JPS62149117A - Method of vapor phase growth - Google Patents

Abstract

PURPOSE:To prevent crystal defects, by performing one process of removing an oxide film from the surface of a substrate and one process of forming an oxide film on the surface of the substrate and then removing the oxide film from the surface of the substrate. CONSTITUTION:A substrate 10 is set on a heating table 100. A reaction chamber 500 is evacuated as it is supplied with H2 through a gas nozzle 200. The substrate 10 is heated to 850 deg.C within the hydrogen. An ultraviolet lamp 300 is lit and ultraviolet rays are applied to the substrate 10, which hydrogen is supplied together with chloride corresponding to about 0.5% to the flow rate of the hydrogen, so that an oxide film is removed from the surface of the substrate 10 A (process A). Subsequently, oxygen is supplied into the chamber, while ultraviolet rays are continuously applied, to oxidize the surface of the substrate 10 (process B). After each of these processes A and B is carried out at least once, the process A is repeated to remove the oxide film 20 from the surface of the substrate 10. Subsequently, hydrogen and dichlorosilane are supplied in the chamber as ultraviolet rays are applied so that a single crystal silicon layer 40 is grown on the substrate 10. According to this method, crystal defects can be prevented effectively.

Description

[Detailed Description of the Invention] (Field of Application of the Invention) The present invention relates to a vapor phase growth method, and particularly relates to a vapor phase growth method in which a substrate surface is cleaned at a low temperature and a thin film is subsequently grown at a low temperature. .

(Background of the invention) In conventional silicon vapor phase growth, cleaning (# treatment) of the surface of a substrate (the inside of which is doped with a predetermined impurity)
K is the substrate in hydrogen or hydrogen containing a trace amount of chlorine,
A method of heat treatment at high temperature of about 1200° C. has been mainly used.

However, in this method, due to high temperature heat treatment.

When performing subsequent vapor phase growth, there is a problem in that autodoping of substrate impurities into the growth layer increases. Although this can be prevented by lowering the temperature of the pretreatment temperature, another problem arises in this case: the substrate surface is not sufficiently cleaned.

As a means to solve this problem, for example, JP-A-60-4
As shown in Publication No. 7414, the substrate surface is irradiated with ultraviolet rays in an oxygen-containing atmosphere to remove carbon-based contamination, and then heated in a vacuum to remove the oxide film. A method is known in which thin film growth is performed subsequently.

However, when the pretreatment and growth are performed at a low temperature of 900° C. or lower, there is a problem that a large number of dislocations and stacking faults, which are types of crystal defects, occur and the crystallinity of the grown layer is insufficient.

(Objective of the Invention) The object of the present invention is to provide a vapor phase growth method capable of preventing the occurrence of crystal defects that occur when a substrate is pretreated at a low temperature and subsequently crystal growth is performed at a low temperature. Our goal is to provide the following.

(Summary of the Invention) The present invention provides a method for irradiating a thin oxide film formed on a substrate surface with ultraviolet light or in a gas atmosphere, for example, in an atmosphere containing hydrogen and halogen gas or a mixed gas of hydrogen and hydrogen halide gas. At least once, the following two steps are performed: a step of converting the material into a plasma state and removing it, and then a step of irradiating the substrate with ultraviolet light in an oxygen-containing atmosphere or making a gas atmosphere into a plasma state and oxidizing the substrate surface. Step 5 Next, by removing the oxide film on the substrate surface, contaminants on the substrate surface that cause crystal defects are sufficiently removed, and then vapor phase growth is continued without taking the substrate out of the reaction chamber. It is characterized by

(Embodiments of the Invention) No. sm is a process explanatory diagram of the vapor phase growth force method of the present invention. 1
0 is a substrate doped with a predetermined impurity.

20 is an oxide film on the substrate 1O, 30 is a surface contaminant on the surface of the substrate 1O or in the oxide film 20, and 40 is a single crystal layer grown on the substrate 10.

Moreover, FIG. 2 shows an example of the loading amount for carrying out the vapor phase growth method of the present invention. 100 is a heating stand, 200
is a gas nozzle, and 300 is an ultraviolet lamp.

400 is a high frequency heating coil, and 5004 is a quartz reaction vessel.

The oxide film on the surface of the substrate is removed with a mixture of hydrofluoric acid and deionized/pure water (hereinafter referred to as pure water), washed with running pure water, and then cleaned with a mixture of ammonia, hydrogen peroxide, and pure water. At this time,
An oxide film 20 is formed on the substrate 10. Further, after washing with running pure water, the substrate is dried (step P in FIG. 1).

Thereafter, the substrate 10 is set on the heating table 100 in the reaction chamber. While flowing hydrogen (H2) from the gas nozzle 200, the inside of the reaction vessel 500 is evacuated to about ITorT,
The substrate is heated to 850°C in hydrogen.

Roughly, the ultraviolet lamp 300 is turned on to irradiate the substrate 10 with ultraviolet light, and chlorine of about 0.5% relative to the hydrogen flow rate is flowed together with hydrogen to remove the oxide film on the substrate surface (human process).
.

Next, while irradiating with ultraviolet light, the surfaces of the four plates are oxidized using V (02) instead of chlorine and hydrogen (step B).

After performing these consecutive steps A and B at least once (FIG. 1 shows an example in which steps A and B are repeated twice), step A is performed after i& to remove the oxide film 20 on the substrate surface. remove.

Subsequently, hydrogen and about 0.1 mo1% dichlorosilane (
A silicon single crystal layer 40 is grown on the substrate while flowing SiHgCAl2) and irradiating S external light (Step E).
.

Figure 3 shows an experimental example of the relationship between the number of consecutive steps A and B (horizontal axis) and the dislocation density of the crystal layer (vertical axis) when the present invention was carried out at a substrate temperature of 850°C. It is.

From this figure, if the continuous steps A and B are performed even once, the crystal 7
The dislocations within 140° decrease rapidly. When this step was repeated two or more times, the number of dislocation concubines was further reduced and a grown layer with good crystallinity was obtained.

This is because, as shown in FIG. 1, when the substrate surface is oxidized, the surface contaminants 30 are desorbed from the substrate surface in the form of oxides into the gas phase, or are incorporated into the oxide film 20. It is thought that this was removed together with the oxide film in the next oxide film removal step.

Figure 4 shows the results when consecutive steps A and B were carried out twice.

This figure shows the relationship between substrate temperature and dislocation density.

From this figure, it can be seen that a relatively high-quality single crystal can be obtained by the present invention even at a low temperature of 1700° C. from the substrate source.

In this example, the oxide film removal-surface oxidation process (A,
Although the case where the substrate 10 was irradiated with ultraviolet light in the continuous step B) and the crystal growth step was described, the same effect could be obtained even if the gas atmosphere was made into a plasma state instead of the ultraviolet light irradiation.

Further, although the description has been made using the vapor phase growth of silicon as an example, the present invention can also be applied to the vapor phase growth of compound semiconductors such as gallium arsenide (GaAs).

Further, although a case has been described in which a mixed gas of hydrogen and halogen gas is used in the step of removing the oxide film, it is of course possible to use a mixed gas of hydrogen and hydrogen halide gas.

(Effects of the Invention) According to the present invention, surface contaminants such as carbon film and carbon remaining on the substrate surface can be sufficiently removed at low temperature. Not only can a smaller growth layer be obtained, but also autodoping from substrate impurities can be reduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the steps of the vapor phase growth method of the present invention, FIG. 2 is a sectional view showing an example of an apparatus for carrying out the vapor phase growth method of the present invention, and FIGS. 3 and 4 are FIG. 3 is a diagram showing an example of the characteristics of a substrate obtained by applying a phase growth method.

Claims (6)

[Claims] (1) A vapor phase growth method for forming a thin film on the surface of a substrate after cleaning the surface, comprising a step A of removing an oxide film on the surface of the substrate, and a step B of forming an oxide film on the surface of the substrate. After carrying out the steps A and B at least once each,
The method comprises a step of removing an oxide film on the surface of the substrate, and a step of subsequently growing a thin film on the surface of the substrate in a vapor phase, and each step is performed continuously without taking out the substrate from the reaction chamber. Phase growth method. (2) The vapor phase growth method according to claim 1, wherein step A is performed in an atmosphere containing a mixed gas of hydrogen and one of halogen gas and halogen hydrogen gas. (3) The vapor phase growth method according to claim 2, wherein step A is performed while the substrate is irradiated with ultraviolet rays. (4) The vapor phase growth method according to claim 2, wherein the step A is carried out with the gas atmosphere in a plasma state. (5) The vapor phase growth method according to claim 1, wherein step B is performed in an oxygen-containing atmosphere while irradiating the substrate with ultraviolet rays. (6) The vapor phase growth method according to claim 1, wherein step B is performed in an oxygen-containing atmosphere with the gas atmosphere in a plasma state.