JP5447014B2 - 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. When a stirrer is provided in this configuration, it is necessary to form a hole through which the rotary drive shaft for stirring is inserted in the reaction vessel. Then, since the inside of the reaction vessel is at a high temperature and the drive shaft is driven to rotate, it is difficult to seal the hole with a gas seal material or the like, and a high temperature is generated from the gap formed between the hole and the drive shaft. Gas leaks and the temperature distribution in the reaction vessel becomes non-uniform, or impurities (for example, components such as binders contained in the heat insulating material of the heat insulation vessel become outgas) enter the reaction vessel through the gap. Or the evaporated flux (Na) leaks out of the reaction vessel to the outside, so that the melt component and the ratio of Na / Ga in the reaction vessel may change.

  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 the melt while keeping the reaction vessel airtight, and obtains large, 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. A crystal growth apparatus having a stirring device for driving the drive shaft provided through the container and stirring the melt, wherein the stirring device drives the drive shaft to move linearly in the axial direction. The reaction vessel is extendable in the axial direction, one end portion is hermetically fixed to the drive shaft, and the other end portion hermetically surrounds a hole through which the drive shaft is formed in the reaction vessel. The structure which has the expansion-contraction pipe | tube currently fixed to is employ | adopted.
By adopting this configuration, in the present invention, when the drive shaft is linearly driven in the axial direction, the telescopic tube expands and contracts along with the linear drive, so that one end of the telescopic tube is rubbed or the like. Without being airtightly fixed to the drive shaft. And since the other end of the telescopic tube is fixed to the reaction vessel so as to hermetically surround the hole through which the drive shaft is inserted, even if there is a gap between the drive shaft and the hole, Since the tip communicates with the airtight space formed by hermetically fixing the drive shaft and one end of the telescopic tube, leakage of high-temperature gas and mixing of impurities through the hole is prevented.

In the present invention, the drive device includes an urging member that applies an urging force toward one side in the axial direction with respect to the drive shaft, and the other side in the axial direction against the urging force. The structure which has a cylinder mechanism to which it moves toward is employ | adopted.
By adopting this configuration, in the present invention, since the drive shaft is urged to one side in the axial direction by the urging member, the cylinder mechanism appropriately applies a force against the urging force to the other side in the axial direction. As a result, the linear motion drive in the axial direction of the drive shaft becomes possible.

Further, in the present invention, a configuration is adopted in which the urging member is the telescopic tube.
By adopting this configuration, in the present invention, the restoring force of the expansion / contraction tube that deforms as the drive shaft is driven linearly is used as the urging force, so that the urging member and the expansion / contraction tube can be used in common. Can be reduced.

In the present invention, the cylinder mechanism has a contact portion that contacts the drive shaft, and the contact portion has a tapered shape.
By adopting this configuration, in the present invention, it is possible to reduce the area that comes into contact with the drive shaft that is exposed to a high-temperature atmosphere and reduce heat loss through the cylinder mechanism due to heat transfer.

Moreover, in this invention, the structure of having a pressure control apparatus which adjusts the pressure in the said reaction container according to the expansion-contraction of the said expansion-contraction tube accompanying the linear drive of the said drive shaft is employ | adopted.
By adopting this configuration, in the present invention, when the telescopic tube expands and contracts with the direct drive of the drive shaft, the volume in the reaction vessel changes and the pressure changes, so the pressure change device adjusts the pressure change. To do.

Further, in the present invention, the pressure adjusting device forms a second hole portion penetrating the reaction vessel separately from the hole portion, and an airtight space that hermetically surrounds the second hole portion. And a second telescopic tube that expands and contracts according to the pressure change in the reaction vessel.
By adopting this configuration, in the present invention, when the expansion and contraction tube expands and contracts in accordance with the direct drive of the drive shaft, the pressure in the reaction vessel changes, but the second expansion and contraction tube expands and contracts according to the pressure change. Since the pressure in the reaction vessel is kept constant, the pressure change in the reaction vessel can be suppressed.

In the present invention, the reaction container has a baffle plate that forms a stirring flow in a predetermined direction in the melt as the drive shaft is linearly driven.
By adopting this configuration, in the present invention, the stirring efficiency of the melt accompanying the direct drive of the drive shaft can be increased by the action of the baffle plate.

According to the present invention, 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, and the reaction vessel are inserted and provided. A crystal growth apparatus having a stirring device for driving the drive shaft to stir the melt, wherein the stirring device is a drive device for linearly driving the drive shaft in the axial direction, and extending and contracting in the axial direction. A telescopic tube having one end portion fixed to the drive shaft in an airtight manner and the other end portion hermetically surrounding a hole through which the drive shaft formed in the reaction vessel is inserted and fixed to the reaction vessel. When the drive shaft is linearly driven in the axial direction by adopting the configuration of having, the expansion and contraction tube expands and contracts along with the linear drive, so that one end portion of the expansion and contraction tube is rubbed. Without being airtightly fixed to the drive shaft. And since the other end of the telescopic tube is fixed to the reaction vessel so as to hermetically surround the hole through which the drive shaft is inserted, even if there is a gap between the drive shaft and the hole, Since the tip communicates with the airtight space formed by hermetically fixing the drive shaft and one end of the telescopic tube, leakage of high-temperature gas and mixing of impurities through the hole is prevented.
Therefore, in the present invention, the melt can be agitated while maintaining the airtightness of the reaction vessel, and a large and high quality crystal can be obtained.

It is a section lineblock diagram showing the gallium nitride manufacturing device in the embodiment of the present invention. It is a cross-sectional block diagram which shows the gallium nitride manufacturing apparatus in another embodiment 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 cross-sectional configuration diagram illustrating 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 10 holding the seed substrate 2 and the mixed melt 3 and the heat insulation surrounding the outside of the reaction vessel 10. The container 20, the pressure vessel 30 that surrounds the outside of the heat insulation vessel 20, the stirring device 40 that stirs the mixed melt 3, and the nitrogen gas (N as a raw material for GaN crystals) inside the reaction vessel 10 and inside the pressure vessel 30 ₂ ) and a pressure adjusting device 50 for adjusting the internal pressure. The side portions of the reaction vessel 10, the heat insulation vessel 20, and the pressure vessel 30 are set in a concentric cylindrical shape, and the posture is set so that the central axis of the cylindrical shape is in the vertical direction.

  The reaction vessel 10 of the present embodiment has a two-layer structure of a ceramic crucible 11 that contains a mixed melt 3 made of Na / Ga and a metal outer vessel 12 that surrounds the outside of the crucible 11. . The crucible 11 has a configuration in which the seed substrate 2 is placed on the bottom and immersed in the mixed melt 3 inside. Moreover, the crucible 11 has a cylindrical baffle plate 13 disposed so as to surround the seed substrate 2. The baffle plate 13 is provided at a predetermined height with a gap between the baffle 11 and the bottom of the crucible 11 by the legs 13a.

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 side and bottom of the reaction container 10.
The pressure vessel 30 is composed of a vacuum vessel whose shape is set in a substantially cylindrical shape so that it can withstand the pressure even when the pressure state changes. The pressure vessel 30 is connected to a vacuum exhaust port (not shown) that evacuates the internal air.

The stirring device 40 has a drive shaft 41 provided through the reaction vessel 10.
One end of the drive shaft 41 in the axial direction is configured to pass through the hole 12 a formed in the outer container 12 and the hole 11 a formed in the crucible 11 and reach the mixed melt 3. The drive shaft 41 includes a stirring body 42 at the tip of one axial end portion thereof. The stirrer 42 has a substantially disk shape that is larger than the diameter of the drive shaft 41 and smaller than the inner diameter of the baffle plate 13.
On the other hand, the other axial end of the drive shaft 41 is arranged outside the reaction vessel 10. The drive shaft 41 includes a flange portion 43 at the tip of the other axial end portion. The flange portion 43 has a substantially disc shape whose diameter is larger than the diameters of the drive shaft 41 and the hole portion 12a.

The agitator 40 has a bellows tube (expandable tube) 44 that surrounds the other axial end of the drive shaft 41.
The bellows tube 44 is configured to be able to expand and contract in the axial direction surrounding the drive shaft 41, and one end thereof is airtightly fixed to the flange portion 43 of the drive shaft 41, and the other end airtightly connects the hole portion 12a. It is enclosed and fixed to the outer container 12. For this reason, the outside of the hole portion 12a communicates with an airtight space formed by the bellows tube 44 and the flange portion 43 being airtightly fixed. The bellows tube 44 of this embodiment is formed of a heat-resistant metal material (for example, a stainless steel material, a nickel-based heat-resistant alloy such as Inconel Hastelloy (trade name)), and when it is contracted and deformed, its restoring force It is the structure which functions also as an urging member which expresses the force (urging force) which lifts the drive shaft 41 upward. Incidentally, the urging member may be provided separately without being replaced with the bellows tube 44.

The stirring device 40 includes a drive device 45 that drives the drive shaft 41 to move linearly in the axial direction. The drive device 45 includes a cylinder mechanism 48 that includes a cylinder rod (contact portion) 46 that contacts the flange portion 43 of the drive shaft 41 in the axial direction and a drive portion 47 that drives the cylinder rod 46 to move linearly.
The drive unit 47 is provided such that its case is hermetically tightly fixed to the outside of the pressure vessel 30. The drive unit 47 of the present embodiment has a configuration in which, for example, a drive source such as a motor or a solenoid is provided therein, and the cylinder rod 46 is driven to move linearly. The cylinder rod 46 is configured to pass through the hole 30 a formed in the pressure vessel 30 and the hole 20 a formed in the heat insulating container 20 and abut on the flange 43 of the drive shaft 41. The tip end portion of the cylinder rod 46 has a tapered shape and is configured to be in substantially point contact with the flange portion 43. According to this configuration, it is possible to reduce the contact area that comes into contact with the drive shaft 41 exposed to a high temperature atmosphere and reduce heat loss through the cylinder mechanism 48 due to heat transfer.

The pressure adjusting device 50 includes a nitrogen gas supply port 51A that introduces nitrogen gas into the reaction vessel 10 and a nitrogen gas supply port 51B that introduces nitrogen gas into the pressure vessel 30.
The nitrogen gas supply port 51A is connected to the outer vessel 12 of the reaction vessel 10, and the nitrogen gas supplied to the outer vessel 12 is supplied into the crucible 11 through the hole 11a and the like. Yes. Further, the nitrogen gas supply port 51B is connected to the pressure vessel 30, and the nitrogen gas supplied to the pressure vessel 30 is configured to be supplied into the heat insulation vessel 20 through the hole 20a and the like. . The pressure adjusting device 50 is configured to control the supply amount of nitrogen gas so that the internal pressure of the reaction vessel 10 and the external pressure of the reaction vessel 10 become the same pressure.

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 otherwise indicated, the said control part controls the following operation | movement as a main body.
First, the air inside the pressure vessel 30 is evacuated from an unillustrated evacuation port. After the vacuum state is reached, nitrogen gas is supplied from the nitrogen gas supply ports 51A and 51B, 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. This agitation is performed by driving the drive shaft 41 linearly in the axial direction by the drive device 45.
More specifically, when the cylinder mechanism 48 is driven, the cylinder rod 46 that is in contact with the flange portion 43 is moved downward and the drive shaft 41 is pushed down, the stirrer 42 causes the mixed melt 3 in the baffle plate 13 to move. Push down to form a stirring stream. In this stirring flow, after the mixed melt 3 pushed downward by the stirring body 42 passes through the gap of the leg portion 13a and comes to the outside of the baffle plate 13, it rises outside the baffle plate 13 and then again the baffle plate 13 It is formed by circulating so as to enter inside.
On the other hand, when the cylinder mechanism 48 is driven and the push-down of the drive shaft 41 by the cylinder rod 46 is released, the drive shaft 41 is moved upward by the restoring force (biasing force) of the bellows pipe 44 contracted and deformed when pushed down. Moving. Accordingly, the stirring body 42 pushes up the mixed melt 3 in the baffle plate 13 upward to form a stirring flow. In this stirring flow, after the mixed melt 3 pushed upward by the stirring body 42 comes out from the upper opening edge of the baffle plate 13, it descends outside the baffle plate 13 and enters the baffle plate 13 again. It is formed by distributing like.
In the present embodiment, the switch of the cylinder mechanism 48 and the release of the push down are switched in a predetermined cycle as described above, so that the drive shaft 41 is linearly driven in the axial direction and the mixed melt 3 is stirred.

The bellows tube 44 expands and contracts with the linear drive of the drive shaft 41 to prevent leakage of high temperature gas from the reaction vessel 10 and mixing of impurities through the hole 12a.
More specifically, since the bellows tube 44 is extendable in the axial direction, even if the drive shaft 41 is linearly driven in the axial direction, the bellows tube 44 expands and contracts in accordance with the linear drive. One end of the tube 44 is airtightly fixed to the drive shaft 41 without rubbing. The other end of the bellows tube 44 is fixed to the outer container 12 so as to airtightly surround the hole 12a through which the drive shaft 41 is inserted, so that there is a gap between the drive shaft 41 and the hole 12a. However, since the tip of the gap communicates with the airtight space formed by airtightly fixing the drive shaft 41 and one end of the bellows tube 44, high temperature gas leakage through the hole 12a, Impurities are prevented from being mixed. In addition, since the inside of the reaction vessel 10 is kept airtight by the bellows tube 44, the holes 12a and the holes are formed during the assembly until the reaction vessel 10 is installed in the pressure vessel 30 and the heat insulation vessel 20. There is no possibility of contamination of the mixed melt 3 via 11a.
When the bellows tube 44 expands and contracts as the drive shaft 41 is linearly driven, the volume in the reaction vessel 10 changes, and the internal pressure changes accordingly. The pressure adjusting device 50 changes the nitrogen in response to this pressure change. By controlling the gas supply amount, the internal pressure of the reaction vessel 10 is kept constant.

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 gallium nitride production apparatus 1 having a reaction vessel 10 to be driven and a stirring device 40 that drives a drive shaft 41 provided through the reaction vessel 10 and stirs the mixed melt 3. A drive device 45 that linearly drives the drive shaft 41 in the axial direction, and a drive shaft that is extendable in the axial direction, one end of which is hermetically fixed to the drive shaft 41 and the other end formed in the reaction vessel 10. When the drive shaft 41 is linearly driven in the axial direction by adopting a structure in which the hole 12a through which the tube 41 is inserted is hermetically surrounded and fixed to the reaction vessel 10, the bellows tube 44 is its linear motion Because stretch with the movement, one end of the bellows tube 44 is hermetically fixed to the drive shaft 41 without Kosudo like. The other end of the bellows tube 44 is fixed to the reaction vessel 10 so as to airtightly surround the hole 12a through which the drive shaft 41 is inserted, so that there is a gap between the drive shaft 41 and the hole 12a. However, since the tip of the gap communicates with the airtight space formed by airtightly fixing the drive shaft 41 and one end of the bellows tube 44, high temperature gas leakage through the hole 12a, Impurities are prevented from being mixed.
Therefore, in this embodiment, the melt can be agitated while maintaining the airtightness of the reaction vessel 10 to obtain large-sized and high-quality crystals.

  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, the shapes of the stirrer 42 and the baffle plate 13 are not limited to the shapes in the above-described embodiment, and are appropriately changed according to the required stirring flow.
For example, as in another embodiment shown in FIG. 2, the stirring body 42 provided on the drive shaft 41 may have a substantially ring shape disposed between the crucible 11 and the baffle plate 13. The stirrer 42 has a streamlined shape having an upper portion of a plane and a lower portion having an acute angle. Since the stirrer 42 has a stronger flow when the stirrer 42 is lifted, a downward flow toward the seed substrate 2 in the central portion. Can be made dominant.

Further, for example, in the above embodiment, it has been described that the change in the internal pressure of the reaction vessel 10 due to the expansion and contraction of the bellows tube 44 is controlled by controlling the supply amount of nitrogen gas, but the present invention is limited to this configuration. Instead, as in another embodiment shown in FIG. 2, the pressure may be adjusted by providing an internal pressure adjusting bellows tube 60 (second telescopic tube).
The bellows tube 60 is configured to hermetically surround a hole (second hole) 12b provided penetrating the outer container 12 to form an airtight space, and to expand and contract in accordance with a pressure change in the reaction container 10. It has become. According to this configuration, when the bellows tube 44 expands and contracts with the direct drive of the drive shaft 41, the bellows tube 60 expands and contracts according to the pressure change, and the pressure (volume) in the reaction vessel 10 is made constant. The pressure change in the reaction vessel 10 can be prevented.

  DESCRIPTION OF SYMBOLS 1 ... Gallium nitride manufacturing apparatus (crystal growth apparatus), 2 ... Seed substrate, 3 ... Mixed melt, 10 ... Reaction container, 12a ... Hole part, 12b ... Hole part (2nd hole part), 13 ... Baffle plate, DESCRIPTION OF SYMBOLS 40 ... Stirring device, 41 ... Drive shaft, 44 ... Bellows tube (expandable tube, urging member), 45 ... Drive device, 46 ... Cylinder rod (contact part), 50 ... Pressure adjusting device, 60 ... Bellows tube (first) 2 telescopic tube)

Claims (6)

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; and a drive shaft provided through the reaction vessel is driven. A crystal growth device having a stirring device for stirring the melt,
The stirring device
A drive device for linearly driving the drive shaft in the axial direction;
It is extendable in the axial direction, one end is fixed to the drive shaft in an airtight manner, and the other end is fixed to the reaction vessel by airtightly surrounding a hole formed in the reaction vessel through which the drive shaft is inserted. have a, and the expansion pipe, which is,
The driving device includes:
A biasing member that applies a biasing force toward one side in the axial direction with respect to the drive shaft;
A cylinder mechanism that moves the drive shaft toward the other side in the axial direction against the biasing force, and
The crystal growth apparatus according to claim 1, wherein the cylinder mechanism has a tapered tapered contact portion that contacts the drive shaft . The crystal growth apparatus according to claim 1 , wherein the biasing member is the telescopic tube. 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; and a drive shaft provided through the reaction vessel is driven. A crystal growth device having a stirring device for stirring the melt,
The stirring device
A drive device for linearly driving the drive shaft in the axial direction;
It is extendable in the axial direction, one end is fixed to the drive shaft in an airtight manner, and the other end is fixed to the reaction vessel by airtightly surrounding a hole formed in the reaction vessel through which the drive shaft is inserted. A telescopic tube, and
A crystal growth apparatus, comprising: a pressure adjusting device that adjusts a pressure in the reaction vessel according to expansion and contraction of the expansion and contraction tube accompanying linear drive of the drive shaft. The pressure regulator is
A second hole provided through the reaction vessel separately from the hole;
4. The crystal growth according to claim 3 , further comprising: a second expansion tube that forms an airtight space that hermetically surrounds the second hole portion and expands and contracts according to a pressure change in the reaction vessel. apparatus. The said reaction container has a baffle plate which forms the stirring flow of a predetermined direction in the said melt with the linear drive of the said drive shaft, The crystal | crystallization as described in any one of Claims 1-4 characterized by the above-mentioned. Growth equipment. 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; and a drive shaft provided through the reaction vessel is driven. A crystal growth device having a stirring device for stirring the melt,
The stirring device
A drive device for linearly driving the drive shaft in the axial direction;
It is extendable in the axial direction, one end is fixed to the drive shaft in an airtight manner, and the other end is fixed to the reaction vessel by airtightly surrounding a hole formed in the reaction vessel through which the drive shaft is inserted. A telescopic tube, and
The crystal growth apparatus, wherein the reaction vessel has a cylindrical baffle plate that serves as a partition between an upward flow and a downward flow formed in the melt as the drive shaft is linearly driven.

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