JPS6150147B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vapor deposition method.

Recently, research has been conducted into methods for forming relatively large-area amorphous silicon vapor deposition films for use in the production of photosensitive drums for electronic copying machines and solar cells. On the other hand, vapor deposition methods have been studied for forming insulating films and protective films, as disclosed in, for example, Japanese Patent Application Laid-Open No. 163792/1983, and various vapor deposition methods have been proposed depending on the application.

Among vapor deposition methods, this application is particularly concerned with chemical vapor deposition methods that utilize photochemical reactions, and this method has advantages such as extremely fast film formation speed and suitability for vapor deposition over large areas. However, it has been attracting particular attention recently.

Conventional chemical vapor deposition methods using photochemical reactions are
As shown in the above publication, a substrate is placed in a container that transmits ultraviolet rays well, a photoreactive gas is passed through it, and the gas is subjected to a photochemical reaction using an ultraviolet lamp from outside the container, and the reaction products are produced. This method is vapor-deposited onto a substrate, and as mentioned above, it has the advantages of a high film formation rate and can be used on large-area substrates, but the reaction product is also deposited on the inner wall of the container, and UV It was found that there is a drawback in that it greatly inhibits the permeation of

In actual deposition film formation work, it is not possible to wash the inner wall of the container so often, and for this reason,
Specialized containers or reaction devices are also being actively researched, but they are quite complex and difficult to handle.

The present invention was made with the aim of providing a new vapor deposition method that fundamentally solves the above-mentioned drawbacks, and its characteristics are as follows: When generating plasma, the substrate is placed at a position farther than the mean free path of ions and electrons generated by the plasma, and the light emitted from the plasma reacts with the photoreactive gas near the substrate. At the very least, a reaction product is generated and the reaction product is deposited on the substrate.

Some embodiments of the present invention will be described below with reference to the drawings.

In the figure, 1a, 1b, and 1c are cathodes, and 2 is an anode, which are arranged at regular intervals in a container 3, and plasma 4 is formed between them. The number of cathodes may be increased depending on the size of the plasma to be created. Chemically reactive gases are
Enters from the inlet 3a of the container 3, and has two outlets 3b, 3
released from c. Exhaust pumps (not shown) are connected to the outlets 3b and 3c, respectively, and if the capacity of each exhaust pump is determined in consideration of the exhaust resistance of the container, etc., the air around the substrate 5 and the plasma 4 can be The amount of gas to be used can be varied. 6 is an infrared heater unit that is installed when it is better to heat the substrate 5 to some extent, and to show an example of the dimensions of the container, the part containing the plasma 4 is cylindrical with an inner diameter of 20 cm (=D);
The cathodes 1a, 1b, and 1c are thoriated tungsten rods with a diameter of 3 mm, the discharge surface of the anode 2 is a tungsten mesh, and the distance between the cathode tip and the tungsten mesh is 25 mm. Therefore, the size of the plasma 4 is a disk shape of approximately 18 cm in diameter x 2.5 cm in height, and the emitted light v from the plasma 4 is directed toward the substrate 5 from the gap in the tungsten mesh. With the size of the plasma 4 described above, it is possible to process substrates 5 up to a diameter of 5 inches. Note that a support base on which the substrate 5 is placed, for example, a circular plate made of quartz glass, is omitted from the illustration.

To show an example of vapor deposition using the above apparatus, a mixed gas of 1 mmHg of argon as a carrier gas, 1×10 ^-3 mmHg of mercury as a photosensitizer, and 0.1 mmHg of silicon tetrahydride as a photoreactive gas is sent, and plasma 4 is generated by causing a discharge of 30 V and 30 A between the above two electrodes, and the value L is 8 cm, which is longer than the mean free path of ions and electrons due to plasma 4 (theoretically calculated value is approximately 0.8 to 1 cm). A substrate 5 maintained at about 50° C. is placed therein. In this case, the deposition rate of amorphous silicon on the substrate reaches a thickness of 4000 Å in 10 minutes.

FIG. 2 shows another embodiment in which a high frequency power source is used to generate the plasma 4. For example, 7 is a 6 MHz, 1.5 kilowatt high frequency power source, L
The board is placed at a distance of 10 cm from the bottom end of the coil portion 7a of the high frequency power source 7. When examining the formation rate of amorphous silicon vapor deposition under the above gas and pressure conditions, it was found that it took about 10 minutes.
A thickness of 4500 Å is obtained.

As can be understood from the above embodiments, since there is no wall such as a container that blocks the plasma 4 and the substrate 5, reaction products adhere and emit light from the plasma 4.
Moreover, since the substrate is placed at a position farther from the mean free path of ions and electrons generated by the plasma 4, the substrate or the deposited film will not be contaminated by them. It will not be exposed or damaged.

Here, the mean free path of ions and electrons can be calculated on a desktop from the ion species generated in the plasma, the electric energy supplied to the discharge, the gas pressure, etc. It is sufficient to select the value of L to be about 10 times the value.

By the way, as mentioned above, in the above reaction, a photoreactive gas is chemically reacted with synchrotron radiation emitted from a plasma, and the reaction product is deposited as a film on a substrate. It is not limited to the examples and can be selected from a wide range.

For example, FIG. 3 shows another embodiment of the vapor deposition method of the present invention, in which an element having a resonance line in the ultraviolet region, such as arsenic, phosphorus, or boron, is in the form of a gas such as a hydrogen compound. It is also possible to flow it toward the plasma space from another supply pipe 8, extract specific ultraviolet rays from those elements, and irradiate various photoreactive gases flowing near the substrate.
Alternatively, a photoreactive gas containing nitrogen oxides such as nitrogen dioxide or nitrogen such as ammonia is flowed from the pipe 9 so as to be mixed into the gas flow near the substrate, thereby forming a vapor deposited film of silicon nitride on the substrate. You can also force it.

Furthermore, hydrogen arsenide, hydrogen phosphide, hydrogen boron, or the like is flowed as a photoreactive gas from the pipe 9, and amorphous silicon formed on the substrate is doped with arsenic, phosphorus, or boron as an impurity. It can also be used to form vapor deposited films.

In the formation of any vapor-deposited film, if the position of the substrate is chosen to be farther than the mean free path of ions and electrons in the plasma, the substrate may be contaminated, damaged, or , the deposited film is not contaminated or damaged, there is no reaction by charged particles near the substrate, rapid film formation can be obtained, and it is easy to deposit over a large area.

As described above, the present invention is a chemical vapor deposition method using a photochemical reaction, in which a plasma, which is an ultraviolet radiation source, and a substrate on which a reaction product is deposited are placed in the same space, and a gap between the plasma and the substrate is provided. However, since the substrate is positioned further away than the mean free path of ions and electrons in the plasma, charged particles can interfere with the substrate and the deposition. The disadvantages of conventional light-based chemical vapor deposition methods can be completely overcome without contaminating or damaging the film.

[Brief explanation of the drawing]

1, 2, and 3 are explanatory diagrams of essential parts of a container used in the vapor deposition method of the present invention, in which 3 represents the container, 4 represents plasma, and 5 represents a substrate.

Claims (1)

[Claims] 1. When plasma is generated in a container filled with a carrier gas such as hydrogen, nitrogen, or a rare gas and a photoreactive gas, the mean freedom of ions and electrons generated by the plasma is arranging a substrate at a position farther from the process, reacting the photoreactive gas near the substrate with synchrotron radiation emitted from the plasma to generate a reaction product, and depositing the reaction product on the substrate. A vapor deposition method characterized by: 2. The vapor deposition method according to item 1, wherein the photoreactive gas contains a hydrogen compound of silicon. 3. The vapor deposition method according to item 2, wherein the plasma contains at least one selected from mercury, arsenic, phosphorus, and boron. 4. The vapor deposition method according to item 2, wherein the photoreactive gas near the substrate contains ammonia or nitrogen oxide. 5. The vapor deposition method according to item 2, wherein the photoreactive gas near the substrate contains hydrogen boride, hydrogen arsenide, or phosphorus hydride.