JPH021235B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention forms an amorphous or semi-amorphous film of silicon or silicide on a surface to be formed on a substrate using a CVD method (vapor phase deposition method) or glow discharge. This was done to prevent the coating that is simultaneously formed on the wall surface or the powder that has been deposited on the wall surface to fly off again and get mixed into the semiconductor coating, seriously deteriorating the characteristics. The present invention is characterized by chemically etching and removing these deposits, and further by preventing or reducing the occurrence of these deposits.

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 coating formed on this inner wall easily separates, and as a result, the separated powder flies and adheres to the substrate, creating snowflakes, etc., and as a result, pinholes, etc. are created in the formed coating. There were some shortcomings. 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 the film formation 5 to 10 times, it was always removed from the apparatus and immersed in a solution such as hydrofluoric acid to dissolve away the deposits. The operations such as checking are extremely complicated, and as a result, lot variations occur, which is a cause of variations in products, especially semiconductor devices.

In the present invention, the coating or powder adhered to the inner wall of the reactor is removed using nitrogen fluoride (an etching gas such as NF, _NF2 , _NF3 , etc. When performing plasma vapor phase etching using NF ₃ ), in order to completely eliminate any residue on the inner wall of the reactor and clean it, water cooling is stopped and the temperature is increased when cleaning this area by plasma etching. It is characterized by promoting the reaction on the wall surface of the reactor and increasing the 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 located away from the region where the coating is formed in the vapor phase method, and the substrate 10 can be heated by an induction or resistance radiation heating electric furnace 7 on a boat 8. did. Furthermore, the reactor in front of this substrate had a double tube on the outside and was water-cooled to prevent or reduce nucleation on the wall. In addition, during plasma cleaning, the entire reactor from which the cooling water has been removed is cleaned intensively, focusing on the area where the boat is installed.
Other features include increasing the etching speed by heating to 100 to 1000°C and eliminating the presence of white powdery residues that are not etched after etching.

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 (SixHyX, Y>1), SiH ₂ Cl ₂ , SiF ₄ ,
These reactive gases diluted with a gas such as SiCl ₄ or an inert gas are introduced from 1, and a reaction is caused by applying 10 to 500 W of induction energy at a frequency of 0.5 to 50 MHz or 1 to 10 GHz using a high frequency induction furnace 6. The atmosphere is reduced to 0.01 to 10 torr in the furnace and turned into plasma. This plasma-formed gas is heated to 200 to 800°C in a heating furnace, and then amorphous, semi-amorphous (semi-amorphous, semi-crystalline, etc.)
Quasi-amorphous, Semi-crystal or Quasi
―Semiconductors with an intermediate structure between amorphous and crystalline, such as crystals, are collectively referred to here).
Form to a film thickness of 10 μm. If this is repeated several more times, reaction products similar to those produced in the formation of the film on the substrate will adhere to the inner wall 9. In particular, the heated area becomes a film, and a powdery film adheres to the inner wall near the exhaust port on the rear side. Of course, most of the reaction products are contained in the needle valve 1 along with the carrier gas.
1. It is discharged outside by a rotary pump 13 via a stop valve 12.

In the present invention, when a reactive gas is chemically activated, decomposed or reacted with induced energy,
At the energy supply section, the active gas collided with the wall of the reactor, raising the temperature of the wall to 200-800°C. 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.
The temperature was kept at 10 to 50°C, and as a result, during film formation, the adhesion of reactants was reduced to 1/10 to 1/30 of that in the case where the wall surface was not cooled.

Furthermore, when the film to be formed is silicon, in order to make the film P or N type conductivity, it is necessary to add valent impurities such as boron and indium, or phosphorus, arsenic,
A V-valent impurity such as antimony may be introduced as a hydride or chloride (halide) through step (4).

In addition, when a film of 0.001 to 10 μC was formed by this film forming method 1 to 3 times, a film 9 with an apparent thickness of 0.01 to 100 μ and a collection of particles was formed on the inner wall. , the present invention removes the film or powder 9 using nitrogen fluoride (hereinafter referred to as NF _{3 )} .
) Furthermore, or by mixing an inert gas such as Ar into the gas from (4), at a pressure of 0.5 to 10 torr.
The experiments were carried out by applying induction energy of 50 MHz or 1 to 10 GHz according to (6) to generate plasma. In place of nitrogen fluoride, other etching gases such as nitrogen chloride, mixed gases thereof, or compounds such as nitrogen fluoride chloride may be used. At this time, active fluorine and nitrogen (N ^* or N ₂ ) are produced in the reactor, and solid carbon, such as CF ₄ that is harmful to semiconductors, is not generated or mixed into the film. In the present invention, the reactive gas on the inner wall of the reactor can be easily removed by heating the area installed in the boat to a temperature at or above the temperature at which it was formed, or further heating it to a temperature of 100 to 1000°C. It was possible to react with the reactive component and remove it by etching, and also to prevent the inner wall from becoming cloudy after the cleaning process.

After sufficient plasma etching, plasma formation is further performed for 15 minutes to 1 hour in an inert gas, nitrogen alone, or a gas containing 2 to 10% hydrogen to remove fluorine, which is an active etching gas, remaining on the inner wall. After removal, the substrate was introduced into the reactor again to form a film of silicide gas.

By doing this, whereas in the past, after forming a film 10 to 100 times, the reactor was removed and chemically etched using a solution to clean it, in the present invention, the process is performed every 1 to 10 times. Since the inner wall can be cleaned without removing the equipment, a uniform coating without pinholes can be formed semi-continuously on the next substrate, and its reproducibility is extremely excellent. Ta.

In the present invention, the reactor constitutes a reaction tube having a tubular shape, and its size is 5 to 30 cm in diameter and 1 to 30 cm in length.
It is particularly effective in the case of CVD equipment with a large diameter of 5m that is difficult to move.Furthermore, it does not generate poisonous substances as a by-product, unlike conventional etching with a solution, and the gas used in the reaction does not emit as a by-product. Since the product is nitrogen, it is a non-reactive gas in terms of semiconductors, so it is less likely to be affected by the generation of lattice defects, which is also preferable.

The present invention is based on a gas phase method for forming silicon or its compounds. But also germanium,
The same applies to -V compounds such as BP and GaAs, and it is also effective when forming metals such as aluminum by the CVD method. Especially when the deposit is aluminum, etching with nitrogen chloride is even more effective. It was big.

The method of the present invention prevents deposits from being mixed in a film as a lump with a large surface area like a powder and a large number of interface states at the grain boundaries, and can be applied to a film such as a semiconductor even on a microscopic level. It was effective in producing a semiconductor having a homogeneous amorphous, semi-amorphous or semi-crystalline structure.

In the past, the unintentionally generated powder conversely spattered the coating during film formation, making it easy to form voids, pinholes, etc. in the coating. However, the method of the present invention has more effects than the combination of the gas phase method and the plasma etching method in the gas phase method, and in particular, it does not perform plasma etching on the substrate, but removes deposits on the inner wall of the reactor. During the removal of fluorine and its deposits, the reaction is promoted by increasing the temperature and converting highly reactive radicals such as fluorine into not only fluorine itself, but also the reaction products such as silicon fluoride, nitrogen fluoride, and inert nitrogen. Another feature of the method of the present invention is that since the gas is chemically stable, it is substantially non-polluting even when the gas is discharged to the outside through a rotary pump.

In the examples of the present invention, cooling was mainly described as water cooling. However, using a refrigerator to cool something 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 cools not only the active area of the reactor, but also the wall surface of the reaction tube in the area where the substrate is provided, and a heater for heating the substrate is installed in the reactor, and the substrate is placed in close contact with it. A method of heating the substrate may also be used.

[Brief explanation of drawings]

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

Claims (1)

[Scope of Claims] 1. A quartz reactor and an electric furnace surrounding the quartz reactor are provided, and a reactive gas is introduced onto a substrate disposed in the reactor to form a film, and the A step of forming a film identical to the film as a film or powder on the inner wall of the reactor, a step of removing the substrate from the reactor, and a step of removing the film or powder attached to the inner wall of the reactor after the step. A method for cleaning the inside of a reactor, comprising the step of cleaning the inner wall of the reactor by heating the reactor in an electric furnace surrounding the reactor and removing the reactor by plasma vapor phase etching. 2 In claim 1, the temperature at which the film was formed or higher, or 100 to 1000
A method for cleaning the inside of a reactor, characterized in that it is removed by plasma vapor phase chemical reaction etching in an atmosphere heated to a temperature of .degree.