the surface of the carrier 61 placed on the carrier support 2 in the deposition chamber 1 is preheated to a temperature below the decomposition temperature of the gas, and then further heated to a temperature above the decomposition temperature. The decomposed raw material gas is discharged from the raw material gas discharge nozzle 8, and a deposited film using the gas as the raw material is formed on the carrier 6.

The raw material gas discharge nozzle 8 includes a raw material gas,
For example, a raw material gas composed of a raw material gas pump 13 for supplying the aforementioned monosilane, etc., a gas pressure regulator 12 for adjusting the supply pressure of the gas, a mass flow controller 11 for adjusting the supply amount of the gas, etc. A source gas adjusted to desired pressure, flow rate, etc. is supplied from the supply system. The raw material gas supplied to the nozzle 8 is heated to a decomposition temperature (for example, 60°C for the monosilane mentioned above) by a heater 10 for preheating the raw material gas provided in the nozzle 8.
After being preheated to a temperature lower than 0 to 700[deg.] C.), the raw material gas is heated to a temperature higher than the decomposition temperature by the raw material gas heating heater 9 and decomposed. Radicals 14 generated by the thermal decomposition of the raw material gas are emitted toward the carrier 6 from the raw material gas discharge hole 18 provided in the nozzle 8, adhere to the carrier 6, and cause a reaction on the surface of the carrier 6, resulting in a reaction on the carrier 6. A deposited film is formed on the surface. Therefore, in this method, a deposited film can be formed on the carrier 6 without heating the carrier 6 itself to a high temperature higher than the decomposition temperature of the source gas.

Since the radicals 14 generated by thermal decomposition of the raw material gas are highly reactive, it is preferable to thermally decompose the raw material gas immediately before forming the deposited film. Therefore, in this example, a heater 9 for heating the raw material gas is provided immediately before the raw material gas discharge hole 1B as shown in the figure, and the raw material gas is decomposed by the heater 9 immediately before discharge. Further, the heater 9 has a large capacity (2 Kw in this example) so that the raw material gas can be decomposed in a short time.

In the present invention, since the raw material gas is preheated to a desired temperature below the decomposition temperature using the preheating heater 10, 1M
In this example, the preheating heater 10, which can heat the raw material gas to a temperature higher than the decomposition temperature in a short time, is provided outside the deposition chamber 1, but it may of course be provided inside the deposition chamber 1. If the preheating temperature exceeds the decomposition temperature of the source gas, a deposited film is formed in the nozzle 8, which is undesirable because it causes nozzle blockage or deteriorates the properties of the deposited film formed. Therefore, a water cooling pipe 15 for cooling the nozzle is installed between the heating heater 9 and the preheating heater 10 as in this example.
It is preferable to take measures to prevent the preheated gas from being heated to a temperature higher than the decomposition temperature by providing a.

In the present invention, as described above, after preheating the raw material gas for forming the deposited film, it is heated to a temperature higher than the decomposition temperature to decompose it and form the deposited film on the carrier, so it is not necessary to heat the carrier. Although not necessarily required, this does not prevent the carrier from being heated or cooled for the purpose of making the carrier temperature uniform and optimizing the film forming conditions.

For example, in the case of this example, the carrier 6 is cooled and heated by a water cooling pipe 3 for cooling the carrier and a heater 4 for heating the carrier provided on the carrier support base 2, and is controlled to a desired temperature. ing. For this reason, a water cooling pipe 3 connected to a cooling water supply source (not shown) is arranged on the carrier support base 2 so that the carrier 6 can be uniformly cooled. The heater 4 is connected to a control circuit 5 for controlling the carrier temperature, and based on the temperature detected by a thermocouple 7 (in this example, an allomelo-cromel thermocouple) for detecting the carrier temperature, a control circuit (not shown) is activated. The carrier temperature is controlled by controlling the power applied to the heater 4 from the power supply source by the control circuit 5.

Although there are no particular limitations on the carrier that can be used in the present invention, it is possible to use materials with low heat resistance that could not be used conventionally due to high temperatures, such as the aforementioned AI, as well as paper and the like. The shape and size of the carrier can be appropriately selected depending on the intended use.

In addition to the above-mentioned monosilane and silicon tetrafluoride, various raw material gases may be used as raw material gases in the present invention, depending on the purpose of the deposited film to be formed, such as a photoconductive film, a semiconductor film, or an insulating film. It can be used separately or mixed.

As means for heating the gas, in addition to the above-mentioned heater, various means generally known as means for heating gas can be widely used.

The means for introducing these gases into the deposition chamber are not limited to the nozzle as described above, and any means that can preheat the raw material gas and thermally decompose the donor gas can be used. . Also.

Even when using the above-mentioned nozzles, it is also possible to arrange a plurality of nozzles in an array to form a deposited film on a large area carrier.

(5) Examples The present invention will be explained in further detail using examples below.

[Example 1] Using the apparatus shown in FIG. 1, a deposited film was formed on a flat quartz glass substrate.

Disilane (Si2H6) is used as a raw material gas, and the gas is preheated to 350°C with a preheating heater lO,
This is further heated to 550°C with a gas heating heater 9 to decompose it, and released from the raw material gas release hole 16 at a rate of 20cc/w.
was released onto the quartz glass substrate 6 at in. Raw material gas release hole 1
B had a diameter of 21 cm, and a quartz glass substrate was placed 5 cm away from the discharge hole 16. In addition, the carrier temperature was
Set the pressure in the deposition chamber to 100 Torr.
I kept it at r. When this state was maintained, an a-5i film having a thickness of 1.5 μm was formed on the quartz glass substrate after 1 hour.

After creating comb-shaped AI electrodes with a spacing of 0.2 mm on the obtained a-9i film by vacuum evaporation, 2×1014ph
When irradiated with an oton/crn' He-Me laser and measured the dark conductivity and attractive conductivity, ad=
7.7 X 1O-10(Ω-cm)-', σp=
It was found that it had a good photoconductivity of 8.5 x 10-'(Ω-crs)-'.

[Example 2] A deposited film was created under the same conditions as in Example 1, except that (CH3)3S izH3 gas was used as the raw material gas, the preheating temperature was 300°C, and the thermal decomposition temperature was 550°C. , an a-9i film with a film thickness of 1.6 scales was obtained. Obtained a
-3i film was evaluated in the same manner as in Example 2, and it was found that σd
= 8 X 10-”(Ω-am)-”, σp=5X1
It was found that it had a good photoconductivity of 0°7 (Ω-cm) −'.

(8) Effects of the Invention As explained above, in the present invention, the raw material gas for forming a deposited film is preheated to a temperature below the decomposition temperature of the gas, and then heated to a temperature above the decomposition temperature. Since it decomposes and forms a deposited film on the carrier, there is no need to heat the carrier itself to a temperature higher than or equal to the decomposition temperature of the raw material gas, as was the case in the past.
Deposited films with good film properties can now be formed at relatively low temperatures. Therefore, it has become possible to use materials with low heat resistance as carriers, which could not be used in the past.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of a deposited film forming apparatus used in the method of the present invention. 1-m-Deposition chamber 2--1-Carrier support stand 3--1Water cooling pipe for cooling carrier 4-m-Heater for heating carrier 5-m-Control circuit 6-m-Carrier 7-m-Thermocouple 8-m - Nozzle for releasing raw material gas 8 - m - Heater for heating raw material gas 10 - - Heater for preheating raw material gas 11 - m - Mass flow controller 12 - - Gas pressure regulator 13 - m - Gas cylinder 14 - m - Radical 15 -1- Water cooling pipe 16 for cooling the nozzle --- Raw material gas discharge hole

Claims (1)

[Claims] A deposited film is formed on the carrier by introducing a raw material gas which is preheated to a temperature below the decomposition temperature and further heated to a temperature above the decomposition temperature to decompose the carrier into a deposition chamber in which the carrier is disposed. Characteristic deposited film formation method.