JP4379195B2 - Method for producing compound semiconductor single crystal - Google Patents

Description

  The present invention relates to a method for producing a compound semiconductor single crystal, and more particularly to a method for producing a gallium arsenide (GaAs) single crystal.

  Among compound semiconductor single crystals, GaAs single crystals are high-frequency devices used as substrates for optical devices such as light-emitting diodes (LEDs) for display and laser diodes (LDs) for light sources such as compact disks, and for satellite broadcasting and mobile phones. Widely used as a substrate for electronic devices such as

  An example of a conventional method for manufacturing such a GaAs single crystal will be described below with reference to the drawings. In the drawings of the present application, the same reference numerals denote the same or corresponding parts.

  First, the crucible 1 shown in the schematic cross-sectional view of FIG. Next, as shown in the schematic configuration diagram of FIG. 4B, the crucible 1 is installed in a container 5 such as a quartz ampoule. Here, the container 5 is connected to a decompression device 6 such as a vacuum pump. Subsequently, as shown in the schematic configuration diagram of FIG. 4C, after the seed crystal 3 is installed in the lower part of the crucible 1, the raw material 4 made of GaAs polycrystal is accommodated in the crucible 1. And after installing the cap 2 in the upper part of the container 5 and sealing the inside of the container 5, the pressure in the container 5 is reduced using the decompression device 6.

  Next, after fusing the container 5 and the cap 2, the container 5 is separated from the decompression device 6, and the portion of the separated container 5 is closed, as shown in the schematic cross-sectional view of FIG. The crucible 1 in which the raw material 4 is accommodated in the container 5 is sealed.

  Then, the container 5 is installed on the support stand 8 above the lower shaft 7 of the crystal growth apparatus shown in the schematic cross-sectional view of FIG. And the container 5 is heated with the heater 9 installed in the outer side of the container 5, and the raw material 4 is fuse | melted. Here, in this crystal growth apparatus, since a temperature gradient is formed so that the temperature decreases from the upper side to the lower side of the crystal growth apparatus, when the lower shaft 7 is moved downward, the molten raw material 4 is The seed crystal 3 gradually solidifies upward from the surface of the seed crystal 3, and a GaAs single crystal grows on the surface of the seed crystal 3.

However, this conventional method for producing a GaAs single crystal has a problem that the specific resistance varies for each produced GaAs single crystal. As a result, there is a problem that the characteristics of optical devices and electronic devices using GaAs single crystals also vary.
Crystal Engineering Handbook Editorial Committee, Crystal Engineering Handbook, First Edition, Kyoritsu Shuppan, September 25, 1990, p. 676-678

  The objective of this invention is providing the manufacturing method of the compound semiconductor single crystal which can reduce the dispersion | variation in the specific resistance of a compound semiconductor single crystal.

  As a result of intensive studies by the present inventors, it has been found that variation in the specific resistance of the compound semiconductor single crystal can be reduced by reducing the amount of water in the container in which the crucible is installed, thereby completing the present invention. It came.

The present invention includes a step of reducing the amount of water in the container in which the crucible containing the raw material is installed by heating the container to 100 ° C. or more and 500 ° C. or less while reducing the pressure in the container, and after stopping the heating. Further , a compound semiconductor single crystal comprising: a step of reducing the pressure in the container to 10 ⁻⁴ Pa or less and closing the container; and a step of growing the compound semiconductor single crystal by solidifying after melting the raw material stored in the crucible. It is a manufacturing method.

  Furthermore, in the method for producing a compound semiconductor single crystal of the present invention, the compound semiconductor single crystal is preferably a gallium arsenide single crystal.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the compound semiconductor single crystal which can reduce the dispersion | variation in the specific resistance of a compound semiconductor single crystal can be provided.

  Hereinafter, a preferred example of the method for producing a compound semiconductor single crystal of the present invention will be described with reference to the drawings.

(Process to reduce the amount of water in the container)
FIG. 1A shows a schematic cross-sectional view of a preferred example of a crucible used in the present invention. The crucible 1 is made of pBN (pyrolytic BN) and has a shape in which the lower part is thin. Here, when the crucible 1 is made of pBN, the heat resistance and chemical stability of the crucible 1 tend to be excellent. In addition, when the crucible 1 is made of pBN, B ₂ O ₃ coating can be performed by forming a B ₂ O ₃ layer on the surface of the inner wall of the crucible 1.

  Next, as shown in the schematic configuration diagram of FIG. 1B, the crucible 1 is installed in a container 5 such as a quartz ampoule. Here, the container 5 is connected to a decompression device 6 such as a vacuum pump that sucks the gas in the container 5, for example, and a heater 10 for heating the container 5 is installed outside the container 5.

Subsequently, as shown in the schematic configuration diagram of FIG. 1C, the seed crystal 3 is placed in the lower part of the crucible 1 and then the raw material 4 is accommodated in the crucible 1. And the cap 2 is installed in the upper part of the container 5, and the inside of the container 5 is sealed. Here, the raw material 4 is not particularly limited as long as a target compound semiconductor single crystal can be produced. For example, a target compound semiconductor polycrystal is used. Further, the raw material 4 may contain B ₂ O ₃ .

  Then, the temperature in the container 5 is heated to 100 ° C. or more and 500 ° C. or less, more preferably 200 ° C. or more and 300 ° C. or less by the heater 10 while reducing the pressure in the container 5 by the decompression device 6. As a result, the water present in the container 5 is heated to become water vapor, and then sucked into the decompression device 6 to reduce the amount of water in the container 5. Here, when the temperature in the container 5 is heated to 100 ° C. or more and 500 ° C. or less, more preferably 200 ° C. or more and 300 ° C. or less, while suppressing deterioration due to heating of the crucible 1, the raw material 4 and the container 5, There is a tendency that the amount of water in the container 5 can be efficiently reduced.

After the heating of the container 5 by the heater 10 is stopped, the pressure in the container 5 can be further reduced by the decompression device 6. That is, the pressure in the container 5 can be further reduced as compared with the conventional case by the amount of water content in the container 5 decreased. Here, the pressure in the container 5 after the heating of the container 5 is stopped is preferably 10 ⁻⁴ Pa or less. In this case, since the moisture has been sufficiently removed from the inside of the container 5, the variation in specific resistance of the compound semiconductor single crystal tends to be further reduced.

  Next, after fusing the container 5 and the cap 2, the container 5 is separated from the decompression device 6, and the container 5 is closed as shown in the schematic sectional view of FIG. The crucible 1 in which the raw material 4 is accommodated in 5 is enclosed. Here, the crucible 1 is enclosed in the container 5 in a state in which the pressure in the container 5 is reduced as compared with the conventional case by the amount of water in the container 5 decreased.

  In the above, the raw material 4 is stored in the crucible 1 after the crucible 1 is installed in the container 5, but the crucible 1 may be installed in the container 5 after the raw material 4 is stored in the crucible 1, After the crucible 1 is installed in the container 5 and the water content in the container 5 is reduced, the raw material 4 may be accommodated in the crucible 1. However, from the viewpoint of preventing the crucible 1 from being broken by the mass of the raw material 4 and reducing the variation in the specific resistance of the compound semiconductor single crystal, the crucible 1 is installed in the container 5 as described above. It is preferable to store the raw material 4 in the crucible 1 later.

(Step of growing compound semiconductor single crystal)
The container 5 in which the crucible 1 shown in FIG. 1D is enclosed is installed on a support base 8 above the lower shaft 7 of the crystal growth apparatus shown in FIG. 2, for example. And the container 5 is heated with the heater 9 installed in the outer side of the container 5, the temperature of the raw material 4 is raised, and the raw material 4 is fuse | melted. In this crystal growth apparatus, a temperature gradient is formed so that the temperature decreases from the heater 9 installed above to the heater 9 installed below. Therefore, when the lower shaft 7 is moved downward, the molten raw material 4 gradually solidifies upward from the surface of the seed crystal 3, and a compound semiconductor single crystal grows on the surface of the seed crystal 3. Here, when the seed crystal 3 is installed, a compound semiconductor single crystal having the same crystal orientation as the seed crystal 3 can be grown on the seed crystal 3.

  Thereafter, the grown compound semiconductor single crystal is gradually cooled. And the crucible 1 is taken out from the container 5, and the compound semiconductor single crystal grown from the crucible 1 is taken out.

  A GaAs single crystal is suitable as the compound semiconductor single crystal that can be produced in the present invention. For example, a compound semiconductor single crystal such as a gallium phosphide (GaP) single crystal or an indium phosphide (InP) single crystal is used. It goes without saying.

Example 1
A crucible 1 shown in FIG. 1A was placed in a quartz ampule as a container 5 shown in FIG. Next, as shown in FIG. 1C, a seed crystal 3 made of a GaAs single crystal was placed at the bottom of the crucible 1, and 10 kg of GaAs polycrystal was accommodated as a raw material 4.

Next, using a vacuum pump as the decompression device 6 connected to the container 5, the pressure in the container 5 was first reduced to about 3 × 10 ⁻³ Pa as shown in FIG. Next, while continuously reducing the pressure in the container 5, the temperature in the container 5 is heated to 240 ° C. from the outside of the container 5 by the heater 10, the moisture in the container 5 is changed to water vapor, and drawn into the vacuum pump. The amount of water in the inside was reduced. And the heating by the heater 10 was stopped when 66 minutes passed from the time of starting the pressure reduction in the container 5. Thereafter, the pressure in the container 5 was continuously reduced, and the pressure in the container 5 was reduced to about 3 × 10 ⁻⁵ Pa. At this time, 143 minutes had elapsed since the start of the pressure reduction in the container 5 by the vacuum pump.

  Then, the crucible 1 was enclosed in the container 5 as shown in FIG. 1D by disconnecting the connection between the container 5 and the decompression device 6 and closing the part of the disconnected container 5.

  After that, the container 5 in which the crucible 1 is sealed is placed on the support base 8 above the lower shaft 7 of the crystal growth apparatus shown in FIG. Melted. Then, a GaAs single crystal was grown on the seed crystal 3 by moving the lower shaft 7 downward in a temperature region where a temperature gradient was formed so that the temperature decreased from above to below. Then, the GaAs single crystal after completion of the growth was cooled and taken out from the crucible 1.

Such a work was repeated several times, and the resistivity of the manufactured GaAs single crystal was examined. The average value of the resistivity was 1.7 × 10 ⁸ (Ω · cm), indicating variations in the resistivity. The standard deviation was 6.3 × 10 ⁷ .

(Comparative Example 1)
A GaAs single crystal was produced in the same manner as in Example 1 except that the container 5 was not heated to reduce the water content in the container 5.

Here, as shown in FIG. 3, in Comparative Example 1, the pressure in the container 5 decreased exponentially from the time when the pressure in the container 5 started to decrease until 60 minutes passed. However, after that, the pressure in the container 5 hardly decreased, and the pressure was reduced from the time when the pressure in the container 5 started to decrease until 180 minutes passed. It could only be reduced to about 10 ⁻⁴ Pa. Thereafter, a GaAs crystal was grown on the seed crystal 3 in the same manner as in Example 1.

Such a work was repeated several times, and the specific resistance of the manufactured GaAs single crystal was examined. As a result, the average value of the specific resistance was 1.6 × 10 ⁸ (Ω · cm), indicating variations in specific resistance. The standard deviation was 9.3 × 10 ⁷ .

  As shown in the above results, the standard deviation of the specific resistance of the GaAs single crystal of Example 1 is smaller than that of Comparative Example 1, and it is confirmed that the variation in specific resistance of the GaAs single crystal of Example 1 is reduced. It was. This is considered to be because the temperature in the container 5 was heated from the outside of the container 5 by the heater 10 while the pressure in the container 5 was reduced, and the water content in the container 5 was reduced.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is suitably used for the production of compound semiconductor single crystals, particularly for the production of GaAs single crystals.

(A) is a schematic cross-sectional view of a preferable example of a crucible used in the present invention, (B) is a schematic configuration diagram of a preferable example of a container, a decompression device and a crucible used in the present invention. (C) is a schematic configuration diagram of a preferable example of a container, a decompression device, and a crucible after the seed crystal and the raw material are stored in the crucible shown in (B), and (D) is a schematic view of the crucible enclosed in the container. It is typical sectional drawing of a preferable example. It is typical sectional drawing of a part of preferable example of the crystal growth apparatus used for this invention. It is the figure which showed the relationship between the change of the pressure in the container in an Example and a comparative example, and elapsed time. (A) is typical sectional drawing of an example of the crucible used in the manufacturing method of the conventional GaAs single crystal, (B) is an example of the container, decompression device, and crucible used for the manufacturing method of the conventional GaAs single crystal. (C) is a schematic configuration diagram of a preferable example of a container, a decompression device, and a crucible after containing a seed crystal and a raw material in the crucible shown in (B), (D ) Is a schematic cross-sectional view of a preferred example of a crucible enclosed in a container.

Explanation of symbols

  1 crucible, 2 cap, 3 seed crystal, 4 raw material, 5 container, 6 decompression device, 7 lower shaft, 8 support base, 9,10 heater.

Claims (2)

A step of reducing the amount of water in a container provided with a crucible containing raw materials by heating the container to 100 ° C. or more and 500 ° C. or less while reducing the pressure in the container; and after the heating is stopped, Reducing the pressure in the vessel to 10 ⁻⁴ Pa or less and closing the vessel; and growing the compound semiconductor single crystal by solidifying after melting the raw material stored in the crucible. A method for producing a compound semiconductor single crystal. The method for producing a compound semiconductor single crystal according to claim 1, wherein the compound semiconductor single crystal is a gallium arsenide single crystal.

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