JP2010163287A - METHOD FOR PRODUCING GaAs SINGLE CRYSTAL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a GaAs single crystal for improving the yield of the acquisition number of wafers, by appropriately controlling the rotation number of a crucible and the pulling speed of a pulling shaft. <P>SOLUTION: The crucible 5 storing a GaAs raw material and boron trioxide as a sealant is placed in a chamber 2 charged with inert gas. The crucible 5 is heated by a heater 8 to produce a GaAs melt 9 in the crucible 5. A seed crystal 7 attached to the lower end of a pulling shaft 3 is brought into contact with the GaAs melt 9 and the seed crystal 7 is pulled while rotating the crucible 5 to produce a GaAs single crystal 10. The rotation number n [rpm] of the crucible 5 and the pulling speed V [mm/h] of the pulling shaft 3 are controlled to satisfy 28≥n≥5.89e<SP>0.07V</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing a GaAs single crystal by a liquid encapsulated Czochralski method (hereinafter referred to as LEC method).

Generally, the LEC method is used as a method for producing a group III-V compound semiconductor single crystal (GaAs, InP, etc.) or a group II-VI compound semiconductor single crystal (ZnS, ZnSe, etc.) containing a volatile element.
In the LEC method, a crucible containing a raw material and a sealing agent is heated by a heater in a chamber filled with an inert gas to melt the raw material and the sealing agent, and the surface of the raw material melt is liquid sealed. After covering with the agent and bringing the seed crystal into contact with the raw material melt, the single crystal is grown by pulling up the seed crystal while rotating the crucible (see, for example, Patent Documents 1 to 6).

  When manufacturing a GaAs single crystal by the LEC method, if the shape of the solid-liquid interface in the crystal growth process is concave on the GaAs melt side, dislocations with the property of propagating perpendicularly to the solid-liquid interface will accumulate. There is a problem of polycrystallization. Therefore, it is necessary to control the shape of the solid-liquid interface so that it is convex toward the GaAs melt side.

Japanese Patent Laid-Open No. 06-56582 Japanese Patent Laid-Open No. 09-77590 Japanese Patent Application Laid-Open No. 09-142997 JP 2002-20193 A JP 2004-10467 A JP 2004-10469 A

  As described above, when manufacturing a GaAs single crystal, it is necessary to control the temperature distribution of the GaAs melt in the crucible so that the shape of the solid-liquid interface is convex toward the GaAs melt. One of the control methods is optimization of the rotation speed of the GaAs single crystal and the crucible. However, this optimization condition has not yet been concluded because it is difficult to grasp the temperature distribution of the GaAs melt.

  The pulling speed of the GaAs single crystal is also one of the parameters that determine the shape of the solid-liquid interface. In general, the slower the pulling speed, the more advantageous it is for heat radiation of solidification heat, and the solid-liquid interface tends to be convex. However, if the pull-up speed is slow, it is disadvantageous in terms of throughput, so the conclusion about the pull-up speed as well as the rotation speed of the crucible has not been reached.

  It is an object of the present invention to provide a method for producing a GaAs single crystal that improves the yield of the number of wafers acquired by appropriately controlling the number of rotations of the crucible and the pulling speed of the pulling shaft.

In order to solve the above problems, the present invention is configured as follows.
In the first aspect of the present invention, a crucible containing a GaAs raw material and a sealing agent is placed in a chamber filled with an inert gas, the crucible is heated by a heater, and the GaAs raw material and the sealing agent are combined. In the method for producing a GaAs single crystal, after the melting, the seed crystal attached to the pulling shaft is brought into contact with the GaAs melt, and the seed crystal is pulled up while the crucible is rotated to grow the GaAs single crystal. In this GaAs single crystal manufacturing method, the relationship between the rotational speed n [rpm] and the pulling speed V [mm / h] of the pulling shaft is 28 ≧ n ≧ 5.89e ^0.07V .

  According to a second aspect of the present invention, in the method for producing a GaAs single crystal according to the first aspect, the GaAs single crystal has a crystal diameter such that a wafer size diameter obtained from the GaAs single crystal is 100 mm or more.

  According to the present invention, the yield of the number of wafers obtained from a GaAs single crystal can be improved.

It is a schematic block diagram of the manufacturing apparatus used for the manufacturing method of the GaAs single crystal which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the heat balance in the solid-liquid interface in the growth process of a GaAs single crystal. It is a graph which shows the relationship between the pulling-up speed of a pulling-up axis | shaft, the rotation speed of a crucible, and the yield of a wafer acquisition number. FIG. 4 is a graph showing measurement data of the pulling speed of the pulling shaft and the number of rotations of the crucible when the yield of the number of wafers acquired satisfies 80% in FIG. 3, and an approximate curve approximating this measurement data.

As described above, as a problem in GaAs single crystal growth, there is a problem of crystal polycrystallization due to accumulation of dislocations. At present, due to this problem, the yield of obtaining wafers from crystals remains at about 80%. Dislocations have the property of propagating perpendicularly to the solid-liquid interface, which is the interface between the crystal and the melt. If the solid-liquid interface is concave on the melt side, dislocations accumulate. Therefore, in order to prevent the accumulation of dislocations, it is necessary to control so that the solid-liquid interface during crystal growth always has a convex shape on the melt side.
In addition, it is known from the investigations so far that the degree of convexity at the solid-liquid interface and the accumulation of dislocations have a correlation that the higher the degree of convexity, the less likely the accumulation of dislocations occurs. The shape of the solid-liquid interface is formed perpendicular to the heat flow. Therefore, to make the solid-liquid interface convex, it can be achieved by radiating the heat of solidification generated at the solid-liquid interface to the outside of the crystal through the crystal. Further, in order to increase the convexity of the solid-liquid interface, it is necessary to adjust the temperature conditions in the chamber which is a crystal growth furnace so that more solidification heat can be dissipated.

  Here, the heat balance at the solid-liquid interface will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining the heat balance at the solid-liquid interface during the growth process of a GaAs single crystal.

The crucible 5 is heated, the seed crystal 7 is brought into contact with the GaAs melt 9 melted in the crucible 5 and covered with the liquid sealing material 6, and the pulling shaft 3 is pulled up while rotating the crucible 5 to pull up the GaAs single crystal 10. Grow.
The amount of heat Q1 is the inflow heat flowing from the GaAs melt 9 into the solid-liquid interface 11, the amount of heat Q2 is the solidification heat generated at the solid-liquid interface 11, and the amount of heat Q3 is the GaAs single crystal 10 already solidified from the solid-liquid interface 11. This is the amount of heat that is transferred to Between these calories,
Q1 + Q2 = Q3
The following relational expression holds. Here, it is considered that the magnitude of the heat quantity Q1 is determined by the temperature gradient of the GaAs melt 9. The magnitude of the heat quantity Q3 is considered to be determined by the temperature gradient in the solidified GaAs single crystal 10.
From the above relational expression, in order to increase the degree of convexity of the solid-liquid interface, as one method of releasing more solidification heat Q2, the amount of heat Q3 is increased, that is, the temperature gradient of the solidified GaAs single crystal 10 is increased. There is a way to do it.
Another possible method is to reduce the amount of heat Q1, that is, to reduce the temperature gradient in the vertical direction (crucible depth direction) in the GaAs melt 9.

  Conventionally, as a method of increasing the amount of heat Q3, that is, increasing the temperature gradient of the GaAs single crystal 10, there is a method of adopting a structure in the chamber 2 that promotes cooling of the GaAs single crystal 10, and an improvement effect is obtained. However, if the cooling of the GaAs single crystal 10 is extremely promoted, slip dislocations are generated in the crystal, and therefore an unlimited method for promoting the cooling of the crystal cannot be adopted.

  On the other hand, in order to realize a method of reducing the amount of heat Q1, that is, a method of reducing the temperature gradient in the vertical direction (crucible depth direction) in the GaAs melt 9, the temperature near the solid-liquid interface 11 is made as low as possible. It is necessary to control the temperature distribution of the GaAs melt 9. From previous studies, it has been found that the forced convection of the GaAs melt 9 caused by the rotation of the crucible 5 affects the temperature distribution of the GaAs melt 9. In general, as the number of rotations of the crucible 5 is increased, the influence of natural convection decreases, and the temperature gradient of the GaAs melt 9 from the center to the outer periphery of the crucible 5 becomes steep. That is, the temperature near the center of the crucible 5 is lowered. However, since it is difficult to actually measure the temperature distribution of the GaAs melt 9, the details are still unclear.

  Further, when the pulling speed of the pulling shaft 3 is changed, the solidification amount per unit time is changed. That is, a change occurs in the solidification heat Q2. Therefore, the pulling-up speed of the pulling-up shaft 3 is one of the important parameters in controlling the convexity of the shape of the solid-liquid interface 11.

From the above, the setting of the number of rotations of the crucible and the pulling speed of the pulling shaft is an important parameter when producing a single crystal. However, since it is difficult to measure the temperature distribution of the GaAs melt, it is difficult to say that the optimization conditions for these settings are sufficiently understood.
From past knowledge, it is known that increasing the number of rotations of the crucible is an effective method for convexing the solid-liquid interface. However, it was not clear how far the crucible rotation speed should be increased with respect to the pulling speed.
Therefore, the present inventors have set how many crucible rotation speeds n [rpm] with respect to various pulling speeds V [mm / h], so that the yield of the number of wafers obtained from the crystal can be improved. An experiment was conducted to determine (see FIG. 3). as a result,
n ≧ 5.89e ^0.07V (e is the base of natural logarithm)
Was found (see FIG. 4).
Furthermore, it was found that when the crucible rotation speed exceeds 28 [rpm], the yield of the number of wafers acquired decreases due to an increase in the eccentricity of the crucible shaft accompanying high-speed rotation. Further, if the high-speed rotation exceeding 28 [rpm] is continued, mechanical troubles of the apparatus such as leakage of gas in the chamber due to wear of the chamber pressure suppression part (seal part) attached to the crucible shaft occur, Production turned out to be difficult.
From these facts, the relationship between the crucible rotation speed n [rpm] and the pull-up shaft pull-up speed V [mm / h] is 28 ≧ n ≧ 5.89e ^{0.07 V}
The knowledge that it is good to set to satisfy is obtained.
Based on this knowledge, a specific embodiment of the method for producing a GaAs single crystal according to the present invention will be described below.

  A method for producing a GaAs single crystal according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a manufacturing apparatus used in a GaAs single crystal manufacturing method according to the present embodiment.

  First, a GaAs single crystal manufacturing apparatus according to this embodiment will be described, and then a GaAs single crystal manufacturing method will be described.

<GaAs single crystal manufacturing equipment>
The GaAs single crystal manufacturing apparatus 1 includes a chamber 2, a pyrolytic boron nitride (PBN) crucible 5, a crucible shaft 4 that supports the crucible 5, a pulling shaft 3 that pulls up the GaAs single crystal 10, A carbon heater 8 as a heater (resistance heater) that is a heating means of the crucible 5 and a heat insulating material 14 are provided.

The chamber 2 is a pressure vessel, and is filled with an inert gas during GaAs single crystal growth. A crucible 5 is installed in the chamber 2. The carbon heater 8 is provided so as to surround the outer peripheral portion and the bottom portion of the crucible 5. Further, a heat insulating material 14 is installed around the carbon heater 8. Ar, N ₂ or the like is used as the inert gas filled in the chamber 2, and the inert gas pressure in the chamber 2 is set to, for example, about 60 atm.

  A crucible shaft 4 is attached to the center of the bottom of the crucible 5, and the crucible 5 is supported by the crucible shaft 4. The crucible 5 is rotatable by the crucible shaft 4. The crucible shaft 4 penetrates the bottom wall of the chamber 2 vertically, and the penetrating portion is sealed with a seal member (not shown).

  The pull-up shaft 3 is provided vertically through the upper wall of the chamber 2 and is configured to be rotatable and liftable. A seed crystal 7 can be attached to the lower end of the pull-up shaft 3.

<GaAs single crystal manufacturing method>
Next, a method for manufacturing a GaAs single crystal according to this embodiment will be described.

  In the crucible 5, Ga and As, and boron trioxide which is an As volatilization preventive agent are housed, and the crucible 5 is placed in the chamber 2. Further, a GaAs seed crystal 7 as a crystal base is attached to the lower end of the pull-up shaft 3. Note that the seed crystal 7 generally has a (100) plane in contact with the GaAs melt 9.

  The chamber 2 is evacuated and then filled with an inert gas. Thereafter, the carbon heater 8 installed in the chamber 2 is energized to heat the crucible 5 to react Ga and As to synthesize GaAs, and then the temperature is raised to produce a GaAs melt 9.

  The pulling shaft 3 is rotated at about 5 rpm in the direction opposite to the crucible 5, and the pulling shaft 3 is lowered until the seed crystal 7 contacts the GaAs melt 9. Subsequently, the seed crystal 7 is pulled up at a constant speed while gradually lowering the set temperature of the carbon heater 8. After the diameter of the single crystal is gradually increased to form the crystal shoulder 13 from the crystal head 12, when the diameter of the crystal reaches the target value, the set temperature and the like are controlled so as to maintain the crystal diameter constant. The GaAs single crystal 10 is manufactured by growing.

When manufacturing the GaAs single crystal 10, as shown in FIG. 1, it manufactures so that the solid-liquid interface 11 in a crystal growth process may be maintained convex on the GaAs melt 9 side. Specifically, the relationship between the rotational speed n [rpm] of the crucible 5 and the pulling speed V [mm / h] of the pulling shaft 3 is
28 ≧ n ≧ 5.89e ^0.07V (e is the base of natural logarithm)
Control to be

By ^setting n ≧ 5.89e 0.07 ^V , it is possible to suppress the accumulation of dislocations in the crystal growth process, and to obtain a wafer with a stable yield. Further, if the rotational speed n of the crucible 5 is 28 ≧ n, an increase in the eccentricity of the crucible shaft 4 and wear of the seal portion of the crucible shaft 4 due to the high-speed rotation of the crucible 5 can be suppressed. Decline can be prevented.

  In the present embodiment, the pull-up shaft 3 is lifted while rotating in the direction opposite to the crucible 5, but the pull-up shaft 3 may not be rotated. Even when only the crucible 5 is rotated without rotating the pull-up shaft 3, it has been confirmed that substantially the same effect can be obtained.

Furthermore, according to the present embodiment, since the convex shape of the solid-liquid interface can be stabilized, a GaAs single crystal having a crystal size with a wafer size diameter of 100 mm or more can be manufactured with a high yield.
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

  Next, examples of the present invention will be described.

  A GaAs single crystal 10 having a crystal diameter of 100 mm was manufactured using the GaAs single crystal manufacturing apparatus 1 in FIG. In a crucible 5 made of PBN having an outer diameter of 280 mm, 11500 g of Ga, 12,500 g of As, and an appropriate amount of boron trioxide necessary for preventing volatilization of As are stored, and the crucible 5 is placed in the chamber 2 and heated. Warm up. The heating temperature of the GaAs melt 9 was 1238 ° C. or higher. The number of rotations of the pulling shaft 3 is set to 5 rpm, and the pulling speed V is set to 2 mm / h, 4 mm / h, 6 mm / h, 8 mm / h, 10 mm / h, 12 mm / h, 14 mm / h, 16 mm / h. , 18 mm / h and 10 mm / h were set. Next, the number of rotations n of the crucible 5 with respect to each pulling speed V was increased by 1 rmp from 0 rmp, and the transition of the yield of the number of wafers obtained from the manufactured GaAs single crystal 10 was investigated. The result is shown in FIG.

As shown in FIG. 3, it was confirmed that the yield of the number of wafers acquired was improved when the rotational speed n of the crucible 5 was increased with respect to each pulling speed V of the pulling shaft 3.
On the other hand, as shown in FIG. 3, when the rotational speed of the crucible 5 exceeded 28 rpm, the yield was greatly reduced. From this, it was found that the optimum upper limit value of the crucible rotation speed n was 28 rpm.

Further, from FIG. 3, the pulling speed V and the rotation speed n of the crucible 5 when the yield of the number of wafers to be acquired is 80% were investigated. The result is shown in FIG. When an approximate curve was drawn from the data obtained by the investigation, n = 5.89e ^0.07V was obtained.
From this, it was found that the wafer can be obtained with a yield of 80% or more when the relationship of n ≧ 5.89e ^0.07V is satisfied.

As described above, in the growth process of the GaAs single crystal by the LEC method, the optimum relationship between the crucible rotation speed n [rpm] and the pulling shaft pulling speed V [mm / h] is 28 ≧ n ≧ 5.89e. ^In this way, a wafer can be obtained with a high yield of 80% or more, and a GaAs single crystal can be produced stably.

1 GaAs single crystal manufacturing equipment 2 chamber 3 pulling shaft 4 crucible shaft 5 crucible 6 boron trioxide melt (liquid sealant)
7 Seed crystal 8 Carbon heater (heater)
9 GaAs melt 10 GaAs single crystal

Claims (2)

A crucible containing a GaAs raw material and a sealing agent is installed in a chamber filled with an inert gas, and the crucible is heated by a heater to melt the GaAs raw material and the sealing agent, and then GaAs melting. In the method for producing a GaAs single crystal, the seed crystal attached to the pulling shaft is brought into contact with the liquid, and the GaAs single crystal is grown by pulling up the seed crystal while rotating the crucible.
The relationship between the rotational speed n [rpm] of the crucible and the pulling speed V [mm / h] of the pulling shaft is
28 ≧ n ≧ 5.89e ^0.07V
A method for producing a GaAs single crystal.   2. The method for producing a GaAs single crystal according to claim 1, wherein the GaAs single crystal has a crystal diameter such that a wafer size diameter obtained from the GaAs single crystal is 100 mm or more.

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