JPS6114651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for vapor phase growth of an epitaxial film of a compound semiconductor (hereinafter referred to as "- group semiconductor") composed of elements of Groups and Groups of the Periodic Table.

The vapor phase epitaxial growth method has many advantages such as excellent mass productivity and ease of changing the mixed crystal ratio, and is therefore widely practiced industrially.

Vapor phase epitaxial growth of - group semiconductors is usually carried out using a vertical vapor phase epitaxial growth apparatus as illustrated in FIG. 1 or a horizontal vapor phase epitaxial growth apparatus as illustrated in FIG.

That is, in FIG. 1, 1 is a vertical reaction vessel, which is usually made of quartz. 2 is a rotary substrate support stand, and 3 is an inlet for the group component. Reference numeral 4 indicates an inlet for hydrogen chloride used for transporting Group Group components such as gallium, and 5 indicates an inlet for carrier gas such as hydrogen. 6 is a reaction gas outlet. 7 is a container for a group component such as metal gallium. 8 is an electric furnace for heating 1, which is usually divided into two or more parts.

In Figure 2, 9 is a horizontal reaction vessel, 10 is 9
It is an electric furnace that heats
It is divided into many parts. Reference numeral 11 denotes an inlet for a group component, and 12 an inlet for hydrogen chloride used for transporting a group component such as metal gallium.
In this case, a carrier gas such as hydrogen is introduced from 11 and 12. 13 is a container for a group component such as metal gallium. 14 is a single crystal substrate support stand. 15 is a reaction gas outlet.

- When performing vapor phase growth of a group V semiconductor epitaxial film, in order to improve the productivity per process, it is necessary to use a single crystal substrate so that the surface of the substrate on which the epitaxial film is grown is suitable for the vapor phase growth of the epitaxial film. parallel or oblique to the direction of the airflow used, i.e.
Preferably, it is placed at an angle that is not perpendicular to the direction of the airflow. For example, in a vertical reactor, as shown in FIG. 1, the single crystal substrate is installed obliquely to the direction of the air flow,
When using a horizontal reactor, it is desirable to install the single crystal substrate horizontally as illustrated in FIG.

However, when a single crystal substrate is placed in a reaction vessel as described above and vapor phase epitaxial growth is performed, the epitaxial film grows faster on the upstream peripheral edge of the single crystal substrate surface than on other parts. , the epitaxial film is raised higher than other parts of the substrate, forming a so-called crown.

Figure 3 shows the above crown formed.
FIG. 2 is a longitudinal cross-sectional view of a group semiconductor epitaxial wafer in the airflow direction. That is, in Figure 3, 16
1 is a single crystal substrate, 17 is an epitaxial film, and 1 is an epitaxial film.
8 is a crown formed upstream of 16.

The formation of the crown 18 becomes more pronounced as the epitaxial film 17 becomes larger, and the crown 18 is usually raised by about 10 μm to 40 μm relative to other parts of the epitaxial wafer.

When a crown as described above is formed, the flatness of the surface of the epitaxial wafer is significantly impaired. Therefore, it interferes with processes such as mask formation and thermal diffusion of impurities for forming semiconductor elements such as light emitting diodes, so conventionally the portion of the substrate on which the crown is formed is removed or the wafer is The surface was polished.

However, removing and polishing the crown is complicated and has problems such as lowering the yield of epitaxial wafers as products.

As a result of extensive research, the present inventors have discovered that the above-mentioned problems can be solved by etching a single crystal substrate prior to vapor phase epitaxial growth, and have arrived at the present invention.

An object of the present invention is to provide a novel method for vapor phase growth of a - group compound semiconductor epitaxial film that does not form a crown and has good planarity.

The above object of the present invention is to provide -
In a method for vapor phase growth of a group compound semiconductor epitaxial film, prior to the vapor phase growth of the epitaxial film, an air flow containing an etching gas is caused to flow in the same direction as the air flow used for the vapor phase growth, and the substrate This is achieved by a method characterized in that the thickness of the peripheral edge of the substrate surface on the upstream side of the airflow is made 3 to 40 μm thinner than the other portion of the substrate surface by etching.

- Group compound semiconductors include gallium arsenide (GaAs), gallium phosphide ( _Gap ), gallium arsenide phosphide (GaAs _1-X P Gallium indium (Ga _1-y In _y P, 0<y<1), Gallium indium arsenide phosphide (Ga _1-y In _y As _1-X P _X , 0<x<1, 0
<y<1), etc. are exemplified.

As the single crystal substrate, it is desirable to use a substrate cut from the same semiconductor single crystal as the - group semiconductor forming the epitaxial film. Further, when a single crystal different from the - group semiconductor used to form the epitaxial film is used as the single crystal substrate, it is desirable that the difference in lattice constant between the substrate and the epitaxial film is as small as possible.

As the single crystal substrate, gallium arsenide, gallium phosphide, germanium, silicon, etc. are usually used. The crystallographic plane orientation of the single crystal substrate surface is
(100) plane, a plane forming an angle of inclination within 5° with the (100) plane,
It is usually selected from the range of (111) and (111) planes.

As the etching gas, chlorine (Cl ₂ ), bromine (Br ₂ ), arsenic trichloride (AsCl ₃ ), phosphorus trichloride (PCl ₃ ), and preferably hydrogen chloride (HCl) are used.

In carrying out the present invention, the single crystal substrate is placed in a reactor under the same conditions as for the epitaxial growth reaction, and etching is performed. That is,
The single crystal substrate surface is parallel or oblique to the direction of the air flow used for the growth reaction, in other words,
Install it so that it forms an angle that is not perpendicular to the direction of the airflow.

Thereafter, the temperature of the reaction vessel is raised to the same temperature as that for epitaxial growth in a hydrogen gas flow in the same direction as the gas flow used for the growth reaction. Usually, the temperature of the single crystal substrate is set in a range of 700°C or more and 80°C or less.

When hydrogen chloride is used as the etching gas, after the reaction vessel reaches a predetermined temperature, hydrogen chloride is added to the hydrogen stream at a concentration of 1% to 10%, preferably 4% to 7%. etching the single crystal substrate for at least 2 minutes and up to 10 minutes to make the peripheral edge of the substrate on the upstream side of the hydrogen gas stream thinner by 3 to 40 μm than other parts of the substrate. do. Since the etching rate of the upstream peripheral edge of the substrate is higher than other parts, by adjusting the concentration of hydrogen chloride and the etching time, the thickness between the upstream peripheral edge of the substrate and the other parts can be adjusted. The difference can be adjusted.

When using chlorine, bromine, etc. as the etching gas, the etching can be carried out under the same conditions as above. As a result, a single-crystal substrate whose upstream peripheral edge is sloped and thin is obtained.

After the above-mentioned etching is completed, vapor phase growth of a - group semiconductor epitaxial film is performed under normal conditions. Although the vapor phase growth of the epitaxial film may be carried out in a reaction vessel different from that used for etching, it is more effective to carry out the vapor phase growth in the same reaction vessel.

In addition, when manufacturing light emitting diodes, the back side of the obtained epitaxial wafer, that is, the single crystal substrate side, may be polished and used, so the part of the epitaxial film close to the single crystal substrate is the same as the single crystal substrate. If the epitaxial film is formed to have a somewhat higher impurity concentration, the electrode can be easily formed.

By carrying out the method of the present invention, the formation of crowns can be suppressed to a minimum. Therefore, the polishing process or the process of removing the crown can be omitted, and the productivity of epitaxial wafers can be improved.

300μ especially used in the production of light emitting diodes
The effect is remarkable when growing an epitaxial film as thick as 100 m.

As described above, the industrial utility value of the present invention is extremely large.

The present invention will be explained in more detail below based on Examples and Comparative Examples.

Example An n-type gallium arsenide single crystal substrate with a carrier concentration of 8×10 ¹⁷ /cm ³ and a surface inclined at an angle of 3° in the <110> direction with respect to the (100) plane was degreased and Polished to remove surface distortion. The obtained gallium arsenide single crystal substrate with a thickness of 320 μm was placed in a horizontal epitaxial reaction vessel (inner diameter 7 cm, length 100 cm) with a structure similar to that shown in Fig. 2 so that the surface was horizontal. , and was installed at the position shown in FIG. 14. Metallic gallium was placed in a quartz container and placed at the position shown in FIG. 13 within the reaction container.

While flowing hydrogen as a carrier gas at a flow rate of 1500 ml/min into the reaction vessel from the inlet 12,
The temperature was raised to 810°C in the part where the metal gallium container was installed, and to 750°C in the part where the single crystal substrate was installed.
After the temperature of each part of the reaction vessel became constant, in order to etch the single crystal substrate, hydrogen chloride was introduced from the inlet 11 at a flow rate of 90 ml/min for 5 minutes so as not to come into contact with the metal gallium. As a result, the upstream peripheral edge of the single crystal substrate became 30 μm thinner than the other parts. After etching, reduce the flow rate of hydrogen chloride to 18ml/
At the same time, hydrogen containing 12% arsine (AsH ₃ ) was introduced from the inlet 11 at 280 ml/min and then into the inlet 12.
Hydrogen containing 10 ppm diethyl tellurium ((C ₂ H ₅ ) ₂ Te) was introduced at a flow rate of 15 ml/min for 5 minutes to form a gallium arsenide epitaxial film. after that,
Arsine flow rate from 280 ml/min to 120 ml/min for 100 minutes
ml/min and increasing the flow rate of hydrogen containing 12% phosphine continuously from 0 to _{60 ml/min to change the mixed crystal percentage from GaAs to GaAs 0.6 P 0.4 .} A gallium arsenide mixed crystal ratio change layer was formed. Next, each component is held at the above flow rate,
A GaAs _0.6 P _0.4 epitaxial layer was formed _for 90 minutes _.

As a result, no crown formation was observed in the obtained gallium arsenide phosphide epitaxial wafer. The thickness of the upstream edge of the epitaxial wafer is 350 μm, and the thickness of the downstream edge is 347 μm.
It was μm.

Comparative Example A GaAs _0.6 P _0.4 epitaxial film was grown on a gallium arsenide single crystal substrate in the same manner as in the example except that etching _{with hydrogen} chloride was not performed.

Formation of a crown was observed in the obtained epitaxial wafer. The thickness of the upstream peripheral edge of the epitaxial wafer was 379 μm, and the thickness of the downstream peripheral edge was 349 μm.

[Brief explanation of the drawing]

FIG. 1 is an example of a longitudinal cross-sectional view of a vertical vapor phase epitaxial reaction apparatus. FIG. 2 is an example of a longitudinal cross-sectional view of a horizontal gas phase epitaxial reactor. FIG. 3 is an example of a longitudinal cross-sectional view in the air flow direction of a - group semiconductor epitaxial wafer in which a crown is formed. DESCRIPTION OF SYMBOLS 1... Vertical reaction vessel, 2... Rotating substrate support stand, 3... Inlet for group component, 4... Inlet for hydrogen chloride for transporting group component, 5... Carrier gas inlet, 6... ...Discharge port, 7...Group component container,
8...Electric furnace, 9...Horizontal reaction vessel, 10...Electric furnace, 11...Inlet for group component, 12...Inlet for hydrogen chloride for transporting group component, 13...Group component container , 14... single crystal substrate support stand, 15...
...Exhaust port, 16...Single crystal substrate, 17...Epitaxial film, 18...Crown.

Claims (1)

[Claims] 1. In a method for vapor phase growing a compound semiconductor epitaxial film made of elements of Groups and V of the periodic table on the surface of a single crystal substrate, prior to the vapor phase growth of the epitaxial film, an air flow used for the vapor phase growth is applied. etching the substrate by flowing an air flow containing an etching gas in the same direction as the etching gas;
A method characterized in that the thickness of the peripheral edge of the substrate surface on the upstream side of the airflow is made thinner by 3 to 40 μm than other parts of the substrate surface.