JP2015074568A - Manufacturing method of single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a high quality single crystal using a vertical boat method.SOLUTION: A manufacturing method of a single crystal according to the invention includes the steps of: arranging a seed crystal in a seed crystal housing part of a crucible and arranging a compound semiconductor raw material and boron oxide raw material in a shoulder part and a straight body part of the crucible; producing a boron oxide melt by melting the boron oxide raw material; producing a compound semiconductor melt by melting the compound semiconductor raw material; and growing a single crystal by solidifying the compound semiconductor melt from a seed crystal side to a crucible axial direction. The compound semiconductor raw material and the boron oxide raw material are laminated in the crucible axial direction, and the boron oxide raw material is formed by pressure.

Description

  The present invention relates to a method for producing a single crystal, and more particularly, to a method for producing a single crystal made of a compound semiconductor using a crucible.

  As a method for producing a single crystal made of a compound semiconductor such as GaAs, GaP, or InP (hereinafter simply referred to as “single crystal”), a vertical bridgman (VB; Vertical Bridgman) is used to grow a single crystal using a crystal growth crucible. ) Method and vertical boat method such as vertical gradient freeze (VGF) method are known. In the vertical boat method, referring to FIG. 8, a straight body portion 81 having a cylindrical shape, a seed crystal accommodating portion 82 having a smaller diameter than the straight body portion, a tapered shape, and a straight body portion 81 and a seed A crucible such as a crucible 80 having a shoulder 83 connecting the crystal accommodating part 82 is used. According to the vertical boat method using the crucible 80, the single crystal is manufactured as follows.

  First, a seed crystal is disposed in the seed crystal accommodating portion 82, and a solid material of the compound semiconductor (hereinafter also referred to as “compound semiconductor material”) is disposed thereon. Next, the inside of the straight body portion 81 and the inside of the shoulder portion 83 are heated, whereby the compound semiconductor raw material is melted to become a melt. The melt is solidified in the axial direction from the seed crystal side of the crucible 82 to produce a compound semiconductor single crystal.

  By the way, 15 group elements, such as As and P, have the characteristic which is easy to volatilize compared with 13 group elements. For this reason, in the vertical boat method as described above, a group 15 element may be volatilized from the melt. When such a group 15 element is lost, the ratio of the group 13 element to the group 15 element in the melt is shifted from the design target ratio, and a single crystal having a desired composition cannot be manufactured. In addition, the deviation of the composition ratio causes an increase in the dislocation density of the single crystal and affects the electrical characteristics of the compound semiconductor.

  Conventionally, in order to prevent such a group 15 element from escaping, a method of introducing boron oxide into a crucible together with a compound semiconductor raw material has been widely employed (for example, Japanese Patent Laid-Open No. 2000-154089 (Patent Document 1). )). The softening point of boron oxide charged into the crucible is about 300 ° C., and softens and melts prior to the compound semiconductor raw material to form a boron oxide melt. Since the specific gravity of the boron oxide melt is smaller than the specific gravity of the compound semiconductor melt, the surface of the melt of the compound semiconductor melted after the boron oxide is located below the boron oxide melt. be able to. With such a configuration, the melt of the compound semiconductor is sealed in the crucible by the boron oxide melt, so that the group 15 elements are prevented from coming off from the melt of the compound semiconductor.

  Japanese Patent Application Laid-Open No. 2004-137096 (Patent Document 2) describes a technique for making the shape of a GaAs compound semiconductor material into a large lump that can be accommodated in a crucible. By making the compound semiconductor raw material into large lumps, the surface area thereof becomes smaller than when using a compound semiconductor raw material composed of a plurality of lumps. Patent Document 2 describes that the loss of As can be suppressed by reducing the surface area.

JP 2000-154089 A JP 2004-137096 A

  However, only the techniques disclosed in Patent Documents 1 and 2 cannot sufficiently suppress the escape of the Group 15 element from the melt of the compound semiconductor raw material. If the loss of the group 15 element is not sufficiently suppressed, the composition of the produced single crystal deviates from the design target, and this deviation causes vacancy defects in the single crystal, resulting in production. The crystal quality of the single crystal is reduced.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a method for producing a single crystal having high crystal quality in the vertical boat method.

  The present invention includes a cylindrical body having a cylindrical body, a seed crystal housing part having a smaller diameter than the straight body part, a tapered part, and a shoulder part connecting the straight body part and the seed crystal housing part, A method for producing a single crystal composed of a compound semiconductor using a crucible comprising a step of disposing a seed crystal in a seed crystal accommodating portion and disposing a compound semiconductor raw material and a boron oxide raw material in a shoulder portion and a straight body portion And a step of melting a boron oxide raw material to generate a boron oxide melt, a step of melting a compound semiconductor raw material to generate a compound semiconductor melt, and a compound semiconductor melt from the seed crystal side in the axial direction of the crucible. And a step of solidifying and growing a single crystal, wherein the compound semiconductor raw material and the boron oxide raw material are stacked in the axial direction of the crucible, and the boron oxide raw material is formed under pressure.

  According to the present invention, it is possible to suppress the escape of the group 15 element from the compound semiconductor melt, and thus it is possible to suppress an increase in dislocation density due to this, and thus, a single crystal having high crystal quality. A manufacturing method can be provided.

1 is a schematic cross-sectional view of a single crystal manufacturing apparatus used in Embodiment 1. FIG. FIG. 3 is a cross-sectional view for schematically explaining the method for producing a single crystal in the first embodiment. FIG. 3 is a cross-sectional view for schematically explaining the method for producing a single crystal in the first embodiment. FIG. 3 is a cross-sectional view for schematically explaining the method for producing a single crystal in the first embodiment. It is a top view of the crucible of FIG. 6 is a cross-sectional view for schematically explaining a method for producing a single crystal in Embodiment 2. FIG. 6 is a cross-sectional view for schematically explaining a method for producing a single crystal in Embodiment 3. FIG. It is a schematic sectional view showing the shape of a general crucible used in the vertical boat method.

[Description of Embodiment of Present Invention]
First, an outline of an embodiment of the present invention will be described.

  As a result of intensive studies on a method for producing a single crystal having high crystal quality, the present inventors have found the following knowledge and completed the present invention.

  The surface area of the melt after all the compound semiconductor raw materials have been melted is equivalent to the cross-sectional area of the space in the crucible (the area of the surface perpendicular to the crucible axis). On the other hand, the surface area of the melt before all the compound semiconductor raw materials are melted, that is, at the stage where the compound semiconductor raw materials are gradually melted is equivalent to the exposed surface area of the compound semiconductor raw materials, which is more than the above case. growing. As the surface area of the melt increases, the frequency of removal of the group 15 element increases. In particular, this increase in frequency becomes significant when a large-diameter single crystal is manufactured, a long single crystal is manufactured, and the like.

  That is, when manufacturing a single crystal having a large diameter, it is necessary to increase the weight of the compound semiconductor raw material used, so that the surface area becomes large. Moreover, when manufacturing a long single crystal, since the compound semiconductor raw material used needs to be piled up bulky in a crucible, the surface area becomes large. By increasing the surface area of the compound semiconductor raw material, the surface area of the melt at the stage where the compound semiconductor raw material is gradually melted relatively increases, and therefore the frequency of removal of the group 15 element is particularly increased.

  For this reason, in order to sufficiently suppress the escape of the Group 15 element from the melt, it is not sufficient to cover the liquid surface of the melt after the compound semiconductor raw material is completely melted. And it is necessary to cover it uniformly.

  In order to quickly and uniformly cover the surface of the compound semiconductor raw material with the boron oxide melt, the present inventors need not only increase the boron oxide raw material to be used, but stably arrange the boron oxide raw material at an appropriate position. We thought that it was necessary to let you. This is because if the arrangement of boron oxide in the crucible is not appropriate, the surface of the compound semiconductor raw material cannot be quickly covered with the boron oxide melt, and if the boron oxide arrangement is not stable, the melt crucible This is because it has been found that the compound semiconductor raw material cannot be covered uniformly because the flow (spread) in the inside is biased.

  The inventors of the present invention have made extensive studies and arranged the compound semiconductor material and the pressure-formed boron oxide material so as to be stacked in the axial direction of the crucible, thereby quickly and uniformly oxidizing the surface of the compound semiconductor material. It was found that a single crystal with high crystal quality can be produced by covering with a raw material boron melt.

  (1) A method for producing a single crystal according to the present embodiment includes a straight body portion having a cylindrical shape, a seed crystal accommodating portion having a diameter smaller than that of the straight body portion, a tapered shape, and the straight body portion and the seed. A method for producing a single crystal composed of a compound semiconductor using a crucible having a shoulder connecting the crystal accommodating portion, wherein the seed crystal is disposed in the seed crystal accommodating portion, and the compound semiconductor is disposed in the shoulder portion and the straight body portion. A step of arranging the raw material and the boron oxide raw material (arrangement step), a step of melting the boron oxide raw material to generate a boron oxide melt (boron oxide melt generating step), a compound semiconductor raw material by melting the compound semiconductor raw material A compound semiconductor comprising: a step of generating a melt (compound semiconductor melt generation step); and a step of growing a single crystal by solidifying the compound semiconductor melt from the seed crystal side in the axial direction of the crucible (growth step). What are raw materials and boron oxide raw materials? Are laminated in the axial direction, the boron oxide material is formed under pressure.

  According to the manufacturing method of the present embodiment, since the boron oxide raw material is formed under pressure, it can have high accuracy with respect to its shape. Thereby, since the boron oxide raw material and the compound semiconductor raw material are stably laminated in the crucible, the uneven flow of the boron oxide raw material melt for covering the surface of the compound semiconductor raw material is suppressed. Furthermore, since the compound semiconductor raw material and the boron oxide raw material are laminated in the axial direction of the crucible, the boron oxide melt generated by melting the boron oxide raw material quickly spreads the surface of the compound semiconductor raw material located nearby. And can be covered uniformly. Thereby, the escape of the group 15 element from the compound semiconductor melt produced by melting the compound semiconductor raw material can be suppressed, and the increase in the dislocation density due to the release of the group 15 element can be suppressed. . Therefore, according to the manufacturing method of this embodiment, a single crystal with high crystal quality can be manufactured.

  (2) In the manufacturing method of the present embodiment, preferably, the boron oxide raw material is pressurized with a load of 5 Pa or more and 2000 Pa or less while being heated to 300 ° C. or more and 500 ° C. or less in a nitrogen atmosphere, an inert gas atmosphere, or a vacuum. It is formed. Thereby, the undulation of the surface of the boron oxide raw material can be sufficiently reduced, and the shape thereof can be appropriately shaped, so that a boron oxide raw material having sufficiently high accuracy with respect to the shape can be formed. it can.

  (3) In the manufacturing method of the present embodiment, preferably, the boron oxide raw material includes a plurality of boron oxide blocks, and in the step of arranging, each of the boron oxide blocks sandwiches the compound semiconductor raw material with respect to the axial direction of the crucible. Be placed. As a result, the boron oxide melt can quickly and uniformly cover the surface of the compound semiconductor raw material from above and below.

  (4) In the manufacturing method of the present embodiment, preferably, the compound semiconductor raw material is composed of a plurality of compound semiconductor blocks, and in the arranging step, each of the boron oxide blocks sandwiches each of the compound semiconductor blocks with respect to the axial direction of the crucible. Are arranged as follows. Thereby, the boron oxide melt can cover the surface of each compound semiconductor raw material quickly and uniformly from above and below.

[Details of the embodiment of the present invention]
Hereafter, the manufacturing method of the single crystal of this invention is demonstrated in detail. In the following description, a method of manufacturing a GaAs single crystal mainly using the VB method will be described. However, the technique of the present invention can be applied to other vertical boat methods, and in addition to GaAs, InAs, InP It is also applicable to other compound semiconductor single crystals such as GaP, GaSb and InSb. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

Embodiment 1
<Configuration of single crystal manufacturing equipment>
First, the structure of the single crystal manufacturing apparatus used in this embodiment will be described.

  With reference to FIG. 1, the single crystal manufacturing apparatus 10 includes an ampoule 11, a crucible base 14, a support shaft 15, a heater 16, a heat insulating material 17, and an airtight container 18. The ampoule 11 includes a container 12 that accommodates the crucible 20 in an inscribed state, and a lid 13 that is disposed on the open end of the container 12. Note that the inside of the ampoule 11 is hermetically sealed by disposing the lid 13 on the open end of the container 12. The ampoule 11 is placed on the crucible table 14, and the crucible table 14 is supported by the support shaft 15. The support shaft 15 can be moved up and down in the vertical direction in the figure by driving means (not shown). Further, the support shaft 15 may be rotatable about the vertical direction in the figure as a central axis. The ampoule 11 is surrounded by a heater 16.

  The heater 16 can give a temperature gradient in the vertical direction in the figure to the ampoule 11 by being controlled by a control means (not shown). As described above, since the ampule 11 is supported by the support shaft 15 that can be moved up and down in the figure, the temperature gradient applied to the ampule 11 as the support shaft 15 moves up and down, in other words, the crucible 20. The temperature gradient given inside will change. The periphery of the heater 16 is surrounded by a heat insulating material 17, and the ampoule 11, the heater 16 and the heat insulating material 17 are accommodated in an airtight container 18. The inside of the airtight container 18 can be kept airtight. Moreover, the airtight container 18 may include an atmospheric pressure adjusting unit for adjusting the internal atmospheric pressure.

<Configuration of crucible>
Next, the structure of the crucible used in this embodiment will be described.

  Referring to FIG. 2, a crucible 20 has a cylindrical body 21 having a cylindrical shape, a seed crystal accommodating part 22 having a diameter smaller than that of the straight body 21, a tapered shape, and the straight body 21 and the seed crystal. A shoulder portion 23 that connects the housing portion 22 is provided. The seed crystal accommodating portion 22 has a cylindrical shape that is closed at one end, and has a shape capable of accommodating a seed crystal therein.

  The crucible 20 is made of pyrolytic boron nitride (PBN; Pyrolytic Boron Nitride), and its wall thickness is preferably 0.3 mm or more and 2 mm or less. Because PBN is a brittle material, if the thickness is too small, it may be easily damaged by handling, and if the thickness is too large, the cost will be high.

<Method for producing single crystal>
Next, the manufacturing method of the single crystal in this embodiment is demonstrated.

1. Arrangement Step First, referring to FIG. 2, seed crystal 24 is arranged in seed crystal accommodating portion 22 of crucible 20, and compound semiconductor raw material 25 and boron oxide raw material 26 are arranged in shoulder portion 23 and straight body portion 21. (Arrangement process).

  The seed crystal 24 accommodated in the seed crystal accommodating portion 22 is a GaAs single crystal. Even when a single crystal made of a compound semiconductor containing a dopant is manufactured, the seed crystal 24 does not necessarily contain a dopant.

  The compound semiconductor raw material (hereinafter also referred to as “GaAs raw material”) 25 is GaAs polycrystal, and is composed of compound semiconductor blocks (hereinafter also referred to as “GaAs blocks”) 25a to 25c. Each of the GaAs blocks 25a to 25c has a cylindrical shape, and the upper surface and the bottom surface thereof are substantially parallel. For this reason, the GaAs blocks 25 a to 25 c are efficiently arranged in the crucible 20 and are stably stacked in this order with respect to the axial direction of the crucible 20.

  The GaAs blocks 25a to 25c can be manufactured, for example, by cutting out from a cylindrical GaAs polycrystal ingot. For example, a cylindrical GaAs polycrystal ingot is cut perpendicularly to the axial direction with a wire saw, a band saw, a laser, or the like, so that the parallel and flatness of the bottom surface and the top surface is high. 25c can be manufactured. The parallelism of the GaAs block is preferably 1 ° or less, more preferably 0.5 ° or less, and further preferably 0.2 ° or less. Further, the flatness of the GaAs block is preferably 5 μm or less, more preferably 3 μm, and further preferably 1 μm or less with respect to the maximum cross-sectional height Rt in an arbitrary cross-sectional curve on the surface. In the present specification, the maximum cross-sectional height Rt is a surface roughness value measured in accordance with JIS (Japanese Industrial Standards) B0601. A stylus-type shape measuring device can be used for measuring the parallelism, but a digital level or the like may also be used.

The boron oxide raw material (hereinafter also referred to as “B ₂ O ₃ raw material”) 26 is made of glassy boron oxide. The B ₂ O ₃ raw material 26 functions as a B ₂ O ₃ melt and suppresses As escape during crystal growth of a GaAs single crystal. The B ₂ O ₃ raw material 26 has a cylindrical shape and is disposed on the GaAs block 25c. The B ₂ O ₃ raw material 26 is further formed by pressurization after the mold is formed. That is, the columnar B ₂ O ₃ raw material is formed by the mold formation, and the parallelism and flatness of the upper surface and the bottom surface of the cylindrical B ₂ O ₃ raw material are increased by the subsequent pressure formation. For this reason, since the B ₂ O ₃ raw material 26 can have high accuracy with respect to its shape, the B ₂ O ₃ raw material 26 is placed on the GaAs block 25c so that its central axis substantially coincides with the axial direction of the crucible 20, as shown in FIG. It can be arranged stably.

The pressurization is performed, for example, from above and below so that a load is applied in the height direction (center axis direction) of the cylinder while heating the cylindrical B ₂ O ₃ raw material after mold formation at a temperature equal to or higher than its softening point. This can be done by pinching with a tool. Since boron oxide has high hygroscopicity, it is preferable to place the B ₂ O ₃ raw material under a nitrogen atmosphere, an inert gas atmosphere such as argon, or under vacuum when the B ₂ O ₃ raw material is pressurized. . Note that the nitrogen atmosphere means an atmosphere filled with nitrogen gas, the inert gas atmosphere means an atmosphere filled with inert gas, and the vacuum means at least 1.5 × 10 ⁻¹ Torr or less. Means under an atmosphere of pressure. Stainless steel, carbon, PBN, etc. can be used as the material of the jig.

The pressure-formed B ₂ O ₃ raw material 26 has a lower degree of surface waviness than that of the mold-formed B ₂ O ₃ raw material, in other words, the shape accuracy is high, and the top and bottom surfaces thereof are further improved. The parallelism and flatness of the are also increased. Therefore, the B ₂ O ₃ raw material 26 is stably laminated on the GaAs raw material 25. Specifically, the pressure-formed B ₂ O ₃ raw material 26 can have a parallelism of 1 ° or less. The parallelism is preferably 0.5 ° or less, more preferably 0.2 ° or less, and further preferably 0.1 ° or less. The parallelism can be set to each of the above values by appropriately adjusting each pressure forming condition such as load, pressing time, and vacuum.

Whether the B ₂ O ₃ raw material 26 is formed under pressure can be confirmed by observing the degree of undulation of the surface. For example, when the maximum cross-sectional height Rt in an arbitrary cross-sectional curve on the surface of the B ₂ O ₃ raw material 26 is 100 μm or less, it can be considered that the B ₂ O ₃ raw material 26 is formed under pressure. The maximum cross-sectional height Rt is preferably 80 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less. Note that the maximum cross-sectional height Rt can also be set to each of the above values by appropriately adjusting the pressure forming conditions such as the load, the pressing time, and the degree of vacuum.

2. Boron Oxide Melt Generation Step and Compound Semiconductor Melt Generation Step Next, referring to FIG. 3, the B ₂ O ₃ raw material 26 is melted to be referred to as a boron oxide melt (hereinafter referred to as “B ₂ O ₃ melt”). ) 31 (boron oxide melt production step), and further, the GaAs raw material 25 is melted to produce a compound semiconductor melt (hereinafter also referred to as “GaAs melt”) 30 (compound semiconductor melt production step). ).

Specifically, first, the crucible 20 in which the seed crystal 24, the GaAs blocks 25a to 25c, and the B ₂ O ₃ raw material 26 are arranged is arranged in the single crystal manufacturing apparatus shown in FIG. The inside of the straight body portion 21 and the shoulder portion 23 is heated by the heater 16.

In the temperature raising process in the crucible 20 by the heating of the heater 16, first, the temperature in the crucible 20 reaches the softening point (300 ° C.) of the B ₂ O ₃ raw material 26. At this stage, the B ₂ O ₃ raw material 26 is softened and starts to melt, whereby a B ₂ O ₃ melt 31 is generated in the crucible 20. At this time, since the B ₂ O ₃ raw material 26 is stably laminated on the GaAs block 25c, the B ₂ O ₃ melt 31 gradually generated from the B ₂ O ₃ raw material 26 is located below the GaAs. The surface of the raw material 25 can flow (spread) uniformly from above to below, and the surface of the GaAs raw material 25 can be covered quickly and uniformly.

Further, in the temperature raising process, the temperature in the crucible 20 reaches the melting point (1238 ° C.) of the GaAs raw material 25. At this stage, the GaAs raw material 25 starts to melt, thereby generating a GaAs melt 30 in the crucible 20. At this time, the GaAs block 25a~25c gradually melted from the surface, the surface, B ₂ O ₃ fusion produced from B ₂ O ₃ raw material 26 which is stably stacked on a GaAs block 25c Since it is covered quickly and uniformly by the liquid 31, As escape from the B ₂ O ₃ melt 31 that is gradually generated from the surface thereof is sufficiently suppressed.

3. Growth Step Next, referring to FIG. 4, the GaAs melt 30 is solidified in the axial direction of the crucible 20 from the seed crystal 24 side to grow a single crystal 40 (growth step).

  Specifically, referring to FIG. 1, after the temperature in the shoulder portion 23 and the straight body portion 21 is equal to or higher than the melting point of GaAs, all of the GaAs raw material 25 is changed to the GaAs melt 30. The ampoule 11 is heated so that the temperature on the seed crystal accommodating part 22 side is lower and the temperature on the upper side of the straight body part 21 is higher than the axial direction of the crucible 20. As a result, a temperature gradient is formed in the crucible 20 such that the temperature in the upward direction in the figure is high and the temperature in the downward direction in the figure is low.

  When the crucible 20 moves downward in the figure with respect to this temperature gradient, or when the heater 16 moves upward in the figure, the positional relationship between the crucible 20 and the temperature gradient is relative. To change. Thereby, the GaAs melt 30 is solidified from the seed crystal 24 side, and a GaAs single crystal 40 is grown as shown in FIG. Although this embodiment relates to the VB method, when the crucible 20 is applied to the VGF method, the liquid source is solidified from the seed crystal side by relatively changing the temperature gradient with respect to the crucible by the heater. be able to.

  The GaAs single crystal 40 can be grown in the crucible 20 through the above steps. The GaAs single crystal 40 is taken out from the crucible 20 and sliced with a wire saw or the like, whereby a plurality of GaAs single crystal substrates are obtained.

<Effect>
Next, the function and effect of the method for producing a single crystal according to this embodiment will be described.

According to the method for producing a single crystal according to the present embodiment, the B ₂ O ₃ raw material 26 is formed under pressure. Therefore, in the B ₂ O ₃ raw material 26, the surface waviness seen in the B ₂ O ₃ raw material after forming the mold is removed, and the shape can be highly accurate. For this reason, the B ₂ O ₃ raw material 26 and the GaAs raw material 25 are stably laminated in the axial direction in the crucible 20. Therefore, the B ₂ O ₃ melt 31 from the B ₂ O ₃ raw material 26 can uniformly cover the surfaces of the GaAs blocks 25 a to 25 c of the GaAs raw material 25 located in the vicinity thereof, and thus the GaAs melt 30. As can be sufficiently suppressed. This will be described more specifically with reference to FIG. 5 as compared to the case where the shape accuracy of the B ₂ O ₃ raw material is low.

FIG. 5 is a top view of FIG. 2, in which the crucible 20 in which the GaAs raw material 25 and the B ₂ O ₃ raw material 26 are arranged is viewed from above. Referring to FIG. 5, if the precision of the shape of the B ₂ O ₃ raw material 26 is low, B ₂ O ₃ raw material 26 is not stably laminated on the GaAs raw material 25, the axis of the crucible 20, as shown in FIG. 5 For example, it slips from the center of the direction to the position indicated by the dotted line. If the B ₂ O ₃ raw material 26 is softened while the B ₂ O ₃ raw material 26 is shifted to the position of the dotted line, the generated B ₂ O ₃ melt 31 flows non-uniformly on the surface of the GaAs raw material 25, so that GaAs A region not covered with the B ₂ O ₃ melt 31 is generated on the surface of the raw material 25. Since the GaAs melt 30 that is gradually generated from this region is not covered with the B ₂ O ₃ melt 31, the As missing is not sufficiently suppressed.

On the other hand, according to the present embodiment, the B ₂ O ₃ raw material 26 is formed under pressure and has a high shape accuracy with the surface waviness removed, so that it is stably laminated on the GaAs raw material 25. The For this reason, the above slip is suppressed. Accordingly, the B ₂ O ₃ melt 31 from the B ₂ O ₃ raw material 26 can quickly and uniformly cover the surfaces of the GaAs blocks 25a to 25c of the GaAs raw material 25 located in the vicinity thereof. As a result, As missing from the surfaces of the GaAs blocks 25a to 25c can be sufficiently suppressed, and an increase in dislocation density of the GaAs single crystal due to As missing can be suppressed. Therefore, as a result, a GaAs single crystal with high crystal quality can be manufactured.

Further, it is known that B ₂ O ₃ has a high hygroscopic property, so that moisture is easily adsorbed on its surface. For example, when the B ₂ O ₃ raw material 26 that has adsorbed moisture is placed in the hermetic container 18, unintentional moisture is brought into the hermetic container 18. This is a factor that causes an increase in pressure in the container 18. Such an increase in pressure is not desirable because it causes a decrease in the quality of the GaAs single crystal 40 and damage to the single crystal manufacturing apparatus 10.

In contrast, according to the present embodiment, the B ₂ O ₃ raw material 26 is formed under pressure in a nitrogen atmosphere, an inert gas atmosphere, or a vacuum, so that moisture adsorbed on the surface is removed. Has been. Therefore, by disposing the B ₂ O ₃ raw material 26 in the crucible 20, the introduction of moisture into the airtight container 18 due to the introduction of moisture adsorbed on the surface of the B ₂ O ₃ raw material 26 is suppressed. be able to. In particular, from the viewpoint of more reliably suppressing moisture from being brought into the airtight container 18, it is preferable to perform the pressure formation of the B ₂ O ₃ raw material 26 immediately before placing it in the crucible 20.

  Further, in the method for producing a single crystal according to the present embodiment, a PBN crucible 20 was used. PBN crucibles are preferable in terms of heat resistance and ease of manufacture. Further, since it can be produced by using a high-temperature chemical vapor deposition method, it can have high purity, so that unintended impurities derived from the crucible 20 into the GaAs single crystal 40 can be suppressed. However, since the cost is higher than quartz and carbon, it is desirable that the thickness of the wall be 2 mm or less from the viewpoint of cost reduction.

In particular, according to the method for producing a single crystal according to the present embodiment, since the GaAs raw material 25 and the B ₂ O ₃ raw material 26 are stably laminated in the crucible, the B ₂ O ₃ raw material 26 slips. It is suppressed. If the GaAs raw material 25, the B ₂ O ₃ raw material 26, and the like are laminated in an unstable manner, these slips may occur due to vibrations that occur during transportation, resulting in damage to the crucible 20. In particular, when the crucible 20 with a small thickness is used from the viewpoint of cost reduction as described above, the possibility of breakage due to the above-mentioned slip is higher than when the crucible 20 with a large thickness is used. On the other hand, according to the method for producing a single crystal according to the present embodiment, since the slip of the B ₂ O ₃ raw material 26 is suppressed, the possibility of such damage can be reduced, and the thickness can be reduced. A small crucible 20 can be suitably used.

  The crucible 20 may employ boron nitride (BN), pyrolytic graphite, graphite, vitrified carbon, or quartz in addition to PBN.

In the method for producing a single crystal according to the present embodiment, the GaAs blocks 25a to 25c are preferably cylindrical, and the upper surface and the bottom surface have high parallelism and / or flatness. Since the shape of each GaAs block 25a-25c is cylindrical, the GaAs blocks 25a-25c can be efficiently arranged in the crucible 20, and the upper surface and the bottom surface thereof have high parallelism and / or high flatness. The GaAs blocks 25a to 25c can be stacked more stably in the axial direction of the crucible 20. More preferably, the GaAs blocks 25 a to 25 c are stacked so that the central axes thereof coincide with the axial direction of the crucible 20. Thus, it is possible to further suppress such slippage of the B ₂ O ₃ raw material 26 disposed thereon.

  The GaAs raw material 25 is particularly preferably a cylindrical shape from the viewpoint of efficient arrangement and ease of manufacture, but the shape is not limited to this, and for example, a rectangular parallelepiped, a prismatic shape, a ring shape (doughnut shape) Or the like. However, from the viewpoint of maintaining stable lamination, it is preferable that the parallelism of the two surfaces penetrating in the axial direction of the crucible 20 is high when it is arranged in the crucible 20 with respect to each shape. Thereby, each block can be stacked stably.

In the method for producing a single crystal according to the present embodiment, preferably, the B ₂ O ₃ raw material 26 is 5 Pa or more and 2000 Pa or less with respect to the thickness direction (the width in the axial direction of the crucible 20 when placed in the crucible 20). Pressurized with a load of. When the B ₂ O ₃ raw material 26 is press-formed with a load of 5 Pa or more, the undulation of the surface is sufficiently reduced, and by being formed with a load of 2000 Pa or less, it is caused by excessive pressurization. Unintentional shape change of the B ₂ O ₃ raw material 26 can be prevented. Therefore, the B ₂ O ₃ raw material 26 having sufficiently high accuracy with respect to its shape can be stably produced. Further, when the B ₂ O ₃ raw material 26 is formed under pressure with a load of 5 Pa or more, moisture on the surface is sufficiently removed.

The B ₂ O ₃ raw material 26 is particularly preferably in the form of a column from the viewpoint of efficient arrangement and ease of manufacture, but the shape is not limited to this, and for example, a rectangular parallelepiped, a prismatic shape, or a ring shape It may be. However, the B ₂ O ₃ raw material 26 is press-formed at least in the thickness direction (the width in the axial direction of the crucible 20 when placed in the crucible 20), and when placed in the crucible 20. The parallelism of the two surfaces penetrating in the axial direction of the crucible 20 is preferably high. As a result, the GaAs raw material 25 can be laminated more stably, and the flow of the B ₂ O ₃ melt 31 becomes more uniform.

Further, regarding the B ₂ O ₃ raw material 26, from the viewpoint of covering the surfaces of the GaAs blocks 25a to 25c more quickly and uniformly, the shape and size of the surface in contact with the GaAs block 25c are preferably the shape of the upper surface of the GaAs block 25c, Similar to size and more preferably match.

In the method for producing a single crystal according to the present embodiment, the GaAs raw material 25 includes GaAs blocks 25a to 25c. However, the GaAs raw material 25 may be composed of one block or a larger number of GaAs blocks. It is sufficient that at least the B ₂ O ₃ raw material 26 and the GaAs raw material 25 are laminated. Therefore, for example, the B ₂ O ₃ raw material 26 may be disposed between any of the GaAs blocks 25a to 25c. Even in this case, since the shape of the B ₂ O ₃ raw material 26 has high accuracy, they are stably laminated, and further, the GaAs raw material 25 placed on the B ₂ O ₃ raw material 26 can slide. Can be suppressed.

<< Embodiment 2 >>
Since the single crystal manufacturing apparatus and the crucible used in the method for manufacturing a single crystal according to the present embodiment are the same as those in the first embodiment, description thereof will not be repeated. Also, the description of the same points as in the first embodiment will not be repeated with respect to the single crystal manufacturing method and effects described below.

<Method for producing single crystal>
1. Arrangement Step First, referring to FIG. 6, the seed crystal 24 is arranged in the seed crystal accommodating part 22 of the crucible 20, and the GaAs raw material 25 and the B ₂ O ₃ raw material 26 are arranged in the shoulder part 23 and the straight body part 21. (Placement process).

  The GaAs material 25 includes GaAs blocks 25d to 25f. Each of the GaAs blocks 25d to 25f has a cylindrical shape, and the upper surface and the bottom surface thereof are substantially parallel. Therefore, the GaAs blocks 25d to 25f are efficiently arranged in the crucible 20 and are stably stacked in this order with respect to the axial direction of the crucible 20.

The B ₂ O ₃ raw material 26 is made up of B ₂ O ₃ blocks 26 a and 26 b, and the B ₂ O ₃ blocks 26 a and 26 b are made of GaAs raw material 25 made up of GaAs blocks 25 a to 25 c having a cylindrical shape with respect to the axial direction of the crucible 20. It is arranged so as to sandwich it.

The B ₂ O ₃ block 26 a has a conical shape with a chipped apex, and is arranged in the shoulder portion 23 so that the chipped apex side is located below the crucible 20. The B ₂ O ₃ block 26a is further press-formed after being cast. That, is formed B ₂ O ₃ raw material conical missing vertices by mold-forming, by the subsequent pressure forming this B ₂ O ₃ raw material of the upper surface (surface in contact with the GaAs block 25d) and bottom (seed crystal 24 The degree of parallelism and flatness with the contact surface) is increased. For this reason, since the B ₂ O ₃ block 26a can have high accuracy with respect to its shape, the B ₂ O ₃ block 26a is placed on the seed crystal 24 so that its central axis substantially coincides with the axial direction of the crucible 20, as shown in FIG. It becomes possible to arrange stably, and the GaAs block 25d can be stably arranged above it.

The B ₂ O ₃ block 26b has a cylindrical shape and is disposed on the GaAs block 25f. The B ₂ O ₃ block 26b is also formed by pressurization after the mold is formed. That is, the columnar B ₂ O ₃ raw material is formed by the mold formation, and the parallelism and flatness of the upper surface and the bottom surface of the cylindrical B ₂ O ₃ raw material are increased by the subsequent pressure formation. For this reason, since the B ₂ O ₃ block 26b can have high accuracy with respect to its shape, the GaAs is formed so that its central axis of the cylindrical shape substantially coincides with the axial direction of the crucible 20, as shown in FIG. It becomes possible to arrange stably on the block 25f.

2. Boron oxide melt production process and compound semiconductor melt production process Next, referring to FIG. 3, the B ₂ O ₃ raw material 26 is melted to produce a B ₂ O ₃ melt 31 (boron oxide melt production process). Further, the GaAs raw material 25 is melted to produce a GaAs melt 30 (compound semiconductor melt producing step).

Specifically, first, the crucible 20 in which the seed crystal 24, the GaAs blocks 25a to 25c, and the B ₂ O ₃ blocks 26a and 26b are arranged is placed in the single crystal manufacturing apparatus shown in FIG. The inside of the straight body portion 21 and the shoulder portion 23 is heated by the heater 16.

In the process of raising the temperature in the crucible 20 by the heating of the heater 16, first, the temperature in the crucible 20 reaches the softening point of the B ₂ O ₃ raw material 26. At this stage, the B ₂ O ₃ blocks 26 a and 26 b start to soften and melt, thereby generating a B ₂ O ₃ melt 31 in the crucible 20. At this time, since the B ₂ O ₃ block 26b is stably laminated on the GaAs block 25f, the B ₂ O ₃ melt 31 that is gradually generated from now on moves the surface of the GaAs raw material 25 downward from above. It can flow (spread) uniformly, and the surface of the GaAs source 25 can be covered quickly and uniformly. Further, B ₂ O ₃ melt 31 is gradually generated from the B ₂ O ₃ blocks 26a can be uniformly spread upward from below the GaAs raw material 25. Therefore, by sandwiching the GaAs raw material 25 from the B ₂ O ₃ raw material 26 above and below, can be covered quickly and uniformly by B ₂ O ₃ melt 31 spreads the surface of the GaAs raw material 25 from above and below.

Further, in the temperature rising process, the temperature in the crucible 20 reaches the melting point of the GaAs raw material 25. At this stage, the GaAs raw material 25 starts to melt, thereby generating a GaAs melt 30 in the crucible 20. At this time, the GaAs blocks 25d to 25f are gradually melted from the respective surfaces, and the surface stably stabilizes the B ₂ O ₃ block 26b and the GaAs raw material 25 stacked on the GaAs block 25f upward. Since the B ₂ O ₃ melt 31 generated from the laminated B ₂ O ₃ block 26a is covered quickly and uniformly, the As missing from the GaAs melt 30 gradually generated from the surface is sufficient. To be suppressed.

<Effect>
Next, the function and effect of the method for producing a single crystal according to this embodiment will be described.

According to the method for producing a single crystal according to the present embodiment, B ₂ O ₃ raw material 26 constituting the B ₂ O ₃ blocks 26a and B ₂ O ₃ blocks 26b are respectively pressure forming. Therefore, in the B ₂ O ₃ raw material 26, the surface waviness seen in the B ₂ O ₃ raw material after forming the mold is removed, and the shape can be highly accurate. For this reason, the B ₂ O ₃ raw material 26 and the GaAs raw material 25 are stably laminated in the axial direction in the crucible 20. Therefore, the B ₂ O ₃ melt 31 from the B ₂ O ₃ blocks 26a and 26b can quickly and uniformly cover the surfaces of the GaAs blocks 25d to 25f of the GaAs raw material 25 located in the vicinity thereof. As missing from the GaAs melt 30 can be sufficiently suppressed. This will be described more specifically as compared with the case where the shape accuracy of the B ₂ O ₃ raw material is low.

When a B ₂ O ₃ raw material having a low shape accuracy, that is, a conventional B ₂ O ₃ raw material not formed under pressure is used to stack a GaAs raw material and a B ₂ O ₃ raw material as shown in FIG. In addition, the GaAs raw material and the B ₂ O ₃ raw material may be inclined. In particular, when the undulation of the upper surface and the bottom surface of the GaAs block a disposed on the shoulder 23 is large, or when the parallelism is low, the inclination becomes significant. When the stacked GaAs material and B ₂ O ₃ material are inclined, the flow of the B ₂ O ₃ melt is biased, and the surface of the GaAs material cannot be uniformly covered. Further, the tilted GaAs material and / or B ₂ O ₃ material comes into contact with the inner wall of the crucible, thereby causing damage to the crucible. In particular, if there is a pointed portion as the undulation, the load is locally concentrated in the contact region between the pointed portion and the inner surface of the crucible, increasing the risk of breakage of the crucible.

On the other hand, according to the present embodiment, the B ₂ O ₃ melt 31 from the B ₂ O ₃ raw material 26 uniformly covers the surfaces of the GaAs blocks 25d to 25f of the GaAs raw material 25 located in the vicinity thereof. Can do. Therefore, the As missing from the surfaces of the GaAs blocks 25d to 25f can be suppressed uniformly and sufficiently, and an increase in the dislocation density of the GaAs single crystal due to the As missing can be suppressed. A high quality GaAs single crystal can be manufactured.

Further, according to the present embodiment, since the B ₂ O ₃ raw material 26 is formed under pressure, the undulation of the surface of the B ₂ O ₃ raw material 26 is reduced as compared with the conventional B ₂ O ₃ raw material that is not formed under pressure. To do. Thereby, the local concentration of the load on the inner surface of the crucible 20 by the B ₂ O ₃ raw material 26 can be avoided, and the risk of breakage of the crucible 20 can be reduced. Therefore, since the crucible 20 with a small thickness, for example, the crucible 20 with a thickness reduced to about 0.3 mm can be suitably used, the manufacturing cost can be reduced.

Furthermore, the inclination of the GaAs raw material 25 and the B ₂ O ₃ raw material 26 stacked in the crucible 20 is suppressed, and the contact between these and the inner surface of the crucible 20 is suppressed. Can be made sufficiently large. That is, referring to FIG. 5, the clearance between the GaAs raw material 25 and the inner surface of the crucible 20 can be reduced. Specifically, conventionally, the clearance L is required to be 1 mm or more in consideration of the inclination, but by using the B ₂ O ₃ raw material 26 formed by pressure, the clearance L is less than 1 mm, More preferably, it can be less than 0.6 mm.

  Since the clearance L can be designed to be small as described above, the filling rate of the raw material in the crucible 20 can be increased, and the bulk of the stacked raw materials can be reduced. Thereby, the length of the crucible 20 itself can be designed to be small, the heating area by the heater can be reduced, and further, the effect of preventing the loss of As is enhanced by improving the filling rate.

In the method for producing a single crystal according to the present embodiment, the B ₂ O ₃ block 26a disposed on the shoulder portion 23 is preferably formed by pressing in addition to the top surface and the bottom surface thereof. That is, it is preferable that both the surface in contact with the GaAs material 25 and the surface in contact with the inner surface of the crucible 20 among the surfaces of the B ₂ O ₃ material 26 are formed under pressure.

Even if the B ₂ O ₃ block 26a slips due to the removal of the undulation on the side surface of the B ₂ O ₃ block 26a due to the pressure formation, the load applied to the inner surface of the crucible 20 by the B ₂ O ₃ block 26a Since local concentration can be avoided, the risk of breakage of the crucible 20 can be reduced. The pressurization of the side surface is easy by using a conical jig whose angle formed by the side surface of the cone coincides with the angle formed by the inner surface of the shoulder 23 and a jig that overlaps. Can be done.

The shape of the B ₂ O ₃ block 26a is particularly preferably a conical shape with missing apexes, but the shape is not limited to this, and for example, a rectangular parallelepiped shape, a cylindrical shape, a pyramid shape, a ring shape, and the like. Also good.

<< Embodiment 3 >>
Since the single crystal manufacturing apparatus and the crucible used in the method for manufacturing a single crystal according to the present embodiment are the same as those in the first embodiment, description thereof will not be repeated. Also, the description of the same points as in Embodiments 1 and / or 2 will not be repeated with respect to the single crystal manufacturing method and effects described below.

<Method for producing single crystal>
1. Arrangement Step First, referring to FIG. 7, a seed crystal 24 is arranged in the seed crystal accommodating part 22 of the crucible 20, and a GaAs raw material 25 and a B ₂ O ₃ raw material 26 are arranged in the shoulder part 23 and the straight body part 21. (Placement process).

The GaAs raw material 25 includes GaAs blocks 25g to 25j. Each of the GaAs blocks 25g to 25j has a cylindrical shape, and the upper surface and the bottom surface thereof are substantially parallel. The B ₂ O ₃ raw material 26 is composed of B ₂ O ₃ blocks 26c to 26g, and each of the B ₂ O ₃ blocks 26c to 26g has a cylindrical shape.

In the present embodiment, each of the B ₂ O ₃ blocks 26 c to 26 g is disposed so as to sandwich each of the GaAs blocks 25 g to 25 j having a columnar shape with respect to the axial direction of the crucible 20. More specifically, the blocks of the B ₂ O ₃ raw material 25 and the GaAs raw material 26 are arranged in an alternately stacked state.

The parallelism of the top and bottom surfaces of the GaAs blocks 25g to 25j can be easily increased due to their properties and the above-described manufacturing method. In addition, since each of the B ₂ O ₃ blocks 26c to 26g is pressed and formed after the mold is formed, the undulation of the top and bottom surfaces is removed, and the parallelism and flatness of the top and bottom surfaces are It is sufficiently enhanced compared to a B ₂ O ₃ block that has only been templated. That is, each of the B ₂ O ₃ blocks 26c to 26g has high accuracy with respect to its shape.

Accordingly, in this step, as shown in FIG. 7, as the central axis of the GaAs block 25g~25j and B ₂ O ₃ blocks 26c~26g substantially coincides with the axial direction of the crucible 20, GaAs block and B ₂ Even in a state where O ₃ blocks are alternately laminated, these can be stably arranged on the seed crystal 24.

2. Boron oxide melt production process and compound semiconductor melt production process Next, referring to FIG. 3, the B ₂ O ₃ raw material 26 is melted to produce a B ₂ O ₃ melt 31 (boron oxide melt production process). Further, the GaAs raw material 25 is melted to produce a GaAs melt 30 (compound semiconductor melt producing step).

Specifically, first, the crucible 20 in which the seed crystal 24, the GaAs blocks 25g to 25j, and the B ₂ O ₃ blocks 26c to 26g are arranged is placed in the single crystal manufacturing apparatus shown in FIG. The inside of the straight body portion 21 and the shoulder portion 23 is heated by the heater 16.

In the process of raising the temperature in the crucible 20 by the heating of the heater 16, first, the temperature in the crucible 20 reaches the softening point of the B ₂ O ₃ raw material 26. At this stage, the B ₂ O ₃ blocks 26 c to 26 g are softened and start to melt, whereby a B ₂ O ₃ melt 31 is generated in the crucible 20. At this time, since the B ₂ O ₃ blocks 26d to 26g are stably laminated on the GaAs blocks 25g to 25j, the gradually generated B ₂ O ₃ melts 31 are formed in the vicinity of the GaAs 25g. The surface of each of ˜25j can flow (spread) uniformly from the upper side to the lower side, so that the surface of the GaAs raw material 25 can be covered uniformly. Further, the B ₂ O ₃ block 26c can spread uniformly from the lower side to the upper side of the GaAs block 25g. Accordingly, each of the B ₂ O ₃ blocks 26c to 26g is arranged so as to sandwich each of the GaAs blocks 25g to 25j having a columnar shape with respect to the axial direction of the crucible 20, so that each surface of the GaAs blocks 25g to 25j It can be covered quickly and uniformly by the B ₂ O ₃ melt 31 spreading from above and below.

Further, in the temperature raising process, the temperature in the next crucible 20 reaches the melting point of the GaAs raw material 25. At this stage, the GaAs raw material 25 starts to melt, thereby generating a GaAs melt 30 in the crucible 20. At this time, the GaAs blocks 25g to 25j are gradually melted from the surface thereof, and the surfaces thereof are the B ₂ O ₃ blocks 26d to 26g and the GaAs raw material 25 which are stably stacked on the GaAs blocks 25g to 25j. Since it is covered quickly and uniformly by the B ₂ O ₃ melt 31 generated from the B ₂ O ₃ block 26c for stably laminating the GaAs melt, the GaAs melt 30 gradually generated from the surface thereof is used. As missing is sufficiently suppressed.

<Effect>
Next, the function and effect of the method for producing a single crystal according to this embodiment will be described.

According to the method for producing a single crystal according to the present embodiment, B ₂ O ₃ blocks 26c~26g constituting the B ₂ O ₃ raw material 26 are respectively pressure forming. Therefore, in the B ₂ O ₃ raw material 26, the surface waviness seen in the B ₂ O ₃ raw material after forming the mold is removed, and the shape can be highly accurate. Further, each of the B ₂ O ₃ blocks 26c to 26g is arranged so as to sandwich each of the GaAs blocks 25g to 25j, and is stably stacked in the axial direction in the crucible 20. Therefore, each B ₂ O ₃ melt 31 from the B ₂ O ₃ blocks 26c to 26g can quickly and uniformly cover the surface of each of the GaAs blocks 25g to 25j located in the vicinity thereof. As missing from the liquid 30 can be sufficiently suppressed. This will be described more specifically as compared with the case where the shape accuracy of the B ₂ O ₃ raw material is low.

When a B ₂ O ₃ raw material having a low shape accuracy, that is, a conventional B ₂ O ₃ raw material not formed under pressure is used to stack a GaAs raw material and a B ₂ O ₃ raw material as shown in FIG. In addition, the GaAs raw material and the B ₂ O ₃ raw material may be inclined. When the stacked GaAs material and B ₂ O ₃ material are inclined, the flow of the B ₂ O ₃ melt is biased, and the surface of the GaAs material cannot be uniformly covered. Further, the tilted GaAs material and / or B ₂ O ₃ material is locally brought into contact with the inner wall of the crucible, thereby causing damage to the crucible 20.

On the other hand, according to the present embodiment, the B ₂ O ₃ melt 31 from the B ₂ O ₃ blocks 26d to 26g uniformly covers the respective surfaces of the GaAs blocks 25g to 25j located under the respective blocks. Can do. Thereby, As missing from the surfaces of the GaAs blocks 25g to 25j can be sufficiently suppressed, and an increase in dislocation density of the GaAs single crystal due to As missing can be suppressed. Therefore, as a result, a GaAs single crystal with high crystal quality can be manufactured.

In particular, this embodiment is particularly effective when a large-diameter single crystal is manufactured or when a long single crystal is manufactured. In order to produce a large-diameter single crystal or a long single crystal, many GaAs raw materials are required. Therefore, the surface area of the GaAs raw material placed in the crucible becomes large, or the stacked GaAs raw materials are bulky. Get higher. In this case, since the GaAs blocks are sandwiched between the B ₂ O ₃ blocks, the surface of each GaAs block can be covered with the B ₂ O ₃ melt more quickly and uniformly.

<Example 1>
Using the single crystal manufacturing apparatus shown in FIG. 1 and the crucible shown in FIG. 2, each raw material is arranged as shown in FIG. 7 to manufacture a GaAs single crystal by the following method, and the crystal quality of the manufactured single crystal is confirmed. did.

1. Preparation of crucible A PBN crucible was prepared. The shape of the straight body of the crucible was 160 mm in inner diameter and 200 mm in length.

2. A GaAs seed crystal consisting of preparing GaAs single crystal material, and GaAs material made of GaAs polycrystal, were prepared and B ₂ O ₃ raw material consisting of a mold formed B ₂ O ₃ blocks.

  Regarding the GaAs raw material, pre-dissolved Ga is injected into the crucible for raw material production, this crucible for raw material production is put into a furnace whose atmosphere can be adjusted, and As vapor is introduced into the furnace to react Ga and As vapor. However, it was kept at 1240 ° C. or higher for 2 hours. Thereafter, the inside of the furnace was naturally cooled. This produced the ingot which consists of a GaAs polycrystal. Then, this ingot was cut using a band saw to produce four cylindrical GaAs blocks having a diameter of 158 mm and a height of 35 mm. For each GaAs block, the parallelism was 0.5 ° and was approximately parallel, and the maximum cross-sectional height Rt was 3 μm. In addition, a stylus type shape measuring device is used for the measurement of parallelism, and the maximum cross-sectional height Rt is JIS B0601 using a contour shape measuring machine (trade name: “Contracer CV-3100”, manufactured by Mitutoyo Corporation). Measured according to

The formed B ₂ O ₃ block was subjected to pressure forming in order to remove waviness on the upper surface and the bottom surface and improve flatness and parallelism. Specifically, a B ₂ O ₃ block inserted with a PBN jig is put into a heating furnace, the inside of the heating furnace is evacuated, and the degree of vacuum in the furnace is 7.5 × 10 ⁻² Torr or less. At that time, the inside of the heating furnace was replaced with nitrogen. And after raising the temperature in a heating furnace to 300 degreeC with the temperature increase rate of 100 degreeC / hour, it hold | maintained at the state of 300 degreeC for 1 hour until temperature stabilized. Then, after raising the temperature in a heating furnace to 425 degreeC with the temperature increase rate of 150 degreeC / hour, the heat processing for 30 minutes were implemented. During the heating, nitrogen was kept flowing in the furnace so that the pressure in the heating furnace became 4.0 × 10 ⁻² Torr. During heating, a load of 390 Pa was applied to the upper surface of the B ₂ O ₃ block as the weight of the jig. After completion of the heat treatment at the furnace temperature of 425 ° C., the furnace temperature was returned to room temperature by cooling the furnace, the pressurized B ₂ O ₃ block was taken out, and immediately sealed in vacuum to prevent moisture absorption.

By the pressure forming process, diameter 150 mm, 4 bract the B ₂ O ₃ blocks cylindrical height of 10 mm, to prepare a single diameter 90 mm, a cylindrical height of 10 mm B ₂ O ₃ blocks. In the above five B ₂ O ₃ blocks produced by pressure forming, the cylindrical top surface and bottom surface were substantially parallel with a parallel degree of 0.2 °, and the measured maximum cross-sectional height Rt was 50 μm. .

3. Manufacture of single crystal First, a GaAs seed crystal is accommodated in the seed crystal accommodating portion, a B ₂ O ₃ block having a diameter of 90 mm is arranged on the shoulder portion, and four GaAs blocks and four B ₂ O ₃ blocks are alternately arranged thereon. 7 to be in a state shown in FIG. And this crucible was vacuum-sealed in the ampule of a single crystal manufacturing apparatus.

Next, the ampoule was heated to about 300 ° C. with the heater of the single crystal manufacturing apparatus, and the GaAs block and B ₂ O ₃ block in the crucible were melted. Then, a temperature gradient is formed from the seed crystal housing part side toward the straight body part side, and the ampoule is moved with respect to this temperature gradient to gradually decrease the temperature from the seed crystal housing part side toward the straight body part side. By doing so, a GaAs single crystal was grown in the crucible.

A polycrystalline region was not confirmed in the obtained GaAs single crystal, and a high-quality GaAs single crystal was manufactured. Further, when the surface of the obtained GaAs single crystal was visually observed, gloss was seen over the entire area of the crystal side surface. For example, when there is a portion that is not covered with the B ₂ O ₃ melt on the inner surface of the crucible, and that portion comes into contact with the GaAs melt, gloss is seen on the side surface of the GaAs single crystal grown here. Absent. From this, it was found that in the GaAs single crystal manufacturing process, the inner surface of the crucible in contact with the growing GaAs crystal was sufficiently covered with the B ₂ O ₃ melt over the entire area. Further, when the surface of the GaAs single crystal was visually observed, no precipitation of Ga was confirmed, and no composition shift due to As loss was confirmed. From this, it was found that in the GaAs single crystal manufacturing process, As loss from the GaAs melt was suppressed, and thus an increase in dislocation density due to As loss was suppressed. Further, during the manufacturing process, no leakage of GaAs melt accompanying breakage of the crucible occurred.

<Example 2>
The B ₂ O ₃ raw material was prepared by the same method as in Example 1 except that the B ₂ O ₃ raw material was pressed at a load of 1200 Pa using a carbon jig coated with a CVD carbon film while heating at 425 ° C. Crystals were produced. In the five B ₂ O ₃ blocks created by pressure forming, the cylindrical upper surface and the bottom surface were approximately parallel with a parallel degree of 0.1 °, and the measured maximum cross-sectional height Rt was 50 μm. It was.

When the produced GaAs single crystal was taken out from the crucible and visually observed, a polycrystalline region was not confirmed in the obtained GaAs single crystal as in Example 1, and a high-quality GaAs single crystal was produced. . Further, when the surface of the obtained GaAs single crystal was visually observed, gloss was seen over the entire area of the crystal side surface. From this, it was found that in the GaAs single crystal manufacturing process, the inner surface of the crucible in contact with the growing GaAs crystal was sufficiently covered with the B ₂ O ₃ coating over the entire area. Further, when the surface of the GaAs single crystal was visually observed, no precipitation of Ga was confirmed, and no composition shift due to As loss was confirmed. From this, it was found that in the GaAs single crystal manufacturing process, As loss from the GaAs melt was suppressed, and thus an increase in dislocation density due to As loss was suppressed. Further, during the manufacturing process, no leakage of GaAs melt accompanying breakage of the crucible occurred.

<Comparative Example 1>
A GaAs single crystal was produced in the same manner as in Example 1 except that no pressure formation was performed on the B ₂ O ₃ raw material. For the five cylindrical B ₂ O ₃ blocks that were not pressed and formed, the parallelism between the top and bottom surfaces was as low as 3 °, and there was undulation on the surface. The height Rt was 450 μm.

By observing the obtained GaAs single crystal by visual observation, it was found that it contained many polycrystalline regions. In addition, since many non-glossy regions were observed on the side surface of the GaAs crystal, the inner surface of the crucible in contact with the GaAs crystal was not sufficiently covered with the B ₂ O ₃ melt in the GaAs single crystal manufacturing process, and the coating was poor. It was found that an area had occurred. Further, it was found that Ga was found on the surface of the grown GaAs crystal and that a composition shift due to As loss occurred.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Single crystal manufacturing apparatus 11 Ampoule 12 Container 13 Cover body 14 Crucible stand 15 Support shaft 16 Heater 17 Heat insulating material 18 Airtight container 20 Crucible 21 Straight body part 22 Shoulder part 23 Seed crystal accommodating part 24 Seed crystal 25 GaAs raw material 25a-25j GaAs block 26 B ₂ O ₃ raw material 26a-26g B ₂ O ₃ block.

Claims (4)

A straight body portion having a cylindrical shape, a seed crystal housing portion having a smaller diameter than the straight body portion, and a shoulder portion having a tapered shape and connecting the straight body portion and the seed crystal housing portion. A method for producing a single crystal composed of a compound semiconductor using a crucible,
A step of disposing a seed crystal in the seed crystal accommodating portion and disposing a compound semiconductor raw material and a boron oxide raw material in the shoulder portion and the straight body portion;
Melting the boron oxide raw material to produce a boron oxide melt;
Melting the compound semiconductor raw material to produce a compound semiconductor melt;
Solidifying the compound semiconductor melt from the seed crystal side in the axial direction of the crucible to grow a single crystal,
The compound semiconductor raw material and the boron oxide raw material are stacked in the axial direction of the crucible, and the boron oxide raw material is formed under pressure.   2. The method for producing a single crystal according to claim 1, wherein the boron oxide raw material is formed under pressure at a pressure of 5 Pa or more and 2000 Pa or less while being heated to 300 ° C. or more and 500 ° C. or less. The boron oxide raw material comprises a plurality of boron oxide blocks,
3. The method for producing a single crystal according to claim 1, wherein in the arranging step, each of the boron oxide blocks is arranged so as to sandwich the compound semiconductor raw material with respect to an axial direction of the crucible. The compound semiconductor raw material is composed of a plurality of compound semiconductor blocks,
4. The method for producing a single crystal according to claim 3, wherein in the arranging step, each of the boron oxide blocks is arranged so as to sandwich each of the compound semiconductor blocks with respect to an axial direction of the crucible.

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