JPH0840798A - Production of single crystal - Google Patents

Abstract

PURPOSE:To produce single crystal of a continuous compound semiconductor having high formation ratio of single crystal in excellent reproducibility. CONSTITUTION:A crucible 14 charged with a raw material and a sealing agent 4 is set in a crucible 14 and heated by a heater 15 to melt the raw material. Seed crystal 2 is brought into contact with the surface of a melt 3 of the raw material and is gradually pulled up while being rotated to grow single crystal 1. In the operation, a lower movable heat insulating member 18 is gradually raised with interlocking the member to a crucible shaft 13 as the crystal grows. An opening amount of an opening part 19 formed between the lower mobile heat insulating member 18 and an upper stationary heat insulating member 17 is gradually narrowed. The crystal is grown while controlling so as to shorten effective length of the heater 15. Consequently, at the beginning of the growth, the effective length of the heater becomes long to prevent formation of polycrystal. As the crystal grows, the effective length of the heater is made short. Since the temperature gradient in the growing crystal in the vicinity of a solid-liquid interface is kept large, formation of polycrystal in the middle of growth is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal, and more particularly to a method useful for producing a compound semiconductor single crystal by the liquid-encapsulated Czochralski (LEC) method.

[0002]

2. Description of the Related Art As a main method for producing a single crystal of a III-V group compound semiconductor such as GaAs, a raw material and a sealant are melted in a crucible, and a seed crystal is brought into contact with the surface of the raw material melt and rotated. The LEC method is known, in which a single crystal is grown by gradually pulling it up. The size of the heater used in this LEC method is selected in advance so that the heat generation length in the crystal pulling direction is optimum for the size of the crucible used and the initial amount of the raw material charged into the crucible.

[0003]

However, in the above-mentioned conventional LEC method, as shown in FIG. 5, polycrystallization occurs from the middle of the straight body portion during crystal growth, and a long single crystal with good reproducibility is obtained. There was a problem that I could not get it.

The present invention has been made to solve the above problems, and an object thereof is to make it possible to reproducibly manufacture a long compound semiconductor single crystal having a high single crystallization rate. It is in.

[0005]

In order to achieve the above object, the present inventors have found that the cause of polycrystallization during crystal growth is that the thermal environment surrounding the solid-liquid interface changes I thought that the shape would not be the ideal downward convex state. As a result of investigating the temperature gradient in the grown crystal near the solid-liquid interface by a simulation using a computer, as shown by ● in FIG. 4, in the case of the conventional heater, the temperature gradient becomes small as the crystal growth proceeds. I knew it would be too much. It is considered that this is because the heating length of the heater becomes too long with respect to the amount of the raw material melt that gradually decreases as the crystal growth progresses. Therefore, a simulation was carried out by making the heat generation length of the heater shorter than that of the conventional heater, and it was found that the temperature gradient can be made larger than that of the conventional heater as shown by ◯ in FIG.

However, by shortening the heat generation length of the heater, if the heat generation length becomes too small compared to the depth of the raw material melt at the start of growth, the convection of the raw material melt becomes large and becomes thermally unstable. However, there is a tendency that polycrystals, especially twin crystals, tend to enter in the initial stage of growth.

The present invention was made based on the above findings. A crucible containing a raw material and a sealant was placed in a furnace, heated by a heater to melt the crucible, and a seed crystal was brought into contact with the surface of the raw material melt. When the single crystal is grown by gradually pulling it up, the effective length (heat generation length) of the heater, which can effectively contribute to the heating of the raw material melt, is controlled to be shortened according to the growth of the crystal. Is characterized by.

Specifically, a heat insulating member having an opening that is movable between the heater and the crucible and whose opening amount is increased or decreased by the movement is provided, and the size of the opening is the size of the raw material melt. The effective length of the heater may be controlled by moving the heat insulating member so as to gradually narrow according to the remaining amount, or the heater may individually increase or decrease the amount of power supply and It has a plurality of heat generation areas that can be stopped, and the effective length of the heater is controlled by individually increasing or decreasing or stopping the power supply amount to each heat generation area in accordance with the remaining amount of the raw material melt. You may do it.

[0009]

According to the above-mentioned means, when growing a single crystal of a compound semiconductor by the LEC method, the effective length of the heater is controlled so as to be shortened in accordance with the growth of the crystal, so that the effective heater becomes effective at the initial growth stage. As the length becomes longer and polycrystallization is prevented, the effective length of the heater becomes shorter as the crystal growth progresses and the temperature gradient in the grown crystal near the solid-liquid interface is kept large. The convex shape is maintained, and a long single crystal can be obtained with good reproducibility.

At this time, a heat insulating member having an opening which is movable between the heater and the crucible and whose opening amount is increased or decreased by the movement is provided, and the size of the opening is changed by moving the heat insulating member. The heater should be gradually narrowed according to the remaining amount of liquid, or the heater shall be configured to have multiple heat generation areas that can individually increase or decrease the amount of power supply and stop, and the amount of power supply to each heat generation area. By individually increasing / decreasing or stopping according to the remaining amount of the raw material melt, as described above, the effective length of the heater becomes long in the initial stage of growth, and the effective length of the heater increases as the crystal growth progresses. The effective length can be controlled so that the length becomes shorter.

[0011]

EXAMPLES Examples of the method for producing a single crystal according to the present invention will be described below. In this manufacturing method, a crucible containing a raw material and a sealant is placed in a furnace, heated by a heater to melt, and a seed crystal is brought into contact with the surface of the raw material melt and gradually pulled up while rotating. LE to grow crystals
In the method C, crystal growth is performed while controlling the effective length of the heater that can effectively contribute to the heating of the raw material melt in accordance with the growth of the crystal.

FIG. 1 is a diagram showing an example of an apparatus for producing a single crystal used for carrying out the present invention. In the figure, 1 is a grown crystal, 2 is a seed crystal, 3 is a raw material melt, and 4 is Sealant, 10
Is a single crystal production apparatus, 11 is a high-pressure chamber having a gas inlet and a gas outlet (not shown), and 12 is a crystal pulling shaft that holds the seed crystal 2 at the lower end and rotates at a predetermined pulling speed while rotating as necessary. , 13 are crucible shafts which hold the crucible 14 and rotate according to the remaining amount of the raw material melt 3 while rotating as necessary, and 15 is a cylindrical heater surrounding the crucible 14. Further, all of 16, 17, and 18 are heat insulating members which have a substantially cylindrical shape and are arranged so as to surround the crucible 14 and the heater 15, 16 is an outer fixed heat insulating member, 17 is an upper fixed heat insulating member, 18 Is a lower movable heat insulating member, 19 is an upper fixed heat insulating member 17 and a lower movable heat insulating member 1.
It is an opening formed by being sandwiched between 8 and.

The upper fixed heat insulating member 17 is fixed at a predetermined position in the high pressure chamber 11 so that the heat of the heater 15 is not excessively supplied to the upper space of the raw material melt 3, that is, the grown crystal 1 side. . The lower movable heat insulating member 18 is interlocked with the crucible shaft 13 so as to move up and down together with the crucible shaft 13. Then, in the single crystal manufacturing apparatus 10, the lower movable heat insulating member 18 gradually rises as the crystal grows, whereby the opening amount of the opening 19 gradually narrows, and the effective length of the heater 15 shortens.

The vertical movement of the lower movable heat insulating member 18 may be controlled independently of the crucible shaft 13, or the upper fixed heat insulating member 17 may be moved up and down.

FIG. 2 is a diagram showing another example of the single crystal production apparatus used for carrying out the present invention. In FIG.
2, 3, 4 are the grown crystal, seed crystal, and
A raw material melt and a sealant, 20 is a single crystal manufacturing apparatus, 2
1, 22, 23, and 24 are the single crystal manufacturing apparatus 1 described above, respectively.
High pressure chamber, crystal pulling shaft, crucible shaft and crucible similar to 0. Further, 25 and 26 are both crucibles 24
Is a cylindrical heater that is concentrically arranged so as to surround the main heater, 25 is a main heater with a short heater length, and 26 is an auxiliary heater with a long heater length that is arranged outside thereof.
Therefore, the heater of the single crystal manufacturing apparatus 20 is composed of a plurality of heat generating regions including the main heater 25 and the auxiliary heater 26. Reference numeral 27 is a heat insulating member similar to the outer fixed heat insulating member 16.

The main heater 25 and the auxiliary heater 26 can be individually operated to increase / decrease and stop the power supply amount. In the initial stage of crystal growth, the effective length of the heater is increased by increasing the power supplied to the auxiliary heater 26, and the main heater 25 grows as the crystal grows.
Power supply to the auxiliary heater 26
The effective length of the heater is shortened by reducing the power supply amount of the heater.

It should be noted that one or more auxiliary heaters may be provided on the outside of the auxiliary heater 26 in order of increasing size.
In that case, increase the amount of power supplied to the outer auxiliary heater at the start of crystal growth, so that as the crystal growth proceeds, the amount of power supplied to the inner heater becomes larger than that of the outer heater. Good.

FIG. 3 is a diagram showing still another example of the single crystal production apparatus used for carrying out the present invention. In FIG. 3, 1, 2, 3, and 4 are grown in the same manner as in FIG. crystal,
A seed crystal, a raw material melt, and a sealant, 30 is a single crystal manufacturing apparatus, and 31, 32, 33, and 34 are high-pressure chambers, crystal pulling shafts, crucible shafts, and crucibles, which are the same as those of the single crystal manufacturing apparatus 10, respectively. is there. Reference numerals 35, 36, and 37 denote cylindrical heaters that form a multi-stage heater having a plurality of heat generating regions, and are all arranged vertically so as to surround the crucible 34. 35 is a main heater, 3
Reference numerals 6 and 37 are auxiliary heaters, but the length of the main heater 35 is preferably equal to or shorter than the depth of the raw material melt 3 at the start of growth. Reference numeral 38 is a heat insulating member similar to the outer fixed heat insulating member 16.

Main heater 35 and auxiliary heaters 36, 3
7, the power supply amount can be individually increased / decreased and stopped. In the initial stage of crystal growth, the effective length of the heater is increased by increasing the electric power supplied to the auxiliary heaters 36 and 37. As the crystal grows, the electric power supply amount to the main heater 35 is increased and the auxiliary heater is increased. By reducing the power supply of 36 and 37, the effective length of the heater is shortened.

The number of auxiliary heaters may be one or three.
It may be more than one. In the case of three or more, as the crystal growth proceeds, the power supply amount to the heaters farther from the main heater 35 may be sequentially decreased.

Next, the features of the present invention will be further clarified with reference to specific examples and comparative examples, but it goes without saying that the present invention is not limited to the following specific examples. In each of the specific examples and comparative examples, a raw material (GaAs polycrystal) with an initial charge of 24.5 kg and B ₂ O ₃ as a sealant were placed in a crucible having an inner diameter of 300 mm, and the crucible was placed under an Ar gas atmosphere of 20 atm. The seed crystal (GaAs single crystal) was pulled at a pulling rate of 8 mm per hour while rotating at a relative rotational speed of 20 rpm to grow a crystal with a straight body diameter of 110 mm, a growing weight of about 21 kg, and a growing orientation of <100>. It was

In the specific example 1, the single crystal manufacturing apparatus 10 shown in FIG. 1 was used, and the opening 19 was narrowed as the crystal grew, and the effective length of the heater was shortened.
As a result, the length of the straight body part from which the single crystal was obtained was 390 to 4
It was 50 mm.

In Example 2, the single crystal manufacturing apparatus 30 shown in FIG. 3 is used to adjust the amount of power supplied to the main heater 35 and the auxiliary heaters 36 and 37 as the crystal grows, thereby shortening the effective length of the heater. Controlled to be. as a result,
The length of the straight body part from which the single crystal was obtained was 400 to 450 mm.

In the comparative example, a manufacturing apparatus having a conventional one-stage heater was used, and the effective length of the heater was kept constant from the start to the end of crystal growth. As a result, the length of the straight body portion from which the single crystal was obtained was 100 to 140 mm.

Therefore, it was confirmed from the above specific examples and comparative examples that a long single crystal can be obtained according to the present invention.

In each of the above specific examples, the case of growing a GaAs single crystal has been taken as an example, but the present invention is based on GaAs.
It is needless to say that it can be applied to the case of growing a compound semiconductor single crystal such as InP other than the above by the LEC method.

[0027]

According to the method for producing a single crystal of the present invention, in growing a single crystal of a compound semiconductor by the LEC method, the effective length of the heater is controlled so as to be shortened according to the growth of the crystal. , In the early stage of growth, the effective length of the heater was increased to prevent polycrystallization, and as the crystal growth proceeded, the effective length of the heater was shortened to maintain a large temperature gradient in the grown crystal near the solid-liquid interface. As a result, the solid-liquid interface shape is maintained in a downward convex state, and a long single crystal can be obtained with good reproducibility.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an example of a single crystal manufacturing apparatus used for carrying out a method for manufacturing a single crystal according to the present invention.

FIG. 2 is a schematic vertical cross-sectional view showing another example of a single crystal production apparatus used for carrying out the method for producing a single crystal according to the present invention.

FIG. 3 is a schematic vertical sectional view showing still another example of a single crystal production apparatus used for carrying out the method for producing a single crystal according to the present invention.

FIG. 4 is a characteristic diagram showing a computer simulation result of a temperature gradient in the vicinity of a solid-liquid interface in a crystal grown by the LEC method.

FIG. 5 is a schematic view showing a defect state of a crystal grown by a conventional LEC method.

[Explanation of symbols]

 1 Growth Crystal 2 Seed Crystal 3 Raw Material Melt 4 Sealant 14, 24, 34 Crucible 15 Heater 25, 35 Main Heater (Heating Area) 26, 36, 37 Auxiliary Heater (Heating Area) 17 Upper Fixed Insulation Member 18 Lower Side Movable heat insulating member 19 opening

Claims (3)

[Claims] 1. A single crystal is grown by placing a crucible containing a raw material and a sealant in a furnace, heating it with a heater to melt it, and bringing a seed crystal into contact with the surface of the raw material melt and gradually pulling it up. In doing so, a method for producing a single crystal, wherein the effective length of the heater that can effectively contribute to the heating of the raw material melt is controlled so as to be shortened according to the growth of the crystal. 2. A heat insulating member having an opening that is movable between the heater and the crucible and whose opening amount is increased or decreased by the movement is provided, and the size of the opening is the remaining amount of the raw material melt. The method for producing a single crystal according to claim 1, wherein the effective length of the heater is controlled by moving the heat insulating member so as to be gradually narrowed correspondingly. 3. The heater has a plurality of heat generation regions capable of individually increasing and decreasing and stopping the power supply amount, and the power supply amount to each heat generation region is set in correspondence with the remaining amount of the raw material melt. The method for producing a single crystal according to claim 1, wherein the effective length of the heater is controlled by individually increasing or decreasing or stopping.