JP5452291B2 - Crystal growth equipment - Google Patents

Description

  The present invention relates to a crystal growth apparatus.

One method for producing gallium nitride (GaN) that is expected as a next-generation semiconductor material is to immerse a seed substrate in a Na / Ga melt at 800 ° C. to 900 ° C. in a high-pressure nitrogen atmosphere of several MPa, A crystal growth method (so-called flux method) for growing a GaN crystal on a substrate is known.
Patent Document 1 below discloses a crystal growth apparatus including an agitator for agitating a melt in order to suppress excessive nucleation and obtain a large and high-quality GaN crystal in a flux method.

JP-A-2005-247615

However, the following problems exist in the conventional technology as described above.
The crystal growth apparatus generally has a configuration in which a reaction vessel holding a melt and a seed substrate is surrounded by a heat insulating vessel and a pressure vessel to maintain a high temperature and high pressure state. Therefore, when providing the said stirring apparatus, you have to form the hole part which inserts the drive shaft for stirring in a heat insulation container. Then, since the inside of the heat insulation container is hot, it is difficult to seal the hole with a gas seal material or the like, and high temperature gas leaks from the gap formed between the hole and the drive shaft, The temperature distribution is non-uniform. In particular, in the flux method, the effect of temperature non-uniformity in the heat insulating container is large and adversely affects crystal growth.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a crystal growth apparatus that stirs a melt while maintaining a uniform temperature distribution in a heat insulating container to obtain large-sized and high-quality crystals. .

In order to solve the above-mentioned problems, the present invention comprises a reaction vessel for reacting a raw material gas and a melt in a heated and pressurized atmosphere to grow crystals on a seed substrate immersed in the melt, and the reaction described above. Stirring that stirs the melt by rotating a heat-insulating container that surrounds the outside of the container, a pressure container that surrounds the outside of the heat-insulating container, and a drive shaft provided through the heat-insulating container and the pressure container. A crystal growth apparatus comprising: a shaft case having a housing space for hermetically housing one end side of the drive shaft; and at least the drive shaft in the axial direction between the heat insulating container and the pressure container. A configuration is adopted in which an expansion and contraction tube is provided that encloses the expansion and contraction and has an airtight space that connects a hole portion through which the other end of the drive shaft formed in the heat insulating container is inserted and the accommodation space.
By adopting this configuration, in the present invention, even if there is a gap between the drive shaft and the hole of the heat insulating container, an airtight space in which the outflow destination from the gap is connected to the housing space of the shaft case. Therefore, it is possible to prevent the high temperature gas from leaking from the inside of the heat insulating container and uneven temperature distribution. In addition, the expansion and contraction tube forming the airtight space connected to the housing space of the shaft case surrounds the drive shaft between the heat insulating container and the pressure container and can be expanded and contracted in the axial direction. Even if it fluctuates, it can be flexibly deformed to cope with the fluctuation.

Further, in the present invention, the pressure vessel has a second hole portion that is inserted through the other end side of the drive shaft and is in airtight communication with the accommodation space, and the expansion tube is formed at one end side thereof. A configuration is adopted in which the hole is hermetically surrounded and the second hole is hermetically surrounded on the other end side to form the hermetic space.
By adopting this configuration, in the present invention, the hole portion of the heat insulating container is hermetically enclosed at one end side of the expansion tube, and is formed in the pressure container at the other end side of the expansion tube and communicates with the housing space of the shaft case in an airtight manner. The airtight space is formed by airtightly surrounding the hole.

In the present invention, the expansion tube employs a configuration in which the hole portion is hermetically surrounded on one end side and the airtight space is formed on the other end side in an airtight communication with the housing space.
By adopting this configuration, in the present invention, the hole of the heat insulating container is hermetically surrounded on one end side of the expansion tube, and the airtight space is communicated with the housing space of the shaft case on the other end side of the expansion tube. Form.

Moreover, in this invention, the structure that the said expansion-contraction pipe | tube is a bellows pipe | tube eccentric freely in the direction orthogonal to the said axial direction is employ | adopted.
By adopting this configuration, in the present invention, the bellows tube is not only telescopic in the axial direction but also eccentric in the direction perpendicular to the axial direction, so the relative distance between the components varies due to the influence of heat. However, it can be deformed more flexibly to cope with the fluctuation.

In the present invention, the stirring device includes a magnetic body integrally provided on one end side of the drive shaft, and a rotation for rotating the magnetic body around the shaft by a magnetic action from the outside of the shaft case. And a drive device.
By adopting this configuration, in the present invention, the drive shaft can be rotated around the shaft by a magnetic action from the outside of the shaft case without destroying the airtightness of the accommodation space.

According to the present invention, a reaction vessel that reacts a raw material gas with a melt under a heating and pressurizing atmosphere to grow crystals on a seed substrate immersed in the melt, and a heat insulating vessel that surrounds the outside of the reaction vessel And a pressure vessel that surrounds the outside of the heat insulation vessel, and a stirring device that stirs the melt by rotating the heat insulation vessel and a drive shaft provided through the pressure vessel around the axis. The device includes a shaft case having a housing space for hermetically housing one end side of the drive shaft, and at least between the heat insulating container and the pressure vessel, the drive shaft is surrounded in an axial direction so as to be extendable and contractible. By adopting a configuration having an expansion tube that forms an airtight space that connects the housing portion and a hole portion through which the other end side of the drive shaft is formed in the heat insulation container, a hole in the drive shaft and the heat insulation container is adopted. Gap between Even so the outflow destination from the gap becomes an airtight space connected to the housing space of the shaft case can be hot gas temperature distribution leaks from the heat insulating container is prevented from becoming nonuniform. In addition, the expansion and contraction tube forming the airtight space connected to the housing space of the shaft case surrounds the drive shaft between the heat insulating container and the pressure container and can be expanded and contracted in the axial direction. Even if it fluctuates, it can be flexibly deformed to cope with the fluctuation.
Therefore, in the present invention, the melt can be stirred while the temperature distribution in the heat insulating container is kept uniform, and a large and high quality crystal can be obtained.

It is a block diagram which shows the gallium nitride manufacturing apparatus in embodiment of this invention. It is a block diagram which shows the gallium nitride manufacturing apparatus in another embodiment of this invention. It is a figure which shows one Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, a gallium nitride manufacturing apparatus will be described as an example of the crystal growth apparatus of this embodiment.

FIG. 1 is a configuration diagram showing a gallium nitride manufacturing apparatus 1 according to an embodiment of the present invention.
The gallium nitride production apparatus 1 is for producing a GaN crystal by growing it on a seed substrate 2 by a flux method. The reaction vessel (crucible) 10 that holds the seed substrate 2 and the mixed melt 3, and the outside of the reaction vessel 10 , A pressure vessel 30 surrounding the outside of the heat insulation container 20, and a stirring device 40 for stirring the mixed melt 3.

The reaction vessel 10 has a mixed melt 3 made of Na / Ga inside. The reaction vessel 10 of the present embodiment is configured such that the seed substrate 2 is placed on the bottom and immersed in the mixed melt 3 inside. The reaction vessel 10 is connected to a nitrogen gas supply port (not shown) for introducing nitrogen gas (N ₂ ), which is a raw material for GaN crystals, from the outside, so that the reaction vessel 10 is filled with nitrogen gas. It has become.

As the heat insulating material of the heat insulating container 20, for example, a fiber heat insulating material such as glass wool is used. Inside the heat insulating container 20, a heater 21 is provided that surrounds and heats the four sides and the lower side of the reaction container 10.
The pressure vessel 30 is composed of a vacuum vessel that is configured in a substantially cylindrical shape so that it can withstand the pressure even when the pressure state changes, and its posture is set so that the central axis of this cylindrical shape is in the vertical direction. Has been. The pressure vessel 30 is connected to a vacuum exhaust port (not shown) that evacuates the internal air.

  The stirrer 40 is a magnetically coupled stirrer, and includes a drive shaft 41, a shaft case 42, and a rotation drive device 43. An inner cylinder 45 having a plurality of permanent magnets (magnetic bodies) 44 at a predetermined interval in the circumferential direction of the outer peripheral surface is attached to one end side of the drive shaft 41. The shaft case 42 has a housing space S1 that houses one end side of the drive shaft 41. The housing space S1 is provided with a bearing 46 that contacts the peripheral surface of the inner cylinder 45 and supports the drive shaft 41 so as to be rotatable about the axis. The shaft case 42 is made of nonmagnetic stainless steel and is tightly fixed to the pressure vessel 30 in an airtight manner. The drive shaft 41 is also made of stainless steel.

  The rotation driving device 43 includes an outer cylinder 48 provided with a plurality of permanent magnets 47 at predetermined intervals in the circumferential direction of the inner peripheral surface outside the shaft case 42. The outer cylinder 48 is supported by a bearing 49 attached to the outside of the shaft case 42 so as to be rotatable around the shaft. Further, the rotation drive device 43 includes a motor 50 that rotates the outer cylinder 48 around the axis. The rotating shaft of the motor 50 and the outer cylinder 48 are connected by a belt 51. According to the above configuration, when the outer cylinder 48 rotates around the axis by driving the motor 50, the permanent magnet 47 fixed to the outer cylinder 48 and the permanent magnet 44 fixed to the inner cylinder 45 are interposed via the shaft case 42. Acting magnetically, the drive shaft 41 rotates around the axis.

The other end side of the drive shaft 41 extending downward from the shaft case 42 is inserted into the pressure vessel 30, the heat insulation vessel 20, and the reaction vessel 10 and reaches the mixed melt 3. The drive shaft 41 is provided with a stirring blade 52 at the tip end on the other end side, and the stirring blade 52 rotates around the shaft in the mixed melt 3 to stir the mixed melt 3.
The drive shaft 41 of the present embodiment is configured by engaging a first drive shaft 41A and a second drive shaft 41B with a shaft coupling 60. The first drive shaft 41A is rotatably supported by the shaft case 42, and the second drive shaft 41B is rotatably supported by a bearing (not shown) provided in the reaction vessel 10.

  The heat insulating container 20 and the pressure container 30 have an insertion hole through which the drive shaft 41 is inserted (hereinafter, the insertion hole of the heat insulating container 20 is the first hole (hole) 22, and the insertion hole of the pressure container 30 is the second hole 31. Is formed). Between the 1st hole 22 and the 2nd hole 31, the bellows pipe | tube (expandable pipe) 53 which can be expanded-contracted to an axial direction and is eccentric to the direction orthogonal to an axial direction is provided. The bellows pipe 53 surrounds the drive shaft 41 between the heat insulating container 20 and the pressure container 30 and is attached so as to airtightly surround the first hole 22 at one end thereof, and the second hole 31 at the other end. It is attached so that it is airtightly enclosed. The second hole 31 communicates with the accommodation space S1 of the shaft case 42 in an airtight manner, and the bellows pipe 53, the second hole 31 and the accommodation space S1 communicate with the outer side of the first hole 22. A space is formed.

Next, the operation and action of the gallium nitride manufacturing apparatus 1 having the above configuration will be described. Note that the gallium nitride manufacturing apparatus 1 of the present embodiment includes a control unit (not shown). And unless there is particular notice, the said control part controls the following operation | movement as a subject.
First, the air inside the pressure vessel 30 is evacuated from the evacuation port. After the vacuum state is reached, nitrogen gas is supplied from the nitrogen gas supply port to fill the reaction vessel 10 and the internal pressure is increased to several MPa. Further, the heater 21 is driven to heat the internal temperature to 800 ° C to 900 ° C. Then, this high temperature and high pressure state is maintained for a predetermined time, and Ga (gallium) and N (nitrogen) are reacted in the mixed melt 3 of the reaction vessel 10 to grow a GaN crystal on the seed substrate 2.

In this crystal growth process, the mixed melt 3 is agitated by the agitator 40 in order to suppress generation of extra nuclei and obtain a large and high quality GaN crystal. Specifically, the outer cylinder 48 is rotated around the axis by driving the motor 50, the drive shaft 41 having the stirring blade 52 is rotated around the shaft by magnetic action, and the mixed melt 3 is stirred by the stirring blade 52. To do.
In the heat insulating container 20, the first hole 22 is formed to allow the drive shaft 41 to pass therethrough. However, in this embodiment, the high temperature gas in the heat insulating container 20 is generated from the gap between the drive shaft 41 and the first hole 22. Even if it tries to flow out to the outside, it cannot flow out because the tip is a sealed path in an airtight space. For example, even if high temperature gas tries to flow out into the space between the heat insulating container 20 and the pressure container 30, the bellows pipe 53 is disposed between the heat insulating container 20 and the pressure container 30. It becomes impossible. Moreover, since the tip of the bellows pipe 53 communicates with the second hole 31 and the housing space S1 of the shaft case 42 and is closed, heat escape due to convection is prevented.
Moreover, even if the relative position in the axial direction between the first hole portion 22 of the heat insulating container 20 and the second hole portion 31 of the pressure vessel 30 fluctuates due to the heating by the heater 21, the bellows pipe 53 is correspondingly increased. Since it expands and contracts, the airtight space is not broken under the influence of heat. Furthermore, even if the thermal expansion by the heating by the heater 21 causes the relative position in the direction perpendicular to the axial direction between the first hole 22 of the heat insulating container 20 and the second hole 31 of the pressure container 30 to fluctuate, the bellows tube Since 53 is eccentric by that amount, the airtight space is not broken under the influence of heat.

Therefore, according to this embodiment described above, a GaN crystal is grown on the seed substrate 2 immersed in the mixed melt 3 by reacting the nitrogen gas and the Na / Ga mixed melt 3 in a heated and pressurized atmosphere. A reaction vessel 10 to be operated, a heat insulating vessel 20 surrounding the outside of the reaction vessel 10, a pressure vessel 30 surrounding the outside of the heat insulating vessel 20, and a drive shaft 41 provided through the heat insulating vessel 20 and the pressure vessel 30 around the axis. A gallium nitride manufacturing apparatus 1 having a stirring device 40 that is rotated in a rotating manner to stir the mixed melt 3, and includes a shaft case 42 having an accommodation space S 1 that hermetically accommodates one end side of the drive shaft 41, and a heat insulating container The drive shaft 41 is extended between the pressure vessel 30 and the pressure vessel 30 in such a manner that the drive shaft 41 can expand and contract in the axial direction and eccentrically in a direction orthogonal to the axial direction, and the other end side of the drive shaft 41 formed in the heat insulating vessel 20 is inserted through the first. Hole 22 Even if there is a gap between the drive shaft 41 and the first hole portion 22 of the heat insulating container 20 by adopting the configuration of having the bellows pipe 53 that forms an airtight space connecting the accommodation space S1, Since the outflow destination from the gap is an airtight space connected to the housing space S1 of the shaft case 42, it is possible to prevent the high temperature gas from leaking from the inside of the heat insulating container 20 and uneven temperature distribution.
Therefore, in the present embodiment, the mixed melt 3 can be stirred while the temperature distribution in the heat insulating container 20 is kept uniform, and a large and high quality GaN crystal can be obtained.

  As mentioned above, although one Embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, while the stirring device 40 of the above embodiment has been described as stirring the mixed melt 3 with the stirring blade 52 provided at the tip of the drive shaft 41, the reaction vessel 10 itself as in another embodiment shown in FIG. The mixed melt 3 may be agitated by rotating it with the drive shaft 41. Even in this case, the first hole portion 22 and the second hole portion 31 are hermetically surrounded by the bellows pipe 53, and the airtight space is formed in cooperation with the housing space S1 of the shaft case 42. Can be prevented from flowing out.

(Example)
Hereinafter, a specific apparatus configuration of the gallium nitride manufacturing apparatus will be described with reference to the embodiment shown in FIG. 3A is a plan view of the stirring device 40, and FIG. 3B is an overall view of the gallium nitride manufacturing device 1. FIG. In the examples described below, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  The gallium nitride manufacturing apparatus 1 includes a reaction vessel 10 that holds a seed substrate 2 and a mixed melt 3, a heat insulating container 20 that surrounds the outside of the reaction vessel 10, a pressure vessel 30 that surrounds the outside of the heat insulating vessel 20, and a mixed melt. And a stirring device 40 for stirring 3.

  The reaction vessel 10 has a three-layer structure of a crucible 11, an inner vessel 12, and an outer vessel 13. In the crucible 11, a holder 14 for holding a plurality of seed substrates 2 is provided. The holder 14 is configured to hold the seed substrate 2 in an oblique posture and arrange a plurality of seed substrates 2 around the stirring blade 52 at equal intervals. A crucible removal jig 15 is provided between the crucible 11 and the inner container 12. The crucible removal jig 15 is provided so as to surround the crucible 11, and the crucible 11 is removed from the inner container 12 by pulling up the crucible removal jig 15. The outer container 13 has a lid shape that covers the four sides and the upper side of the inner container 12. The outer container 13 surrounds the inner container 12 in cooperation with the support surface of the support base 16 with which the opening edge abuts, and is configured to fix the inner container 12.

  A nitrogen gas supply port 17 is connected to the top of the outer container 13. The nitrogen gas supply port 17 is connected to a nitrogen gas supply device (not shown), and is configured to fill the inside of the outer container 13 with nitrogen gas. Nitrogen gas is supplied into the crucible 11 through a gap formed by inserting the drive shaft 41 through the crucible 11 and the inner container 12. Specifically, nitrogen gas flows through a gas flow path between the crucible 11 and the inner container 12 formed by a gap between the bearing sleeve 70A1 and the drive shaft 41. Similarly, nitrogen gas flows through a gas flow path between the inner container 12 and the outer container 13 formed by a gap between the bearing sleeve 70A2 and the drive shaft 41. Further, a nitrogen gas discharge port 18 for extracting excess nitrogen gas to the heat insulating container 20 side is connected to the top of the outer container 13.

  The heat insulating container 20 has a leg portion 23 fixed to the bottom of the pressure container 30. The support 16 is fixed on a support plate 24 that supports the bottom of the heat insulating container 20. The heat insulating container 20 includes a lid pressing mechanism 25 that urges the outer container 13 toward the support base 16. The lid pressing mechanism 25 is fixed on a top plate 26 fixed to the top of the heat insulating container 20. The lid pressing mechanism 25 includes a shaft 27 that has a spring mechanism on one end side and contacts the top of the outer container 13 on the other end side, and suppresses vibration and displacement of the reaction container 10 due to stirring. In addition, the hole formed in the heat insulating container 20 through which the shaft 27 is inserted is configured to communicate with an airtight space covered by a case 28 that houses a spring mechanism.

  A vacuum exhaust port 33 is connected to the side of the pressure vessel 30. The vacuum exhaust port 33 is connected to a vacuum pump (not shown). The top part of the pressure vessel 30 is integrally fixed to the top part of the heat insulating container 20 by the connecting tool 35, and the top part of the pressure vessel 30 and the top part of the heat insulating container 20 are configured to be integrally removable. ing. The space between the body portion and the top portion of the pressure vessel 30 is hermetically sealed by the sealing material 34.

  The other end side of the drive shaft 41 extending from the shaft case 42 is inserted through the layers of the pressure vessel 30, the heat insulation vessel 20, and the reaction vessel 10 to reach the mixed melt 3. The drive shaft 41 is configured such that the first drive shaft 41A and the second drive shaft 41B are engaged by the shaft coupling 60A, and the second drive shaft 41B and the third drive shaft 41C are engaged by the shaft coupling 60B. It is configured. The first drive shaft 41A is rotatably supported by the shaft case 42, the second drive shaft 41B is rotatably supported by a bearing 70C provided in the heat insulating container 20, and the third drive shaft 41C is a reaction It is rotatably supported by bearing sleeves 70A1, 70A2 and 70B provided in the container 10.

  The bellows tube 53 is configured to surround the drive shaft 41 between the heat insulating container 20 and the shaft case 42. One end of the bellows tube 53 is screwed to a fixture 29 that fixes the bearing 70C to the heat insulating container 20 to airtightly surround the first hole portion 22, and the other end fixes the shaft case 42 to the pressure vessel 30. The fixing device 36 is screwed to communicate with the accommodation space S1 (see FIG. 1) in an airtight manner. Therefore, an airtight space in which the bellows tube 53 and the accommodation space S1 communicate with each other is formed outside the first hole portion 22.

According to the embodiment described above, even if there is a gap between the drive shaft 41 and the first hole portion 22 of the heat insulating container 20, the airtight space where the outflow destination from the gap is connected to the housing space S <b> 1 of the shaft case 42. Therefore, it is possible to prevent the high temperature gas from leaking from the inside of the heat insulating container 20 and causing the temperature distribution to become non-uniform.
Therefore, the gallium nitride production apparatus 1 can produce a large and high quality GaN crystal by stirring the mixed melt 3 while keeping the temperature distribution in the heat insulating container 20 uniform.

  DESCRIPTION OF SYMBOLS 1 ... Gallium nitride manufacturing apparatus (crystal growth apparatus), 2 ... Seed substrate, 3 ... Mixed melt, 10 ... Reaction container, 20 ... Thermal insulation container, 22 ... 1st hole (hole), 30 ... Pressure vessel, 31 ... 2nd hole, 40 ... Stirring device, 41 ... Drive shaft, 42 ... Shaft case, 43 ... Rotation drive device, 44 ... Permanent magnet (magnetic body), 53 ... Bellows tube (expandable tube), S1 ... Storage space

Claims (5)

A reaction vessel for reacting a raw material gas and a melt in a heating and pressurizing atmosphere to grow crystals on a seed substrate immersed in the melt, a heat insulating vessel surrounding the reaction vessel, and A crystal growth apparatus comprising: a pressure vessel that surrounds the outside; and a stirring device that stirs the melt by rotating a drive shaft provided through the heat insulation vessel and the pressure vessel around the axis;
A shaft case having an accommodating space for hermetically accommodating one end side of the drive shaft;
At least between the heat insulating container and the pressure container, the drive shaft is enclosed in an expandable manner in the axial direction, and a hole portion through which the other end of the drive shaft formed in the heat insulating container is inserted is connected to the accommodating space. A crystal growth apparatus comprising: a telescopic tube that forms an airtight space. The pressure vessel has a second hole portion that is inserted through the other end side of the drive shaft and communicates with the accommodation space in an airtight manner,
2. The crystal growth according to claim 1, wherein the expansion tube hermetically surrounds the hole portion at one end side and hermetically surrounds the second hole portion at the other end side thereof to form the airtight space. apparatus.   2. The crystal growth apparatus according to claim 1, wherein the expansion tube hermetically surrounds the hole portion at one end side and forms the airtight space in airtight communication with the accommodation space at the other end side. .   The crystal growth apparatus according to any one of claims 1 to 3, wherein the telescopic tube is a bellows tube that is eccentric in a direction orthogonal to the axial direction. The stirring device
A magnetic body integrally provided on one end side of the drive shaft;
The crystal growth apparatus according to claim 1, further comprising: a rotation driving device that rotates the magnetic body around the axis by a magnetic action from the outside of the shaft case.

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