JP2000302588A - Production of compound semiconductor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily withdraw a grown compound semiconductor crystal from a crucible by solidifying all of a raw material melt in such a state that the front end of a suspension means (such as metal wire) placed above the crucible is immersed in the raw material melt so as to attain a prescribed depth, and thereafter, in the furnace inside cooling stage, elevating the suspension means or lowering the crucible before solidification of a liquid encapsulating medium, to withdraw the objective grown compound semiconductor crystal from the crucible. SOLUTION: This production process comprises: growing a compound semiconductor crystal 4 by relatively moving a heater 6 and a crucible 1 to each other or controlling the temperature of the heater 6, to gradually solidify a raw material 3 melt in the direction upward from the side of a seed crystal 2; then immersing the front end 9 of a suspension means 8 whose upper end is connected to an elevating/lowering device or the ceiling of a furnace, in the raw material melt 3; and in that state as it is, solidifying all of the raw material melt 3 to complete the growth of the crystal 4; wherein in the cooling stage, the suspension means 8 is pulled up before the solidification of a liquid encapsulating medium, to withdraw the grown crystal 4 from the crucible 1 and to cool the crystal 4 to room temperature while holding the crystal 4 above the crucible 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a compound semiconductor crystal, and more particularly to a method for producing a compound semiconductor crystal suitable for producing a compound semiconductor single crystal by a vertical Bridgman method or a vertical temperature gradient solidification method.

[0002]

2. Description of the Related Art As a technique for producing a compound semiconductor single crystal such as GaAs, a pulling method such as an LEC method (liquid sealing Czochralski method), an HB method (horizontal Bridgman method), and a GF method (temperature A horizontal boat method such as an inclined solidification method has been put to practical use.

In recent years, there has been an increasing demand for large single crystals having a low dislocation density and large-sized single crystals. As a technique that can replace the pulling method and the horizontal boat method, VB method (vertical Bridgman method) and VGF method (vertical temperature gradient solidification method) (Collectively referred to as the “VB method”) has attracted attention.

FIG. 4 is an explanatory view showing a conventional VB method.
In FIG. 1, reference numeral 1 denotes a crucible made of PBN (pyrolytic boron nitride), on which a seed crystal 2 is disposed, and on which the raw material melt 3 of a compound semiconductor crystal such as GaAs is accommodated. Have been. Reference numeral 4 denotes a crystal obtained by solidifying and growing the raw material melt 3 from the seed crystal 2. The upper portion of the raw material melt 3 is covered with a liquid sealant 5 such as B ₂ O _{3 in} order to prevent highly volatile elements such as As from volatilizing from the raw material melt. Numeral 6 denotes a heater for forming a temperature distribution in the furnace where the temperature is low on the seed crystal 2 side and high on the upper side in the furnace. By moving the heater 6 and the crucible 1 relatively, or by controlling the temperature of the heater 6 to move the temperature distribution, the raw material melt 3 is gradually solidified from the seed crystal 2 side, and Growth is performed. Reference numeral 7 denotes a crucible support for supporting the crucible 1.

[0005]

However, in the VB method, even if the crystal is grown and then cooled to room temperature and the crystal is taken out of the crucible, the liquid sealant interposed between the crucible and the crystal is firmly attached to the crucible. The crystal cannot be taken out because it is burned in. Therefore, conventionally, the crucible was immersed in an organic solvent to dissolve the liquid sealant, and the crystal was taken out from the liquid sealant.However, the dissolution of the liquid sealant took from several tens of hours to several days, resulting in poor productivity. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a compound semiconductor crystal having excellent productivity in which a crystal after growth can be easily taken out of a crucible in view of the above-mentioned problems of the prior art.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method for accommodating a raw material melt of a compound semiconductor in a crucible disposed in a furnace and using a liquid sealant to cover the upper part of the raw material melt. In the method for manufacturing a compound semiconductor crystal in which the raw material melt is gradually solidified from a seed crystal disposed at the bottom of the crucible to grow a compound semiconductor crystal, a hanging tool is provided above the crucible, The raw material melt is solidified in a state in which the tip of the tool is immersed to a predetermined depth in the raw material melt, and then the hanging tool is used before the liquid sealant solidifies in the process of cooling the furnace. Or the crucible is lowered to take out the compound semiconductor crystal from the crucible.

The tip of the hanging tool may be immersed in the remaining material melt after growing the compound semiconductor crystal for a predetermined length, or the material may be immersed before growing the compound semiconductor crystal. It may be immersed in the melt. In the former case,
There is less risk of contamination from lifting gear than the latter. However, in the former case, the raw material melt may be rapidly solidified when the hanging tool is immersed and the crystal may be broken, but in the latter case, there is no such concern.

Incidentally, contamination can be avoided by applying a boron nitride coating to at least the tip of the hanging tool.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a PBN crucible,
A seed crystal 2 is arranged at the bottom, and a raw material melt 3 of a compound semiconductor crystal such as GaAs is accommodated on the seed crystal 2. Reference numeral 4 denotes a crystal obtained by solidifying and growing the raw material melt 3 from the seed crystal 2 side. The upper part of the raw material melt 3 is A
B ₂ to prevent the volatilization of highly volatile elements such as
It is covered with a liquid sealant 5 such as O ₃ . The liquid sealant 5 does not necessarily exist only on the upper part of the raw material melt 3, but actually extends between the raw material melt 3 and the crystal 4 and the crucible 1. Numeral 6 denotes a heater for forming a temperature distribution in the furnace where the temperature is low on the seed crystal 2 side and high on the upper side in the furnace. Reference numeral 7 denotes a crucible support for supporting the crucible 1. These growth jigs are arranged in a furnace (not shown) composed of a high-pressure vessel, and the inside of the furnace has an inert gas atmosphere.

The crystal 4 is grown by the heater 6 and the crucible 1.
Is relatively moved or the temperature of the heater 6 is controlled to gradually solidify the raw material melt 3 upward from the seed crystal 2 side. In the present embodiment, the top end 9 of the hanging tool 8 whose upper end is connected to the ceiling of the furnace or the elevating device (not shown) is immersed in the raw material melt 3, and the entire raw material melt 3 is solidified as it is. The crystal growth is completed.

Thereafter, in the process of cooling the inside of the furnace to room temperature, before the liquid sealant solidifies, the lifting tool 8 is pulled up to take out the crystal 4 from the crucible 1, and the crystal 4 is held above the crucible 1 while maintaining the room temperature. Cool down to

Here, when the crystal 4 is taken out of the crucible 1, if the take-out speed is high, the liquid sealant 5 overflows from above the crucible 1.
It is desirable to take it out at such a speed that it can flow into the bottom of the container.

As shown in FIG. 3, the upper portion 10 of the crucible 1 has a tapered shape whose diameter increases upward, thereby further reducing the risk of the liquid sealant 5 overflowing. be able to. In this case, the tapered portion is desirably above the position where the crystal grows.

Further, the bottom of the crucible 1 is provided with an air hole 11 for preventing the inside of the crucible 1 from being evacuated when the crystal 4 is taken out. However, if the air hole 11 is left open, the liquid sealant leaks downward, so the lid 12 is provided. However, if the crucible support 7 is made hollow so that the liquid sealant 5 can be stored, the lid 12
May be omitted.

In the present embodiment, the tip 9 of the hanging tool 8 may be immersed in the raw material melt 3 at any time before the start of growth or immediately before the end of the growth. When the tip portion 9 of 8 is brought into contact with the raw material melt 3, the raw material melt 3 may be rapidly solidified and the crystal may be broken. Therefore, the crystal 9 is immersed in the raw material melt 3 before crystal growth. Is preferred.

Further, it is preferable that the tip 9 of the hanging tool 8 is bent into an L-shape so that the hanging tool 8 has a shape that is hard to come off the crystal 4. The hanging member 8 is made of a material that is heat-resistant and does not react with the raw material melt or is coated with BN, and is as thin as possible such as a metal wire and has a thermal expansion coefficient equal to or larger than that of the semiconductor crystal. It is desirable.

[0019]

According to the present invention, the crystal after growth can be easily taken out of the crucible, so that the productivity can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a method for manufacturing a compound semiconductor according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a state in which a crystal is taken out from a crucible in the method for manufacturing a compound semiconductor according to one embodiment of the present invention.

FIG. 3 is an explanatory view showing a cross section of a crucible suitable for the method for producing a compound semiconductor of the present invention.

FIG. 4 is an explanatory view showing a conventional method for manufacturing a compound semiconductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible 2 seed crystal 3 Raw material melt 4 Crystal 5 Liquid sealant 6 Heater 7 Crucible support stand 8 Hanging tool 9 Hanging tool tip 11 Air hole 12 Lid

Claims (4)

[Claims] 1. A seed wherein a raw material melt of a compound semiconductor is accommodated in a crucible arranged in a furnace, the upper part of the raw material melt is covered with a liquid sealant, and the raw material melt is disposed at the bottom of the crucible. In the method of manufacturing a compound semiconductor crystal in which a compound semiconductor crystal is grown by gradually solidifying from the crystal side, a hanging tool is installed above the crucible, and a tip of the hanging tool is immersed in the raw material melt to a predetermined depth. In this state, all of the raw material melt is solidified, and then, in a process of cooling the furnace, the hanging tool is raised or the crucible is lowered before the liquid sealant is solidified. A method for producing a compound semiconductor crystal, comprising extracting a crystal from the crucible. 2. The method according to claim 1, wherein after growing the compound semiconductor crystal for a predetermined length, the tip of the hanging tool is immersed in the remaining raw material melt. 3. The method according to claim 1, wherein before growing the compound semiconductor crystal,
The method for producing a compound semiconductor crystal according to claim 1, wherein the tip of the hanging tool is immersed in the raw material melt. 4. The method for producing a compound semiconductor crystal according to claim 1, wherein a boron nitride coating is applied to at least a tip portion of said hanging tool.