JPS6136194A - Production of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To produce a compound semiconductor in high purity in producing the compound semiconductor from a raw material melt in a crucible by the liquid- encapsulated Czochralski (LEC) method, by removing impurities in the melt with a <111> axis seed crystal, and growing the single crystal using a seed crystal in the different orientation. CONSTITUTION:A raw material melt 6 for a compound semiconductor, e.g. GaAs, is placed in a crucible 3 in a closed vessel 1, and B2O3 7 as a sealing agent for carbon is placed thereon. A <111> seed crystal 8 is dipped from above and then slowly pulled up to grow a <111> crystal. At this time, the carbon as an impurity in the melt 6 is removed into the <111> crystal by the facet growth. The <111> crystal is then pulled up, and the vessel 1 is divided into the upper and lower chambers by a shutter 12. The <111> crystal is exchanged with the <100> seed crystal 9 in the upper chamber. The shutter 12 is then opened to dip the seed crystal 9 in the melt 6 free of the impurity carbon and then slowly pulled up to pull up and grow the aimed GaAs semiconductor single crystal of high purity with almost no carbon content.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention effectively removes impurities in a raw material melt, particularly impurities with a large segregation coefficient, when manufacturing compound semiconductor single crystals by the LEC method, thereby achieving high purity. The present invention relates to a method of manufacturing a compound semiconductor single crystal.

[Technical background of the invention and its problems]

Compound semiconductor single crystals such as GaAs, GaP, InP and InSb have characteristics that cannot be obtained with 8i,
It is used as a substrate for electronic devices and optical devices.

Among them, GaAs has been increasingly used as a substrate for ultra-high-speed ICs in recent years, since a semi-insulating substrate can be obtained even when undoped. This GaAs single crystal for IC is directly synthesized by undoping and then manufactured by liquid-filled high-pressure pulling method (LFfC method).

In order to obtain an undoped semi-insulating substrate without thermal alteration with good reproducibility, it is necessary to reduce residual impurities in the crystal as much as possible, and in particular, it is required to reduce carbon, which is a P-type groove conductive impurity. .

However, the purity of the crystal raw material used (usually 6N to 7N)
) is not sufficient, and the heating elements and heat shields in the crystal manufacturing furnace are usually made of carbon products, so they are easily oxidized by trace amounts of oxygen, water vapor, etc. in the atmospheric gas.
There is a problem in that the raw material melt is contaminated by oxidation products. Therefore, the total amount of these residual carbons and contaminant carbons is usually ~1×10 cm in the crystal.

However, attempts have been made to remove such carbon by utilizing a reaction with B2O3, which is a carbon sealant in the melt, but the removal mechanism is unknown and the rate of removal has not been controlled. is the current situation. This is Ga in the LEC method.
This contributes to the difficulty in quality and manufacturing yield of As single crystals.

[Purpose of the invention]

The present invention improves the above-mentioned drawbacks when producing compound semiconductor single crystals by pulling using the LEC method, and provides a method for producing compound semiconductor single crystals that can improve and maintain the quality of the single crystal and the production yield. The purpose is to

[Summary of the invention]

The present invention provides a method for growing compound semiconductor single crystals with <11 D
This method focused on the phenomenon that facet growth occurs in axially pulled crystals, and the effective segregation coefficient of impurities becomes abnormally large in this region.This effectively removes impurities in the melt, especially impurities with large segregation coefficients. This method is characterized by subsequently pulling a highly pure single crystal. That is, the present invention provides a method for producing a compound semiconductor single crystal from a raw material melt in a crucible by the LEC method.
> and both seed crystals with the same or different orientations, a <111> single crystal is first grown using the <111> seed crystal, and at this time, impurities in the melt are removed using facet growth. Next, after replacing the seed crystal with a seed crystal of the same type or a different orientation, a highly pure single crystal of the same type or a different orientation is subsequently pulled from the remaining melt. Since the segregation coefficient of carbon in GaAs is about 1.4, it can be effectively removed.

〔Effect of the invention〕

As described above, the effects obtained by the present invention are as follows.

(1) Since impurities in the melt, especially impurities with a large segregation coefficient, can be effectively removed, a highly pure single crystal can be obtained.

(2) The reproducibility and stability of crystal production and crystal quality are improved.

(3) Productivity is improved by industrial application.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a single crystal manufacturing apparatus equipped with the functions of the present invention. In the figure, 1 is a container, 2 is a heater, 3 is a crucible, 4 is a crucible movement rotation axis, 5 is a seed movement rotation axis,
6 is melt, 7 is B2O3, 8 is <11 D seed crystal, 9
is <ioo> seed crystal, 10 is an exhaust valve, 11 is a pressure balance valve, 12 is a shutter, 13 is a shutter switch, 14
1 is a shutter guide, and 15 is a flange. In this example, first, a <11 D single crystal is grown from the melt 6 in the crucible 3 using the <11 D seed crystal 8 housed in the container 1 . At this time, the crystal grows in facets under appropriate temperature conditions and pulling parameters, and impurities are incorporated into the facet region at a high concentration, and it is well known that this effect is more pronounced for impurities with large segregation coefficients. be. Therefore, when a <111> single crystal has grown appropriately, the crystal is separated from the melt 6 and moved above the container 1. Next, the shutter 12 is moved by the introducer 13 along the guide 14 to separate the container 1 into two upper and lower chambers. The shutter 12 and the switch 13 can be implemented using a known magnetic coupling method or the like. Next, when the exhaust valve 10 is opened and the -F chamber of the container 1 is released to atmospheric pressure, the lower chamber of the container 1 is kept airtight by the shutter 12 and the guide 14 due to the pressure difference, so the royal chamber of the container 1 is closed to the inert gas. The <111> seed crystal 8 can be replaced with the <100> seed crystal 9 by opening the flange 15 while purging. Then, after closing the flange 15 and evacuating the upper chamber of the container 1, the pressure balance valve l
By opening the chamber 1 to balance the pressure between the upper and lower chambers of the container 1 and opening the shutter 12, it is possible to continuously grow a 100> single crystal without high purity.

Next, as a specific example, a case of manufacturing a GaAs single crystal will be described in detail. Internal diameter 10 by direct synthesis method
Approximately 1 kg of GaAs melt 6 was prepared in a crucible 3 of 0.0 mm. <111> seed crystal 8 installed at the beginning
After seeding was carried out using the same method, pulling was started at a speed of 5 h/h, and about 100 g of 1<111> crystals with a diameter of 80 mvi were grown. After that, it was replaced with <100> seed crystal 9 and seeded, and the pulling speed was 9 my/min.
Start pulling at h, and pull up (1
00> A single crystal was grown.

When the carbon concentration near the center of the cross section of the single crystal thus prepared was measured by infrared absorption method, it was found that (111>
It was found that the single crystal contains an extremely high concentration of carbon, about 3 XIO"/cm'. On the other hand,
>In a single crystal, it was found to be approximately 4×10′ α3, which is less than half of the conventional value. Next, when the resistivity of the <100> crystal was measured, it showed a value of 10 7 to 10 8 Ω·capacity from the head to the tail. Further, even after heat treatment at 800° C. for 15 minutes under A3 pressure, the resistivity remained at 10 7 Ω·cm or more, indicating excellent semi-insulating properties.

As explained above, there was carbon contamination of about I x 101@/an' in the crystal produced by the conventional method, but in the method of the present invention, the amount of carbon contamination was about 4 x to'7 Crn.
3, less than half of the conventional value, and a highly pure and excellent semi-insulating GaAs single crystal was obtained.

Furthermore, in the embodiments of the present invention, carbon impurities in GaAs pulling have been described, but other materials such as InP, GaP,
Of course, the present invention can also be applied to In8b and the like when impurities with particularly large segregation coefficients are effectively removed and high-purity single crystals are produced.

Further, in the embodiment of the present invention, the container 1 is closed to the container 2 by the shutter 12.
Although the seed crystals are separated and the seed crystals are replaced, the present invention is not limited to this example, and the same effects can be obtained as long as the functions of the present invention can be implemented substantially.

[Brief explanation of the drawing]

FIG. 1 is a schematic drawing for explaining one embodiment of the present invention. 1: Container, 2: Heater, 3 Nil acupuncture point, 4 Nil acupoint movement rotation axis, 5: Seed movement rotation axis, 6: Crystal liquid, 7:
B2O3,8: <111> Seed crystal, 9: <1
00> Seed crystal, 10: Exhaust valve, 11: FE balance valve, 12: Shutter, 13: Shutter switch, 14: Shutter guide, 15: Flange

Claims (1)

[Claims] LE from raw material melt in a crucible placed in a high-pressure container
When manufacturing a compound semiconductor single crystal by method C, <1
11> and both seed crystals with the same or different orientations,
First, a <111> single crystal is grown offset using a <111> seed crystal to remove impurities from the melt, and then a single crystal of the same or different orientation is grown from the remaining melt using a seed crystal of the same or different orientation. A method for producing a compound semiconductor single crystal, comprising a step of growing a crystal.