JPH0322050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing amorphous or semi-amorphous (semi-amorphous) silicon or silicide material using a plasma CVD method (vapor phase accumulation method) or a glow discharge method (hereinafter collectively referred to as a gas phase method or CVD method). When forming an amorphous (amorphous) film on the surface on which it is formed, the adhesion or powder that is formed on the wall surface at the same time tends to fly away again and get mixed into the semiconductor film, seriously deteriorating its characteristics. This was done in response to
It is characterized in that it can be chemically etched and removed without removing the reactor from the apparatus, and that the generation of the deposits can be prevented or reduced.

When forming an amorphous amorphous or semi-amorphous amorphous film on a substrate, the present invention is very sensitive to the influence of deposits formed on the wall surface of the reactor and has a negative effect on the wall surface of the reactor. It is characterized by reducing or eliminating the adhesion of reaction products.

Conventionally, when a film is formed by such a gas phase method, a part of the reaction product is formed as a film on the inner wall of a reaction tube made of quartz or the like due to the high temperature of the inner wall, or is deposited as a powder. was.
However, the adhesion formed on the inner wall easily separates, so the separated powder tries to fly away and adheres to the substrate, creating snowflakes, etc., and as a result, pinholes etc. in the formed film. There were other drawbacks. Furthermore, since this powder has distinct grain boundaries, dangling bonds are generated intensively at the grain boundaries, deteriorating the characteristics of the semiconductor. For this reason, in the reaction, after repeating film formation 5 to 10 times, the film was always removed from the apparatus and immersed in a solution such as hydrofluoric acid to dissolve away the deposits. However, the operations are extremely complicated, such as removing the tube from the device, etching the inner wall of the reaction tube, drying the tube, attaching it to the device, and checking for vacuum leaks.As a result, lot variations occur, and products, especially semiconductor devices This was causing variations in the

In order to eliminate this drawback, the present invention is characterized in that the inner wall of the reactor is cooled by water cooling to reduce or eliminate the adhesion of reaction products thereto. In particular, when particles adhere to a wall surface, if a coating forms on that surface, it tends to become larger particles centered around the core. Water cooling of the wall surface was particularly effective in stopping this nucleation. Furthermore, the present invention uses the same equipment as in the gas phase method to remove a mixed gas of nitrogen fluoride (NF, NF ₂ , NF ₃ , etc.) from the inner wall of the reactor.
It is characterized by the fact that cleaning can be carried out by plasma vapor phase etching using NF ₃ ) without removing the reactor. In addition, in order to particularly clean the inner area of the reactor where the film is formed during this etching, when cleaning this area by plasma etching, water cooling is stopped and the temperature is increased to promote the reaction on the reactor wall surface. It is characterized by increased cleanliness.

Examples thereof will be described below with reference to the drawings.

FIG. 1 is a diagram showing an outline of a reactor using the present invention. The present invention has a plasma generation source 6 apart from a region where a coating is formed in a vapor phase method,
The substrate 10 was held on a boat 3 and could be heated by an electric furnace 7 of induction or resistance radiation heating type. Furthermore, the outside of the reactor in front of the substrate is double-walled and water-cooled to prevent or reduce nucleation on the wall. In addition, in plasma cleaning, the reactor is heated to 100 to 1000°C to increase the etching rate so that the entire reactor from which the cooling water has been removed is thoroughly cleaned, focusing on the area where the boat is installed. It is characterized by the fact that

The reaction product 9 is deposited on the inner wall of the reactor 5 in the form of a film or powder.

That is, silicide gases such as silane (SiH ₄ ), polysilane (SixHy (x, y>1)), SiH ₂ Cl ₂ ,
A gas such as SiF ₄ SiCl ₄ or a gas diluted with an inert gas is introduced from 1, and induction energy of 10 to 500 W at a frequency of 0.5 to 50 MHz or 1 to 10 GHz is applied by the high frequency induction furnace 6. The atmosphere is reduced to 0.01 to 10 torr and turned into plasma. Amorphous, semi-amorphous, quasi-
amorphous, Semi−crystal or Quasi−
A film (hereinafter collectively referred to as semiconductors having an intermediate structure between amorphous and crystalline, such as crystal) is formed to a thickness of 0.001 to 10 μm. If this process is repeated several times, reaction products similar to those used to form the film on the substrate will adhere to the inner wall 9. In particular, the heated area forms a film, and then the area near the exhaust port adheres to the inner wall in powder form. Of course, most of the reaction products are discharged to the outside by the rotary pump 13 through the needle valve 11 and the stop valve 12 together with the carrier gas.

In the present invention, when the reactive gas is chemically activated, decomposed, or reacted by induced energy, the activated gas collides with the wall surface of the reactor at the energy supply section, raising the temperature of this wall surface to 200 to 800 degrees Celsius. It was. As a result, reactants adhered to the wall surface and formed a film.

In order to eliminate such drawbacks, the present invention cools the reactor wall surface including the portion to which the induction energy is applied and the reactor inner walls before and after the portion, and lowers the temperature of the wall surface.
It is characterized in that the temperature is kept at 10 to 50°C, resulting in a temperature of 1/10 to 1/30 compared to the case where no reactant is attached.

In order to make silicon conductive as P or N type, impurities with a valence such as boron indium or phosphorus, arsenic, or antimony may be introduced as hydrides or chlorides (halides).

Further, by repeating the coating of 0.001 to 10 .mu.m by this method 1 to 3 times, a film of 0.01 to 100 .mu.m in thickness or a film with an apparent thickness consisting of a collection of grains was formed. After this, in the present invention, the coating or powder 9 is removed using nitrogen fluoride (hereinafter referred to as _NF3 ) or a reactive gas prepared by adding 1 to 5% oxygen or hydrogen to nitrogen fluoride from 4 to an inert gas such as Ar. 0.5~50MHz or 1 at a pressure of 0.01~10torr with gas mixed in
This was carried out by applying induction energy of ~10 GHz to generate plasma. Instead of nitrogen fluoride, nitrogen chloride or other etching gas or a mixture thereof, or a compound such as nitrogen fluoride or ammonium fluoride may be used. At this time, active fluorine and nitrogen (N or N ₂ ) are produced in the reactor, and solid carbon harmful to semiconductors such as CF ₄ is not generated or mixed into the film, which has been the case in the past. The area where the boat is installed is heated to a temperature at or above that temperature or further heated to a temperature of 200 to 1000°C to facilitate the reaction of the reactive gases on the inner wall of the reactor with the reaction products on the inner wall. I was able to remove the etching.

After sufficient plasma etching, plasma formation is further performed for 15 minutes to 1 hour in an inert gas or a gas with 2 to 10% hydrogen added to it to remove active fluorine remaining on the inner wall. The substrate was again introduced into the reactor and a silicide gas film was formed.

In this way, the inner wall can be cleaned in just 1 to 10 times, compared to the previous method where the film was formed 10 to 100 times and then cleaned, making it possible to semi-continuously form a uniform film without pinholes on the substrate. can be made,
The reproducibility was extremely remarkable.

In the present invention, the reaction tube is 5 to 30 cm and the length is 1 to 5 m.
It is particularly effective in the case of large-diameter, difficult-to-move equipment that has a size of It is a non-reactive gas in terms of semiconductors and has no adverse effects such as the generation of lattice defects, which is also preferable.

The present invention is based on a gas phase method for forming silicides or their compounds. But germanium or
The same is true for compounds such as BP and GaAs, and it is similarly effective when forming metals such as aluminum by the CVD method. Particularly in the case of aluminum, nitrogen chloride was even more effective.

The method of the present invention prevents the adherends from being mixed in the semiconductor as a lump having a large surface area like a powder and having many interfacial units at the grain boundaries, and converts the semiconductor into a homogeneous amorphous, semi- This was effective in producing a semiconductor having an amorphous or semicrystalline structure. In addition, these particularly effective powders conversely tend to spatter the film during film formation, resulting in the formation of voids or pinholes in the film. Plasma in phase method
It has an effect greater than that of a combination of etching methods, and in particular, it removes deposits on the inner wall of the reactor and accelerates the reaction by increasing the temperature during the removal of the deposits, rather than performing plasma etching on the substrate. Another aspect of the present invention is that, instead of fluorine, which is a highly reactive radical such as fluorine, the reaction products are silicon fluoride, nitrogen fluoride, and inert nitrogen, which are released to the outside through a rotary pump. It is a characteristic of

In the examples of the present invention, cooling was mainly described as water cooling. However, using a refrigerator to cool a material other than water, such as fluorocarbon gas, and lowering the temperature to an appropriate temperature of -30°C was effective in preventing the reaction products from adhering to the walls.

In addition, the corresponding part is cooled not only in the activation area of the reactor, but also in the area where the substrate is provided, along with the wall surface of the reaction tube (in addition, a heater for heating the substrate is installed in the reactor and placed in close contact with it). Alternatively, a method may be used in which the substrate is placed and heated.

[Brief explanation of drawings]

FIG. 1 shows an overview of a reactor for carrying out the invention.

Claims (1)

[Claims] 1. Cooling the inner wall surface of the high-frequency induction furnace using a reaction furnace having a high-frequency induction furnace and a heating furnace therein, and applying induction energy to the film-forming gas in the cooled region. In addition, activating the gas,
a step of forming a film on the substrate heated in the heating furnace; and a step of cleaning the inner wall surface of the reaction furnace with activated etching gas after stopping cooling of the inner wall surface of the high frequency induction furnace. A plasma vapor phase method characterized by having the following. 2. In claim 1, the wall surface of the reaction chamber is heated to -30°C by a refrigerator using fluorocarbon gas.
A plasma vapor phase method characterized by cooling to temperatures up to .