JP2016132599A - Sapphire single crystal production device and sapphire single crystal production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sapphire single crystal production device capable of preventing crack generation at cooling time to ambient temperature, after growing a single crystal by a temperature gradient coagulation method.SOLUTION: In the sapphire single crystal production method for growing the single crystal by setting a single crystal 44 at a bottom side in a crucible 41, melting a raw material 45 under temperature gradient of rising temperature from a bottom to a top of the crucible 41, and solidifying the raw material melt, from a single crystal 44 side, includes: the crucible 41 having a side wall 411 of a taper form with an inner diameter getting larger from the bottom to the top; a growing crystal support section 421 for supporting a growing crystal 46 in the crucible 41; a growing crystal transfer mechanism 42 connected to the growing crystal support section 421, including a crystal transfer axis 422 which vertically moves the growing crystal support section 421 in the crucible 41. A bottom opening 412A is provided in the bottom section 412 of the crucible 41, and the crystal transfer axis 422 passes through the bottom opening 412A, with at least a part of that housed in the crucible 41 in the sapphire single crystal production device.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a sapphire single crystal manufacturing apparatus and a sapphire single crystal manufacturing method.

  A sapphire single crystal is a crystal having a corundum structure of aluminum oxide, and has excellent mechanical and thermal properties, chemical stability, and light transmittance, and thus is used in many fields. The sapphire single crystal is used as a substrate for growing a light emitting layer of a gallium nitride (GaN) light emitting diode or a substrate for a silicon-on-sapphire (SOS) device, particularly in the semiconductor field. As the importance of these applications increases, the demand for them has increased dramatically.

  As a method for producing a sapphire single crystal, the Czochralski method (Cz method), the Cairo porous method (KY method), the EFG method (edge-defined film-fed growth method) and the like are known. These methods are methods for growing a single crystal by melting a sapphire raw material in a crucible, bringing a seed crystal into contact with the surface of the raw material melt and gradually pulling it up.

  As other sapphire single crystal manufacturing methods, the Bridgman method and the gradient freeze method (GF method) are known. In these methods, a seed crystal is previously placed in a crucible together with the raw material, and the raw material melt is unidirectionally solidified starting from the seed crystal under a temperature gradient formed so that the temperature of the seed crystal portion is lowest. This is a method for obtaining a single crystal. In the Bridgman method or the GF method, when a seed crystal is installed at the bottom of the crucible and crystal growth is performed upward from the seed crystal at the bottom of the crucible under a temperature gradient in which the temperature increases from the bottom to the top of the crucible Are called the vertical Bridgman method (VB method) and the vertical GF method (VGF method).

  In addition, the sapphire single crystal grown by these methods is processed into a substrate shape with a predetermined crystal orientation, and the surface is mirror-polished and shipped as a sapphire single crystal substrate.

  In recent years, a sapphire substrate for light-emitting diode production whose demand has been increasing is generally grown by the Cz method, the KY method, and the EFG method. In these methods, control of the temperature at which the seed crystal is immersed in the raw material melt (seeding temperature) and optimization of the temperature gradient during growth and cooling are factors that determine the yield and reproducibility of crystal growth.

  However, since the melting point of aluminum oxide, which is a raw material for the sapphire single crystal, exceeds 2000 ° C., when the sapphire single crystal is grown by the Cz method or the like, the heat transfer in the furnace in which the crucible is installed is mainly radiation. . Therefore, as the growth crystal is enlarged for cost reduction, the difficulty of controlling the seeding temperature and obtaining the appropriate temperature gradient for obtaining a crystal having a desired shape increases. In order to improve the controllability and reproducibility of crystal growth, it is advantageous to increase the temperature gradient, but crystals grown under a high temperature gradient are strained by thermal stress caused by temperature differences within the crystal. This is disadvantageous in that crystallinity is deteriorated and cracks are generated.

  On the other hand, a method of growing a single crystal by setting a seed crystal in a part of a container (in a crucible) like the VB method or VGF method and solidifying the raw material melt from the seed crystal according to the shape of the container. Since the crystal shape is defined by the container shape, it is not necessary to control the crystal shape. For this reason, it is possible to grow under a low temperature gradient and to obtain a high quality crystal.

  For example, in Patent Document 1, in a method for producing a high melting point single crystal material made of a metal or a metal compound having a melting point of 1700 ° C. or higher, a single crystal is grown by moving a crucible filled with a molten raw material through a furnace having a temperature gradient. A method of manufacturing a single crystal using the Bridgman method is disclosed.

  By the way, in the sapphire single crystal grown in the shape along the inner wall shape of the container in the container by the VB method or the VGF method as described above, there is a problem that the crack generation rate is high. This is presumably due to the difference in thermal expansion coefficient between the sapphire single crystal and the crucible material. That is, when the thermal expansion coefficient of the metal member used in the crucible is larger than the thermal expansion coefficient of the sapphire single crystal, in the process of cooling to room temperature after completion of the growth, the surrounding area rather than the contraction rate of the sapphire single crystal Therefore, the shrinkage rate of the crucible in (1) becomes larger, so that compressive stress is applied to the grown crystal as the temperature drops. This compressive stress causes cracks in the grown crystal.

  Therefore, for example, in Patent Document 2, the crucible has a linear expansion coefficient between two points of the sapphire melting point and room temperature between the sapphire melting point and the room temperature in the direction perpendicular to the growth axis of the produced sapphire single crystal. Discloses a method for producing a sapphire single crystal using a crucible made of a material smaller than the linear expansion coefficient. As specific crucible materials, tungsten, molybdenum, and alloys of tungsten and molybdenum are disclosed.

JP 2007-119297 A JP 2011-042560 A

  However, even if the method disclosed in Patent Document 2 is used, it has been difficult to completely suppress cracks. In particular, the crack generation rate increases as the size of the sapphire single crystal to be grown increases. For example, when a 6-inch φ sapphire single crystal is grown, cracks are generated with a probability of almost 100%.

  This is because, when compared with the same elapsed time from the start of cooling, as the diameter of the grown crystal increases, the temperature of the crucible existing at the outer periphery of the crystal is higher than the temperature at the center of the crystal existing inside the crucible. Becomes lower, and the temperature difference in the radial direction during cooling increases. For this reason, when compared with the same elapsed time from the start of cooling, it is considered that the crucible has a larger shrinkage rate than the crystal and stress is applied to the crystal by the crucible.

  Accordingly, in one aspect of the present invention, in view of the problems of the above-described conventional technology, a seed crystal is installed on the bottom side in the crucible, and the seed crystal is subjected to a temperature gradient in which the temperature increases from the bottom to the top of the crucible. It aims at providing the sapphire single crystal manufacturing apparatus which can suppress generation | occurrence | production of a crack when growing a sapphire single crystal by solidifying a raw material melt.

In order to solve the above-described problem, according to one aspect of the present invention, a seed crystal is installed on the bottom side in the crucible, and under the temperature gradient in which the temperature increases from the bottom to the top of the crucible, A sapphire single crystal manufacturing apparatus for growing a single crystal by solidifying a raw material melt,
A crucible having a tapered side wall whose inner diameter increases from the bottom toward the top;
A growth crystal support portion for supporting a growth crystal in the crucible, and a growth crystal movement mechanism including a crystal movement axis connected to the growth crystal support portion and capable of moving the growth crystal support portion vertically in the crucible. Prepared,
It is possible to provide a sapphire single crystal manufacturing apparatus in which a bottom opening is provided at the bottom of the crucible, the crystal moving axis passes through the bottom opening, and at least a part of the crystal moving shaft is accommodated in the crucible.

  According to one aspect of the present invention, the seed crystal is installed on the bottom side in the crucible, and the raw material melt is solidified from the seed crystal under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. It is possible to provide a sapphire single crystal manufacturing apparatus capable of suppressing the generation of cracks when growing a sapphire single crystal.

The structural example of the sapphire single crystal manufacturing apparatus in the case of manufacturing a sapphire single crystal by VGF method. Explanatory drawing of the procedure in the case of manufacturing a sapphire single crystal by VGF method, and a temperature distribution change. Explanatory drawing of the heat flow at the time of growing and cooling a sapphire single crystal by VGF method. BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing of the sapphire single-crystal manufacturing apparatus in embodiment of this invention. Explanatory drawing of the taper angle of the side wall of a crucible.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.
(Sapphire single crystal manufacturing equipment)
One structural example of the sapphire single crystal manufacturing apparatus of this embodiment is demonstrated.

  The sapphire single crystal manufacturing apparatus of this embodiment sets a seed crystal on the bottom side in the crucible, and solidifies the raw material melt from the seed crystal side under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. Thus, the sapphire single crystal manufacturing apparatus that performs single crystal growth can have the following configuration.

A crucible having a tapered side wall whose inner diameter increases from the bottom toward the top.
A growth crystal moving mechanism including a growth crystal support portion that supports a growth crystal in the crucible, and a crystal movement axis that is connected to the growth crystal support portion and can move the growth crystal support portion vertically in the crucible.
And the bottom opening part is provided in the bottom part of the crucible, A crystal moving axis | shaft can be set as the structure accommodated in the said crucible through the bottom part opening part.

  As described above, the sapphire single crystal manufacturing apparatus of the present embodiment has the seed crystal installed on the bottom side in the crucible, and the raw material from the seed crystal side under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. The present invention relates to a sapphire single crystal manufacturing apparatus for growing a single crystal by solidifying a melt. Specifically, for example, the present invention relates to a sapphire single crystal manufacturing apparatus that can be suitably used when manufacturing a sapphire single crystal by a VB method or a VGF method.

  First, a configuration example of a conventional sapphire single crystal manufacturing apparatus and a sapphire single crystal manufacturing procedure when manufacturing a sapphire single crystal by the VGF method will be described with reference to FIGS.

  Conventionally, when manufacturing a sapphire single crystal by the VGF method, a sapphire single crystal manufacturing apparatus 10 having a configuration as shown in FIG. 1 has been used. FIG. 1 shows a cross-sectional configuration diagram in a plane passing through the central axis of a crucible of a sapphire single crystal manufacturing apparatus.

  The sapphire single crystal manufacturing apparatus 10 is provided with a heat insulating material 12 along the inner wall of the chamber 11. In the internal space surrounded by the heat insulating material 12, a heater 13 and a crucible 14 are provided so as to be surrounded by the heater 13. The crucible 14 can be supported from the bottom side by the crucible shaft 15. In the crucible 14, when the production of the sapphire single crystal is started, the seed crystal 141 can be disposed on the bottom side of the crucible 14 and the seed crystal 141 can be filled with a raw material.

  The material of the crucible 14 is preferably a material which is stable even at a temperature exceeding the melting point of sapphire of 2050 ° C. and does not react with the raw material melt. Therefore, for example, iridium (Ir), molybdenum (Mo), tungsten (W), molybdenum-tungsten alloy (Mo—W alloy) or the like can be used as the material of the crucible 14. In particular, a material having a linear expansion coefficient close to that of the sapphire single crystal or smaller than that of the sapphire single crystal, such as Mo, W, and Mo—W alloy, can be preferably used.

  Although the material of the heater 13 and the heat insulating material 12 is not specifically limited, For example, it can be set as the structure of the heater made from tungsten, and the reflectors made from tungsten and molybdenum. Moreover, it can also be set as the structure of a carbon heater and a carbon laminated heat insulating material.

  The heater 13 has a structure in which, for example, a plurality of heaters are combined in the height direction so that a desired temperature gradient can be formed in a region surrounded by the heater 13 in which the crucible 14 is disposed. It can also be configured to control the temperature.

  And in order to measure the temperature of the seed crystal 141 when growing a sapphire single crystal, the bottom side temperature measuring means 16 can be provided. As the bottom side temperature measuring means 16, for example, a radiation thermometer or a thermocouple can be used, and the temperature can be measured through a through hole formed so as to penetrate the crucible shaft 15 or an observation window 151. Further, in order to measure the temperature of the raw material filled in the crucible 14 or the raw material melt 142 in which the raw material is melted, an upper side temperature measuring means 17 can be provided. As the upper temperature measuring means 17, for example, a radiation thermometer can be used, and the temperature can be measured through a through-hole penetrating the chamber 11 and the heat insulating material 12 and the observation window 18.

  In addition, in order to make the inside of the chamber 11 into a predetermined atmosphere, a gas supply means, a gas exhaust means, etc. which are not shown in figure can be provided. Various means can be optionally provided as required.

  Then, when a sapphire single crystal is manufactured by the VGF method using the sapphire single crystal manufacturing apparatus shown in FIG. 1, a procedure in a single crystal growth process for growing the sapphire single crystal and a change in temperature distribution are shown in FIG. This will be described with reference to FIG. 2A to 2C, the distribution of the seed crystal 141, the raw material melt 142, and the grown sapphire single crystal 21 in the crucible 14 is schematically shown on the right side, and the crucible 14 is shown on the left side. The temperature distribution in the height direction is shown. In addition, in FIG. 2 (a)-FIG.2 (c), description is abbreviate | omitted about structures other than the crucible 14 and the heater 13. FIG. In the graphs of the temperature distribution shown on the left side of FIGS. 2A to 2C, the vertical axis indicates the position in the height direction of the crucible 14, and the horizontal axis indicates the temperature. Tm on the horizontal axis indicates the melting point of sapphire (aluminum oxide).

  FIG. 2A shows a state in which the raw material melting step is started in which the raw material filled in the crucible 14 is melted and the growth of the sapphire single crystal is started as shown in the diagram on the right side.

  Before starting the single crystal growing step, the seed crystal 141 can be installed in the bottom of the crucible 14 and the raw material can be placed on the top thereof. In the raw material melting step shown in FIG. 2A, the temperature of the bottom portion of the crucible 14 is raised under a temperature gradient that is lower than the upper portion of the crucible 14, and the entire raw material is melted to form the raw material melt 142. Can do. In particular, as shown in the diagram on the left side, the temperature distribution can be controlled so that the portion of the seed crystal 141 is equal to or lower than the melting point of sapphire and the portion of the raw material melt 142 is equal to or higher than the melting point of sapphire.

  In the raw material melting step of FIG. 2A, the seed crystal 141 is melted in the range of several mm to 1 cm on the upper surface portion of the seed crystal 141 in order to remove the processing strain layer generated during the shape processing of the seed crystal 141 and remaining on the surface. it can. By melting the upper surface portion of the seed crystal, the surface of the seed crystal 141 from which the strain is removed can be made to be well adapted to the raw material melt 142.

  And after raising the temperature to the state of the temperature distribution shown in FIG. 2A, it is preferable to allow sufficient time to stabilize the temperature. At this time, the boundary (solid-liquid interface) between the melting surface of the seed crystal 141 and the raw material melt 142 can be set to 2050 ° C., which is the melting point of sapphire.

  In the raw material melting step shown in FIG. 2A, it is preferable to control the temperature so that the raw material and the seed crystal 141 are not sufficiently melted or the seed crystal 141 is not excessively melted. For example, as explained in the sapphire single crystal manufacturing apparatus 10 shown in FIG. 1, the bottom side temperature measuring means 16 and the top side temperature measuring means 17 are used to control the temperature on the bottom side of the crucible 14 and the raw material melt 142. The temperature of the surface can be monitored and implemented based on the monitored temperature. At this time, it is preferable to perform the control while confirming that the temperature distribution in the crucible matches the appropriate temperature profile obtained in the preliminary test from the monitored temperature.

  The atmosphere in the chamber 11 can be arbitrarily selected according to the material of the member installed in the chamber, and is not particularly limited. For example, an inert gas atmosphere or a vacuum atmosphere is preferable.

  As described with reference to FIG. 2A, the temperature lowering step can be performed after determining that the raw material is completely melted and that the upper surface of the seed crystal 141 is melted and has become familiar with the raw material melt 142. .

  As shown in FIG. 2B, in the temperature lowering step, the entire temperature can be lowered at a predetermined speed while maintaining the temperature gradient in the vertical direction.

  Specifically, as shown in the graph on the left side of FIG. 2B, the temperature distribution was indicated by the dotted line A in the raw material melting step, and the temperature gradient was maintained so as to be the temperature distribution of the solid line B. The overall temperature can be lowered. As is clear from the graph on the left side of FIG. 2B, by lowering the overall temperature while maintaining the temperature gradient, the position where the temperature is the same as the melting point of sapphire in the crucible according to the temperature gradient is Move to. Along with this movement, the solid-liquid interface also moves upward. That is, based on the seed crystal, a sapphire single crystal having the same crystal orientation as the seed crystal is grown from the bottom of the crucible toward the top, and as shown in the right side of FIG. The seed crystal 141, the grown crystal 21, and the raw material melt 142 are arranged from the bottom side.

  In the temperature lowering step, after the entire temperature is lowered from the dotted line A indicating the temperature distribution in the raw material melting step to the temperature distribution of the solid line B as described above, it is further shown in the graph on the left side of FIG. Thus, the entire temperature can be lowered to the temperature distribution indicated by the solid line C. In the temperature distribution indicated by the solid line C, the entire raw material melt 142 in the crucible 14 is less than the melting point of sapphire, and the entire portion that was the raw material melt 142 in FIG. At this point, the crystal growth is finished.

  Thereafter, a cooling step of lowering the temperature to room temperature at a predetermined cooling rate is performed, and the grown crystal 21 can be taken out from the crucible 14 to be a sapphire single crystal. The obtained sapphire single crystal can be processed in various ways to form a product substrate, for example.

  However, as described above, when a sapphire single crystal is manufactured by the VGF method or the like, the obtained sapphire single crystal sometimes includes a crack or the like. Therefore, the inventors of the present invention have studied a specific mechanism in which a crack or the like occurs in a sapphire single crystal using a conventional sapphire single crystal manufacturing apparatus. This will be described below.

  In FIG. 3A, after the seed crystal 141 and the raw material are filled in the crucible 14, the heater 13 is heated from the outer periphery of the crucible 14 to melt the raw material to obtain the raw material melt 142. A state is shown in which a part of the raw material melt 142 is used as the grown crystal 21 by being lowered. The arrows in the figure indicate the heat flow. 3 (a) and 3 (b) are enlarged views showing only the periphery of the crucible 14 and the heater 13, and the description of the surrounding members such as a heat insulating material is omitted.

  As shown in FIG. 3A, the seed crystal 141, the raw material melt 142, and the grown crystal 21 inside the crucible 14 are heated through the crucible 14 by the heater 13 installed on the outer periphery of the crucible 14. For this reason, when the temperatures of the crucible 14 and the grown crystal 21 are compared in the horizontal direction along the dotted line X1-X1 ′ in the figure, for example, the crucible 14 is higher. 3A, the heat applied to the raw material melt 142 and the like by the heater 13 flows through the seed crystal 141 toward the crucible shaft 15.

  In the outer wall of the crucible 14, the growing interface Y of the crystal being grown exists in the horizontal direction inside the portion that is higher than the melting point of sapphire, 2050 ° C. The diameter of the grown crystal 21 is determined by the inner diameter of the crucible 14. For this reason, the crucible 14 is first exposed to a temperature higher than the melting point of sapphire, and the inner diameter of the crucible 14 is expanded according to the expansion coefficient determined by the temperature. The grown crystal 21 is grown with the diameter defined by the enlarged inner diameter of the crucible 14.

  In order to suppress the occurrence of crystal defects such as cracks, dislocations, and lineage caused by thermal strain due to temperature differences in the crystal during growth, the temperature difference in the crystal should be made as small as possible. It exists under the set temperature gradient. And in order to advance crystal growth, after producing the raw material melt, the temperature is lowered as a whole while maintaining the temperature gradient, but the temperature lowering rate at this time is extremely low in order to avoid deterioration of crystallinity due to rapid growth. Slow.

  Specifically, for example, the temperature gradient in the vertical direction in the single crystal growth step of the sapphire single crystal, that is, the height direction of the crucible 14 is performed at about 10 ° C./cm or less. Further, the forward speed (crystal growth speed) at the growth interface is set to about 3 mm / h to 5 mm / h or less in order to suppress deterioration of crystallinity. For this reason, the temperature lowering speed when the temperature is lowered as a whole while maintaining the above temperature gradient is about several degrees C per hour.

  Further, as described above, as the material of the crucible 14, for example, a material having a linear expansion coefficient close to or smaller than that of a sapphire single crystal, such as Mo, W, or Mo—W alloy, is preferably used. Can do. Therefore, when the crystal growth is in progress, because of the low temperature gradient and the low cooling rate, the compressive stress on the crystal is caused by the difference in shrinkage between the already crystallized portion and the crucible around it. Is considered very small or zero.

  However, in the cooling step of cooling the grown sapphire single crystal to room temperature after completion of the single crystal growth step, heat is transferred from the outer wall of the crucible 14 or the surface of the grown crystal 21 to the outside as indicated by arrows in FIG. It flows toward the space. Therefore, when the temperature of the crucible 14 and the temperature of the grown crystal 21 are compared in the horizontal direction along, for example, the dotted line X2-X2 'in the figure, the grown crystal 21 is higher. In addition, in the cooling process, in order to efficiently take out the grown crystal 21 in a short period of time, the temperature lowering rate is generally set to a value larger by one digit or more than the temperature lowering rate in the single crystal growing step.

  Therefore, when the shrinkage rate of the crucible 14 in the horizontal direction along the dotted line X2-X2 'in the drawing and the shrinkage rate of the growth crystal 21 are compared in the cooling process, the linear expansion coefficient of the crucible 14 is higher than that of the sapphire single crystal. Even if a slightly smaller Mo-W crucible or the like is used, the crucible 14 is larger. Therefore, compressive stress is applied to the grown crystal 21 by the crucible 14 in the cooling step. This compressive stress caused cracks in the grown crystal 21 and deteriorated crystallinity.

  And, as the diameter of the crystal to be grown increases, the temperature difference in the horizontal plane increases, so the compressive stress applied to the grown crystal increases, and the crack generation rate is considered to increase as described above.

  In order to avoid the generation of cracks in the cooling process, it is also conceivable that the temperature lowering rate in the cooling process is made as low as that during the growth. However, with such slow cooling, it takes 2 weeks to 1 month to lower the temperature from the growth temperature of the sapphire single crystal exceeding 2000 ° C. to room temperature, so it is very inefficient and used for production. I can't.

  Therefore, the inventors of the present invention have studied a sapphire single crystal manufacturing apparatus that can suppress the occurrence of cracks, and have completed the sapphire single crystal manufacturing apparatus of the present invention. This will be specifically described below.

  FIG. 4 shows a cross-sectional configuration diagram of the sapphire single crystal manufacturing apparatus of the present embodiment. FIG. 4 shows a cross-sectional view in a cross section passing through the central axis of the crucible, and shows an enlarged view of the crucible and members connected thereto. For this reason, description is abbreviate | omitted except the crucible shown in FIG. 4, and the member connected to this.

  The structure of the sapphire single crystal manufacturing apparatus of this embodiment is demonstrated using FIG.

  As shown in FIGS. 4A and 4B, the sapphire single crystal manufacturing apparatus 40 of this embodiment can include a crucible 41 and a growth crystal moving mechanism 42.

  The crucible 41 may have a tapered shape in which the side wall 411 has an inner diameter that increases from the bottom toward the top. That is, the upper diameter L2 can be configured to be longer than the diameter L1 of the bottom (bottom surface) of the crucible 41 shown in FIG.

  The growth crystal moving mechanism 42 includes a growth crystal support portion 421 that supports the growth crystal in the crucible 41, a crystal movement axis 422 that is connected to the growth crystal support portion 421 and can move the growth crystal support portion in the crucible 41 in the vertical direction. including.

  The grown crystal support part 421 may be configured to support the seed crystal 44, the raw material 45 disposed on the seed crystal 44, and the grown grown crystal 46, and the shape thereof is not particularly limited. 4 (a) and (b) can be plate-shaped. In this case, the grown crystal support 421 preferably has a shape that matches the shape of the bottom of the crucible 41. For example, when the bottom (bottom) of the crucible 41 has a circular shape, the grown crystal support 421 has a disk shape. It is preferable to have.

  As shown in FIGS. 4A and 4B, the grown crystal support portion 421 can be provided with a seed crystal 44 or the like on the upper surface side, and a crystal moving shaft 422 can be connected to the lower surface side.

  When the grown crystal support portion 421 has a disk shape as described above, the diameter of the grown crystal support portion 421 may be the same as or slightly smaller than the diameter L1 of the bottom portion (bottom surface) of the crucible 41. preferable.

  Further, the diameter of the grown crystal support part 421 is preferably 3% or more and 10% or less smaller than the diameter of the seed crystal 44 supported on the grown crystal support part 421. That is, when the diameter of the seed crystal 44 is 100, the diameter of the grown crystal support portion 421 is preferably 90 or more and 97 or less. This is because the diameter of the grown crystal support part 421 is made smaller than the diameter of the seed crystal 44, so that even when the raw material melt flows along the side surface of the seed crystal 44 to the grown crystal support part 421, the grown crystal support part This is because adhesion between the 421 and the crystal moving shaft 422 and the crucible 41 can be prevented.

  Note that the side surface of the seed crystal 44 may have a tapered shape from the bottom side (the surface side facing the bottom of the crucible 41) toward the top side according to the shape of the crucible 41.

When the side surface of the seed crystal 44 has a tapered shape, the diameter of the surface of the grown crystal support portion 421 facing the seed crystal 44 and the diameter of the surface of the seed crystal 44 facing the grown crystal support portion 421 satisfy the above relationship. It is preferable.
The bottom 412 of the crucible 41 is provided with a bottom opening 412A, and the crystal moving shaft 422 passes through the bottom opening 412A and at least a part of the crystal moving shaft 422 is accommodated in the crucible 41. Since the bottom opening 412A also constitutes the crucible 41, even when the crystal movement shaft 422 is arranged in the bottom opening 412A as shown in FIG. Some will be housed.

  The diameter of the crystal moving shaft 422 is not particularly limited, and can be arbitrarily determined according to the weight of the grown crystal 46 and the strength and thermal conductivity depending on the material of the crystal moving shaft 422.

  The bottom opening 412A formed in the bottom 412 of the crucible 41 is preferably formed in the center of the bottom 412 of the crucible 41, and the opening diameter is not particularly limited. However, since the crystal moving shaft 422 is inserted into the bottom opening 412A as shown in FIGS. 4A and 4B, it can be selected according to the diameter of the crystal moving shaft 422.

  Further, in order to support the crucible 41, a crucible shaft 43 can be provided below the crucible 41. In this case, a through hole is also provided in the center of the crucible shaft 43, and the crystal moving shaft 422 can be accommodated in the through hole. Regarding the through hole provided in the crucible shaft 43, the diameter of the through hole can be selected according to the diameter of the crystal moving shaft 422 so that the crystal moving shaft 422 can be accommodated. At this time, it is preferable to select the diameter of the through hole to such an extent that the vertical movement of the crystal moving shaft 422 is not hindered.

  The material of the crucible 41 is not particularly limited, but is preferably a material that is stable even at a temperature exceeding the melting point of sapphire of 2050 ° C. and does not react with the raw material melt. For this reason, as a material of the crucible 41, for example, iridium (Ir), molybdenum (Mo), tungsten (W), molybdenum-tungsten alloy (Mo—W alloy), or the like can be used. In particular, a material having a linear expansion coefficient close to that of the sapphire single crystal or smaller than that of the sapphire single crystal, such as Mo, W, and Mo—W alloy, can be preferably used.

  Further, the material of the growth crystal moving mechanism 42 is not particularly limited. However, since it is in contact with the crucible 41 and the seed crystal 44 disposed in the crucible 41 and is similarly heated by the heater, the melting point of sapphire is reduced. It is preferable to be stable even at a temperature exceeding. In particular, since the crystal moving shaft 422 is inserted into the bottom opening 412A of the crucible 41, it is preferable that the material has the same or close thermal expansion coefficient as the crucible 41. In particular, the growth crystal moving mechanism 42 is more preferably made of the same material as the crucible 41.

  Note that the sapphire single crystal manufacturing apparatus 40 shown in FIG. 4 shows only the crucible 41 and the members connected thereto in an enlarged manner as described above, and further includes various members necessary for manufacturing the sapphire single crystal. be able to. For example, instead of the crucible 14 and the crucible shaft 15 in FIG. 1, the crucible 41, the grown crystal moving mechanism 42, and the crucible shaft 43 shown in FIG.

  Specifically, a heater can be provided so as to surround the side surface of the crucible 41 as described with reference to FIG. Further, a heat insulating material can be provided along the chamber and the inner wall surface of the chamber so as to surround the heater and the crucible 41. The heat insulating material and the heater are not particularly limited, and for example, they can be configured in the same manner as described in the sapphire single crystal manufacturing apparatus 10 in FIG.

  And when growing a sapphire single crystal, in order to measure the temperature of the bottom part side of the crucible 41, especially the temperature of a seed crystal, a bottom part side temperature measurement means can be provided. Moreover, in order to measure the temperature of the raw material and raw material melt with which the crucible 41 was filled, an upper side temperature measuring means can be provided. As the bottom side temperature measuring means and the top side temperature measuring means, a thermocouple or a radiation thermometer can be used, and an observation window or the like can be provided as necessary as described in FIG.

  When the bottom side temperature measuring means is provided, the crystal moving shaft 422 has the crystal moving shaft 422 as shown in FIGS. 4A and 4B so that the bottom side temperature measuring means can measure the temperature on the bottom side of the crucible 41. It is desirable to form a through-hole 422A in the hollow structure. An observation window (not shown) is formed at the lower end of the through-hole 422A, and the temperature on the bottom side of the crucible 41 can be measured through the observation window by the bottom side temperature measuring means.

  Moreover, about the sapphire single crystal manufacturing apparatus of this embodiment, an arbitrary member can be further provided as needed. For example, a gas supply means, a gas exhaust means or the like (not shown) can be provided in order to make the inside of the chamber have a predetermined atmosphere.

  Here, the procedure in the case of growing a sapphire single crystal using the sapphire single crystal manufacturing apparatus 40 of the present embodiment will be described.

  When growing a sapphire single crystal using the sapphire single crystal manufacturing apparatus 40, the grown crystal support portion 421 constituting the grown crystal moving mechanism 42 is positioned on the bottom 412 side of the crucible 41 as shown in FIG. Thus, the crystal movement axis 422 can be pulled down in the drawing. In this case, the grown crystal support portion 421 can be in contact with the bottom of the crucible 41 as shown in FIG.

  And before starting a single crystal growth process, as shown to Fig.4 (a), the seed crystal 44 and the raw material 45 can be arrange | positioned on the growth crystal support part 421. FIG.

  During the single crystal growth step, the raw material melt obtained by melting the raw material 45 and the grown crystal 46 formed from the raw material melt are in contact with the side wall 411 of the crucible 41. In the single crystal growth step, almost no compressive stress is applied from the crucible 41 to the grown crystal. For this reason, there is no possibility of causing cracks or the like in the grown crystal 46.

  Next, after the completion of the single crystal growth step, the growth crystal is moved as shown in FIG. 4B before starting a cooling step, which will be described later, of the cooling step for cooling the growth crystal 46 to room temperature or at a predetermined timing after the start. The crystal moving shaft 422 constituting the mechanism 42 can be pushed up into the crucible 41. As a result, the grown crystal support 421 connected to the crystal moving shaft 422 can be moved upward in the crucible 41. Since the seed crystal 44 and the grown crystal 46 are supported on the grown crystal support portion 421, the seed crystal 44 and the grown crystal 46 are also moved as the grown crystal support portion 421 moves upward in the crucible 41. The crucible 41 can be moved upward independently of the crucible 41.

  At this time, as described above, the side wall 411 of the crucible 41 has a tapered shape in which the inner diameter increases from the bottom toward the top, so that the grown crystal 46 faces the grown crystal 46 at a position after the movement, rather than the diameter of the grown crystal 46. The side wall has a larger diameter. For this reason, a gap (space) can be formed between the outer peripheral portion of the grown crystal 46 and the side wall 411 of the crucible 41 by moving the grown crystal 46 upward as shown in FIG. .

  In this way, after the growth of the sapphire single crystal is completed, an operation (gap forming step) is performed to form a gap between the grown crystal 46 and the crucible 41 during cooling, thereby reducing the difference in contraction rate between the grown crystal 46 and the crucible 41. As a result, it is possible to avoid applying compressive stress to the crystal. Thereby, deterioration of crystallinity of the grown crystal and generation of cracks can be prevented.

  As described above, when the sapphire single crystal manufacturing apparatus of the present embodiment is used, it is possible to suppress the growth crystal from being cracked in the cooling process. For this reason, in the cooling process, it becomes possible to cool the grown crystal at a cooling rate practically higher than that of the single crystal growth process, which is one order of magnitude higher, and the high-quality sapphire single crystal is efficiently and highly It can be obtained in a yield.

  Here, the structure of the sapphire single crystal manufacturing apparatus 40 of this embodiment is further demonstrated.

  In the sapphire single crystal manufacturing apparatus 40 of the present embodiment, the taper angle of the side wall of the crucible 41 used for growth can be arbitrarily selected depending on the linear expansion coefficient of the material of the crucible 41, but the taper angle of the side wall of the crucible 41. Is preferably 0.3 ° or more and 3 ° or less.

  When the taper angle is less than 0.3 °, the width is sufficient to prevent stress on the grown crystal 46 between the outer periphery of the grown crystal 46 and the side wall of the crucible 41 in the gap forming step. In some cases, it is necessary to increase the distance of the crystal rise performed to form the gap. Accordingly, in order to ensure the thermal uniformity during cooling, it is necessary to increase the ratio of the heater height to the grown crystal length, the crucible height, and the overall height of the sapphire single crystal manufacturing apparatus. This is because the members and devices are large and not efficient.

  When a part of the grown crystal is moved above the region surrounded by the crucible and the heater in the gap formation step described above, the grown crystal is surrounded by the region surrounded by the crucible and the crucible. In some cases, a non-existing region is generated, and a large temperature difference is generated between the two regions. And when the above big temperature differences arise in the growth crystal | crystallization, there exists a possibility of producing a crack in a growth crystal | crystallization.

  For this reason, in the gap forming step, for example, as shown in FIG. 4B, the grown crystal 46 is preferably arranged in a region surrounded by the crucible 41 and a heater (not shown).

  On the other hand, if the taper angle is larger than 3 °, for example, the diameter of the grown crystal goes away from the required diameter as it goes to the latter half of the growth. There are cases where the machining allowance during molding increases. For this reason, it takes a long time to grind, and the ground portion is wasted raw material, which is not efficient.

  In particular, the taper angle of the side wall 411 of the crucible 41 is more preferably not less than 0.5 ° and not more than 2 °.

  The taper angle means an inclination angle of the side wall 411 from a plane perpendicular to the bottom 412 of the crucible 41. Here, the taper angle will be described with reference to FIG. 5 in which a region a surrounded by a dotted line in FIG. 4B is enlarged. FIG. 5 shows the bottom (bottom) 412 and the side wall 411 of the crucible 41. A dotted line in the drawing shows a surface 51 perpendicular to the bottom 412. Then, in FIG. 5, the angle 52 formed by the surface 51 perpendicular to the bottom 412 of the crucible 41 and the side wall 411 indicates the taper angle of the side wall 411.

  Further, when a gap (space) is formed between the outer periphery of the grown crystal 46 and the side wall of the crucible 41 by the grown crystal moving mechanism 42 at the start of the cooling process, the gap L is particularly limited. Instead, it can be arbitrarily selected according to the linear expansion coefficient of the material of the crucible 41. However, the width L of the gap between the outer peripheral portion of the grown crystal 46 and the side wall of the crucible 41 is preferably set to 0.1 mm or more and 3 mm or less, for example.

  This is because if the width L of the gap is smaller than 0.1 mm, there is a high possibility that a compressive stress due to the shrinkage of the crucible 41 is loaded on the grown crystal 46 during cooling.

  On the other hand, if the width L of the gap is larger than 3 mm, it may be necessary to increase the distance for raising the grown crystal to form the gap. Accordingly, it may be necessary to increase the ratio of the heater height to the grown crystal length, the crucible height, and the overall height of the sapphire single crystal manufacturing apparatus. This is because it is not efficient.

According to the sapphire single crystal manufacturing apparatus of the present embodiment described above, the seed crystal is placed on the bottom side in the crucible, and the seed crystal is melted from the seed crystal under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. After solidifying the liquid and growing the sapphire single crystal, a gap can be formed between the crucible and the grown crystal during cooling. For this reason, it can suppress that a crack generate | occur | produces in a sapphire single crystal.
(Method for producing sapphire single crystal)
Next, a configuration example of the method for producing a sapphire single crystal of the present embodiment will be described.

  In the method for producing a sapphire single crystal of this embodiment, a seed crystal is installed on the bottom side in the crucible, and the raw material melt is poured from the seed crystal side under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. It can have the following processes regarding the manufacturing method of a sapphire single crystal which grows a single crystal by solidifying.

A single crystal growth step of growing a sapphire single crystal in a crucible having a tapered side wall whose inner diameter increases from the bottom toward the top.
A cooling step for cooling the sapphire single crystal after completion of the single crystal growth step.

  And in a cooling process, it can have a clearance gap formation step which raises the position of a sapphire single crystal by a growth crystal movement mechanism, and forms a clearance gap between the perimeter part of a sapphire single crystal, and the side wall of a crucible. The growth crystal moving mechanism is connected to the growth crystal support portion supporting the sapphire single crystal grown in the crucible and the growth crystal support portion, and passes through the bottom opening provided at the bottom of the crucible, A crystal moving axis that can move the support portion in the vertical direction within the crucible is included.

  Each step will be specifically described below. In addition, in the manufacturing method of the sapphire single crystal of this embodiment, the above-mentioned sapphire single crystal manufacturing apparatus can be used suitably. For this reason, description is partially abbreviate | omitted about the part which description overlaps with the sapphire single crystal manufacturing apparatus.

  In the single crystal growth step, a sapphire single crystal can be grown in a crucible having a tapered side wall whose inner diameter increases from the bottom toward the top.

  Specifically, a seed crystal is installed on the bottom side in the crucible, and a single crystal is grown by solidifying the raw material melt from the seed crystal under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. It can be carried out. In particular, a sapphire single crystal can be grown by the VB method (Vertical Bridgeman method) or the VGF method (Vertical Gradient Freeze method). Note that the crucible used in the single crystal growth step can be provided with a growth crystal movement mechanism for use in a cooling step described later.

  The single crystal growth process can include the following steps.

  First, after placing the seed crystal on the bottom side in the crucible and the aluminum oxide polycrystalline particles as the raw material on the top, a raw material melting step for melting the raw material can be performed. At this time, a temperature gradient in which the temperature increases from the bottom to the top of the crucible can be formed, for example, the boundary between the seed crystal and the raw material (raw material melt) can be made to be the melting point of sapphire. .

  Then, while maintaining the temperature gradient formed in the raw material melting step, the whole temperature is lowered to move the crystal growth interface (solid-liquid interface) toward the upper part of the crucible, and the temperature lowering step to grow the sapphire single crystal Can be implemented.

  These steps of the single crystal growth process are performed in the same manner as described with reference to FIG. 2 except that the shape of the crucible is different and a crucible equipped with a growth crystal movement mechanism is used. Therefore, detailed description is omitted here.

  There are no particular limitations on the magnitude of the temperature gradient in the single crystal growth process, the rate of temperature drop when lowering the overall temperature after melting the raw material filled in the crucible to form the raw material melt, and the crucible to be used. The size can be arbitrarily selected according to the size and the like.

  In the single crystal growth step, it is preferable that the crucible periphery is an inert atmosphere or a vacuum atmosphere. For example, an argon atmosphere can be used.

  A crucible having a tapered side wall whose inner diameter increases from the bottom toward the top, which can be used in the single crystal growth step, is as already described with reference to FIG. The taper angle of the side wall of the crucible is not particularly limited and can be arbitrarily selected according to the linear expansion coefficient of the material of the crucible, but the taper angle of the side wall of the crucible is 0.3 ° or more and 3 °. The following is preferable.

  This is sufficient when the taper angle is less than 0.3 ° so that stress is not applied to the grown crystal between the outer peripheral portion of the grown crystal 46 and the side wall of the crucible in the gap forming step of the cooling process described later. In some cases, the distance of the crystal rise required to form the gap of the interval becomes long. And accordingly, in order to ensure the thermal uniformity during cooling, there is a need to increase the ratio of the heater height to the growth crystal length, the crucible height, and the overall height of the growth apparatus. This is because the size is large and is not efficient.

  On the other hand, if the taper angle is larger than 3 °, for example, the diameter of the grown crystal goes away from the required diameter as it goes to the latter half of the growth. There are cases where the machining allowance during molding increases. For this reason, since the grinding time is also long, waste of raw materials and waste of time are generated, which is not efficient.

  In particular, the taper angle is more preferably 0.5 ° to 2 °.

  Next, the cooling process will be described. In the cooling step, the grown sapphire single crystal can be cooled to room temperature after completion of the single crystal growth step.

  In the single crystal growth step, as described above, a temperature gradient is formed in which the temperature increases from the bottom side to the top side of the crucible, and the entire temperature is lowered while maintaining the temperature gradient, thereby reducing the sapphire unit. Crystals can be grown. Therefore, the sapphire single crystal is grown from the bottom side where the seed crystal of the crucible is arranged to the upper side. For this reason, the time when the temperature of the upper end portion of the raw material (raw material melt) filled in the crucible becomes lower than the melting point of sapphire can be regarded as the end of the single crystal growth step.

  As described above, the shrinkage ratio of the crucible in the cooling process is higher than the shrinkage ratio of the grown sapphire single crystal. In the conventional method for producing a sapphire single crystal, a compressive stress is applied to the sapphire single crystal by the crucible. In some cases, cracks may occur in the sapphire single crystal.

  Therefore, in the cooling process of the method for manufacturing a sapphire single crystal according to the present embodiment, the position of the sapphire single crystal is raised independently of the crucible by a growth crystal moving mechanism, and between the outer periphery of the sapphire single crystal and the side wall of the crucible. A gap forming step for forming a gap (space). The growth crystal movement mechanism has already been described with reference to FIG.

  In the gap formation step described above, the width of the gap formed between the outer periphery of the grown crystal and the side wall of the crucible is not particularly limited, and should be selected according to the linear expansion coefficient of the crucible material. Can do. The width of the gap between the outer peripheral portion of the grown crystal and the side wall of the crucible is preferably set to 0.1 mm or more and 3 mm or less, for example.

  This is because if the gap is smaller than 0.1 mm, there is a high possibility that compressive stress due to crucible contraction will be applied to the grown crystal during cooling.

  On the other hand, if the gap is larger than 3 mm, it is necessary to increase the distance for raising the grown crystal to form the gap. The heater height relative to the grown crystal length, the crucible height, and the entire growing apparatus There may be a need to increase the height ratio. This is because it is not efficient.

  And a cooling process can have a cooling step which cools the sapphire single crystal (growth crystal) grown by the single crystal growth process to room temperature as mentioned above. In the cooling step, the sapphire single crystal can be cooled at a desired temperature drop rate by adjusting the output of the heater arranged around the crucible.

  The timing for performing the gap forming step is not particularly limited, but it is preferably performed before compressive stress is applied to the sapphire single crystal due to shrinkage of the crucible.

  For example, the cooling step and the gap forming step can be performed in parallel. Specifically, after completion of the single crystal growth process, the gap forming step can be performed while starting the cooling step by controlling the output and temperature of the heater.

  In particular, in order to prevent cracks and the like from occurring in the sapphire single crystal more reliably, it is more preferable to carry out a gap forming step after the single crystal growth process is completed and before the cooling step for cooling the grown sapphire single crystal to room temperature. preferable.

  After completion of the cooling step, the sapphire single crystal can be taken out from the crucible and processed into a desired shape according to the application, and any step can be performed as necessary.

  For example, in the case of a sapphire single crystal substrate (sapphire wafer), a cutting step for slicing the sapphire single crystal into a plate shape, a polishing step for polishing the main plane and end face of the sapphire single crystal substrate, and the like can be performed. .

  According to the sapphire single crystal manufacturing method of the present embodiment described above, the seed crystal is placed on the bottom side in the crucible, and the seed crystal is subjected to a temperature gradient in which the temperature increases from the bottom to the top of the crucible. From the solidification of the raw material melt, the generation of cracks can be suppressed when growing the sapphire single crystal. For this reason, it becomes possible to manufacture a sapphire single crystal with a high yield.

  Specific examples and comparative examples will be described below, but the present invention is not limited to these examples.

Here, first, an evaluation method of a sapphire single crystal grown in the following examples and comparative examples will be described.
(Polarization inspection)
Polarization inspection was performed by immersing a sapphire single crystal obtained by growth in methylene iodide and irradiating with a white light source.
(X-ray topographic imaging and evaluation)
X-ray topographic image photography was performed using a large sample Lang camera (manufactured by Rigaku Corporation, LGL-8), and the obtained X-ray topographic image was evaluated.
(Full width at half maximum of X-ray diffraction)
The full width at half maximum (FWHM) of X-ray diffraction was measured, calculated and evaluated using a precision X-ray diffractometer (manufactured by PANalytical, X'Pert PRO).

Next, the growth conditions of the sapphire single crystal in each example and comparative example will be described.
[Example 1]
In this example, a sapphire single crystal was manufactured using a sapphire single crystal manufacturing apparatus having the following configuration and evaluated.

  First, the used sapphire single crystal manufacturing apparatus will be described.

  The sapphire single crystal manufacturing apparatus shown in FIG. 1 is the same as the crucible 14 and the crucible shaft 15 shown in FIG. 1 except that the crucible 41, the growth crystal moving mechanism 42, and the crucible shaft 43 shown in FIG. A sapphire single crystal manufacturing apparatus having the same cross-sectional structure was used.

  As the crucible, as shown in FIGS. 4A and 4B, a crucible 41 having a tapered side wall whose inner diameter increases from the bottom toward the top is used. Specifically, a tungsten crucible having a bottom (bottom) diameter L1 of 150 mmφ, an upward side wall taper angle of 1.5 °, and an inner height of 500 mm was used.

  Then, as shown in FIGS. 4A and 4B, a grown crystal moving mechanism 42 having a grown crystal support portion 421 and a crystal moving shaft 422 was provided. At this time, the crystal moving shaft 422 is connected to the grown crystal support portion 421 and inserted into the bottom opening 412A formed in the bottom portion 412 of the crucible 41, so that the crystal moving shaft 422 is partially accommodated in the crucible 41. It is configured.

  The grown crystal support portion 421 has a disk shape and is made of tungsten having a diameter of 95 mmφ and a thickness of 10 mm. The crystal moving shaft 422 is a rod-shaped body having a cylindrical shape with a diameter of 35 mmφ and made of tungsten.

  In the sapphire single crystal manufacturing apparatus, as shown in FIG. 1, the heater 13 is disposed so as to surround the side surface of the crucible, and the crucible and the heater 13 are disposed in the chamber 11. A heat insulating material 12 is provided along the inner wall of the chamber 11.

  In this embodiment, as the heater 13, a three-zone heater configured to control the temperature gradient and the temperature for each of the three regions divided in the height direction was used. The material of the heater 13 and the heat insulating material 12 was carbon.

  The temperature in the sapphire single crystal manufacturing apparatus was measured using the upper side temperature measuring means 17 and the bottom side temperature measuring means 16 from the vertical direction on the center axis of the apparatus as shown in FIG. A two-color radiation thermometer was used as each temperature measuring means. The bottom temperature measuring means 16 was configured to observe through an observation window provided at the lower end of the through hole 422A provided in the crucible shaft 43.

  Moreover, in order to make the inside of the chamber 11 into a predetermined atmosphere, it has a gas supply means and a gas exhaust means (not shown).

  Next, the manufacturing method of a sapphire single crystal is demonstrated.

  First, the seed crystal 44 was placed on the bottom side of the crucible, that is, on the grown crystal support portion 421 in FIG. As the seed crystal 44, a sapphire single crystal disk having a diameter of 150 mmφ and a thickness of 40 mm was used. The plane orientation (growth orientation) of the seed crystal disk was c-plane. Next, as shown in FIG. 4A, 25 kg of aluminum oxide polycrystal particles were charged on the seed crystal 44 in the crucible 41 as a raw material 45 of sapphire single crystal.

  Next, the single crystal growing process was started.

  Specifically, first, the chamber 11 of the sapphire single crystal manufacturing apparatus was sealed, the inside of the chamber 11 was replaced with Ar gas, and then the temperature was started to melt the raw material (raw material melting step).

  In addition, a melting test is carried out in advance, and the relationship between the temperature measured by the upper side temperature measuring means 17 and the bottom side temperature measuring means 16, the amount of melting of the seed crystal in the crucible, the temperature gradient, and the temperature of the lower surface of the crystal stage is obtained. Oita.

  And at the time of temperature rise, based on the measured value by the upper side temperature measuring means and the bottom side temperature measuring means and the result of the melting test, the output ratio of the three zone heater is adjusted, from the crucible bottom to the upper part, A temperature distribution was formed in which the temperature increased with a gradient of 5 ° C./cm on average.

  At this time, the total output value of the heater was adjusted so that the measured value of the bottom side temperature measuring means became a desired value, and the upper end surface of the seed crystal was melted by about 5 mm.

  After standing for 30 minutes in the temperature distribution state when the upper end surface of the seed crystal was melted by about 5 mm, the heater output was gradually lowered overall to start crystal growth (temperature lowering step). Specifically, the temperature decrease rate of the heater output was adjusted so that the temperature decrease rate of the furnace temperature was 2.5 ° C./H.

  It is estimated that the forward speed (growth speed) of the growth interface at this time is 5 mm / H. The temperature was kept constant until the entire raw material was crystallized at a constant temperature drop rate. When the temperature measured by the upper temperature measuring means became lower than the melting point of sapphire, it was judged that the single crystal growth process was completed.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal moving mechanism 42, and the growth crystal support part 421 connected to this are raised 4 mm at a speed | rate of 1 mm / min, and a sapphire single-crystal outer peripheral part A gap forming step was performed in which a gap having a width of 0.1 mm was formed between the crucible and the crucible side wall.

  Next, as described above, the cooling step is performed such that a gap is formed between the outer periphery of the sapphire single crystal and the side wall of the crucible as described above, and then the heater output is set so that the average cooling rate becomes 50 ° C./H. Was cooled to room temperature.

  Then, it was confirmed that the grown sapphire single crystal was cooled to room temperature, and the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Thereafter, when the crystal was taken out from the crucible, it was confirmed that the growth part excluding the seed crystal part had a length of about 310 mm and was a 6 inch φ crystal with no cracks. The maximum diameter of the obtained crystal (crystal upper end diameter) was about 168 mm.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that a sapphire single crystal having no cracks could be obtained 10 times.

  The obtained sapphire single crystal was evaluated.

  Among the obtained sapphire single crystals, when the sapphire single crystal produced for the first time was evaluated for crystallinity by polarization inspection as described above, it was confirmed that the single crystal had no grain boundaries.

  Similarly, a c-plane substrate was cut out from the first-produced sapphire single crystal and mirror-finished, and then X-ray topographic images were photographed and evaluated, and the full width at half maximum of X-ray diffraction was evaluated. These evaluations were performed using a total of three substrates, one each cut out from three locations immediately above the seed crystal, ½ part of the crystal length, and the vicinity of the final growth part. Furthermore, the evaluation of the full width at half maximum of X-ray diffraction was performed on all three substrates, a total of 5 points of 4 points at 90 ° intervals 10 mm inside from the central part and the outermost peripheral part of the substrates.

  When an X-ray topographic image was taken, no accumulation of dislocations such as lineage was observed on the three substrates, and it was confirmed that the crystal was homogeneous throughout the crystal.

The evaluation result of the full width at half maximum of X-ray diffraction is 10 ″ as the average value of 5 points on the substrate immediately above the seed crystal, 9 ″ as the average value of 5 points for the substrate having a crystal length of ½ part, It was confirmed that this was a high quality crystal with no distribution in the crystal.
[Example 2]
Single crystal growth process under the same configuration and conditions as in Example 1 except that the material of the crucible used, the growth crystal support part constituting the growth crystal movement mechanism, and the material of the crystal movement axis were changed to Mo. Carried out.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal moving mechanism 42, and the growth crystal support part 421 connected to this are raised by 120 mm at a speed of 1 mm / min, and the sapphire single crystal outer peripheral part and The clearance gap formation step which forms a clearance gap with a width of 3 mm between the crucible side wall was implemented.

  Next, as described above, the cooling step is performed such that a gap is formed between the outer periphery of the sapphire single crystal and the side wall of the crucible as described above, and then the heater output is set so that the average cooling rate becomes 50 ° C./H. Was cooled to room temperature.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Thereafter, when the crystal was taken out from the crucible, as in Example 1, it was confirmed that it was a 6-inch φ crystal having a growth part length of about 310 mm excluding the seed crystal part and having no cracks. The maximum diameter of the obtained crystal (crystal upper end diameter) was about 168 mm.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that a sapphire single crystal having no cracks could be obtained 10 times.

  The obtained sapphire single crystal was evaluated in the same manner as in Example 1.

The results of polarization inspection, X-ray topographic image photographing, evaluation, and full width at half maximum evaluation of X-ray diffraction were the same as in Example 1, and it was confirmed that the crystals were high quality.
[Example 3]
The single crystal growth step was performed under the same configuration and the same conditions as in Example 1 except that the taper angle of the side wall of the crucible used was 0.3 °.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal moving mechanism 42, and the growth crystal support part 421 connected to this are raised by 50 mm at a speed of 1 mm / min, and a sapphire single crystal outer peripheral part and A gap forming step for forming a gap having a width of 0.1 mm between the side wall of the crucible and the crucible was performed.

  Next, the cooling step is performed so that the average temperature decreasing rate is 50 ° C./H after the gap forming step for forming a gap between the outer periphery of the sapphire single crystal and the crucible side wall as described above. It was.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Thereafter, when the crystal was taken out from the crucible, it was confirmed that the growth part excluding the seed crystal part had a length of about 310 mm and was a 6 inch φ crystal with no cracks. The maximum diameter of the obtained crystal (diameter at the upper end of the crystal) was about 156 mm.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that a sapphire single crystal having no cracks could be obtained 10 times.

When the obtained crystal was evaluated in the same manner as in Example 1, the results of polarization inspection, X-ray topographic image photographing, evaluation, and full width at half maximum evaluation of X-ray diffraction were the same as in Example 1. It was confirmed to be a crystal.
[Example 4]
The single crystal growth step was performed with the same configuration and the same conditions as in Example 1 except that the taper angle of the side wall of the crucible used was 3 °.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal movement mechanism 42, and the growth crystal support part 421 connected to this are raised 2 mm at a speed | rate of 1 mm / min, and a sapphire single-crystal outer peripheral part and A gap forming step for forming a gap having a width of 0.1 mm between the side wall of the crucible and the crucible was performed.

  Next, the cooling step is performed so that the average temperature decreasing rate is 50 ° C./H after the gap forming step for forming a gap between the outer periphery of the sapphire single crystal and the crucible side wall as described above. It was.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Thereafter, when the crystal was taken out from the crucible, it was confirmed that the length of the growing portion excluding the seed crystal portion was about 310 mm and that it was 6 inches φ with no cracks. The maximum diameter of the obtained crystal (crystal upper end diameter) was about 186 mm.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that a sapphire single crystal having no cracks could be obtained 10 times.

When the obtained crystal was evaluated in the same manner as in Example 1, the results of polarization inspection, X-ray topographic image photographing, evaluation, and full width at half maximum evaluation of X-ray diffraction were the same as in Example 1. It was confirmed to be a crystal.
[Example 5]
The single crystal growth step was carried out under the same configuration and the same conditions as in Example 1.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal movement mechanism 42, and the growth crystal support part 421 connected to this are raised 2 mm at a speed | rate of 1 mm / min, and a sapphire single-crystal outer peripheral part and A gap having a width of 0.05 mm was formed between the side wall and the crucible.

  Next, the cooling step is performed so that the average temperature decreasing rate is 50 ° C./H after the gap forming step for forming a gap between the outer periphery of the sapphire single crystal and the crucible side wall as described above. It was.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Then, when the crystal was taken out from the crucible, it was confirmed that the length of the growing part excluding the seed crystal part was about 310 mm and was a 6 inch φ crystal. However, cracks occurred in about 1/3 of the crystal.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that sapphire single crystal without any cracks was obtained 6 times out of 10 times.

  About the sapphire single crystal containing the crack produced initially, the 6-inch (phi) board | substrate was processed from the part without a crack, the imaging | photography of the X-ray topograph image similar to Example 1, and the evaluation of the full width at half maximum of X-ray diffraction were performed. .

  When an X-ray topographic image was photographed, it was confirmed that there were many lineages that are accumulation of dislocations, particularly in the vicinity of the outer periphery of the substrate.

Further, the evaluation result of the full width at half maximum of X-ray diffraction was 10 ″, which was the same as the crystal obtained in Example 1, but the value at the outer periphery of the substrate was 20-30. In other words, the crystallinity was inferior to that of the crystal obtained in Example 1.
[Example 6]
Single crystal growth process under the same configuration and conditions as in Example 1 except that the material of the crucible used, the growth crystal support part constituting the growth crystal movement mechanism, and the material of the crystal movement axis were changed to Mo. Carried out.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal moving mechanism 42, and the growth crystal support part 421 connected to this are raised by 140 mm at a speed of 1 mm / min, and the sapphire single crystal outer peripheral part and The clearance gap formation step which forms a clearance gap with a width of 3.5 mm between the crucible side wall was implemented.

  Next, as described above, the cooling step is performed such that a gap is formed between the outer periphery of the sapphire single crystal and the side wall of the crucible as described above, and then the heater output is set so that the average cooling rate becomes 50 ° C./H. Was cooled to room temperature.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Then, when the crystal was taken out from the crucible, it was confirmed that the length of the growing part excluding the seed crystal part was about 310 mm and was a 6 inch φ crystal. However, cracks occurred at the upper end of the crystal.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that sapphire single crystal without any cracks was obtained 6 times out of 10 times.

For the first produced sapphire single crystal containing cracks, a 6-inch φ substrate was processed from the crack-free part, and the X-ray topographic image was photographed and evaluated in the same manner as in Example 1, and the full width at half maximum of X-ray diffraction was evaluated. As a result, the results were the same as in Example 1 in any of the tests, and it was confirmed that the crystals were high quality except for the upper end of the crystal.
[Example 7]
The single crystal growth step was performed under the same configuration and the same conditions as in Example 1 except that the taper angle of the side wall of the crucible used was 0.2 °.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. And while starting a cooling step, the crystal moving shaft 422 which comprises the growth crystal moving mechanism 42, and the growth crystal support part 421 connected to this are raised by 140 mm at a speed of 1 mm / min, and the sapphire single crystal outer peripheral part and A gap forming step for forming a gap having a width of 0.1 mm between the side wall of the crucible and the crucible was performed.

  Next, the cooling step is performed so that the average temperature decreasing rate is 50 ° C./H after the gap forming step for forming a gap between the outer periphery of the sapphire single crystal and the crucible side wall as described above. It was.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Thereafter, when the crystal was taken out from the crucible, it was confirmed that the grown portion excluding the seed crystal portion had a length of about 310 mm and was a 6 inch φ crystal. However, cracks occurred at the upper end of the crystal.

  Similarly, when the sapphire single crystal was grown ten times in total including the above-mentioned one time, it was confirmed that a sapphire single crystal having no cracks was obtained six times.

A 6-inch φ substrate was processed from a portion free from cracks, and X-ray topographic images were taken and evaluated in the same manner as in Example 1, and the full width at half maximum of X-ray diffraction was evaluated. It was the same result, and it was confirmed that it was a high quality crystal except for the upper end of the crystal.
[Example 8]
The single crystal growth step was performed under the same configuration and the same conditions as in Example 1 except that the taper angle of the side wall of the crucible used was 3.5 °.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed.

  First, the cooling step was started by adjusting the output and the output ratio of the heater so that the temperature difference between the upper temperature measuring means and the lower temperature measuring means was 3 ° C. or less. Then, the cooling step is started, and the crystal movement shaft 422 constituting the growth crystal movement mechanism 42 and the growth crystal support portion 421 connected thereto are raised by 0.5 mm at a speed of 1 mm / min, and the outer periphery of the sapphire single crystal A gap forming step for forming a gap having a width of 0.1 mm between the part and the crucible side wall was performed.

  Next, the cooling step is performed so that the average temperature decreasing rate is 50 ° C./H after the gap forming step for forming a gap between the outer periphery of the sapphire single crystal and the crucible side wall as described above. It was.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. After that, when the crystal was taken out from the crucible, it was confirmed that the growth portion excluding the seed crystal portion had a length of about 310 mm and the maximum diameter (crystal upper end portion diameter) was a crystal containing no cracks at all. It was. However, when the outer peripheral portion of the crystal was ground to 6 inφ, the production efficiency was reduced in comparison with Example 1 and the like in terms of time and cutting allowance loss.

  Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, it was confirmed that a sapphire single crystal having no cracks could be obtained 10 times.

When the obtained crystal was evaluated in the same manner as in Example 1, the results of polarization inspection, X-ray topographic image photographing, evaluation, and full width at half maximum evaluation of X-ray diffraction were the same as in Example 1. It was confirmed to be a crystal.
[Comparative Example 1]
A single crystal growth step was performed using a sapphire single crystal manufacturing apparatus having the same configuration as in Example 1 except that the growth crystal movement mechanism was not provided. In addition, since it does not have a growth crystal movement mechanism, the bottom part of the crucible was not provided with the bottom part opening part, but the seed crystal was directly arrange | positioned at the bottom part of the crucible. The conditions for the single crystal growth step were the same as those in Example 1.

  Immediately after judging that the single crystal growth process was completed, the cooling process was performed. In the cooling process, only the cooling step was performed without performing the gap forming step.

  In the cooling step, cooling was performed to room temperature at an average temperature drop rate of 50 ° C./H.

  After confirming that the grown sapphire single crystal was cooled to room temperature, the crucible and the crystal were taken out from the growing apparatus about two days after the completion of the single crystal growing process. Thereafter, when the crystal was taken out from the crucible, the size of the crystal was 6 inches φ, which was the same as in Example 1, and the length of the growing portion was about 310 mm. Had occurred. Similarly, when the sapphire single crystal was grown a total of 10 times including the above 1 time, cracks occurred in the sapphire single crystal in all 10 times.

  A 6-inch φ substrate was processed from the crack-free portion of the sapphire single crystal produced first, and the X-ray topographic image was photographed and evaluated in the same procedure as in Example 1, and the full width at half maximum of X-ray diffraction was evaluated. .

  An X-ray topographic image was taken, and it was confirmed that a large number of lineage, which is an accumulation of dislocations, was present particularly near the periphery of the substrate.

  Further, the evaluation result of the full width at half maximum of X-ray diffraction was 10 ″, which was the same as the crystal obtained in Example 1, but the value at the outer periphery of the substrate was 25-30. It was confirmed that the result was inferior in crystallinity to the crystal obtained in Example 1.

  When Examples 1-8 are compared with Comparative Example 1, in Comparative Example 1 using a sapphire single crystal manufacturing apparatus that does not have a growth crystal movement mechanism, it is confirmed that cracks occur in all manufactured sapphire single crystals. It could be confirmed.

  On the other hand, when Examples 1-4 and 8 were implemented 10 times, it has confirmed that the sapphire single crystal which does not contain a crack could be manufactured 10 times. Moreover, when it implemented 10 times also in Examples 5-7, it has confirmed that the sapphire single crystal which does not contain a crack can be manufactured 6 times. From these results, it was confirmed that the occurrence of cracks could be suppressed by using a sapphire single crystal manufacturing apparatus equipped with a growth crystal moving mechanism.

  In Example 5, although the growth crystal movement mechanism was provided, the gap between the outer peripheral portion of the sapphire single crystal and the side wall of the crucible was small, so the sapphire single crystal was produced 10 times. It is thought that cracks occurred four times.

  In Example 6, by raising the sapphire single crystal by the growth crystal moving mechanism, it was possible to sufficiently secure the distance between the outer periphery of 3.5 mm and the sapphire single crystal and the side wall of the crucible. However, since a part of the sapphire single crystal was removed from the region covered with the crucible or heater, a large temperature gradient was formed in the sapphire single crystal, and cracks occurred four times after the sapphire single crystal was produced ten times. It is thought that.

  In Example 7, since the taper angle of the side wall of the crucible was 0.2 °, which was small compared to other examples, an attempt was made to make a sufficient distance between the outer peripheral portion of the sapphire single crystal and the inner wall of the crucible. The increase of the sapphire single crystal due to the crystal growth mechanism has been increased. For this reason, as in the case of Example 6, since a part of the sapphire single crystal was removed from the region covered with the crucible or the heater, a temperature gradient was formed in the sapphire single crystal, and the sapphire single crystal was It is considered that cracks occurred four times during the production.

DESCRIPTION OF SYMBOLS 10 Sapphire single crystal manufacturing apparatus 14, 41 Crucible 411 Side wall 412 Bottom part 412A Bottom part opening part 141, 44 Seed crystal 142 Raw material melt 421 Growth crystal support part 422 Crystal movement axis 42 Growth crystal movement mechanism 21, 46 Growth crystal (sapphire single crystal )
52 Taper angle

Claims (4)

A sapphire single crystal is grown by setting a seed crystal on the bottom side in the crucible and solidifying the raw material melt from the seed crystal side under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. A crystal manufacturing apparatus,
A crucible having a tapered side wall whose inner diameter increases from the bottom toward the top;
A growth crystal support portion for supporting a growth crystal in the crucible, and a growth crystal movement mechanism including a crystal movement axis connected to the growth crystal support portion and capable of moving the growth crystal support portion vertically in the crucible. Prepared,
An apparatus for producing a sapphire single crystal, wherein a bottom opening is provided at the bottom of the crucible, the crystal movement axis passes through the bottom opening, and at least a part thereof is accommodated in the crucible. A seed crystal is placed on the bottom side of the crucible, and a sapphire single crystal is grown by solidifying the raw material melt from the seed crystal side under a temperature gradient in which the temperature increases from the bottom to the top of the crucible. A method for producing a sapphire single crystal,
A single crystal growth step of growing a sapphire single crystal in a crucible having a tapered side wall whose inner diameter increases from the bottom toward the top;
A cooling step of cooling the sapphire single crystal after completion of the single crystal growth step;
The cooling step is connected to the grown crystal support unit supporting the sapphire single crystal grown in the crucible and the grown crystal support unit, and passes through the bottom opening provided at the bottom of the crucible and the grown The position of the sapphire single crystal is raised by a growth crystal movement mechanism including a crystal movement axis capable of moving the crystal support portion in the vertical direction in the crucible, and between the outer periphery of the sapphire single crystal and the side wall of the crucible. The manufacturing method of the sapphire single crystal which has the clearance gap formation step which forms a clearance gap.   The method for producing a sapphire single crystal according to claim 2, wherein a width of a gap between the outer peripheral portion of the sapphire single crystal and the side wall of the crucible formed in the gap forming step is 0.1 mm or more and 3 mm or less.   The method for producing a sapphire single crystal according to claim 2 or 3, wherein a side wall taper angle of the crucible is not less than 0.3 ° and not more than 3 °.

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