JP2005343737A - Apparatus for manufacturing compound semiconductor single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing a compound semiconductor single crystal, with which the shape of the solid-liquid interface can be effectively made into a projected shape, the assembly of dislocations generated in crystal is reduced, and the crystallization degree of the single crystal can be enhanced. <P>SOLUTION: The apparatus for manufacturing the compound semiconductor single crystal by an LEC method is constituted so that a compound semiconductor melt 11 is formed in a crucible 2 by heating Ga, As and the like in the crucible 2 with a resistance-heating heater 4, a seed crystal 9 is brought into contact with the upper part of the melt 11, the compound semiconductor single crystal 12 is pulled while being grown, and the crucible 2 is raised so as to keep the solid-liquid interface constant. A cylindrical heat-shielding tube 13 is provided between the curved part close to the bottom part of the crucible 2 and the resistance-heating heater 4 so as to suppress the increase of the temperature gradient in the compound semiconductor melt 11 by shielding the thermal radiation from the resistance-heating heater 4 and to enhance the projection degree of the solid-liquid interface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for producing a compound semiconductor single crystal by LEC (liquid encapsulated Czockralski method), and in particular, it can effectively project a solid-liquid interface shape, and dislocation generated in the crystal. The present invention relates to an apparatus for manufacturing a compound semiconductor single crystal that can reduce aggregation and improve the crystallization rate.

  FIG. 2 shows a conventional compound semiconductor single crystal manufacturing apparatus. The compound semiconductor single crystal manufacturing apparatus 1 includes a crucible 2 made in a pot shape using PBN (Pyrolytic Boron Nitride) and the like, and a crucible shaft 3 attached to the bottom surface of the crucible 2 to rotate and move the crucible 2 up and down. A resistance heater 4 installed so as to surround the side surface of the crucible 2, a heat insulating material 5 disposed on the bottom of the crucible 2 and outside the resistance heater 4, a seed holder 6 for holding a seed crystal, With the seed holder 6 attached to the lower end, a pulling shaft 7 that rises while rotating during crystal growth and a chamber 8 as a furnace body that forms a sealed space on the crucible 2 are provided.

  The operation of the manufacturing apparatus in FIG. 2 will be described. This manufacturing apparatus manufactures a compound semiconductor single crystal, particularly a GaAs single crystal, by the LEC method. A seed crystal 9 as a crystal base is attached to the seed holder 6. The seed crystal 9 has a (100) plane that is in contact with the GaAs melt in the crucible 2. Furthermore, in addition to gallium (Ga) and arsenic (As), boron trioxide 10 which is an As volatilization preventive material is put in the crucible 2 as a raw material.

  After the raw material is set in the chamber 8, the inside of the chamber 8 is evacuated and filled with an inert gas. Thereafter, the resistance heater 4 is energized, the temperature in the chamber 8 is raised, and Ga and As in the crucible 2 are synthesized to produce GaAs. Thereafter, the temperature is further raised to produce melted GaAs (compound semiconductor melt 11).

  Next, the pull-up shaft 7 and the crucible shaft 3 are rotated in opposite directions. In this state, the seed crystal 9 attached to the seed holder 6 is lowered until it contacts the melted GaAs. Next, while gradually lowering the set temperature of the resistance heater 4, the pulling shaft 7 is raised at a constant speed, and the crystal diameter is gradually increased from the seed crystal 9 to form a crystal shoulder.

  After the formation of the crystal shoulder, the GaAs single crystal (compound semiconductor single crystal 12) is manufactured while controlling the outer shape in order to keep the outer diameter constant when the target crystal outer diameter is reached. Further, during the growth of the GaAs single crystal, the GaAs single crystal is grown so that the melted GaAs liquid level is always at a fixed position, and the pulling shaft 7 is increased by the amount corresponding to the decrease in the melted GaAs liquid level. Control to raise. In the growth of a GaAs single crystal, since the crystal is a dislocation crystal, in order to prevent dislocation aggregation, the solid-liquid interface shape is generally a shape that protrudes toward the melt side.

  One of the problems in GaAs crystal growth is crystal polycrystallization by dislocation aggregation. Dislocations have the property of propagating perpendicularly to the solid-liquid interface, which is the boundary surface between the GaAs single crystal and the melt. If the solid-liquid interface has a concave shape on the melt side, a set of dislocations occurs. Therefore, in order to prevent dislocation aggregation, it is necessary to control the shape of the solid-liquid interface so that it always protrudes toward the melt during the growth of the GaAs single crystal. Further, it is known from the investigations so far that the convexity of the solid-liquid interface and the set of dislocations have a correlation that the higher the convexity, the less likely the dislocation set is generated.

  The solid-liquid interface shape is formed perpendicular to the heat flow. Therefore, the convex shape of the solid-liquid interface can be achieved by releasing the heat of solidification generated at the solid-liquid interface to the outside of the crystal through the GaAs single crystal (compound semiconductor single crystal 12). Moreover, in order to increase the convexity of the solid-liquid interface, it is necessary to adjust the temperature conditions in the furnace so that the heat of solidification can be dissipated more.

FIG. 3 shows a heat balance model at the solid-liquid interface. As heat flowing into the solid-liquid interface, there is a heat quantity Q1 coming from melted GaAs (compound semiconductor melt 11). The magnitude of the heat quantity Q1 is considered to be determined by the temperature gradient of melted GaAs. There is also a solidification heat Q2 generated at the solid-liquid interface. Furthermore, there is an amount of heat Q3 released from the solid-liquid interface to the already solidified GaAs single crystal. The magnitude of the heat quantity Q3 is considered to be determined by the temperature gradient in the solidified GaAs single crystal 12. The following equation (1) is established for these three heat quantities.
Q1 + Q2 = Q3 (1)

  From this equation (1), in order to increase the degree of convexity at the solid-liquid interface, in order to further dissipate the heat of solidification, the amount of heat Q3 is increased, that is, the temperature of the solidified crystal part. There is a method to increase the gradient. As another method, a method of reducing the amount of heat Q1, that is, a method of reducing a temperature gradient in melted GaAs can be considered.

  Conventionally, in order to improve the degree of convexity of the solid-liquid interface by increasing the amount of heat Q3, the cooling of the crystal is promoted and the in-furnace structure in which the temperature gradient of the crystal part becomes large is obtained. We are trying to improve.

In addition, in the manufacture of GaAs crystals by the LEC method, a single crystal that controls the amount of melt decrease due to solidification of the crystal by raising the crucible in order to keep the GaAs melt surface constant during crystal growth. A manufacturing apparatus is disclosed (for example, refer to Patent Document 1).
JP-A-5-330974 ([0013] to [0016], FIG. 1)

    However, according to the conventional compound semiconductor single crystal manufacturing apparatus, when the furnace structure is designed to increase the temperature gradient of the crystal part, slip dislocation occurs in the crystal when the crystal is extremely cooled. Therefore, there is no way to promote crystal cooling without limitation.

  Further, in the manufacturing apparatus of Patent Document 1, as the crystal grows, the bottom surface of the crucible gradually approaches the heater, the influence of thermal radiation from the heater increases, and the temperature near the bottom surface of the crucible gradually increases. The phenomenon that occurs. This phenomenon means that the temperature gradient in the GaAs melt gradually increases as the crystal grows, that is, the amount of heat Q1 in the above equation (1) increases. Therefore, as the crystal growth proceeds, the convexity of the solid-liquid interface decreases, sometimes resulting in a concave surface, and there arises a problem that a crystal polycrystal is generated due to dislocation aggregation. As a countermeasure against this problem, attempts have been made to control the structure of the heater in the furnace in a number of zones, but problems such as complicated control and increased cost of the manufacturing apparatus remain.

  An object of the present invention is to provide an apparatus for producing a compound semiconductor single crystal capable of effectively projecting a solid-liquid interface shape, reducing the number of dislocations generated in the crystal, and improving the crystallization rate. It is to provide.

  In order to achieve the above object, the present invention comprises a crucible for storing a melt of a compound semiconductor and a heating means for heating the crucible from the side surface. An apparatus for manufacturing a compound semiconductor single crystal, comprising: a compound semiconductor single crystal manufacturing apparatus, wherein a cylindrical heat shield member is disposed between a curved portion near the bottom of the crucible and the heating means. provide.

  According to the compound semiconductor single crystal manufacturing apparatus of the present invention, it is possible to effectively project the solid-liquid interface shape, reduce the number of dislocations generated in the crystal, and improve the crystallization rate. Become.

[Embodiment]
(Configuration of manufacturing equipment)
FIG. 1 shows a configuration of a manufacturing apparatus according to an embodiment of the present invention. The compound semiconductor single crystal manufacturing apparatus 1 is installed so as to surround the crucible 2 as a raw material container made of PBN or the like, the crucible shaft 3 attached to the center of the crucible 2, and the outer periphery of the crucible 2. A resistance heater 4 as a heating means, a heat insulating material 5 disposed on the bottom of the crucible 2 and outside the resistance heater 4, a seed holder 6 for holding a seed crystal, and the seed holder 6 are attached to the lower end. A pulling shaft 7 that rises while rotating in a closed state, a chamber 8 as a furnace body that forms a sealed space on the crucible 2, and a heat shielding cylinder 13 as a heat shielding member surrounding the lower side of the crucible 2. . The heat shielding cylinder 13 is formed in a cylindrical shape using a material having excellent heat shielding characteristics, for example, graphite or the like, and is provided between the lower curved portion of the crucible 2 and the resistance heater 4.

(Operation of manufacturing equipment)
Since the operation for manufacturing the semiconductor single crystal in the above embodiment is the same as that in the conventional configuration of FIG. 2, the description thereof is omitted here. As described above, if the crystal is extremely cooled in order to increase the amount of heat Q3 in order to increase the convexity of the solid-liquid interface, slip dislocation occurs and cooling is limited. Accordingly, the present invention provides a heat shielding cylinder as means for reducing the amount of heat Q1 and suppressing an increase in temperature gradient in melted GaAs (compound semiconductor melt 11) due to a temperature rise near the bottom of the crucible 2 accompanying crystal growth. 13 is provided to shield the heat radiation from the resistance heater 4 and suppress the temperature rise near the bottom of the crucible 2 due to the rise of the crucible 2.

(Effect of embodiment)
According to this embodiment, since the heat shielding cylinder 13 is provided, the heat radiation from the resistance heater 4 can be shielded, so that the solid-liquid interface shape can be effectively convex, and the crystal This reduces the number of dislocations that occur in the crystallographic structure and improves the crystallization rate. Further, since it is only necessary to provide the heat shielding cylinder 13, the configuration can be simplified and the cost can be prevented from increasing.

  Next, examples of the present invention will be described. Here, a 6φ size GaAs single crystal (compound semiconductor single crystal 12) was prototyped by the LEC method using the compound semiconductor single crystal manufacturing apparatus 1 having the configuration shown in FIG. Crucible 2 was charged with 12,000 g of Ga as a raw material, 13,000 g of As, and 2,000 g of boron trioxide 10 which is an As volatilization preventive material. In addition, a seed crystal 9 as a crystal base was attached to the seed holder 6. The seed crystal 9 has a (100) plane in contact with the melted GaAs (compound semiconductor melt 11).

  After the raw material is set in the chamber 8, the inside of the chamber 8 is evacuated and filled with an inert gas, and then the resistance heater 4 is energized to raise the temperature in the chamber 8, and Ga and As And GaAs was produced, and the temperature was further raised to melt the GaAs. Subsequently, the pull-up shaft 7 was rotated at 10 rpm, and the crucible shaft 3 was rotated at 20 rpm in the direction opposite to the pull-up shaft 7. In this state, the pull-up shaft 7 is lowered until the seed crystal 9 comes into contact with the melted GaAs, and then the pull-up shaft is raised at a speed of 10 mm / h while gradually lowering the set temperature of the resistance heater 4. GaAs single crystal (compound semiconductor single crystal 12) was grown.

  For comparative verification, a crystal serving as a comparative example was prototyped using the manufacturing apparatus configured as shown in FIG. This comparative example and the example according to the present invention were comparatively investigated with respect to the degree of convexity of the solid-liquid interface and the single crystallization rate of crystals having a strong correlation. In the examples and comparative examples, 10 lots were produced for each trial.

  Table 1 shows the single crystallization ratios of the crystals of the comparative example and the example. Here, the single crystallization ratio of the crystal is an index indicating the ratio of the effective length of the single crystal portion that is not polycrystal in the crystal appearance to the ideal effective length that can be obtained for the crystal wafer.

  As is clear from Table 1, it was confirmed that according to the example of the present invention, the single crystallization rate can be improved as compared with the comparative example.

[Other embodiments]
In the above embodiment, a GaAs single crystal is manufactured by the LEC method. However, the present invention is also applicable to an LEC method single crystal manufacturing apparatus using a material other than GaAs.

  Moreover, in the said embodiment, although the resistance heater 4 was used as a heating means, you may use the heating means by another operating principle.

It is sectional drawing which shows the manufacturing apparatus of the compound semiconductor single crystal which concerns on embodiment of this invention. It is sectional drawing which shows the manufacturing apparatus of the conventional compound semiconductor single crystal. It is explanatory drawing which shows the heat balance model in a solid-liquid interface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compound semiconductor single crystal manufacturing apparatus 2 Crucible 3 Crucible shaft 4 Resistance heater 5 Thermal insulation material 6 Kind holder 7 Pulling-up axis 8 Chamber 9 Seed crystal 10 Boron trioxide 11 Compound semiconductor melt 12 Compound semiconductor single crystal 13 Heat shield cylinder Q1 Amount of heat Q2 Heat of solidification Q3 Amount of heat

Claims (3)

In a compound semiconductor single crystal manufacturing apparatus for manufacturing a compound semiconductor single crystal by an LEC method, comprising a crucible for storing a melt of a compound semiconductor and a heating means for heating the crucible from the side,
An apparatus for producing a compound semiconductor single crystal, wherein a cylindrical heat shielding member is disposed between a curved portion near the bottom of the crucible and the heating means.   The apparatus for producing a compound semiconductor single crystal according to claim 1, wherein the heat shielding member uses graphite.   2. The apparatus for producing a compound semiconductor single crystal according to claim 1, wherein the heating means is a resistance heater.

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