JP2010006645A - Crucible for apparatus for growing single crystal, method for growing single crystal, and apparatus for growing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crucible for an apparatus for growing a single crystal, wherein the cost required to grow a single crystal is reduced. <P>SOLUTION: The crucible 10 is arranged in the apparatus for growing a single crystal and has a sidewall 12 heated by induction heating and an upper face 11 opened. The sidewall 12 has a step part, and the partial sidewall 12b on the lower face side of the step part is closer to the central axis passing the center of the opening in comparison with the partial sidewall 12a on the upper face 11 side of the stage part. Both cross-sectional shapes of the partial sidewall 12a on the upper face 11 side and the partial sidewall 12b on the lower face side are nearly circular. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a crucible for a single crystal growth apparatus, a single crystal growth method, and a single crystal growth apparatus.

For example, as described in the following Patent Document 1, a crucible filled with a raw material is heated to a high temperature to melt the raw material, and a single crystal is grown by dipping a seed crystal from above into the liquid surface of the molten raw material in the crucible The method is conventionally practiced. In such a single crystal growth method, a heating body is arranged around the crucible, and the side wall of the crucible is mainly heated by induction heating by the heating body.
JP 2002-68884 A

  In such a single crystal growing apparatus, since the side wall of the crucible is heated, the molten raw material in the crucible has a relatively high temperature in the vicinity of the side wall, and a relatively low temperature in the crucible center portion away from the side wall. For this reason, in such a single crystal growing apparatus, crystal growth is likely to proceed in the direction toward the lower surface of the crucible at the crucible center portion away from the side wall, even below the liquid surface of the molten raw material. When crystal growth toward the lower side of such a crucible proceeds, the tip of the grown crystal finally reaches the bottom of the crucible, and a relatively early stage (i.e., the degree of single crystal growth by pulling, In a relatively small number of stages, it was necessary to finish the crystal growth. This application is an invention made in order to solve such a problem.

  In order to solve the above problems, the present invention provides a crucible having an upper surface opened, the side wall being heated by induction heating and disposed on a single crystal growth apparatus, the side wall having a step portion, and the step A crucible for a single crystal growth apparatus, wherein the partial side wall on the lower surface side of the step portion is closer to the central axis passing through the center of the opening than the partial side wall on the upper surface side of the portion. provide.

  In addition, in the crucible for a single crystal growth apparatus, it is preferable that the cross-sectional shapes of the partial side wall on the upper surface side and the partial side wall on the lower surface side are both substantially circular. Moreover, it is preferable to contain at least one of molybdenum, iridium, tungsten, and rhenium.

  In the present invention, the raw material is placed in the crucible for a single crystal growth apparatus, power is supplied to an induction coil wound so as to surround the side wall of the crucible, and the side wall of the crucible is heated by induction heating. Thus, there is provided a method for growing a single crystal, in which the raw material in the crucible is melted and the single crystal of the raw material is pulled and grown from the opened upper surface of the crucible in a state where the raw material in the crucible is melted.

  The single crystal is preferably any of sapphire single crystal, YAG single crystal, and LBO single crystal.

  The present invention also corresponds to a crucible whose upper surface is opened, an induction coil wound around the side wall of the crucible, a power source connected to the induction coil, and a central axis passing through the center of the opening. A single crystal pulling shaft disposed at a position and movable along the central axis, and the crucible has a stepped portion on a side wall, and a partial side wall on the upper surface side of the stepped portion. In comparison, the present invention also provides a single crystal growth apparatus characterized in that the partial side wall on the lower surface side is closer to the central axis passing through the center of the opening than the stepped portion.

  The crucible preferably contains at least one of molybdenum, iridium, tungsten, and rhenium.

  According to the crucible for a single crystal growth apparatus, the single crystal growth method, and the single crystal growth apparatus of the present invention, a single crystal having a relatively large growth length can be obtained using a growth apparatus having a relatively simple configuration. . In addition, the use efficiency of the raw material can be made relatively high, and the number of uses of the crucible itself can be made relatively long. According to the present invention, the cost for single crystal growth can be made relatively low.

  Hereinafter, embodiments of a crucible for a single crystal growth apparatus, a single crystal growth method, and a single crystal growth apparatus according to the present invention will be described in detail. FIG. 1 is a schematic configuration diagram showing a configuration of a single crystal growth apparatus 1 which is an embodiment of the single crystal growth apparatus of the present invention. Hereinafter, an embodiment of growing a sapphire single crystal using the single crystal growth apparatus 1 will be described.

  The single crystal growing apparatus 1 includes a crucible 10, which is an embodiment of the crucible of the present invention, a crucible holding container 16, a heat insulating material 17, a coil 20 wound so as to surround a side wall 12 of the crucible 10, and an alternating current with the coil 20. A high-frequency power source 30 for flowing current, a crystal pulling mechanism 40, and a control unit 50 are included. The crucible holding container 16 is provided with a heat retaining disc 18 and an external heat insulating wall 19.

  The crucible 10 is disposed in a crucible holding container 16 surrounded by a heat insulating material 17. The heat insulating material 17 suppresses heat radiation from the crucible 10 and contributes to maintaining the temperature of the crucible 10 stably. The upper surface side of the crucible 10 is opened, and the pulling shaft 42 of the crystal pulling mechanism 40 is inserted into the crucible 10 from the opening upper surface 11. The crystal pulling mechanism 40 includes a pulling shaft 42 and a power source 44 that moves the pulling shaft 42 in the vertical direction in the figure. The crystal pulling mechanism 40 and the high frequency power supply 30 are connected to the control unit 50. The control part 50 consists of a well-known computer provided with CPU and memory, for example, and the control part 50 controls operation | movement of the single crystal growth apparatus 1 whole.

  The crucible 10 of this embodiment has a step portion 21 on the side surface 12, and the lower side on the lower surface side of the step portion 21 with respect to the upper partial side surface 12 a on the opening upper surface 11 side of the step portion 21. The partial side surface 12b is disposed at a position closer to a central axis C (indicated by a broken line C in the figure) passing through the center of the upper surface 11 of the opening. In the crucible 10, the cross-sectional shapes of the upper partial side surface 12a and the lower partial side surface 12b are both substantially circular. The crucible 10 of this embodiment is comprised, for example with iridium.

  In the single crystal growing apparatus 1, an eddy current is induced particularly on the side surface 12 of the coil 20 by flowing an AC power source through the coil 20 wound around the crucible 10, and the side surface 12 is heated (heated up). ). In the single crystal growth apparatus 1 of the present embodiment, the lower partial side surface 12b is disposed at a position relatively close to a central axis C (shown by a broken line C in the drawing) passing through the center of the opening upper surface 11. For example, when a resistance heater or the like is disposed around the crucible 10 with the crucible holding container 16 and the heat insulating material 17 sandwiched therebetween, the amount of heat that reaches the upper portion side surface 12a is transferred to the crucible holding container 16 and the heat insulating material 17 by heat. In comparison, the lower partial side surface 12b is smaller. In the single crystal growing apparatus 1 of the present embodiment, in the single crystal growing apparatus 1 of the present embodiment, induction heating is performed by a current flowing through a coil wound around the crucible 10, and the side surface 12 of the crucible 10 is The partial side surface 12a and the lower partial side surface 12b are heated to a relatively uniform temperature. The external heat insulation wall 19 prevents the heat in the crucible holding container 16 from flowing out of the crucible holding container 16. Further, the heat retaining disc 18 prevents the heat in the crucible 10 from flowing out of the crucible 10.

  In the growth of a sapphire single crystal in the single crystal growth apparatus 1, first, a raw material of a single crystal to be grown (in this embodiment, a sapphire single crystal) is placed in the crucible 10. In this state, a high frequency current is passed through the coil 20 by the high frequency power supply 30 to heat the side wall 12 of the crucible 10. By heating the crucible 10, the sapphire single crystal raw material in the crucible 10 is melted and the molten sapphire single crystal raw material (molten raw material) is stored in the crucible 10.

  In this manner, the seed crystal 13 is immersed in the liquid surface of the molten raw material in the crucible 10 in a state where the molten sapphire single crystal is stored. The seed crystal 13 is attached to the tip of the pulling shaft 42, and the pulling shaft 42 with the seed crystal 13 attached to the tip is inserted into the crucible 10 from the opening upper surface 11 of the crucible 10. The seed crystal 13 is immersed in the liquid surface of the molten raw material. The pulling shaft 42 is disposed at a position corresponding to the central axis C passing through the center of the opening upper surface 11 of the crucible 10, and the seed crystal 13 is immersed in a position corresponding to the central axis C.

  After the seed crystal 13 is immersed in the molten raw material, the pulling shaft 42 is pulled upward while rotating about the central axis C. Thereafter, starting from the seed crystal 13, the single crystal (sapphire single crystal 15) of the melting raw material is grown so as to be pulled upward.

  In the crucible 10 of the present embodiment, the lower partial side surface 12b located on the lower surface side of the stepped portion 21 with respect to the upper partial side surface 12a has a central axis C (broken line C in the figure) passing through the center of the opening upper surface 11. It is arranged at a position closer to In the single crystal growing apparatus 1, the lower partial side surface 12 b of the crucible 10 is also heated (heated) by induction heating. In the single crystal apparatus 1, the vicinity of the central axis C of the crucible 10 is also heated in the lower part. The side surface 12b heats relatively well. For example, as shown in the enlarged sectional view shown in FIG. 2, the side wall of the lower partial side surface 12b of the crucible 10 is also heated relatively well, and a relatively high temperature molten material flows in the vicinity of the central axis C. That is, the molten material heated on the lower partial side surface 12b generates an upward flow (indicated by an arrow in FIG. 2) from the lower partial side surface 12b, and at the position corresponding to the central axis C, the lower surface of the crucible 10 A relatively high-temperature molten material is supplied from the side toward the opening upper surface 11.

In the vicinity of the side wall 12, the temperature of the molten raw material in the crucible 10 is relatively easily increased by the induction-heated side wall 12, and the temperature is compared in the central part of the crucible 10 away from the side wall 12 (near the central axis C). It is difficult to rise. Furthermore, the single crystal 15 is located in the vicinity of the central axis C, and the heat of the molten raw material in the crucible 10 is easily radiated to the outside of the crucible 10 through the single crystal 15. For this reason, in the crucible 10, the temperature of the molten raw material tends to be relatively lower in the vicinity of the central axis C than in the vicinity of the side wall 12. In particular, a crystal having a relatively high transmittance with respect to infrared light or visible light, such as sapphire, YAG (Yttrium Aluminum Garnet), or LBO (Li ₂ B ₄ O ₇ ; lithium tetraborate) of this embodiment, Since radiant heat is transferred through the inside, the amount of heat transfer is relatively large. When such a crystal is grown by a pulling method, the temperature in the vicinity of the central axis C tends to be relatively low. In the present embodiment, for example, the heat retaining disc 18 suppresses the outflow of heat from the crucible 10, but a relatively large amount of heat flows out of the crucible 10 through the single crystal 15 during the pulling growth.

  For this reason, in the central portion of the crucible 10 away from the side wall 12, crystal growth easily proceeds in the direction toward the lower surface of the crucible 10 even below the liquid surface of the molten raw material. For example, in the conventional single crystal growth apparatus shown in FIG. 3, the side wall 52 of the crucible 50 has a uniform side surface from the upper surface 51 of the opening to the lower surface, and the position corresponding to the central axis C is compared to the vicinity of the side wall 52. Temperature tends to be low. For this reason, the crystal growth of the molten raw material in the crucible 50 is relatively easy to proceed in the direction toward the lower surface of the crucible 50 below the liquid surface of the molten raw material at the center of the crucible 50 away from the side wall 52. . That is, in the crucible 50 having the conventional structure as shown in FIG. 3, the tip of the lower growth portion 55a grown toward the lower surface at the relatively early stage after the start of crystal growth is located on the lower surface of the crucible 50. To reach. When the tip of the lower growth portion 55a reaches the lower surface of the crucible 50, for example, the rotation and operation of the pulling shaft may fluctuate, and stable crystal growth may not be possible.

  In the single crystal growth apparatus 1 of the present embodiment, the lower partial side surface 12b of the crucible 10 is disposed at a position relatively close to a central axis C (shown by a broken line C in the drawing) passing through the center of the opening upper surface 11. The molten raw material causes a flow of a relatively high-temperature molten material from the lower surface side of the crucible 10 toward the opening upper surface 11 at a position corresponding to the central axis C. That is, in the single crystal growth apparatus 1 of the present embodiment, the temperature of the molten raw material is maintained at a relatively high temperature even in the central portion of the crucible 10 that is away from the side wall 12 (near the central axis C). The progress of crystal growth is suppressed in the direction toward. For this reason, in the single crystal growth apparatus 1 of the present embodiment, the length of the lower growth portion 15a grown toward the lower surface of the crucible 10 is the length of the upper growth portion 15b pulled up above the liquid surface of the molten raw material. On the other hand, it can be made sufficiently short.

  In the single crystal growth apparatus 1 of this embodiment, the upper growth portion 15b of the single crystal 15 can be obtained relatively long in one pulling growth process. The upper growth portion 15b is formed in a cylindrical shape with uniform diameters and the like. For example, by slicing the upper growth portion 15b, a sapphire single crystal substrate having the same diameter can be produced in a relatively large amount. it can. In the single crystal growth apparatus 1 of this embodiment, the molten raw material in the crucible 10 can be used up sufficiently in one pulling growth process. More specifically, as shown in FIG. 4, until the tip of the lower growth portion 55a is immersed only in the lower partial side surface 12b, that is, until the molten raw material remains only on the lower partial side surface 12b. The molten raw material can be used up.

  When the crystal growth is finished and the heating of the crucible 10 is stopped, the raw material (sapphire in this embodiment) is fixed to the inner wall of the crucible 10. Before the crucible 10 is used again, it is necessary to remove the fixed sapphire, but in the process of physically removing the fixed sapphire, labor and cost are relatively large. Further, in the process of removing the fixed sapphire, the crucible itself may be relatively damaged. In the crucible 10 of this embodiment, since the raw material (sapphire) adheres only to the portion corresponding to the lower side surface 12b of the crucible 10, labor and cost for removing sapphire are relatively small. Moreover, the crucible 10 is regenerated relatively easily by removing only the lower part 12b and fixing a new lower part 12b to which no raw material is adhered. In the single crystal growth apparatus 1 of the present embodiment, the upper portion 12a occupying a relatively large volume can be continuously used, and only the lower portion 12a of the relatively small deposition can be replaced and used. It can be used for a long time with low running cost.

  In the above-described embodiment, only one step portion is provided on the side surface of the crucible, but the number of step portions provided on the side surface of the crucible in the present invention is not particularly limited. Moreover, although the said embodiment demonstrated the example which grows a sapphire single-crystal substrate, the single-crystal raw material made to grow in this invention is not specifically limited.

  In the above-described embodiment, a method of growing a single crystal while pulling up a seed crystal from the liquid surface of the molten raw material, which is called a so-called Czochralski method, has been described. In the present invention, the single crystal may be grown by the so-called kiloporous method without being limited to the Czochralski method. In the kiloporous method, the crucible filled with the raw material is heated to a high temperature by high frequency induction heating to melt the raw material, the seed crystal is immersed in the molten raw material from above, and the temperature of the molten raw material is gradually lowered by adjusting the heating. The single crystal is grown by crystallization in a crucible without pulling. In the present invention, even in crystal growth by the kiloporous method, temperature drop near the central axis is suppressed, and relatively large crystals can be grown efficiently. The present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the scope of the present invention.

It is a schematic block diagram which shows the structure of one Embodiment of the single crystal growth apparatus of this invention. It is a schematic sectional drawing which expands and shows a part of single crystal growth apparatus shown in FIG. It is a schematic sectional drawing which expands and shows a part of conventional single crystal growth apparatus. It is a schematic sectional drawing which expands and shows a part of single crystal growth apparatus shown in FIG.

Explanation of symbols

10 crucible 12 side wall 16 crucible holding container 17 heat insulating material 20 coil 20
30 High-frequency power supply 40 Crystal pulling mechanism 50 Control unit 50

Claims (8)

A crucible having an upper surface opened, the side wall being heated by induction heating placed in a single crystal growth apparatus,
The side wall has a step;
Compared to the partial side wall on the upper surface side with respect to the stepped portion, the partial side wall on the lower surface side with respect to the stepped portion is closer to the central axis passing through the center of the opening, for a single crystal growing apparatus crucible.   The crucible for a single crystal growth apparatus according to claim 1, wherein the cross-sectional shapes of the partial side wall on the upper surface side and the partial side wall on the lower surface side are substantially circular.   The crucible for single crystal growth apparatus according to claim 1 or 2, comprising at least one of molybdenum, iridium, tungsten, and rhenium. A raw material is arranged in the crucible for single crystal growth apparatus according to any one of claims 1 to 3,
Power is supplied to the induction coil wound so as to surround the side wall of the crucible, the side wall of the crucible is heated by induction heating to melt the raw material in the crucible,
Single crystal growth in which the single crystal of the raw material is grown by immersing the raw material seed crystal into the molten liquid surface of the raw material from the upper surface where the raw material in the crucible is melted. Method.   The method for growing a single crystal according to claim 4, wherein the single crystal is any one of a sapphire single crystal, a YAG single crystal, and an LBO single crystal. A crucible with an open top surface;
An induction coil wound around the side wall of the crucible;
A power source connected to the induction coil;
A single crystal pulling axis disposed at a position corresponding to the central axis passing through the center of the opening and movable along the central axis,
The crucible has a step on the side wall,
Single crystal growth characterized in that the partial side wall on the lower surface side of the step portion is closer to the central axis passing through the center of the opening than the partial side wall on the upper surface side of the step portion. apparatus. The side wall is covered with a heat insulating material,
The crucible for single crystal growth apparatus according to claim 6, wherein the induction coil surrounds the heat insulating material.   The single crystal growing apparatus according to claim 6 or 7, wherein the crucible contains at least one of molybdenum, iridium, tungsten, and rhenium.

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