JP5494414B2 - Crystal growth equipment - Google Patents

Description

  The present invention relates to a crystal growth apparatus.

One method for producing gallium nitride (GaN), which is expected as a next-generation semiconductor material, is to immerse a seed substrate (seed crystal) in a Na / Ga melt at 800 ° C. to 900 ° C. in a high-pressure nitrogen atmosphere of several MPa. Then, a crystal growth method (so-called flux method) is known in which a GaN crystal is grown on the seed substrate.
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

By the way, in order to grow a crystal thickly on a larger seed substrate, a large amount of melt as a raw material is required. If it does so, it is necessary to make the liquid depth of a melt deeper than before. In order to promote crystal growth that thickens the rod-shaped seed crystal, it is necessary to place the rod-shaped seed crystal vertically in the reaction vessel. Similarly, it is necessary to increase the depth of the melt. is there.
However, when the depth of the melt is increased, there is a problem that the raw material gas that dissolves from the melt surface becomes difficult to reach the liquid bottom. In the above-described conventional stirring method, since the downward flow and the upward flow of the melt are mixed in the reaction vessel, it is difficult for the melt near the liquid surface to reach the liquid bottom.

  The present invention has been made in view of the above problems, and provides a crystal growth apparatus that can quickly reach the bottom of the melt in which the raw material gas dissolves to the bottom of the liquid and obtain large, high-quality crystals. Objective.

In order to solve the above-mentioned problems, the present invention is a crystal growth apparatus having a reaction vessel for growing a seed crystal immersed in the melt by reacting a raw material gas and the melt in a heated and pressurized atmosphere. Are disposed in the reaction vessel with a gap therebetween, and extend in the vertical direction in the melt, the upper end opening is separated from the liquid surface of the melt, and the lower end opening is A configuration is adopted in which a cylindrical member that is spaced apart from the bottom surface of the reaction vessel and a rotary blade that rotates relative to the reaction vessel to form a vertical flow of the melt are employed.
By adopting this configuration, in the present invention, when a cylindrical member is disposed with a gap inside the reaction vessel, the cylindrical member extends in the vertical direction, and thus extends in the vertical direction within the reaction vessel. Two melt flow paths can be formed on the inside and outside of the tubular member. Further, the upper end opening of the cylindrical member is separated from the liquid surface of the melt, and the one lower end opening is separated from the bottom surface of the reaction vessel. Distribution between the outside becomes possible. When the reaction vessel is provided with a rotating blade that rotates relative to each other and a vertical flow is given to the melt, the downward flow of the melt from the liquid surface to the liquid surface and the upward flow of the melt from the liquid surface to the liquid surface Circulate between the inside and the outside of the cylindrical member without mixing. For this reason, the raw material gas component dissolved in the melt at the liquid level is likely to reach the bottom of the melt quickly.

Moreover, in this invention, the structure that the said rotary blade is arrange | positioned inside the said cylindrical member is employ | adopted.
By adopting this configuration, in the present invention, the rotor blade is disposed inside the cylindrical member, so that the rotor blade is disposed between the liquid surface and the liquid bottom more efficiently than when the rotor blade is disposed outside the cylindrical member. A circulating flow of the melt can be formed.

In the present invention, a configuration is adopted in which a rectifying plate that cancels at least a part of the swirling component included in the vertical flow formed by the rotary blades is provided inside the cylindrical member. .
By adopting this configuration, the present invention can form a uniform melt flow in the vertical direction inside the cylindrical member.

In the present invention, the current plate is arranged between the rotor blade and the seed crystal.
By adopting this configuration, in the present invention, a uniform vertical melt flow can be supplied to the seed crystal inside the cylindrical member.

According to the present invention, there is provided a crystal growth apparatus having a reaction vessel for growing a seed crystal immersed in the melt by reacting a raw material gas with a melt under a heating and pressurizing atmosphere. With a gap in between, and extending in the vertical direction in the melt, the upper end opening is separated from the liquid level of the melt, and the lower end opening is separated from the bottom of the reaction vessel. By adopting a configuration that includes a cylindrical member that is spaced apart from each other and a rotary blade that rotates relative to the reaction vessel to form a vertical flow of the melt, a gap is formed inside the reaction vessel. When the cylindrical member is arranged with the gap opened, the cylindrical member extends in the vertical direction, so that two melt flow paths extending in the vertical direction in the reaction vessel can be formed inside and outside the cylindrical member. it can. Further, the upper end opening of the cylindrical member is separated from the liquid surface of the melt, and the one lower end opening is separated from the bottom surface of the reaction vessel. Distribution between the outside becomes possible. When the reaction vessel is provided with a rotating blade that rotates relative to each other and a vertical flow is given to the melt, the downward flow of the melt from the liquid surface to the liquid surface and the upward flow of the melt from the liquid surface to the liquid surface Circulate between the inside and the outside of the cylindrical member without mixing. For this reason, the raw material gas component dissolved in the melt at the liquid level is likely to reach the bottom of the melt quickly.
Therefore, in the present invention, a large-sized and high-quality crystal can be obtained by quickly reaching the bottom of the melt near the liquid surface where the raw material gas dissolves.

It is a block diagram which shows the gallium nitride manufacturing apparatus in 1st 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 block diagram which shows the gallium nitride manufacturing apparatus in 2nd Embodiment of this invention. It is a plane sectional view of the reaction container in a 2nd embodiment of the present 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.

(First embodiment)
FIG. 1 is a configuration diagram showing a gallium nitride manufacturing apparatus 1 according to the first embodiment of the present invention.
The gallium nitride manufacturing apparatus 1 grows and manufactures a GaN crystal on a seed substrate (seed crystal) 2 by a flux method, and a reaction vessel (crucible) 10 holding the seed substrate 2 and the mixed melt 3, a reaction The heat insulating container 20 that surrounds the outside of the container 10, the pressure container 30 that surrounds the outside of the heat insulating container 20, and the stirring device 40 that stirs the mixed melt 3.
The side portions of the reaction vessel 10, the heat insulating vessel 20, and the pressure vessel 30 are set in a concentric cylindrical shape, and the posture is set so that the cylindrical axis is in the vertical direction.

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 ) as a raw material for the GaN crystal from the outside, so that the reaction vessel 10 is filled with nitrogen gas. It has become.

  The reaction vessel 10 is provided with a cylindrical member 11. The cylindrical member 11 is formed from a heat-resistant metal material or ceramic material. The cylindrical member 11 has a cylindrical shape having a smaller diameter than the reaction vessel 10 and is fixed to the reaction vessel 10 via the legs 11 a so that the axial center thereof coincides with the axial center of the reaction vessel 10. . A plurality of leg portions 11 a are provided along the edge of the lower end opening 13 of the cylindrical member 11 at a predetermined interval in the circumferential direction.

The cylindrical member 11 is disposed with a gap inside the reaction vessel 10 and extends in the vertical direction in the mixed melt 3. The cylindrical member 11 has a vertical flow path of the mixed melt 3 formed on the inner side thereof and a vertical direction of the mixed melt 3 formed on the outer side (annular space between the reaction vessel 10 and the cylindrical member 11). The directional flow path is partitioned in the mixed melt 3.
The upper end opening 12 of the cylindrical member 11 is disposed so as to be separated from the liquid surface 4 of the mixed melt 3, and the mixed melt 3 is between the inner side and the outer side of the cylindrical member 11 in the vicinity of the liquid surface 4. It can be distributed. Further, the lower end opening 13 of the cylindrical member 11 is disposed away from the bottom surface 10a of the reaction vessel 10, and the mixed melt 3 flows between the inside and the outside of the cylindrical member 11 in the vicinity of the bottom surface 10a. It can be configured.

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 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 mounted on 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 formed of a non-magnetic stainless steel material and is airtightly fixed to the pressure vessel 30. The drive shaft 41 is also formed from a stainless steel material.

  The rotation drive device 43 includes an outer cylinder 48 that includes a plurality of permanent magnets 47 at predetermined intervals in the circumferential direction of the inner circumferential 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 includes a stirring blade (rotary blade) 52 at the tip end on the other end side, and the stirring blade 52 rotates around the axis in the mixed melt 3 so that the mixed melt 3 flows in the vertical direction. (In this embodiment, a downward flow) is formed. The stirring blade 52 of the present embodiment has a screw propeller shape that can rotate inside the cylindrical member 11.
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 insulation 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 insulation container 20 is referred to as a first hole portion 22 and the insertion hole of the pressure vessel 30 is referred to as a second hole portion 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. According to this structure, the outflow of the high temperature gas from the heat insulation container 20 can be suppressed.

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, and the drive shaft 41 having the stirring blades 52 is rotated around the axis by magnetic action. When the drive shaft 41 rotates around the axis, the stirring blade 52 rotates relative to the reaction vessel 10, and a downward flow of the mixed melt 3 is formed inside the cylindrical member 11. The downward flow of the mixed melt 3 flows inside the cylindrical member 11 and flows out from the lower end opening 13 toward the bottom surface 10a.

  The mixed melt 3 that flows out from the lower end opening 13 and reaches the vicinity of the bottom surface 10 a flows out from the inside of the cylindrical member 11 to the outside through the gap between the lower end opening 13 and the bottom surface 10 a and rises outside the cylindrical member 11. It reaches the vicinity of the liquid level 4 as a flow. The mixed melt 3 that has reached the vicinity of the liquid surface 4 takes in a nitrogen component in the vicinity of the liquid surface 4, and then flows into the cylinder member 11 from the upper end opening 12. Then, the mixed melt 3 in which the nitrogen component has been taken up and the nitrogen concentration has increased becomes a downward flow again by the stirring blade 52 inside the cylindrical member 11 and flows out from the lower end opening 13 toward the bottom surface 10a.

  In this way, the downward flow of the mixed melt 3 from the liquid surface 4 toward the bottom surface 10a and the upward flow of the mixed melt 3 from the bottom surface 10a toward the liquid surface 4 are not mixed, and the inside of the cylindrical member 11 Since it circulates between the outside and the outside, the nitrogen component dissolved in the mixed melt 3 near the liquid surface 4 quickly reaches the vicinity of the bottom surface 10 a of the reaction vessel 10. Therefore, a large and high quality GaN crystal can be grown on the seed substrate 2 at high speed.

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 disposed, which is disposed inside the reaction vessel 10 with a gap, extends in the vertical direction in the mixed melt 3, and has an upper end opening 12 in the mixed melt. 3 is separated from the liquid surface 4 and the lower end opening portion 13 is separated from the bottom surface 10a of the reaction vessel 10 and the reaction vessel 10 is rotated relatively to the mixed melt 3 When the cylindrical member 11 is arranged with a gap inside the reaction vessel 10 by adopting a configuration having a stirring blade 52 that forms a vertical flow of the cylindrical member 11, the cylindrical member 11 extends in the vertical direction. The reaction vessel 10 The flow path of the two melt mixture 3 extending in the vertical direction can be formed inside and outside of the cylindrical member 11 at. Further, the upper end opening 12 of the cylindrical member 11 is separated from the liquid surface 4 of the mixed melt 3, and the one lower end opening 13 is separated from the bottom surface 10 a of the reaction vessel 10. Distribution between the inner side and the outer side of the mixed melt 3 is enabled at the lower end of the upper end. When a relatively rotating stirring blade 52 is provided in the reaction vessel 10 and a vertical flow is applied to the mixed melt 3, a downward flow of the mixed melt 3 from the liquid level 4 toward the liquid bottom, and a liquid level from the liquid bottom to the liquid level. The upward flow of the mixed melt 3 toward 4 circulates between the inside and the outside of the cylindrical member 11 without being mixed. For this reason, the nitrogen gas component dissolved in the mixed melt 3 at the liquid level 4 easily reaches the liquid bottom of the mixed melt 3 quickly.
Therefore, in the present embodiment, a large and high-quality crystal can be obtained by quickly reaching the bottom of the melt near the liquid surface 4 where the nitrogen gas dissolves.

  In the above-described embodiment, the configuration in which the stirring blade 52 is disposed inside the cylindrical member 11 has been described. However, as illustrated in FIG. 2, the stirring blade 52 is disposed outside the cylindrical member 11 (the reaction vessel 10 and the cylindrical member 11). It may be arranged in an annular space between the two. In this case, in order to form the vertical flow (in FIG. 2, the upward flow) of the mixed melt 3 outside the cylindrical member 11 evenly, the stirring blade 52 is formed between the reaction vessel 10 and the cylindrical member 11. It is preferable to arrange a plurality of the annular spaces with a space therebetween. However, since the number of the agitating blades 52 is increased and each of them needs to be controlled to rotate synchronously, the configuration in which the agitating blades 52 are arranged inside the cylindrical member 11 as in the present embodiment is more costly. Therefore, the circulating flow of the mixed melt 3 between the liquid surface 4 and the liquid bottom can be efficiently formed both in terms of control and control.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.
FIG. 3 is a configuration diagram showing a gallium nitride manufacturing apparatus 1 according to the second embodiment of the present invention.
As shown in the figure, in the second embodiment, the rectifying plate 14 that cancels at least a part of the swirling component included in the vertical flow of the mixed melt 3 formed by the stirring blade 52 is provided inside the cylindrical member 11. It differs from the above embodiment in that it is provided.

FIG. 4 is a cross-sectional plan view of the reaction vessel 10 in the second embodiment of the present invention.
First, the structure of the baffle plate 14a shown to Fig.4 (a) is demonstrated.
The rectifying plate 14 a has a plurality of plate members 15 that extend radially from the axis of the cylindrical member 11 at intervals. The plate member 15 extends a predetermined length in the vertical direction. According to this configuration, the swirl component included in the vertical flow of the mixed melt 3 formed by the stirring blades 52 collides with the plate surface of each plate member 15 and cancels out when passing through the rectifying plate 14a. Therefore, a uniform flow of the mixed melt 3 in the vertical direction can be formed inside the cylindrical member 11.

Next, the structure of the baffle plate 14b shown in FIG.4 (b) is demonstrated.
The rectifying plate 14 b includes a plurality of plate members 15 that extend radially from the axis of the cylinder member 11 and a plurality of cylinder members (second cylinder members) 16 that are filled between adjacent plate members 15. And have. The cylindrical member 16 extends a predetermined length in the vertical direction. According to this configuration, the swirl component included in the vertical flow of the mixed melt 3 formed by the stirring blade 52 collides with each inner surface of the cylindrical member 16 and is canceled when passing through the rectifying plate 14b. Therefore, a uniform vertical melt flow can be formed inside the cylindrical member 11. Moreover, since the flow of the mixed melt 3 in the vertical direction can be subdivided by the plurality of cylindrical members 16 in the rectifying plate 14b, the flow of the mixed melt 3 in the vertical direction is more uniform inside the cylindrical member 11. Can be formed. It should be noted that the same effect can be obtained even if the tubular member 16 is formed in a hexagonal tubular shape instead of a cylindrical shape to form a honeycomb structure.

  The rectifying plate 14 is supported inside the cylindrical member 11. The rectifying plate 14 is disposed between the stirring blade 52 and the seed substrate 2. Therefore, according to the second embodiment described above, the mixed melt 3 in which the nitrogen concentration is increased by taking in the nitrogen component in the vicinity of the liquid surface 4 becomes a uniform vertical flow inside the cylindrical member 11, Since the seed substrate 2 is sequentially supplied, a large and high-quality GaN crystal can be grown on the seed substrate 2 at a high speed.

  As mentioned above, although preferred 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, in the above-described embodiment, the form in which the seed crystal is formed in a substrate shape has been described.

  DESCRIPTION OF SYMBOLS 1 ... Gallium nitride manufacturing apparatus (crystal growth apparatus), 2 ... Seed substrate (seed crystal), 3 ... Mixed melt (melt), 4 ... Liquid surface, 10 ... Reaction container, 10a ... Bottom surface, 11 ... Cylindrical member, 12 ... upper end opening, 13 ... lower end opening, 14 ... current plate, 52 ... stirring blade (rotary blade)

Claims (4)

A crystal growth apparatus having a reaction vessel for growing a seed crystal immersed in the melt by reacting a raw material gas and the melt under a heating and pressurizing atmosphere,
The reaction vessel is disposed inside the reaction vessel with a gap, extends in the vertical direction in the melt, the upper end opening is separated from the liquid surface of the melt, and the lower end opening is the reaction. A cylindrical member spaced from the bottom surface of the container;
A crystal growth apparatus comprising: a rotating blade that rotates relative to the reaction vessel to form a vertical flow of the melt.   The crystal growth apparatus according to claim 1, wherein the rotary blade is disposed inside the cylindrical member.   3. The crystal according to claim 2, wherein a rectifying plate that cancels at least a part of a swirling component included in the vertical flow formed by the rotor blades is provided inside the cylindrical member. Growth equipment.   The crystal growth apparatus according to claim 3, wherein the rectifying plate is disposed between the rotary blade and the seed crystal.

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