JP2013193942A - Single crystal manufacturing apparatus and method for manufacturing single crystal using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single crystal manufacturing apparatus for growing a high quality single crystal ingot in high yield, and a method for manufacturing a single crystal using the same.SOLUTION: A single crystal manufacturing device for growing a single crystal ingot from a raw material melt stored in a crucible includes: a heater disposed outside beyond the plane of the crucible ahead in the single crystal ingot growing direction when the single crystal ingot is grown; a heat insulation member disposed between the plane of the crucible and the heater; a heat conductive member disposed in the outer circumference of the crucible to cover the crucible throughout in the crucible axial direction and thermally connected to the heater at its end part; and a mechanism making a gas for controlling the temperature of the heat conducive member circulate along the outer circumference of the heat conductive member.

Description

  The present invention relates to a single crystal manufacturing apparatus for growing a high-quality single crystal ingot with a high yield, and a single crystal manufacturing method using the same.

  Single-crystal substrates of semiconductors (eg, silicon, gallium arsenide, etc.) are indispensable for the manufacture of electronic devices that support modern society (eg, integrated circuits (ICs), light emitting diodes (LEDs), laser diodes (LDs), etc.) It has become. A single crystal substrate is usually manufactured by slicing and polishing a single crystal ingot.

  Typical methods for producing single crystal ingots (single crystal growth methods) are boat methods (eg, horizontal Bridgman method, vertical Bridgman method, horizontal temperature gradient solidification method, vertical temperature gradient solidification method) and pulling up. (For example, Czochralski method, liquid-sealed Czochralski method, vapor pressure control Czochralski method, etc.).

  In the boat method, one end of the seed crystal is brought into contact with a melt obtained by melting the raw material (raw material melt), and the seed crystal side is cooled and solidified little by little from the seed crystal side while keeping the melt portion above the melting point. This is a method for obtaining a single crystal ingot.

  For example, in Patent Document 1, in a crystal growth furnace based on the vertical Bridgman method, an upper portion that is disposed substantially horizontally with the melt surface above the opening of a crucible containing the melt and heats the melt from above. A heating heater, a plurality of outer peripheral heating heaters arranged in a multi-stage along a direction from the upper part to the lower part of the crucible, and heating the crucible from the side surface; one outer peripheral heating heater and another outer peripheral heating heater; A crystal growth furnace having a heat insulating material provided therebetween is disclosed. According to Patent Document 1, by providing the upper heater, the temperature gradient in the radial direction in the crucible during crystal growth can be moderated, and the temperature gradient in the vicinity of the crystal growth interface can be kept substantially constant. Therefore, it is said that the occurrence of defects (dislocations, twins, polycrystallization, etc.) in the grown crystal can be reduced.

  On the other hand, the pulling method is a method of obtaining a single crystal ingot while bringing one end of a seed crystal into contact with a raw material melt and then slowly pulling up the seed crystal.

  For example, Patent Document 2 discloses a CZ method single crystal ingot manufacturing apparatus that pulls a single crystal ingot from a raw material melt, and surrounds the single crystal ingot being pulled (hereinafter referred to as a single crystal ingot). In the CZ method single crystal ingot manufacturing apparatus provided with a heat shield that adjusts the amount of heat poured into the pulled single crystal ingot, measuring means for measuring the distance from the bottom of the heat shield to the raw material melt surface, There is disclosed a CZ method single crystal ingot manufacturing apparatus including a controller that controls a pulling condition of a single crystal ingot based on a distance measured by the measuring means. According to Patent Document 2, the temperature gradient G can be more easily controlled without using a complicated mechanism as in the prior art, thereby extending the complete crystal region in the direction of crystal growth with high reproducibility. It is supposed to be possible.

  Further, Patent Document 3 has a bottom portion and a wall portion that rises from the peripheral edge of the bottom portion, and is provided so as to surround the crucible without being in contact with the crucible containing the raw material melt and close to the crucible. A first cylindrical member, a second cylindrical member made of carbon or a material containing carbon provided so as to surround the first cylindrical member, and an outer side of the second cylindrical member And a coil for inductively heating the second cylindrical member by supplying an alternating current, and a pulling unit that is disposed above the crucible and pulls up the columnar single crystal from the raw material melt contained in the crucible A single crystal pulling apparatus including a member is disclosed. According to Patent Document 3, in the single crystal pulling apparatus using the Czochralski (CZ) method, it is possible to use an inexpensive crucible, and the temperature gradient of the melt in the crucible can be relaxed. It is said that distortion of a single crystal can be suppressed.

JP 2009-149492 A JP 2000-313691 A JP 2011-105575 A

  The above-mentioned single crystal growth method is to grow the single crystal by gradually solidifying the raw material melt in any case, and in order to obtain a good quality single crystal with few defects, It is the same that it is important to control the temperature gradient of the growth interface and the vicinity thereof to be gentle and constant. In the prior art, it is common to place a plurality of heaters in the growth furnace and operate them to control the temperature so that a desired temperature gradient is obtained.

  However, when there are a plurality of heaters, each heater has a small temperature gradient at its central portion and a large temperature gradient at both end portions (including the vicinity of the joint between adjacent heaters). There is a problem that the temperature distribution in the growth direction tends to be wavy. Furthermore, since adjacent heaters influence each other, there is a problem that it is difficult to control the temperature such that the temperature in the entire growth furnace is lowered while the temperature gradient is kept constant.

  On the other hand, when temperature control is performed with only one heater, the wave-like temperature distribution is not as in the case of multiple heaters, but the temperature gradient is small at the center of the heater and the temperature gradient is large at both ends. Therefore, it is difficult to control a desired temperature distribution (including a temperature gradient) throughout the growth furnace. In order to overcome the difficulty of temperature control using only one heater, the history of the technology is that temperature control of a plurality of heaters has been performed.

  With the progress of miniaturization and high integration of circuits in electronic devices, the demand for high quality (for example, reduction of defects) for single crystal substrates has become severe. In addition, the demand for cost reduction for single crystal substrates is becoming strict. In order to satisfy these requirements, it is essential to grow a high-quality single crystal ingot with a high yield.

  Accordingly, an object of the present invention is to provide a single crystal manufacturing apparatus for growing a high-quality single crystal ingot with a high yield, and a single crystal manufacturing method using the same.

  According to one aspect of the present invention, there is provided a single crystal manufacturing apparatus for growing a single crystal ingot from a raw material melt accommodated in a crucible, the growth direction of the single crystal ingot when the single crystal ingot is grown. A heater disposed on the outer side of the surface of the crucible, a heat insulating material disposed between the surface of the crucible and the heater, and a crucible shaft disposed on the outer periphery of the crucible. A heat-conducting member that covers all in the direction and one end of which is thermally connected to the heater, and a mechanism for circulating a gas for controlling the temperature of the heat-conducting member along the outer periphery of the heat-conducting member. An apparatus for producing a single crystal is provided.

Further, the present invention can add the following improvements and changes to the single crystal manufacturing apparatus according to the present invention.
(I) The growth direction of the single crystal ingot is a direction directed vertically downward, the surface of the crucible at the tip of the growth direction is the bottom surface of the crucible, and the one end portion of the heat conducting member is The lower end of the heat conducting member.
(Ii) The growth direction of the single crystal ingot is a direction vertically upward, the surface of the crucible at the tip of the growth direction is the upper surface of the crucible, and the one end portion of the heat conducting member is The upper end of the heat conducting member.
(Iii) It further includes a heat sink that is thermally connected to the other end of the heat conducting member.
(Iv) The heat conducting member is divided into a plurality of members in the circumferential direction.

  According to another aspect of the present invention, a single crystal ingot is grown from the seed crystal side by contacting a seed crystal with the raw material melt using the single crystal manufacturing apparatus according to the present invention. A single crystal production method is provided.

Further, the present invention can add the following improvements and changes to the above-described method for producing a single crystal according to the present invention.
(V) The single crystal ingot is a compound semiconductor.
(Vi) The compound semiconductor is gallium arsenide.

  ADVANTAGE OF THE INVENTION According to this invention, the single crystal manufacturing apparatus with which desirable temperature distribution (a temperature gradient is included) is implement | achieved over the wide range in a growth furnace can be provided. Further, by using the single crystal manufacturing apparatus, it is possible to provide a single crystal manufacturing method in which a high-quality single crystal ingot is grown with a high yield.

It is a cross-sectional schematic diagram which shows an example of the process which is growing the single crystal ingot using the single crystal manufacturing apparatus which concerns on the 1st Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the process which is growing the single crystal ingot using the single crystal manufacturing apparatus which concerns on the 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the process which is growing the single crystal ingot using the conventional LEC method single crystal manufacturing apparatus. 6 is a graph showing an example of a temperature distribution in a portion located 1 mm outside the crucible surface in the single crystal production apparatus of Example 1 and Comparative Example 1. It is a cross-sectional schematic diagram which shows an example of the process which is growing the single crystal ingot using the conventional VGF method single crystal manufacturing apparatus. 6 is a graph showing an example of a temperature distribution in a portion located 1 mm outside from the surface of the quartz ampule in the single crystal manufacturing apparatus of Example 2 and Comparative Example 2.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described here, and can be appropriately combined and improved without departing from the technical idea of the present invention. In addition, members and parts having the same meaning are denoted by the same reference numerals and redundant description is omitted.

  In this specification, a single crystal manufacturing apparatus and a single crystal manufacturing method according to the present invention will be described by taking as an example the case of growing a single crystal ingot of gallium arsenide (GaAs). Needless to say, the present invention does not limit the single crystal ingot to be grown to GaAs, but other inorganic crystalline substances that can be grown by a boat method or a pulling method (for example, silicon (Si), It can also be applied to gallium phosphide (GaP), indium phosphide (InP), and the like.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing an example of a process of growing a single crystal ingot using the single crystal manufacturing apparatus according to the first embodiment of the present invention. As shown in FIG. 1, a single crystal manufacturing apparatus 10 is a single crystal manufacturing apparatus used in a liquid-sealed Czochralski method (LEC method), and includes a high-pressure vessel 11, and the high-pressure vessel 11 has a single-crystal ingot. A crucible 12 (made of PBN (Pyrolytic Boron Nitride)) for containing 21 raw material melt 22 and liquid sealant melt 23 is provided. The high-pressure vessel 11 is filled with an inert gas at a high pressure so as to prevent dissociation and evaporation of the raw material melt 22 and the liquid sealant melt 23.

The raw material melt 22 is obtained by melting a polycrystal used as a raw material of the single crystal ingot 21 to be grown. In the present embodiment, since a GaAs polycrystal is used as a raw material, the raw material melt 22 is a GaAs melt. The liquid sealant melt 23 is a liquid for preventing evaporation of the raw material melt 22, and preferably does not chemically react with the raw material melt 22 or the crucible 12, and is lower in density and transparent than the raw material melt 22. . In growing a GaAs single crystal ingot, boron oxide (B ₂ O ₃ ) is usually used as a liquid sealant, and the melt becomes a liquid sealant melt 23.

  Below the crucible 12, a crucible shaft (lower shaft) 18 that can be moved up and down is provided. By attaching the crucible 12 to the upper end of the crucible shaft 18, the crucible 12 can be raised and lowered and rotated freely. Above the crucible 12, a seed shaft (upper shaft) 19 that can be moved up and down is provided, and a seed crystal 20 is attached to the lower end thereof so that the seed crystal 20 can be moved up and down. The seed shaft 19 is connected to speed control means (not shown) for controlling the ascending / descending speed of the seed crystal 20. The seed crystal 20 is a crystal serving as a nucleus of a single crystal ingot to be grown, and here is a small single crystal of GaAs.

  By lowering the seed shaft 19 to bring the seed crystal 20 into contact with the raw material melt 22, and pulling up the seed shaft 19 while adjusting the temperature of the raw material melt 22, the single crystal ingot 21 is moved downward from the seed crystal 20. grow up. At this time, by pulling up the seed shaft 19 and rotating the crucible shaft 18 at the same time, the single crystal ingot 21 to be grown has a cylindrical shape.

  The above part has basically the same configuration as a conventional LEC method single crystal manufacturing apparatus. On the other hand, the single crystal manufacturing apparatus 10 according to the first embodiment has a configuration different from the conventional single crystal manufacturing apparatus in the following points.

  In the conventional LEC method single crystal manufacturing apparatus, a heater is usually disposed at the same height as the side surface of the crucible (see FIG. 3 to be described later), but the single crystal manufacturing apparatus 10 according to the first embodiment The heater 13 is disposed below the bottom surface 12 b of the crucible 12, and a heat insulating material 14 is disposed between the bottom surface 12 b of the crucible 12 and the heater 13. A heat conducting member 15 is disposed on the outer periphery of the side surface 12s of the crucible 12 so as to surround the crucible 12. The heat conducting member 15 has a length sufficiently larger than the height of the crucible 12, covers the crucible 12 in the crucible axial direction, and one end thereof (the lower end in the present embodiment) is connected to the heater 13. Thermally connected.

  Further, the single crystal manufacturing apparatus 10 includes a mechanism for circulating gas along the outer periphery of the heat conducting member 15. Specifically, the gas inlet 16 is provided at the lower part of the high-pressure vessel 11 (lower end of the heat conducting member 15 or below), and the upper part of the high-pressure vessel 11 (upper end of the heat conducting member 15 or above). A gas discharge port 17 is provided, and a mass flow controller (not shown) for controlling the flow rate of the gas to be circulated is connected to the gas introduction port 16. As a result, the gas introduced from the gas introduction port 16 flows from the bottom to the top along the outer periphery of the heat conducting member 15, and is discharged from the gas discharge port 17. The arrangement and shape of the gas inlet 16 and the gas outlet 17 are set so that gas can be evenly distributed along the outer periphery of the heat conducting member 15.

  As described above, the heater 13 is disposed below the bottom surface 12 b of the crucible 12, and the heat insulating material 14 is disposed between the bottom surface 12 b of the crucible 12 and the heater 13. Further, the lower end portion of the heat conducting member 15 is thermally connected to the heater 13. That is, the heater 13 is not intended to heat the crucible 12 directly, but exists to heat one end of the heat conducting member 15. The crucible 12 is heated by radiation from the heat conducting member 15, and the raw material melt 22 and the liquid sealing material melt 23 are heated through the crucible 12.

  Since the heat conducting member 15 receives heat only from one end portion, a temperature distribution having a uniform temperature gradient is formed in which the temperature is higher at a portion closer to the heater 13 and the temperature is lower at a far portion. In other words, in the single crystal production apparatus 10, a temperature distribution is formed in the high-pressure vessel 11 such that the temperature is lower at the lower part and lower at the upper part. Further, when gas is introduced from the gas introduction port 16 and gas flows along the outer periphery of the heat conducting member 15, heat is taken from the outer peripheral surface of the heat conducting member 15 according to the flow rate. By controlling the output of the heater 13 (the amount of heat input to the heat conducting member 15) and the flow rate of the gas to be circulated (the amount of heat removed from the heat conducting member 15), both the temperature and the temperature gradient of the heat conducting member 15 (ie, in the growth furnace) Can be controlled. As a result, the single crystal ingot 21 can be grown at an appropriate temperature and a uniform temperature gradient.

  The material of the heat conducting member 15 is “to withstand the growth temperature of the single crystal ingot”, “not to be a source of contamination to the single crystal ingot”, “sufficient thermal conductivity”, “temperature dependence of thermal conductivity” As long as it meets “small”, there is no particular limitation. Specific examples include metals with low chemical reactivity (for example, gold, platinum, molybdenum, etc.), graphite, and ceramics with high thermal conductivity (for example, silicon carbide).

  The heat conducting member 15 is preferably cylindrical so that the temperature and the temperature gradient are not biased. From the viewpoint of workability at the time of starting up and shutting down the single crystal manufacturing apparatus 10, the heat conducting member 15 has a cylindrical shape and is divided into a plurality of members (so-called vertically divided members) in the circumferential direction. Also good. However, even in this case, it is preferable that there is no gap in the circumferential direction when the heat conducting member 15 is assembled.

  It is preferable that the crucible 12 and the heat conducting member 15 are arranged so that their central axes coincide with each other. Further, the crucible 12 and the heat conducting member 15 are arranged with a gap that does not contact each other. The gap is not particularly limited, but is preferably about 1 mm to 3 cm, for example. The too close crucible 12 and the heat conducting member 15 are likely to come into contact with each other, and if contact is made, the radiant heat transfer changes to the contact heat transfer, making it difficult to control the temperature and temperature gradient. On the other hand, if the gap is too large, the heating efficiency decreases.

(Modification of the first embodiment)
In the single crystal manufacturing apparatus 10 according to the first embodiment, a heat sink (not shown) at the end of the heat conducting member 15 opposite to the side thermally connected to the heater 13 (at the upper end of the heat conducting member 15) It is more preferable to provide a mechanism for connecting and cooling the heat sink. By cooling the heat sink, the temperature gradient of the heat conducting member 15 (that is, the temperature gradient in the growth furnace) can be more actively controlled.

[Second Embodiment]
FIG. 2 is a schematic cross-sectional view showing an example of a process of growing a single crystal ingot using the single crystal manufacturing apparatus according to the second embodiment of the present invention. As shown in FIG. 2, the single crystal manufacturing apparatus 30 is a single crystal manufacturing apparatus used in the vertical temperature gradient solidification method (VGF method), and includes a high pressure vessel 31, and a single crystal ingot 43 is placed in the high pressure vessel 31. A crucible 32 (manufactured by PBN) that accommodates the raw material melt 44 and the liquid sealant melt 45 is provided. As in the first embodiment, the high-pressure vessel 31 is filled with an inert gas at a high pressure to prevent dissociation and evaporation of the raw material melt 44 and the liquid sealant melt 45.

  The crucible 32 is installed in a quartz ampoule 33 and sealed with a quartz cap 34. The quartz cap 34 has a hole so that the pressure in the high-pressure vessel 31 can be transmitted to the crucible 32 as it is. The quartz ampoule 33 is connected to the crucible shaft 36 through the susceptor 35 and can be moved up and down. The crucible shaft 36 is connected to speed control means (not shown) for controlling the lifting speed of the quartz ampule 33.

A seed crystal 42 is installed at the bottom of the crucible 32. As in the first embodiment, the seed crystal 42 is a small single crystal of GaAs. Above the seed crystal 42, a polycrystal (here, GaAs polycrystal) as a raw material for the single crystal ingot to be grown is disposed, and above that a liquid seal for preventing evaporation of the raw material melt in which the raw material has melted. A stop agent (B ₂ O ₃ ) is placed. When the raw material (GaAs polycrystal) and the liquid sealant (B ₂ O ₃ ) are dissolved, a raw material melt 44 and a liquid sealant melt 45 are obtained, respectively.

  The temperature in the high-pressure vessel 31 (more specifically, the crucible 32) is adjusted, the raw material immediately above the seed crystal 42 is melted, and the raw material melt 44 and the seed crystal 42 are brought into contact with each other. Thereafter, the single crystal ingot 43 grows upward from the seed crystal 42 in the crucible 32 by gradually lowering the temperature in the growth furnace while maintaining a desired temperature gradient. The shape of the single crystal ingot 43 to be grown is a columnar shape defined by the inner shape of the crucible 32.

  The above part has basically the same configuration as a conventional VGF single crystal manufacturing apparatus. On the other hand, the single crystal manufacturing apparatus 30 according to the second embodiment has a different configuration from the conventional single crystal manufacturing apparatus in the following points.

  In a conventional VGF method single crystal manufacturing apparatus, a heater is usually disposed so as to cover all the crucible in the height direction (at least at the same height as the side surface of the crucible) (see FIG. 5 described later). The heater 37 of the single crystal manufacturing apparatus 30 according to the second embodiment is disposed above the upper surface of the crucible 32 (quartz ampule 33), and heat insulation is provided between the upper surface of the crucible 32 and the heater 37. A material 38 is disposed. The upper surface of the crucible 32 means the opening surface of the crucible 32, and the upper surface of the quartz ampoule 33 includes the quartz cap 34.

  A heat conducting member 39 is disposed on the outer periphery of the crucible 32 (quartz ampule 33) so as to surround the crucible 32 (quartz ampule 33). The heat conducting member 39 has a length sufficiently larger than the height of the crucible 32 (quartz ampule 33) and covers the crucible 32 (quartz ampule 33) in the crucible axial direction, and one end thereof (this embodiment) In the embodiment, the upper end portion) is thermally connected to the heater 37.

  Further, the single crystal manufacturing apparatus 30 includes a mechanism for circulating gas along the outer periphery of the heat conducting member 39. Specifically, a gas inlet 40 is provided at the lower part of the high-pressure vessel 31 (lower end of the heat conducting member 39 or below it), and the upper part of the high-pressure vessel 31 (upper end of the heat conducting member 39 or above). A gas discharge port 41 is provided, and a mass flow controller (not shown) for controlling the flow rate of gas to be circulated is connected to the gas introduction port 40. Thereby, the gas introduced from the gas introduction port 40 flows from the bottom to the top along the outer periphery of the heat conducting member 39 and is discharged from the gas discharge port 41. The arrangement and shape of the gas inlet 40 and the gas outlet 41 are set so that the gas can be evenly distributed along the outer periphery of the heat conducting member 39.

  As described above, the heater 37 is disposed above the upper surface of the crucible 32 (quartz ampule 33), and the heat insulating material 38 is disposed between the upper surface of the crucible 32 (quartz ampule 33) and the heater 37. The The upper end portion of the heat conducting member 39 is thermally connected to the heater 37. That is, the heater 37 is not intended to heat the crucible 32 directly, but exists to heat one end of the heat conducting member 39. The crucible 32 is heated by radiation from the heat conducting member 39, and the raw material melt 44 and the liquid sealing material melt 45 are heated through the crucible 32.

  Since the heat conducting member 39 receives heat only from one end portion, a temperature distribution having a uniform temperature gradient is formed in which the temperature is higher at a portion closer to the heater 37 and the temperature is lower at a far portion. In other words, in the single crystal manufacturing apparatus 30, a temperature distribution is formed in the high-pressure vessel 31, where the temperature is higher at the upper part and lower at the lower part. Further, when gas is introduced from the gas introduction port 40 and gas flows along the outer periphery of the heat conducting member 39, heat is taken from the outer peripheral surface of the heat conducting member 39 according to the flow rate. By controlling the output of the heater 37 (the amount of heat input to the heat conducting member 39) and the flow rate of the gas to be circulated (the amount of heat removed from the heat conducting member 39), both the temperature and the temperature gradient of the heat conducting member 39 (ie, in the growth furnace) Can be controlled. As a result, the single crystal ingot 43 can be grown at an appropriate temperature and a uniform temperature gradient.

  The specifications (material, shape, etc.) required for the heat conducting member 39 are the same as in the case of the first embodiment described above.

(Modification of the second embodiment)
In the single crystal manufacturing apparatus 30 according to the second embodiment, a heat sink (not shown) at the end of the heat conducting member 39 opposite to the side thermally connected to the heater 37 (at the lower end of the heat conducting member 39) It is more preferable to provide a mechanism for connecting and cooling the heat sink. By cooling the heat sink, the temperature gradient of the heat conducting member 39 (that is, the temperature gradient in the growth furnace) can be more actively controlled.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these.

(Growth and evaluation of single crystal ingot by LEC method)
A GaAs single crystal ingot was manufactured using the single crystal manufacturing apparatus according to the first embodiment shown in FIG. 1 (Example 1). For comparison, a GaAs single crystal ingot was manufactured using the conventional LEC method single crystal manufacturing apparatus shown in FIG. 3 (Comparative Example 1).

  FIG. 3 is a schematic cross-sectional view showing an example of a process of growing a single crystal ingot using a conventional LEC method single crystal manufacturing apparatus. As shown in FIG. 3, the conventional LEC method single crystal manufacturing apparatus 50 includes a heater 51 disposed so as to directly heat the side surface 12s of the crucible 12, and a heat conducting member and an outer periphery of the heat conducting member. 1 is different from the single crystal manufacturing apparatus 10 of FIG. 1 in that it does not have a mechanism for circulating gas.

Details of the manufacturing method will be described below. First, a raw material GaAs polycrystal (mass 25000 g) and a liquid sealant B ₂ O ₃ (mass 2000 g) are placed in a PBN crucible 12 and stored in a high-pressure vessel 11. Nitrogen gas was filled so that the pressure in 11 was 9.2 × 10 ⁻⁵ Pa (9.0 kg / cm ² ). In Example 1, the heat conducting member 15 was made of graphite, and the distance between the heat conducting member 15 and the crucible 12 was 2 mm.

  Next, heating was performed by the heaters 13 and 51 so as to be equal to or higher than the melting point of GaAs, and the raw material and the liquid sealant were melted to form the raw material melt 22 and the liquid sealant melt 23. The liquid sealant melt 23 floats on the raw material melt 22 because the density thereof is lower than that of the raw material melt 22.

  The position of the crucible 12 that moves the crucible shaft 18 up and down was adjusted so that the surface temperature of the raw material melt 22 was appropriate. Next, the seed shaft 19 was lowered to bring the seed crystal 20 into contact with the raw material melt 22, and the outputs of the heaters 13 and 51 were adjusted to start crystal growth from around the seed crystal 20.

Then, while rotating the crucible shaft 18, the seed shaft 19 was pulled up at 6 mm / h to grow a single crystal ingot 21 (diameter 110 mm, length 440 mm). At this time, in Example 1, the output of the heater 13 during the growth was 35 kW, and the gas flow rate for adjusting the temperature gradient in the growth furnace was 100 cm ³ / min (0 ° C., 1013 hPa equivalent). In Comparative Example 1, the output of the heater 51 at the start of growth was 40 kW.

  Under the above conditions, 20 GaAs single crystal ingots of Example 1 and Comparative Example 1 were grown. As a result, in Example 1, the occurrence of the polycrystallization phenomenon (the phenomenon that polycrystallized during the growth of the single crystal) occurred at 300 mm from the upper end of the single crystal ingot (that is, the yield). 100%). In contrast, in Comparative Example 1, there were five cracks (minute cracks) in the range of 300 mm from the upper end of the single crystal ingot (yield 75%). From this result, it was confirmed that a high-quality single crystal ingot can be grown with a high yield by using the single crystal manufacturing apparatus according to the present invention.

  In order to investigate the factors resulting in the above, in the single crystal manufacturing apparatus 10 of Example 1 and the single crystal manufacturing apparatus 50 of Comparative Example 1, the surface of the crucible 12 at the start of the growth of the single crystal ingot was used. The temperature distribution of the part located 1 mm outside was measured. The result is shown in FIG.

  FIG. 4 is a graph showing an example of a temperature distribution in a portion located 1 mm outside the crucible surface in the single crystal production apparatus of Example 1 and Comparative Example 1. As shown in FIG. 4, in the single crystal manufacturing apparatus 10 of Example 1, it can be seen that the temperature gradient is substantially constant over the entire axial length of the crucible 12. On the other hand, in the single crystal manufacturing apparatus 50 of the comparative example 1, it turns out that temperature falls rapidly from the intermediate part of the crucible 12 upwards.

  From the above results, in Comparative Example 1, it was considered that cracking occurred because the single crystal ingot was rapidly cooled when the single crystal ingot was pulled up. On the other hand, it was confirmed that the single crystal manufacturing apparatus according to the present invention achieves a desirable temperature distribution (including a temperature gradient) over a wide range in the growth furnace.

(Growth and evaluation of single crystal ingot by VGF method)
A GaAs single crystal ingot was manufactured using the single crystal manufacturing apparatus according to the second embodiment shown in FIG. 2 (Example 2). For comparison, a GaAs single crystal ingot was manufactured using the conventional LEC method single crystal manufacturing apparatus shown in FIG. 5 (Comparative Example 2).

  FIG. 5 is a schematic cross-sectional view showing an example of a process of growing a single crystal ingot using a conventional VGF method single crystal manufacturing apparatus. As shown in FIG. 5, the conventional VGF method single crystal manufacturing apparatus 60 includes a plurality of heaters 61 to 67 arranged to directly heat the crucible 32 (quartz ampule 33), a heat conducting member, 2 is different from the single crystal manufacturing apparatus 30 of FIG. 2 in that it does not have a mechanism for circulating gas along the outer periphery of the heat conducting member.

Details of the manufacturing method will be described below. First, the raw material GaAs polycrystal (mass 10000 g) and the liquid sealant B ₂ O ₃ (mass 200 g) were put into a crucible 32 made of PBN. This crucible 32 was placed in a quartz ampoule 33 and sealed with a quartz cap 34. The distance between the quartz ampoule 33 and the crucible 32 was 1 mm. The quartz ampoule 33 containing the crucible 32 was housed in a high-pressure vessel 31 and filled with nitrogen gas so that the pressure in the vessel 31 was 9.2 × 10 ⁻⁵ Pa (9.0 kg / cm ² ). Silicon carbide was used as the heat conducting member 39 in Example 2, and the distance between the heat conducting member 39 and the quartz ampoule 33 was 2 mm.

Next, heating was performed by the heaters 37 and 61 to 67 so as to be equal to or higher than the melting point of GaAs, and the raw material and the liquid sealant were melted to form the raw material melt 44 and the liquid sealant melt 45. Since the liquid sealant melt 45 has a lower density than the raw material melt 44, it floats on the raw material melt 44. Further, the raw material melt 44 comes into contact with the seed crystal 42.

  The position of the crucible 32 that raises and lowers the crucible shaft 36 is adjusted so that the temperature of the raw material melt 44 in contact with the seed crystal 42 is appropriate, and the outputs of the heaters 37 and 61 to 67 are adjusted to adjust the seed crystal 42. Crystal growth was started from around the area.

Thereafter, the temperature in the growth furnace was gradually lowered while adjusting the outputs of the heaters 37, 61 to 67, and a single crystal ingot 43 (diameter 106 mm, length 220 mm) was grown at a growth rate of 1.6 mm / h. At this time, in Example 2, the output of the heater 37 at the start of growth was 30 kW, and the gas flow rate for adjusting the temperature gradient in the growth furnace was 50 cm ³ / min (converted to 0 ° C. and 1013 hPa). . In Comparative Example 2, the outputs of the heaters 61 to 67 at the start of growth were sequentially changed from the upper heater to 6 kW, 10 kW, 8 kW, 6 kW, 4 kW, 2 kW, and 1 kW.

  Under the above conditions, 20 GaAs single crystal ingots of Example 2 and Comparative Example 2 were grown. As a result, in Example 2, the occurrence of the polycrystallization phenomenon at the position 190 mm from the lower end of the single crystal ingot was zero (that is, the yield was 100%). On the other hand, in Comparative Example 2, there were four cases in which polycrystallization occurred in the range of 190 mm from the lower end of the single crystal ingot (yield 80%). From this result, it was confirmed that a high-quality single crystal ingot can be grown with a high yield by using the single crystal manufacturing apparatus according to the present invention.

  In order to investigate the factors that resulted in the above, in the single crystal manufacturing apparatus 30 of Example 2 and the single crystal manufacturing apparatus 60 of Comparative Example 2, the surface of the quartz ampule 33 at the start of the growth of the single crystal ingot was used. The temperature distribution of the part located 1 mm outside was measured. The result is shown in FIG.

  FIG. 6 is a graph showing an example of a temperature distribution in a portion located 1 mm outside the quartz ampoule surface in the single crystal manufacturing apparatus of Example 2 and Comparative Example 2. As shown in FIG. 6, in the single crystal manufacturing apparatus 30 of Example 2, it can be seen that the temperature gradient is substantially constant over the entire length of the quartz ampoule 33 (the crucible 12) in the axial direction. On the other hand, in the single crystal manufacturing apparatus 60 of Comparative Example 2, there is a region where the temperature is greatly decreased locally in the middle part of the quartz ampoule 33 (crucible 12) (around 150 mm from the top of the seed crystal part). I understand. When compared with the size of each member in the growth furnace, it was found that this local temperature drop region corresponds to the joint between the heater 63 and the heater 64.

  From the above results, it is considered that in Comparative Example 2, the single crystal ingot was grown as a polycrystal due to experiencing a rapid temperature change (temperature drop) when the growth interface passes through the region. It was. On the other hand, it was confirmed that the single crystal manufacturing apparatus according to the present invention achieves a desirable temperature distribution (including a temperature gradient) over a wide range in the growth furnace.

10 ... Single crystal manufacturing equipment, 11 ... High pressure vessel, 12 ... Crucible,
12b ... (bottom crucible) bottom, 12s ... (crucible) side, 13 ... heater, 14 ... heat insulation,
15 ... Heat conducting member, 16 ... Gas inlet, 17 ... Gas outlet,
18 ... Crucible axis, 19 ... Seed axis,
20 ... Seed crystal, 21 ... Single crystal ingot, 22 ... Raw material melt, 23 ... Liquid sealant melt,
30 ... Single crystal production equipment, 31 ... High pressure vessel, 32 ... Crucible, 33 ... Quartz ampule,
34 ... Quartz cap, 35 ... susceptor, 36 ... crucible shaft, 37 ... heater, 38 ... insulation,
39 ... Heat conducting member, 40 ... Gas inlet, 41 ... Gas outlet, 42 ... Seed crystal,
43 ... single crystal ingot, 44 ... raw material melt, 45 ... liquid sealant melt,
50 ... Single crystal manufacturing equipment, 51 ... Heater,
60 ... Single crystal manufacturing equipment, 61, 62, 63, 64, 65, 66, 67 ... Heater.

Claims (8)

A single crystal production apparatus for growing a single crystal ingot from a raw material melt contained in a crucible,
A heater disposed outside the surface of the crucible ahead of the growth direction of the single crystal ingot when the single crystal ingot is grown;
A heat insulating material disposed between the surface of the crucible and the heater;
A heat-conducting member disposed on the outer periphery of the crucible, covering all the side surfaces of the crucible in the crucible axial direction, and having one end portion thermally connected to the heater;
And a mechanism for introducing a gas for controlling the temperature of the heat conducting member along the outer periphery of the heat conducting member. In the single crystal manufacturing apparatus according to claim 1,
The growth direction of the single crystal ingot is a direction directed vertically downward,
The surface of the crucible ahead of the growth direction is the bottom of the crucible;
The one end part of the heat conducting member is a lower end part of the heat conducting member. In the single crystal manufacturing apparatus according to claim 1,
The growth direction of the single crystal ingot is a direction directed vertically upward,
The surface of the crucible at the tip of the growth direction is the upper surface of the crucible;
The one end part of the heat conducting member is an upper end part of the heat conducting member. In the single-crystal manufacturing apparatus in any one of Claims 1 thru | or 3,
The single crystal manufacturing apparatus further comprising a heat sink thermally connected to the other end of the heat conducting member. In the single crystal manufacturing apparatus according to any one of claims 1 to 4,
The single crystal manufacturing apparatus, wherein the heat conducting member is divided into a plurality of members in the circumferential direction.   A single crystal ingot is grown from the seed crystal side by contacting a seed crystal with the raw material melt using the single crystal manufacturing apparatus according to any one of claims 1 to 5. Crystal manufacturing method. The method for producing a single crystal according to claim 6,
A method for producing a single crystal, wherein the single crystal ingot is a compound semiconductor. The method for producing a single crystal according to claim 7,
A method for producing a single crystal, wherein the compound semiconductor is gallium arsenide.

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