JP5228286B2 - Crystal growth equipment - Google Patents

Description

The present invention relates to crystal growth equipment for crystal growth of III-nitride crystal.

  At present, most of InGaAlN (group III nitride semiconductor) -based devices used as ultraviolet, violet to blue to green light sources have sapphire and silicon carbide (SiC) as substrates, and MOCVD (organometallic) is formed on the substrate. Chemical vapor deposition) and MBE (molecular beam crystal growth) are used.

  Thus, when sapphire and silicon carbide are used as the substrate, the thermal expansion coefficient and the lattice constant are greatly different between the substrate and the group III nitride semiconductor, so that many crystal defects are present in the group III nitride semiconductor. Will be included. This crystal defect degrades device characteristics, and is directly related to defects such as short lifetime and high operating power in a light emitting device, for example.

  Further, since the sapphire substrate is an insulator, it has been impossible to take out the electrode from the substrate side like a conventional light emitting device. Thereby, it is necessary to take out the electrode from the group III nitride semiconductor side. As a result, there is a disadvantage that the area of the device is increased and the cost is increased. And when the area of a device becomes large, the new problem of the curvature of a board | substrate accompanying the combination of a dissimilar material called a sapphire substrate and a group III nitride semiconductor will generate | occur | produce.

  Further, the group III nitride semiconductor device fabricated on the sapphire substrate is difficult to separate by chip cleavage, and it is not easy to obtain a resonator end face required in a laser diode (LD). Therefore, at present, the end face of the resonator is formed by dry etching or separating the sapphire substrate into a shape close to cleavage after polishing to a thickness of 100 μm or less. Therefore, unlike the conventional LD, it is difficult to perform the formation of the resonator end face and the chip separation in a single process, resulting in high costs due to the complicated process.

  In order to solve these problems, it has been proposed to reduce crystal defects by devising such as selectively growing a group III nitride semiconductor in a lateral direction on a sapphire substrate. This makes it possible to reduce crystal defects, but the problems relating to the insulating properties of the sapphire substrate and the aforementioned difficulty of cleavage still remain.

  In order to solve these problems, a gallium nitride (GaN) substrate that is the same as the material for crystal growth on the substrate is optimal. Therefore, various methods for crystal growth of bulk GaN by vapor phase growth and melt growth have been proposed. However, a GaN substrate having a high quality and a practical size has not been realized yet.

As one method for realizing a GaN substrate, a GaN crystal growth method using sodium (Na) as a flux has been proposed (Patent Document 1). In this method, sodium azide (NaN ₃ ) and metallic Ga are used as raw materials, and NaN ₃ and metallic Ga are placed in a nitrogen atmosphere in a stainless steel reaction vessel (inner dimensions: inner diameter = 7.5 mm, length = 100 mm). The GaN crystal grows by encapsulating the reaction vessel and holding the reaction vessel at a temperature of 600 to 800 ° C. for 24 to 100 hours.

This method is characterized in that crystal growth is possible at a relatively low temperature of 600 to 800 ° C., and the pressure in the container is relatively low at about 100 kg / cm ² at most, which is a practical growth condition.

Recently, a high-quality group III nitride crystal has been realized by reacting a mixed melt of an alkali metal and a group III metal with a group V raw material containing nitrogen (Patent Document 2).
US Pat. No. 5,868,837 JP 2001-58900 A

  However, in a conventional crystal growth apparatus for crystal growth of GaN crystals, the mixing ratio of metal Na and metal Ga, the gas pressure of nitrogen gas as the nitrogen source, and the temperature of the mixed melt of metal Na and metal Ga are GaN. This is the main condition for crystal growth, and it has been difficult to grow a GaN crystal by controlling the mixing ratio, gas pressure and temperature.

  Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide a crystal growth apparatus for growing a group III nitride crystal by controlling the mixing ratio, gas pressure and temperature. It is.

According to this invention, the pressure and temperature are determined according to the mixing ratio indicating the quantitative ratio of the alkali metal to the total amount of the alkali metal and the group III metal, and when the group III nitride crystal is grown or dissolved. Is a crystal growth apparatus for growing a group III nitride crystal using a pressure / temperature correlation diagram that defines the relationship between and a mixed melt containing an alkali metal and a group III metal at a predetermined mixing ratio. A crucible, a gas supply device that supplies a nitrogen source gas to a container space in contact with the mixed melt in the crucible and sets the gas pressure in the container space to a predetermined pressure, and sets the temperature of the mixed melt to a predetermined temperature A desired pressure and a desired pressure included in a predetermined pressure / temperature correlation diagram determined according to the predetermined mixing ratio from a plurality of pressure / temperature correlation diagrams provided corresponding to the heating device and the plurality of mixing ratios. Said volume to temperature A control device that controls the gas supply device and the heating device so as to set the gas pressure of the nitrogen source gas in the space and the temperature of the mixed melt, respectively, and a plurality of pressure / temperature correlation diagrams are obtained from the seed crystal. FIG. 5 is a pressure / temperature correlation diagram suitable for crystal growth of a group III nitride crystal and a group III nitride crystal having a columnar shape, and a first pressure / determined according to a first mixing ratio; FIG. 4 is a temperature correlation diagram and a pressure / temperature correlation diagram suitable for crystal growth of a group III nitride crystal having a plate shape, and is determined according to a second mixing ratio larger than the first mixing ratio. 2 is a pressure / temperature correlation diagram of 2 and a pressure / temperature correlation diagram suitable for crystal growth of a group III nitride crystal from a seed crystal, and is determined according to a third mixing ratio larger than the second mixing ratio. A third pressure / temperature correlation diagram A predetermined pressure / temperature correlation diagram is selected depending from the third pressure / temperature correlation diagram from the first to determine the predetermined mixing ratio, the controller crystalline group III nitride crystal comprising a plate-like shape When growing, the gas pressure of the nitrogen source gas and the temperature of the mixed melt in the container space are respectively set to the second desired pressure and the second desired temperature included in the second pressure / temperature correlation diagram. The gas supply device and the heating device are controlled.

  Preferably, the crystal growth device further includes a support device. The supporting device supports a seed crystal made of a group III nitride crystal at the interface between the container space and the mixed melt or in the mixed melt. When the group III nitride crystal is grown from the seed crystal, the control device causes the nitrogen source gas in the container space to reach the third desired pressure and the third desired temperature included in the first pressure / temperature correlation diagram. The gas supply device and the heating device are controlled to set the gas pressure and the temperature of the mixed melt, respectively, or the fourth desired pressure and the fourth desired temperature included in the third pressure / temperature correlation diagram. The gas supply device and the heating device are controlled so as to set the gas pressure of the nitrogen source gas in the container space and the temperature of the mixed melt respectively.

  Preferably, each of the first to third pressure / temperature correlation diagrams includes: a first region for dissolving the group III nitride crystal; a second region for crystal growing the group III nitride crystal from the seed crystal; A third region for growing a group III nitride crystal having a columnar shape and a fourth region for growing a group III nitride crystal having a plate shape are included. The control device then selects at least one of the first to fourth regions in the predetermined pressure / temperature correlation diagram selected from the first to third pressure / temperature correlation diagrams according to the determination of the predetermined mixing ratio. The gas supply device and the heating device are controlled so as to set the gas pressure of the nitrogen source gas in the container space and the temperature of the mixed melt to the desired pressure and desired temperature contained in the region, respectively.

  Preferably, the crystal growth apparatus further includes a mixture ratio changing unit and a selection unit. The mixing ratio changing means changes the mixing ratio of the alkali metal and the group III metal in the mixed melt within a range of a plurality of mixing ratios. The selecting means selects a pressure / temperature correlation diagram corresponding to the mixing ratio changed by the mixing ratio changing means from a plurality of pressure / temperature correlation diagrams as a predetermined pressure / temperature correlation diagram. Then, the control device sets the gas pressure of the nitrogen source gas and the temperature of the mixed melt in the container space to the desired pressure and the desired temperature included in the pressure / temperature correlation diagram selected by the selection means, respectively. The gas supply device and the heating device are controlled.

  Preferably, the mixing ratio changing means changes the mixing ratio by controlling supply / stop of the alkali metal to the mixed melt.

  Preferably, the mixing ratio changing means includes an outer container and a vapor pressure controller. The outer container is in contact with the outer container space communicating with the container space and holds the alkali metal melt. The vapor pressure controller changes the relative relationship between the first vapor pressure of the alkali metal evaporated from the alkali metal melt and the second vapor pressure of the alkali metal evaporated from the mixed melt to supply / stop the alkali metal. To control.

  Preferably, the vapor pressure controller changes the relative relationship between the first vapor pressure and the second vapor pressure by changing the temperature of the alkali metal melt.

  In the present invention, the mixing ratio indicating the quantitative ratio of the alkali metal and the group III metal is determined in a range of a plurality of mixing ratios, and the desired pressure included in the pressure / temperature correlation diagram corresponding to the determined mixing ratio. And a group III nitride crystal is grown using the desired temperature.

  Therefore, according to the present invention, the group III nitride crystal can be grown by controlling the mixing ratio, gas pressure and temperature.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
1 is a schematic cross-sectional view of a crystal growth apparatus according to Embodiment 1 of the present invention. Referring to FIG. 1, a crystal growth apparatus 100 according to Embodiment 1 of the present invention includes a crucible 10, a reaction vessel 20, a pipe 30, a melt holding member 60, heating devices 70 and 80, and a temperature sensor. 71, 81, gas supply pipes 90, 110, valves 120, 121, 160, pressure regulator 130, gas cylinder 140, exhaust pipe 150, vacuum pump 170, pressure sensor 180, and metal melt 190. And a control device 300 and a pressure sensor 310.

  The crucible 10 has a substantially cylindrical shape and is made of boron nitride (BN) or SUS316L. The reaction vessel 20 is arranged around the crucible 10 with a predetermined distance from the crucible 10. That is, the reaction vessel 20 includes the crucible 10 inside. The reaction vessel 20 includes a main body portion 21 and a lid portion 22. Each of the main body portion 21 and the lid portion 22 is made of SUS316L, and the space between the main body portion 21 and the lid portion 22 is sealed by a metal O-ring.

  The pipe 30 has one end connected to the reaction vessel 20 below the crucible 10 and the other end connected to the gas supply pipe 110 in the gravity direction DR1.

  The melt holding member 60 is made of, for example, metal and ceramic, and is installed in the pipe 30 below the connecting portion between the reaction vessel 20 and the pipe 30.

  The heating device 70 is disposed so as to surround the outer peripheral surface 20 </ b> A of the reaction vessel 20. The heating device 80 is disposed to face the bottom surface 20B of the reaction vessel 20. The temperature sensors 71 and 81 are disposed close to the heating devices 70 and 80, respectively.

  The gas supply pipe 90 has one end connected to the reaction vessel 20 via the valve 120 and the other end connected to the gas cylinder 140 via the pressure regulator 130. The gas supply pipe 110 has one end connected to the pipe 30 via the valve 121 and the other end connected to the gas supply pipe 90.

  The valve 120 is attached to the gas supply pipe 90 in the vicinity of the reaction vessel 20. The pressure regulator 130 is attached to the gas supply pipe 90 in the vicinity of the gas cylinder 140. The gas cylinder 140 is connected to the gas supply pipe 90.

  One end of the exhaust pipe 150 is connected to the reaction vessel 20 via the valve 160, and the other end is connected to the vacuum pump 170. The valve 160 is attached to the exhaust pipe 150 in the vicinity of the reaction vessel 20. The vacuum pump 170 is connected to the exhaust pipe 150.

  The pressure sensor 180 is attached to the reaction vessel 20. The metal melt 190 is made of a metal sodium (metal Na) melt and is held in the pipe 30 by the melt holding member 60.

  The crucible 10 holds a mixed melt 290 containing metal Na and metal gallium (metal Ga). The reaction vessel 20 covers the periphery of the crucible 10. The pipe 30 holds the metal melt 190.

  The melt holding member 60 has a concavo-convex structure on the outer peripheral surface so that a hole of several tens of μm is formed between the inner wall of the pipe 30 and the nitrogen gas supplied to the space 31 in the pipe 30 is melted with metal. Passing in the direction of the liquid 190, nitrogen gas is supplied into the space 23 through the metal melt 190. The melt holding member 60 holds the metal melt 190 in the pipe 30 by the surface tension of the metal melt 190.

  The heating device 70 includes a heater and a current source. Then, the heating device 70 supplies current to the heater by a current source in accordance with the control signal CTL1 from the control device 300, and heats the crucible 10 and the reaction vessel 20 from the outer peripheral surface 20A of the reaction vessel 20 to the crystal growth temperature. The temperature sensor 71 detects the temperature T1 of the heater of the heating device 70, and outputs the detected temperature T1 to the control device 300.

  The heating device 80 also includes a heater and a current source. Then, the heating device 80 causes a current to flow through the heater with a current source in accordance with the control signal CTL2 from the control device 300, and heats the crucible 10 and the reaction vessel 20 from the bottom surface 20B of the reaction vessel 20 to the crystal growth temperature. The temperature sensor 81 detects the temperature T2 of the heater of the heating device 80, and outputs the detected temperature T2 to the control device 300.

  The gas supply pipe 90 supplies nitrogen gas supplied from the gas cylinder 140 via the pressure regulator 130 into the reaction vessel 20 via the valve 120. The gas supply pipe 110 supplies nitrogen gas supplied from the gas cylinder 140 via the pressure regulator 130 into the pipe 30 via the valve 121.

  The valve 120 supplies nitrogen gas in the gas supply pipe 90 into the reaction vessel 20 or stops supply of nitrogen gas into the reaction vessel 20. The valve 121 supplies the nitrogen gas in the gas supply pipe 110 into the pipe 30 or stops supplying the nitrogen gas into the pipe 30. The pressure regulator 130 supplies the nitrogen gas from the gas cylinder 140 to the gas supply pipes 90 and 110 at a predetermined pressure in accordance with the control signal CTL3 from the control device 300.

  The gas cylinder 140 holds nitrogen gas. The exhaust pipe 150 allows the gas in the reaction vessel 20 to pass to the vacuum pump 170. The valve 160 spatially connects the inside of the reaction vessel 20 and the exhaust pipe 150 or spatially blocks the inside of the reaction vessel 20 and the exhaust pipe 150. The vacuum pump 170 evacuates the reaction vessel 20 through the exhaust pipe 150 and the valve 160.

  The pressure sensor 180 detects the pressure in the reaction vessel 20 that is not heated by the heating device 70. Nitrogen gas is introduced into the space 23 via the metal melt 190 and the melt holding member 60.

  Control device 300 receives temperatures T1 and T2 from temperature sensors 71 and 81, respectively, and, based on the received temperatures T1 and T2, control signal CTL1 for setting the temperatures of crucible 10 and reaction vessel 20 to desired temperatures. , CTL2 are generated. Then, the control device 300 outputs the generated control signals CTL1 and CTL2 to the heating devices 70 and 80, respectively.

  Further, the control device 300 receives the hydrostatic pressure Ps from the pressure sensor 310, and obtains the pressure Pin of the space 23 based on the received hydrostatic pressure Ps. More specifically, if the pressure Pin of the space 23 in the reaction vessel 20 is relatively high, the hydrostatic pressure Ps of the metal melt 190 is relatively high in proportion to the pressure Pin. Moreover, if the pressure Pin of the space 23 in the reaction vessel 20 is relatively low, the hydrostatic pressure Ps of the metal melt 190 is relatively low in proportion to the pressure Pin.

  As described above, the hydrostatic pressure Ps is proportional to the pressure Pin in the space 23. Therefore, the control device 300 holds the proportional coefficient between the hydrostatic pressure Ps and the pressure Pin, and obtains the pressure Pin based on the hydrostatic pressure Ps by multiplying the hydrostatic pressure Ps by the held proportional coefficient. .

  Then, when determining the pressure Pin of the space 23, the control device 300 generates a control signal CTL3 for setting the determined pressure Pin to a desired pressure, and outputs the generated control signal CTL3 to the pressure regulator 130. To do.

  The pressure sensor 310 detects the hydrostatic pressure Ps of the metal melt 190 and outputs the detected hydrostatic pressure Ps to the control origin 300.

  FIG. 2 is a perspective view of the melt holding member 60 shown in FIG. Referring to FIG. 2, melt holding member 60 includes a plug 61 and a convex portion 62. The stopper 61 has a substantially cylindrical shape. The protrusion 62 has a substantially semicircular cross-sectional shape, and is formed on the outer peripheral surface of the stopper 61 along the length direction DR <b> 2 of the stopper 61.

  FIG. 3 is a plan view showing a state where the melt holding member 60 is attached to the pipe 30. Referring to FIG. 3, a plurality of convex portions 62 are formed in the circumferential direction of plug 61, and the plurality of convex portions 62 are formed at intervals d of several tens of μm. The convex portion 62 has a height H of several tens of μm. The plurality of convex portions 62 of the melt holding member 60 are in contact with the inner wall 30 </ b> A of the pipe 30. Thereby, the melt holding member 60 is fitted to the inner wall 30 </ b> A of the pipe 30.

  As a result of the convex portion 62 having a height H of several tens of μm and being arranged on the outer peripheral surface of the stopper 61 at an interval d of several tens of μm, the melt holding member 60 is fitted to the inner wall 30A of the pipe 30. A plurality of gaps 63 having a diameter of about several tens of μm are formed between the melt holding member 60 and the inner wall 30 </ b> A of the pipe 30.

  The gap 63 allows nitrogen gas to pass in the length direction DR2 of the plug 61 and holds the metal melt 190 by the surface tension of the metal melt 190, so that the metal melt 190 passes in the length direction DR2 of the plug 61. To stop doing.

  FIG. 4 is a diagram showing a pressure / temperature correlation diagram for defining the relationship between pressure and temperature when growing a GaN crystal with respect to the mixing ratio of metal Na and metal Ga. In addition, the mixing ratio r of metal Na and metal Ga is defined by r = [metal Na] / ([metal Na] + [metal Ga]). [Metal Na] and [Metal Ga] are the molar amount of metallic Na and the molar amount of metallic Ga, respectively.

  4A shows a pressure / temperature correlation diagram when the mixing ratio r is r = 0.4, and FIG. 4B shows a case where the mixing ratio r is r = 0.7. The pressure / temperature correlation diagram is shown, and FIG. 4C shows the pressure / temperature correlation diagram when the mixing ratio r is r = 0.95.

  4 (a), (b), and (c), the vertical axis represents the gas pressure of nitrogen gas in the space 23 in the reaction vessel 20, and the horizontal axis represents the crucible 10 and the reaction vessel 20. (Reciprocal of absolute temperature).

  Referring to (a) of FIG. 4, the pressure / temperature correlation diagram PT1 includes regions REG11, REG12, REG13, and REG14. The region REG11 is partitioned from the region REG12 by a straight line k1, the region REG12 is partitioned from the region REG13 by a straight line k2, and the region REG13 is partitioned from the region REG14 by a straight line k3.

  The region REG11 is a region where the GaN crystal is dissolved, and the region REG12 is a region where the generation of a new nucleus is suppressed and the GaN crystal grows from the seed crystal. The region REG13 is a region where the columnar GaN crystal grows, and the region REG14 is a region where the plate-shaped GaN crystal grows.

  As described above, the pressure / temperature correlation diagram PT1 includes the region REG11 in which the GaN crystal is dissolved and the regions REG12, REG13, and REG14 in which the GaN crystals having different shapes or growth mechanisms are grown.

  Referring to FIG. 4B, the pressure / temperature correlation diagram PT2 has regions REG21, REG22, REG23, and REG24. The region REG21 is partitioned from the region REG22 by a straight line k4, the region REG22 is partitioned from the region REG23 by a straight line k5, and the region 23 is partitioned from the region REG24 by a straight line k6.

  The region REG21 is a region where the GaN crystal is dissolved, and the region REG22 is a region where the generation of a new nucleus is suppressed and the GaN crystal grows from the seed crystal. The region REG23 is a region where a columnar GaN crystal grows, and the region REG24 is a region where a plate-shaped GaN crystal grows.

  As described above, the pressure / temperature correlation diagram PT2 also includes the region REG21 in which the GaN crystal is dissolved and the regions REG22, REG23, and REG24 in which the GaN crystals having different shapes or growth mechanisms are grown.

  Referring to FIG. 4C, the pressure / temperature correlation diagram PT3 includes regions REG31, REG32, REG33, and REG34. The region REG31 is partitioned from the region REG32 by a straight line k7, the region REG32 is partitioned from the region REG33 by a straight line k8, and the region 33 is partitioned from the region REG34 by a straight line k9.

  The region REG31 is a region where the GaN crystal is dissolved, and the region REG32 is a region where the generation of a new nucleus is suppressed and the GaN crystal grows from the seed crystal. The region REG33 is a region where a columnar GaN crystal grows, and the region REG34 is a region where a plate-shaped GaN crystal grows.

  Thus, the pressure / temperature correlation diagram PT3 also includes a region REG31 in which GaN crystals are dissolved and regions REG32, REG33, and REG34 in which GaN crystals having different shapes or growth mechanisms are grown.

  As described above, each of the pressure / temperature correlation diagrams PT1 to PT3 includes a region for dissolving a GaN crystal, a region for growing a GaN crystal from a seed crystal, a region for growing a columnar GaN crystal, and a plate-like shape. The region REG12, REG13 in the pressure / temperature correlation diagram PT1 is wider than the regions REG22, REG23 in the pressure / temperature correlation diagram PT2, and the region REG24 in the pressure / temperature correlation diagram PT2 is composed of a region for growing a GaN crystal. Is wider than the regions REG14, REG34 of the pressure / temperature correlation diagram PT1, PT3, and the regions REG32, REG33 of the pressure / temperature correlation diagram PT3 have the same area as the regions REG12, REG13 of the pressure / temperature correlation diagram PT1. GaN crystal is grown while replenishing metal Ga.

  Accordingly, the pressure / temperature correlation diagram PT1 is a pressure / temperature correlation diagram suitable for crystal growth of a GaN crystal from a seed crystal and a crystal growth of a GaN crystal having a columnar shape, and the pressure / temperature correlation diagram PT2 is a plate shape. It is a pressure / temperature correlation diagram suitable for crystal growth of a GaN crystal having a shape, and the pressure / temperature correlation diagram PT3 is a region suitable for crystal growth of a GaN crystal from a seed crystal.

  Although the regions REG32 and REG33 of the pressure / temperature correlation diagram PT3 have the same width as the regions REG12 and REG13 of the pressure / temperature correlation diagram PT1, the pressure / temperature correlation diagram PT3 is a crystal growth of a GaN crystal from the seed crystal. Only when the GaN crystal is grown using the pressure / temperature correlation diagram PT3, it is necessary to replenish the metal Ga, and the crystal growth in the region REG32 (the crystal growth of the GaN crystal from the seed crystal). This is because the consumption of metal Ga is smaller than the crystal growth in the region REG33 (crystal growth of a GaN crystal having a columnar shape).

  In the present invention, a pressure / temperature correlation diagram used for crystal growth of a GaN crystal is selected from the pressure / temperature correlation diagrams PT1 to PT3 according to the mixing ratio r, and the selected pressure / temperature correlation diagram (pressure / temperature correlation diagram) is selected. A gas pressure in the space 23 and a temperature of the mixed melt 290 are set to a desired pressure and a desired temperature included in any one of PT1 to PT3, respectively, and a GaN crystal is grown.

  FIG. 5 is a timing chart of the temperatures of the crucible 10 and the reaction vessel 20. FIG. 6 is a schematic diagram showing the state in the crucible 10 and the reaction vessel 20 between the two timings t1 and t2 shown in FIG. In FIG. 5, a straight line k <b> 10 indicates the temperatures of the crucible 10 and the reaction vessel 20.

  Referring to FIG. 5, heating devices 70 and 80 heat crucible 10 and reaction vessel 20 so that the temperature rises according to straight line k10 and is maintained at 725 ° C. When the heating devices 70 and 80 start to heat the crucible 10 and the reaction vessel 20, the temperatures of the crucible 10 and the reaction vessel 20 begin to rise, reach 98 ° C. at timing t1, and reach 725 ° C. at timing t2.

  Then, in the process where the temperature of the crucible 10 and the reaction vessel 20 is raised to 725 ° C., the temperature of the pipe 30 above the melt holding member 60 is raised to 98 ° C. or higher, and the metal Na held in the pipe 30 is The metal melt 190 (= metal Na melt) is generated in the pipe 30 by melting. Further, the metal Na and the metal Ga in the crucible 10 are melted, and the mixed melt 290 is generated in the crucible 10.

  As a result, the nitrogen gas 4 in the space 23 cannot diffuse into the space 31 in the pipe 30 via the metal melt 190 (= metal Na melt) and the melt holding member 60, so It is confined (see FIG. 6).

In this case, part of the pipe 30 in contact with the metal melt 190, substantially coincides with the vapor pressure _{P Na-Ga} of the metal Na vapor pressure _{P Na} metal Na evaporated from the metal melt 190 is evaporated from the melt mixture 290 The temperature is raised by the heating device 80. That is, the portion of the pipe 30 in contact with the metal melt 190 is heated by the heating device 80 to a temperature at which the evaporation of the metal Na from the metal melt 190 and the evaporation of the metal Na from the mixed melt 290 are substantially in equilibrium. Is done.

  Therefore, the movement of the metal Na from the metal melt 190 to the mixed melt 290 and the movement of the metal Na from the mixed melt 290 to the metal melt 190 are substantially balanced, and apparently mixed with the metal melt 190. The movement of the metal Na between the melt 290 is stopped. As a result, fluctuations in the mixing ratio of metal Na and metal Ga in mixed melt 290 due to evaporation of metal Na from metal melt 190 and mixed melt 290 are suppressed. The movement of metal Na referred to here is vapor phase transport.

Thus, when the crucible 10 and the reaction vessel 20 are heated to 725 ° C., the vapor pressure P _{Na of} metal Na evaporating from the metal melt 190 vaporizes the metal Na vapor pressure P _Na—Ga evaporating from the mixed melt 290. In the space 23, the nitrogen gas 4 and the metal Na vapor 5 are mixed.

  In a high temperature state where the temperature of the crucible 10 and the reaction vessel 20 is about 725 ° C., the nitrogen gas 4 in the space 23 is taken into the mixed melt 290 through the metal Na. A GaN crystal grows from the side wall and bottom surface of the crucible 10.

  Thereafter, when the nitrogen gas in the space 23 is consumed as the GaN crystal grows, the pressure P1 in the space 23 becomes lower than the pressure P2 in the space 31 in the pipe 30. Then, nitrogen gas is replenished from the space 31 to the space 23 according to the pressure difference between the pressure P <b> 1 of the space 23 and the pressure P <b> 2 of the space 31. In this case, the melt holding member 60 allows the nitrogen gas in the space 31 to pass through the metal melt 190, and the metal melt 190 guides the nitrogen gas to the space 23 as bubbles 191. When the pressure P1 in the space 23 rises to the same extent as the pressure P2 in the space 31, the supply of nitrogen gas from the space 31 to the space 23 is stopped.

  FIG. 7 is a schematic view of a GaN crystal grown or dissolved using the crystal growth apparatus 100 shown in FIG. 7A shows a case where a GaN crystal is grown using a desired pressure and a desired temperature included in the region REG13 of the pressure / temperature correlation diagram PT1 shown in FIG. 4, and FIG. ) Shows a case where a GaN crystal is grown using a desired pressure and a desired temperature included in the region REG14 of the pressure / temperature correlation diagram PT1 shown in FIG.

  FIG. 7C shows a case where a GaN crystal is grown from a seed crystal using a desired pressure and a desired temperature included in the region REG12 of the pressure / temperature correlation diagram PT1 shown in FIG. FIG. 7D shows a case where the GaN crystal is dissolved using a desired pressure and a desired temperature included in the region REG11 of the pressure / temperature correlation diagram PT1 shown in FIG.

  Referring to FIG. 7A, when a GaN crystal is grown using a desired pressure and a desired temperature included in region REG13, a plurality of GaN crystals 6 grow from the bottom surface 11 of crucible 10. . Each of the plurality of GaN crystals 6 has a columnar shape in which a sharp tip is in contact with the bottom surface 11 of the crucible 10 and crystal is grown in the c-axis (<0001>) direction. The plurality of GaN crystals 6 have different sizes and grow in different directions with respect to the bottom surface 11 of the crucible 10.

  With reference to FIG. 7B, when a GaN crystal is grown using a desired pressure and a desired temperature included in region REG 14, a plurality of GaN crystals 7 grow in the crucible 10. Each of the plurality of GaN crystals 7 has a plate-like shape grown in the c-plane ((0001)) direction (direction perpendicular to the c-axis). The plurality of GaN crystals 7 have different sizes.

  Referring to FIG. 7C, when a GaN crystal is grown using a desired pressure and a desired temperature included in region REG12, GaN crystal 8 is grown from seed crystal 6A. The seed crystal 6A is composed of one GaN crystal among a plurality of GaN crystals 6 (see FIG. 7A) grown using a desired pressure and a desired temperature included in the region REG13. In this case, unnecessary GaN crystals are removed from the plurality of GaN crystals 6, and the GaN crystals 6 grown substantially perpendicularly to the bottom surface 11 of the crucible 10 are left on the bottom surface 11 as seed crystals 6 </ b> A. Thereby, the seed crystal 6A fixed to the bottom surface 11 of the crucible 10 can be easily manufactured.

  As described above, since the plurality of GaN crystals 6 grow in the c-axis direction, the seed crystal 6A is also composed of a GaN crystal grown in the c-axis direction. Accordingly, the GaN crystal 8 grown from the seed crystal 6A using the desired pressure and desired temperature contained in the region REG12 also grows in the c-axis direction. At this time, since the seed crystal 6A grows and grows, the crystal size also expands in the c-axis and c-plane directions. In the GaN crystal growth using the desired pressure and desired temperature contained in the region RE12, the generation of nuclei on the side wall and the bottom surface 11 of the crucible 10 is suppressed. Can grow.

  Referring to FIG. 7D, when the GaN crystal is processed using a desired pressure and a desired temperature included in region REG11, GaN crystal 9 is dissolved and GaN crystal 9A remains on bottom surface 11 of crucible 10. .

  The regions REG23, REG24, and REG22 of the pressure / temperature correlation diagram PT2 shown in FIG. 4 and the regions REG33, REG34, and REG32 of the pressure / temperature correlation diagram PT3 are shown in FIGS. 7 (a), (b), and (c), respectively. ) Crystal growth is performed, and the region REG21 of the temperature correlation diagram PT2 and the region REG31 of the pressure / temperature correlation diagram PT3 dissolve the GaN crystal 9 shown in FIG.

  FIG. 8 is a flowchart in the first embodiment for explaining a method of manufacturing a GaN crystal. Referring to FIG. 8, when a series of operations is started, crucible 10, reaction vessel 20 and piping 30 are put into a glove box filled with Ar gas. And metal Na is put in the piping 30 in Ar gas atmosphere (step S1). The Ar gas is an Ar gas having a water content of 1 ppm or less and an oxygen content of 1 ppm or less (hereinafter the same).

  Thereafter, metal Na and metal Ga are put into the crucible 10 at a predetermined mixing ratio r in an Ar gas atmosphere (step S2). In this case, for example, metal Na and metal Ga are put into the crucible 10 at a mixing ratio r = 0.4. Then, a crucible 10 containing metal Na and metal Ga is placed in the reaction vessel 20.

  Subsequently, the crucible 10, the reaction vessel 20 and the pipe 30 are taken out from the glove box, and the crucible 10 and the reaction vessel 20 are set in the crystal growth apparatus 100 in a state where the crucible 10 and the reaction vessel 20 are filled with Ar gas. Then, the valve 160 is opened, and the Ar gas filled in the crucible 10 and the reaction vessel 20 is exhausted by the vacuum pump 170. After evacuating the crucible 10 and the reaction vessel 20 to a predetermined pressure (0.133 Pa or less) with the vacuum pump 170, the valve 160 is closed and the valves 120 and 121 are opened to supply nitrogen gas from the gas cylinder 140 to the gas supply pipe 90, The crucible 10 and the reaction vessel 20 are filled through 110. In this case, nitrogen gas is supplied into the crucible 10 and the reaction vessel 20 so that the pressure in the crucible 10 and the reaction vessel 20 is about 0.1 MPa by the pressure regulator 130.

  Then, when the pressure in the reaction vessel 20 detected by the pressure sensor 180 reaches about 0.1 MPa, the valves 120 and 121 are closed, the valve 160 is opened, and the nitrogen filled in the crucible 10 and the reaction vessel 20 by the vacuum pump 170. Exhaust the gas. Also in this case, the inside of the crucible 10 and the reaction vessel 20 is evacuated to a predetermined pressure (0.133 Pa or less) by the vacuum pump 170.

  The evacuation of the crucible 10 and the reaction vessel 20 and the filling of the crucible 10 and the reaction vessel 20 with nitrogen gas are repeated several times.

  Thereafter, the inside of the crucible 10 and the reaction vessel 20 is evacuated to a predetermined pressure by the vacuum pump 170, the valve 160 is closed, the valves 120 and 121 are opened, and nitrogen gas is supplied to the space 23 of the crucible 10 and the reaction vessel 20. (Step S3).

  Thereafter, when the GaN crystal is grown using the region REG13 of the pressure / temperature correlation diagram PT1 determined according to the mixing ratio r = 0.4, the control device 300 performs a desired pressure included in the region REG13. And receiving a desired temperature from the outside. For example, control device 300 receives a pressure of 5.05 MPa and a temperature of 725 ° C. from the outside as a desired pressure and a desired temperature included in region REG13, respectively.

  Then, control device 300 generates control signals CTL1 and CTL2 for setting the temperatures of crucible 10 and reaction vessel 20 to desired temperatures (= 725 ° C.), and generates the generated control signals CTL1 and CTL2 respectively as heating devices. 70 and 80, a control signal CTL3 for setting the gas pressure of the nitrogen gas in the space 23 to a desired pressure (= 5.05 MPa) is generated, and the generated control signal CTL3 is sent to the pressure regulator 130. Output.

  Then, the heating device 70 heats the crucible 10 and the reaction vessel 20 from the outer peripheral surface 20A to 725 ° C. according to the control signal CTL1 from the control device 300, and the heating device 80 responds to the control signal CTL2 from the control device 300. Accordingly, the crucible 10 and the reaction vessel 20 are heated to 725 ° C. from the bottom surface 20B. Further, the pressure regulator 130 supplies nitrogen gas to the gas supply pipes 90 and 110, the pipe 30 and the melt holding member 60 so that the pressure in the space 23 becomes 5.05 MPa in response to the control signal CTL3 from the control device 300. Is supplied to the space 23.

  That is, the pressure of the nitrogen gas in the space 23 and the crucible to the desired pressure (= 5.05 MPa) and the desired temperature (= 725 ° C.) included in the pressure / temperature correlation diagram PT1 determined according to the predetermined mixing ratio r A temperature of 10 is set (step S4).

  Then, a desired pressure and a desired temperature are maintained for a predetermined time (step S5), and when the predetermined time has elapsed, the temperatures of the crucible 10 and the reaction vessel 20 are lowered (step S6). Thereby, a GaN crystal having a columnar shape is manufactured, and a series of operations is completed.

  In the above description, the case where the GaN crystal is grown using the desired pressure and the desired temperature included in the region REG13 of the pressure / temperature correlation diagram PT1 has been described. However, the regions REG11, REG11, GaN crystal growth or GaN crystal using desired pressure and desired temperature contained in regions REG21, REG22, REG23, REG24, REG31, REG32, REG33, REG34 of REG12, REG14 and pressure / temperature correlation diagram PT2, PT3 The operation of dissolving the is also performed according to the free chart shown in FIG.

  Thus, in the present invention, a plurality of pressure / temperature correlation diagrams PT1 to PT3 are provided corresponding to a plurality of mixing ratios (r = 0.4, 0.7, 0.95), A GaN crystal is grown or dissolved using a pressure / temperature correlation diagram (any of pressure / temperature correlation diagrams PT1 to PT3) determined according to the mixing ratio r.

  Therefore, according to the present invention, the GaN crystal can be grown or dissolved by controlling the mixing ratio r, gas pressure, and temperature.

  In the above description, the case where a GaN crystal is grown or dissolved using a desired pressure and a desired temperature included in one region of the pressure / temperature correlation diagrams PT1 to PT3 has been described. The GaN crystal may be grown using a desired pressure and a desired temperature included in a plurality of regions of the pressure / temperature correlation diagrams PT1 to PT3. In this case, step S4 in the flowchart shown in FIG. 8 includes a plurality of steps.

  FIG. 9 illustrates the detailed operation of step S4 shown in FIG. 8 when a GaN crystal is grown using a desired pressure and a desired temperature included in a plurality of regions of the pressure / temperature correlation diagrams PT1 to PT3. It is a flowchart for.

  Referring to FIG. 9, when step S3 shown in FIG. 8 is completed, the pressure of space 23 and the temperature of crucible 10 are respectively set to the desired pressure and the desired temperature included in region REG13 of pressure / temperature correlation diagram PT1. (Step S41), a GaN crystal is grown. As a result, a plurality of GaN crystals having a columnar shape are formed on the bottom surface 11 of the crucible 10.

  Thereafter, the pressure of the space 23 and the temperature of the crucible 10 are respectively set to the desired pressure and the desired temperature included in the region REG11 of the pressure / temperature correlation diagram PT1 (step S42), and the GaN crystal grown in step S41 is dissolved. To do. As a result, the small GaN crystal is dissolved, and the large GaN crystal remains on the bottom surface 11 of the crucible 10. The GaN crystal remaining on the bottom surface 11 of the crucible 10 becomes a seed crystal.

  Subsequently, the pressure of the space 23 and the temperature of the crucible 10 are respectively set to a desired pressure and a desired temperature included in the region REG12 of the pressure / temperature correlation diagram PT1 (step S43), and a GaN crystal is grown from the seed crystal.

  Thereafter, the series of operations proceeds to step S5 shown in FIG.

  Thus, by sequentially using a plurality of desired pressures and a plurality of desired temperatures included in the region REG13, the region REG11, and the region REG12 of the pressure / temperature correlation diagram PT1, a plurality of columnar-shaped GaN crystals 6 are crucible. A crystal is grown on the bottom surface 11 of 10, and a part of the plurality of GaN crystals 6 on which the crystal is grown is dissolved to produce a seed crystal. Further, a GaN crystal 8 can be grown from the produced seed crystal. As a result, it is possible to enlarge the crystal using a small number of columnar crystals as seed crystals, and it is possible to increase the raw material efficiency and grow a large crystal. Furthermore, crystal growth can be performed without taking out the seed crystal, and the crystal can be grown on the clean surface of the seed crystal. As a result, a GaN crystal can be grown.

  FIG. 10 illustrates the detailed operation of step S4 shown in FIG. 8 when a GaN crystal is grown using a desired pressure and a desired temperature included in a plurality of regions of the pressure / temperature correlation diagrams PT1 to PT3. It is another flowchart for.

  In addition, the flowchart shown in FIG. 10 is a flowchart in case the seed crystal is previously installed in the bottom face 11 of the crucible 10.

  Referring to FIG. 10, when step S3 shown in FIG. 8 is completed, the pressure of space 23 and the temperature of crucible 10 are respectively set to the desired pressure and the desired temperature included in region REG11 of pressure / temperature correlation diagram PT1. (Step S41A), the seed crystal is dissolved.

  Thereafter, the pressure of the space 23 and the temperature of the crucible 10 are respectively set to a desired pressure and a desired temperature included in the region REG12 of the pressure / temperature correlation diagram PT1 (step S42A), and a GaN crystal is grown from the seed crystal.

  Thereafter, the series of operations proceeds to step S5 shown in FIG.

  Thus, by sequentially using a plurality of desired pressures and a plurality of desired temperatures included in the region REG11 and the region REG12 of the pressure / temperature correlation diagram PT1, a part of the seed crystal is dissolved, and the dissolved seed crystal GaN crystal can be grown from.

  When a seed crystal is previously set on the bottom surface 11 of the crucible 10 and a GaN crystal is grown from the set seed crystal, the surface of the seed crystal is oxidized or impurities such as moisture are attached to the surface of the seed crystal. Therefore, by setting the pressure of the space 23 and the temperature of the crucible 10 to the desired pressure and the desired temperature included in the region REG11 and dissolving a part of the seed crystal, a clean surface of the crystal can be obtained. Thereafter, the pressure of the space 23 and the temperature of the crucible 10 are respectively set to a desired pressure and a desired temperature included in the region REG12, and a GaN crystal is grown from the seed crystal after dissolution. Thereby, a high quality GaN crystal can be continuously grown from the seed crystal.

[Embodiment 2]
In Embodiment 2, the GaN crystal is grown using a temperature of 950 ° C. and a nitrogen pressure of 5 MPa. The temperature of 950 ° C. and the nitrogen pressure of 5 MPa are the seed crystal growth conditions (included in the region REG12) in the pressure / temperature correlation diagram PT1 shown in FIG.

  FIG. 11 is a schematic cross-sectional view of the crystal growth apparatus according to the second embodiment. Referring to FIG. 11, the crystal growth apparatus 100A according to the second embodiment is different from the crystal growth apparatus 100 shown in FIG. 1 in the bellows 40, the support device 50, the pipe 200, the thermocouple 210, the vertical mechanism 220, and the vibration applying device 230. A detection device 240, a gas supply pipe 250, a flow meter 260, a gas cylinder 270, and a temperature control device 280 are added, and the others are the same as the crystal growth device 100.

  In crystal growth apparatus 100A, temperature sensor 71 outputs detected temperature T1 to temperature control apparatus 280 and control apparatus 300, and temperature sensor 81 outputs detected temperature T2 to temperature control apparatus 280 and control apparatus 300. Output.

  The bellows 40 is connected to the reaction vessel 20 on the upper side of the crucible 10 in the gravity direction DR1. The support device 50 has a hollow cylindrical shape, and a part thereof is inserted into the space 23 of the reaction vessel 20 through the bellows 40.

  The pipe 200 and the thermocouple 210 are inserted into the support device 50. The vertical mechanism 220 is attached to the support device 50 above the bellows 40. The gas supply pipe 250 has one end connected to the pipe 200 and the other end connected to the gas cylinder 270 via the flow meter 260. The flow meter 260 is attached to the gas supply pipe 250 in the vicinity of the gas cylinder 270. The gas cylinder 270 is connected to the gas supply pipe 250.

  The bellows 40 holds the support device 50 and blocks the inside and outside of the reaction vessel 20. The bellows 40 expands and contracts in the gravity direction DR1 as the support device 50 moves in the gravity direction DR1. The support device 50 supports the seed crystal 6 </ b> B made of GaN crystal at one end inserted into the reaction vessel 20.

  The pipe 200 discharges the nitrogen gas supplied from the gas supply pipe 250 into the support device 50 from one end to cool the seed crystal 6B. The thermocouple 210 detects the temperature T3 of the seed crystal 6B and outputs the detected temperature T3 to the temperature control device 280.

  In accordance with the vibration detection signal BDS from the vibration detection device 240, the vertical mechanism 220 moves the support device 50 up and down so that the seed crystal 6B contacts the gas-liquid interface 3 between the space 23 and the mixed melt 290 by a method described later. To do.

  The vibration application device 230 is made of, for example, a piezoelectric element, and applies vibration having a predetermined frequency to the support device 50. The vibration detection device 240 includes, for example, an acceleration pickup, detects vibration of the support device 50, and outputs a vibration detection signal BDS indicating the vibration of the support device 50 to the vertical mechanism 220.

  The gas supply pipe 250 supplies nitrogen gas supplied from the gas cylinder 270 via the flow meter 260 to the pipe 200. The flow meter 260 adjusts the flow rate of the nitrogen gas supplied from the gas cylinder 270 in accordance with the control signal CTL 4 from the temperature control device 280 and supplies it to the gas supply pipe 250. The gas cylinder 270 holds nitrogen gas.

  Temperature controller 280 receives temperatures T1 and T2 from temperature sensors 71 and 81, respectively, and receives temperature T3 from thermocouple 210. Then, when the temperature T1, T2 received from the temperature sensors 71, 81 reaches 950 + α ° C. which sets the temperature of the crucible 10 and the reaction vessel 20 to 950 ° C., the temperature control device 280 sets the temperature T3 which is the temperature of the seed crystal 6B. A control signal CTL4 for lowering from 950 ° C. is generated, and the generated control signal CTL4 is output to the flow meter 260.

  Since the temperature of the crucible 10 and the reaction vessel 20 has a predetermined temperature difference α from the temperature of the heaters of the heating devices 70 and 80, when the temperature of the heater of the heating devices 70 and 80 reaches 950 + α ° C. Is set at 950 ° C. Further, the temperature of the mixed melt 290 is equal to the temperatures of the crucible 10 and the reaction vessel 20, and the temperature of the seed crystal 6B in contact with the mixed melt 290 is equal to the temperature of the mixed melt 290.

  Therefore, when the temperatures T1 and T2 respectively received from the temperature sensors 71 and 81 reach 950 + α ° C., the temperature controller 280 determines the temperature of the crucible 10 and the reaction vessel 20, that is, the temperature of the seed crystal 6B in contact with the mixed melt 290. Is set to 950 ° C., the control signal CTL 4 for reducing the temperature of the seed crystal 6 B from 950 ° C. is generated and output to the flow meter 260.

  12 is an enlarged view of the supporting device 50, the pipe 200, and the thermocouple 210 shown in FIG. Referring to FIG. 12, support device 50 includes a cylindrical member 51 and fixing members 52 and 53. The cylindrical member 51 has a substantially circular cross-sectional shape. The fixing member 52 has a substantially L-shaped cross-sectional shape, and is fixed to the outer peripheral surface 51 </ b> A and the bottom surface 51 </ b> B of the cylindrical member 51 on the one end 511 side of the cylindrical member 51. The fixing member 53 has a substantially L-shaped cross-sectional shape, and the outer peripheral surface 51 </ b> A and the bottom surface 51 </ b> B of the cylindrical member 51 are arranged symmetrically with the fixing member 52 on the one end 511 side of the cylindrical member 51. Fixed to. As a result, a space 54 is formed in a region surrounded by the cylindrical member 51 and the fixing members 52 and 53.

  The pipe 200 has a substantially circular cross-sectional shape and is disposed inside the cylindrical member 51. In this case, the bottom surface 200 </ b> A of the pipe 200 is disposed so as to face the bottom surface 51 </ b> B of the tubular member 51. A plurality of holes 201 are formed in the bottom surface 200 </ b> A of the pipe 200. Nitrogen gas supplied into the pipe 200 is blown to the bottom surface 51 </ b> B of the cylindrical member 51 through the plurality of holes 201.

  The thermocouple 210 is disposed inside the tubular member 51 so that one end 210A is in contact with the bottom surface 51B of the tubular member 51 (see FIG. 12A).

  The seed crystal 6 </ b> B has a shape that fits into the space portion 54, and is supported by the support device 50 by fitting into the space portion 54. In this case, the seed crystal 6B is in contact with the bottom surface 51B of the cylindrical member 51 (see FIG. 12B).

  Therefore, the thermal conductivity between the seed crystal 6B and the cylindrical member 51 is increased. As a result, the temperature of the seed crystal 6B can be detected by the thermocouple 210, and the seed crystal 6B can be easily cooled by the nitrogen gas blown from the pipe 200 to the bottom surface 51B of the cylindrical member 51.

  In the second embodiment, the seed crystal itself has a shape that can be fitted like the seed crystal 6B. However, as long as the seed crystal 6B is in contact with the support device 50, the seed crystal 6B has a hexagonal column-shaped seed through an adapter in the shape of the seed crystal 6B. Crystals may be retained.

  FIG. 13 is a schematic diagram showing the configuration of the vertical mechanism 220 shown in FIG. Referring to FIG. 13, the vertical mechanism 220 includes an uneven member 221, a gear 222, a shaft member 223, a motor 224, and a control unit 225.

  The concavo-convex member 221 has a substantially triangular cross-sectional shape and is fixed to the outer peripheral surface 51 </ b> A of the tubular member 51. The gear 222 is fixed to one end of the shaft member 223 and meshes with the concavo-convex member 221. The shaft member 223 has one end connected to the gear 222 and the other end connected to a shaft (not shown) of the motor 224.

  The motor 224 rotates the gear 222 in the direction of the arrow 226 or 227 in accordance with the control from the control unit 225. The controller 225 controls the motor 224 to rotate the gear 222 in the direction of the arrow 226 or 227 based on the vibration detection signal BDS from the vibration detection device 240.

  If the gear 222 rotates in the direction of the arrow 226, the support device 50 moves upward in the direction of gravity DR1, and if the gear 222 rotates in the direction of the arrow 227, the support device 50 moves downward in the direction of gravity DR1. Move to.

  Therefore, rotating the gear 222 in the direction of the arrow 226 or 227 corresponds to moving the support device 50 up and down in the gravity direction DR1. The length of the concavo-convex member 221 in the gravitational direction DR1 is a length corresponding to a distance for moving the support device 50 up and down.

  FIG. 14 is a timing chart of the vibration detection signal BDS. Referring to FIG. 14, vibration detection signal BDS detected by vibration detection device 240 includes signal component SS1 when seed crystal 6B is not in contact with mixed melt 290, and seed crystal 6B is mixed with mixed melt 290. When in contact, it is composed of the signal component SS2, and when the seed crystal 6B is immersed in the mixed melt 290, it is composed of the signal component SS3.

  When the seed crystal 6B is not in contact with the mixed melt 290, the seed crystal 6B greatly vibrates due to the vibration applied by the vibration applying device 230, so that the vibration detection signal BDS is generated from the signal component SS1 having a relatively large amplitude. Become. On the other hand, when the seed crystal 6B is in contact with the mixed melt 290, the seed crystal 6B cannot vibrate greatly due to the viscosity of the mixed melt 290 even when vibration is applied from the vibration applying device 230. Therefore, the vibration detection signal BDS is The signal component SS2 has a relatively small amplitude. Further, when the seed crystal 6B is immersed in the mixed melt 290, the seed crystal 6B is more difficult to vibrate due to the viscosity of the mixed melt 290 even when vibration is applied from the vibration applying device 230. The signal BDS is composed of a signal component SS3 having an amplitude smaller than that of the signal component SS2.

  Referring to FIG. 13 again, upon receiving vibration detection signal BDS from vibration detection device 240, control unit 225 detects the signal component of vibration detection signal BDS. Then, when the detected signal component is composed of the signal component SS1, the control unit 225 causes the motor 224 to lower the support device 50 in the gravity direction DR1 until the signal component of the vibration detection signal BDS becomes the signal component SS2. Control.

  More specifically, the control unit 225 controls the motor 224 to rotate the gear 222 in the direction of the arrow 227, and the motor 224 moves the gear 222 through the shaft member 223 through the arrow according to the control from the control unit 225. Rotate in the direction of 227. As a result, the support device 50 moves downward in the gravity direction DR1.

  Then, when the signal component of the vibration detection signal BDS received from the vibration detection device 240 is switched from the signal component SS1 to the signal component SS2, the control unit 225 controls the motor 224 so as to stop the rotation of the gear 222. Stops the rotation of the gear 222 according to the control from the control unit 225. As a result, the support device 50 stops moving and holds the seed crystal 6B at the gas-liquid interface 3.

  Further, the control unit 225 controls the motor 224 so as to stop the movement of the support device 50 when receiving the vibration detection signal BDS including the signal component SS2 from the vibration detection device 240. This is because the seed crystal 6B is already in contact with the mixed melt 290 in this case.

  Further, when the control unit 225 receives the vibration detection signal BDS including the signal component SS3 from the vibration detection device 240, the control unit 225 raises the support device 50 in the gravity direction DR1 until the signal component of the vibration detection signal BDS becomes the signal component SS2. The motor 224 is controlled so that

  More specifically, the control unit 225 controls the motor 224 to rotate the gear 222 in the direction of the arrow 226, and the motor 224 controls the gear 222 via the shaft member 223 according to the control from the arrow 226. Rotate in the direction of 226. As a result, the support device 50 moves upward in the gravity direction DR1.

  Then, when the signal component of the vibration detection signal BDS received from the vibration detection device 240 is switched from the signal component SS3 to the signal component SS2, the control unit 225 controls the motor 224 so as to stop the rotation of the gear 222. Stops the rotation of the gear 222 according to the control from the control unit 225. As a result, the support device 50 stops moving and holds the seed crystal 6B at the gas-liquid interface 3.

  In this manner, the vertical mechanism 220 moves the support device 50 in the gravity direction DR1 so that the seed crystal 6B contacts the mixed melt 290 based on the vibration detection signal BDS detected by the vibration detection device 240.

  FIG. 15 is another timing chart of the temperatures of the crucible 10 and the reaction vessel 20. FIG. 16 is a diagram showing the relationship between the temperature of the seed crystal 6B and the flow rate of nitrogen gas.

  In FIG. 15, a straight line k11 indicates the temperature of the crucible 10 and the reaction vessel 20, and a curved line k12 and a straight line k13 indicate the temperature of the seed crystal 6B.

  Referring to FIG. 15, when heating devices 70 and 80 begin to heat crucible 10 and reaction vessel 20, the temperatures of crucible 10 and reaction vessel 20 begin to rise and reach 98 ° C. at timing t1, and at timing t2. It reaches 950 ° C.

  Then, as described in FIG. 5, nitrogen 4 and metal Na vapor 5 are confined in space 23 (see FIG. 6).

  Then, at the timing t2 when the temperatures of the crucible 10 and the reaction vessel 20 reach 950 ° C., the vertical mechanism 220 moves the support device 50 up and down by the method described above based on the vibration detection signal BDS from the vibration detection device 240, Crystal 6B is brought into contact with mixed melt 290.

In a high temperature state where the temperature of the crucible 10 and the reaction vessel 20 is about 950 ° C., the nitrogen gas 4 in the space 23 is taken into the mixed melt 290 through metal Na. In this case, the nitrogen concentration or Ga _x N _y (x and y are real numbers) in the mixed melt 290 is the highest in the vicinity of the gas-liquid interface 3 between the space 23 and the mixed melt 290. The growth starts from the seed crystal 6B in contact with the liquid interface 3.

In the present invention, Ga _x N _{y is referred} to as “Group III nitride”, and the Ga _x N _y concentration is referred to as “Group III nitride concentration”.

  When nitrogen gas is not supplied into the pipe 200, the temperature T3 of the seed crystal 6B is 950 ° C., which is the same as the temperature of the mixed melt 290, but in the second embodiment, in the mixed melt 290 near the seed crystal 6B. In order to increase the degree of supersaturation of nitrogen or group III nitride, nitrogen gas is supplied into the pipe 200 to cool the seed crystal 6B, and the temperature T3 of the seed crystal 6B is made lower than the temperature of the mixed melt 290.

  More specifically, the temperature T3 of the seed crystal 6B is set to a temperature Ts1 lower than 950 ° C. according to the curve k12 after the timing t2. This temperature Ts1 is, for example, 900 ° C. A method for setting the temperature T3 of the seed crystal 6B to the temperature Ts1 will be described.

  When the temperatures T1 and T2 received from the temperature sensors 71 and 81 reach 950 + α ° C., the temperature controller 280 determines that the temperature of the seed crystal 6B is set to 950 ° C., and sets the temperature T3 of the seed crystal 6B to the temperature Ts1. A control signal CTL4 for flowing nitrogen gas having a flow rate set to be generated and output to the flow meter 260.

  Then, according to the control signal CTL4, the flow meter 260 causes nitrogen gas having a flow rate that sets the temperature T3 to the temperature Ts1 to flow from the gas cylinder 270 into the pipe 200 via the gas supply pipe 250. The temperature of the seed crystal 6B decreases from 950 ° C. approximately in proportion to the flow rate of the nitrogen gas, and when the flow rate of the nitrogen gas reaches the flow rate fr1 (sccm), the temperature T3 of the seed crystal 6B is set to the temperature Ts1 ( FIG. 16).

  Therefore, the flow meter 260 allows the nitrogen gas having the flow rate fr <b> 1 to flow into the pipe 200. The nitrogen gas supplied into the pipe 200 is blown from the plurality of holes 201 of the pipe 200 to the bottom surface 51 </ b> B of the cylindrical member 51.

  As a result, the seed crystal 6B is cooled through the bottom surface 51B of the cylindrical member 51, and the temperature T3 of the seed crystal 6B is decreased to the temperature Ts1 at the timing t4, and thereafter is maintained at the temperature Ts1 until the timing t3.

  In the second embodiment, preferably, the temperature T3 of the seed crystal 6B is controlled so as to decrease according to the straight line k13 after the timing t2. That is, the temperature T3 of the seed crystal 6B is decreased from 950 ° C. to the temperature Ts2 (<Ts1) between the timing t2 and the timing t3. In this case, the flow meter 260 increases the flow rate of nitrogen gas flowing into the pipe 200 from 0 to the flow rate fr2 according to the straight line k14 based on the control signal CTL4 from the temperature control device 280. When the flow rate of the nitrogen gas becomes the flow rate fr2, the temperature T3 of the seed crystal 6B is set to a temperature Ts2 that is lower than the temperature Ts1. And temperature Ts2 is 850 degreeC, for example.

  As described above, the difference between the temperature of the mixed melt 290 (= 950 ° C.) and the temperature T3 of the seed crystal 6B is gradually increased for the following two reasons.

  The first reason is that, as the crystal growth of the GaN crystal proceeds, the GaN crystal adheres to the seed crystal 6B. Therefore, unless the temperature of the seed crystal 6B is gradually decreased, the GaN crystal that has grown from the seed crystal 6B. This is because it is difficult to set this temperature to a temperature lower than the temperature of the mixed melt 290.

  The second reason is that as the crystal growth of the GaN crystal progresses, Ga in the mixed melt 290 is consumed, the mixing ratio r increases, and the nitrogen concentration or group III nitride concentration in the mixed melt 290 becomes supersaturated. This is because if the temperature of the seed crystal 6B is not lowered gradually, it is difficult to keep the nitrogen concentration or the group III nitride concentration in the mixed melt 290 supersaturated.

  Accordingly, by gradually lowering the temperature of the seed crystal 6B as the crystal growth of the GaN crystal proceeds, the degree of supersaturation of nitrogen or group III nitride in the mixed melt 290 near the seed crystal 6B gradually increases. At least the crystal growth of the GaN crystal can be maintained. As a result, the size of the GaN crystal can be increased.

  FIG. 17 is a flowchart for explaining an operation of manufacturing a GaN crystal using the crystal growth apparatus 100A shown in FIG. In the flowchart shown in FIG. 17, step S2A is inserted between step S2 and step S3 of the flowchart shown in FIG. 8, step S4A is inserted between step S4 and step S5, and step S5 and step S6. Steps S5A and 5B are inserted between them, and the rest is the same as the flowchart shown in FIG.

  Referring to FIG. 17, when step S2 described above is completed, seed crystal 6B is set above metal Na and metal Ga in crucible 10 in an Ar gas atmosphere (step S2A). More specifically, by fitting the seed crystal 6B into the space 54 formed on the one end 511 side of the support device 50 (see FIG. 12B), the seed crystal 6B is placed in the metal Na in the crucible 10. And set above metal Ga.

  Thereafter, steps S3 and S4 described above are executed. In this case, in step S4, the pressure of the nitrogen gas is set to 5 MPa, and the temperatures of the crucible 10 and the reaction vessel 20 are set to 950 ° C. And after step S4, in the process in which the crucible 10 and the reaction vessel 20 are heated to a desired temperature, the metal Na and metal Ga in the crucible 10 also become liquid, and the mixed melt 290 of metal Na and metal Ga becomes a liquid. It occurs in the crucible 10. Then, the vertical mechanism 220 brings the seed crystal 6B into contact with the mixed melt 290 by the method described above (step S4A).

  Thereafter, in a high temperature state where the temperature of the crucible 10 and the reaction vessel 20 is 950 ° C., the nitrogen gas in the space 23 is taken into the mixed melt 290 via the metal Na, and the GaN crystal starts to grow from the seed crystal 6B.

  Then, step S5 described above is executed, and the temperature T3 of the seed crystal 6B is set to a temperature Ts1 (or temperature Ts2) lower than the temperature of the mixed melt 290 (= 950 ° C.) by the method described above (step S5A). .

  As the growth of the GaN crystal proceeds, the nitrogen gas in the space 23 is consumed and the nitrogen gas in the space 23 decreases. Then, the pressure P1 in the space 23 becomes lower than the pressure P2 in the space 31 in the pipe 30 (P1 <P2), a differential pressure is generated between the space 23 and the space 31, and nitrogen gas in the space 31 is generated. Are sequentially supplied into the space 23 via the melt holding member 60 and the metal melt 190 (= metal Na melt).

  Thereafter, the seed crystal 6B is lowered by the method described above so that the seed crystal 6B comes into contact with the mixed melt 290 (step S5B). As a result, a large GaN crystal grows. And step S6 mentioned above is performed and manufacture of the GaN crystal from seed crystal 6B is completed.

  In the flowchart shown in FIG. 17, it has been described that when crucible 10 and reaction vessel 20 are heated to 950 ° C., seed crystal 6B is brought into contact with mixed melt 290 of metal Na and metal Ga (step S4). In this invention, the crucible 10 and the reaction vessel 20 are heated to 950 ° C. (see step S4). In step S4A, the seed crystal 6B is mixed with metal Na and metal Ga. It may be held in the mixed melt 290. That is, when the crucible 10 and the reaction vessel 20 are heated to 950 ° C., the seed crystal 6B may be immersed in the mixed melt 290 to grow a GaN crystal from the seed crystal 6B.

  The operation of bringing the seed crystal 6B into contact with the mixed melt 290 is detected in step A in which vibration is applied to the support device 50 by the vibration application device 230 and the vibration detection signal BDS indicating the vibration of the support device 50 is detected. From step B in which the support device 50 is moved by the vertical mechanism 220 so that the vibration detection signal BDS becomes the vibration detection signal (component SS2 of the vibration detection signal BDS) when the seed crystal 6B contacts the mixed melt 290. Become.

  Further, the operation of holding the seed crystal 6B in the mixed melt 290 includes a step A in which vibration is applied to the support device 50 by the vibration application device 230 and a vibration detection signal BDS indicating the vibration of the support device 50 is detected. The support device 50 is moved by the vertical mechanism 220 so that the vibration detection signal BDS thus obtained becomes a vibration detection signal (component SS3 of the vibration detection signal BDS) when the seed crystal 6B is immersed in the mixed melt 290. C.

  In step B and step C, the support device 50 is moved by the vertical mechanism 220 because the relationship between the volume of the crucible 10 and the total amount of metal Na and metal Ga contained in the crucible 10 When the position of the liquid surface (= gas-liquid interface 3) of the mixed melt 290 generated in the step fluctuates and the mixed melt 290 is generated in the crucible 10, the seed crystal 6B is immersed in the mixed melt 290. Since the seed crystal 6B may be held in the space 23, in order to contact the seed crystal 6B with the mixed melt 290 or immerse the seed crystal 6B in the mixed melt 290, the seed crystal This is because it is necessary to move 6B up and down in the gravity direction DR1.

  Further, in step S5B of the flowchart shown in FIG. 17, it has been described that the seed crystal 6B is lowered so that the seed crystal 6B comes into contact with the mixed melt 290. However, in the present invention, step S5B of the flowchart shown in FIG. In general, the step consists of step D in which the supporting device 50 is moved by the vertical mechanism 220 so that the GaN crystal grown from the seed crystal 6B contacts the mixed melt 290 during crystal growth of the GaN crystal.

  As the GaN crystal grows, Ga in the mixed melt 290 is consumed and the liquid level of the mixed melt 290 (= the gas-liquid interface 3) decreases, but this liquid level (= the gas-liquid interface 3) decreases. Depending on the relationship between the speed and the crystal growth rate of the GaN crystal, the GaN crystal grown from the seed crystal 6B may be moved upward, or the GaN crystal grown from the seed crystal 6B may be moved downward. Because there is.

  That is, when the liquid surface (= gas-liquid interface 3) has a lowering speed faster than the crystal growth rate of the GaN crystal, the GaN crystal grown from the seed crystal 6B is moved downward to cause the GaN crystal to move into the mixed melt 290. Contact the liquid surface (= gas-liquid interface 3). On the other hand, when the liquid surface (= gas-liquid interface 3) has a lowering rate slower than the crystal growth rate of the GaN crystal, the GaN crystal grown from the seed crystal 6B is moved upward to move the GaN crystal to the mixed melt 290. Contact the liquid surface (= gas-liquid interface 3).

  As described above, the GaN crystal grown from the seed crystal 6B needs to be moved up and down in the gravity direction DR1 depending on the relationship between the lowering speed of the liquid surface (= gas-liquid interface 3) and the crystal growth speed of the GaN crystal. In Step D, “the support device 50 is moved by the vertical mechanism 220”.

  In Step D, the operation of bringing the GaN crystal grown from the seed crystal 6B into contact with the mixed melt 290 includes Step A and Step B described above.

  In the crystal growth apparatus 100A, since the seed crystal 6B is installed in the reaction vessel 20 in the glow box, the detailed operation in step S4 is composed of the flowchart shown in FIG.

  As described above, when the GaN crystal is grown from the seed crystal 6B by bringing the seed crystal 6B into contact with the gas-liquid interface 3 between the space 23 and the mixed melt 290, the pressure / pressure determined according to the mixing ratio r A GaN crystal is grown using a temperature correlation diagram (any one of pressure / temperature correlation diagrams PT1 to PT3).

  The gas cylinder 140, the pressure regulator 130, the gas supply pipes 90 and 110, the valve 121, the pipe 30, the melt holding member 60, and the metal melt 190 constitute a “gas supply device”.

[Embodiment 3]
FIG. 18 is a schematic cross-sectional view of the crystal growth apparatus according to the third embodiment. Referring to FIG. 18, crystal growth apparatus 100B according to Embodiment 3 adds pipes 320 and 330, heating apparatuses 350, 360, and 370 and temperature sensor 351 to crystal growth apparatus 100 shown in FIG. 190 is replaced with the metal melt 340, the control device 300 is replaced with the control device 300A, and the rest is the same as the crystal growth device 100.

  In the crystal growth apparatus 100B, the melt holding member 60 is installed in the pipe 320, and the pressure sensor 310 is attached to the pipe 320.

  The pipe 320 has one end connected to the gas supply pipe 110 and the other end connected to one end of the pipe 330. The pipe 330 has one end connected to the other end of the pipe 320 and the other end connected to the reaction vessel 20.

  The metal melt 340 is held in the pipe 320 by the melt holding member 60. The heating device 350 is installed at a position facing the metal melt 340, and the temperature sensor 351 is arranged close to the heating device 350. The heating device 360 is installed facing the space 322 of the pipe 320, and the heating device 370 is installed facing the pipe 330.

  The heating device 350 includes a heater and a current source. Then, heating device 350 causes a current to flow through the heater with a current source in accordance with control signal CTL5 from control device 300A, and sets the temperature of metal melt 340 to a predetermined temperature. The temperature sensor 351 detects the temperature T4 of the heater of the heating device 350 and outputs the detected temperature T4 to the control device 300A.

  The heating device 360 heats the space 322 of the pipe 320 to the crystal growth temperature (= 725 ° C.), and the heating device 370 heats the space 331 of the pipe 330 to the crystal growth temperature (= 725 ° C.).

  Control device 300A receives temperatures T1, T2, and T4 from temperature sensors 71, 81, and 351, respectively, and hydrostatic pressure Ps from pressure sensor 310. Then, control device 300A generates control signal CTL5 for setting the temperature of metal melt 340 to a predetermined temperature based on temperature T4 received from temperature sensor 351, and uses the generated control signal CTL5 as a heating device. To 350.

  The temperature of the heater of the heating device 350 has a predetermined temperature difference β from the temperature of the metal melt 340. When the temperature of the heater of the heating device 350 is Tm + β ° C., the temperature of the metal melt 340 is set to the temperature Tm.

  Therefore, control device 300A generates control signal CTL5 for setting temperature T4 from temperature sensor 351 to Tm + β ° C., and outputs it to heating device 350 to set the temperature of metal melt 340 to a predetermined temperature Tm. . The control device 300A performs the same functions as the control device 300 in other respects.

FIG. 19 is a conceptual diagram for explaining a method of controlling the mixing ratio r of metal Na and metal Ga in the mixed melt 290. Figure. 19 (a), if substantially equal to the vapor pressure _{P Na-Ga} of metal Na evaporated from the vapor pressure _{P Na} mixed melt 290 of the metal Na evaporated from the metal melt 340 (= metal Na melt) are shown, (b) in FIG. 19, the vapor pressure _{P Na} indicates is higher than the vapor pressure _{P Na-Ga,} (c) in FIG. 19, also the vapor pressure _{P Na} is the vapor pressure _{P Na-Ga} Indicates a low case.

When the temperature of the metal melt 340 is equal to the temperature of the mixed melt 290, the vapor pressure _PNa is higher than the vapor pressure _PNa-Ga . Therefore, when the temperature of the metal melt 340 is set to a temperature lower than the temperature of the mixed melt 290 (= 725 ° C.), the vapor pressure P _Na becomes substantially equal to the vapor pressure P _Na—Ga , and the metal melt 340 The vapor phase transport of metal Na between the molten melt 290 and the mixed melt 290 apparently disappears (see FIG. 19A). As a result, the amounts of the mixed melt 290 and the metal melt 340 are kept substantially constant.

When the vapor pressure _PNa is higher than the vapor pressure _PNa-Ga , the metal Na is vapor-phase transported from the metal melt 340 to the mixed melt 290, the metal melt 340 decreases, and the mixed melt 290 increases ( (See FIG. 19B). As a result, the mixing ratio r increases.

When the vapor pressure _PNa is lower than the vapor pressure _PNa-Ga , the metal Na is vapor-transported from the mixed melt 290 to the metal melt 340, the mixed melt 290 decreases, and the metal melt 340 increases ( (See (c) of FIG. 19). As a result, the mixing ratio r becomes small.

Thus, the amount of the mixed melt 290 and the metal melt 340 is maintained or increased or decreased depending on the relationship between the vapor pressure P _Na and the vapor pressure P _Na—Ga .

  FIG. 20 is a block diagram showing a partial configuration of control device 300A shown in FIG. Referring to FIG. 20, control device 300 </ b> A includes input buttons 301 to 307, a CPU (Central Processing Unit) 308, and a memory 309.

  The input button 301 is a button for setting the mixing ratio r to “0.4”, the input button 302 is a button for setting the mixing ratio r to “0.7”, and the input button 303 is , A button for setting the mixing ratio r to “0.95”.

  The input button 304 is a button for designating one of the region REG11 of the pressure / temperature correlation diagram PT1, the region REG21 of the pressure / temperature correlation diagram PT2, and the region REG31 of the pressure / temperature correlation diagram PT3. Reference numeral 305 denotes a button for designating one of a region REG12 of the pressure / temperature correlation diagram PT1, a region REG22 of the pressure / temperature correlation diagram PT2, and a region REG32 of the pressure / temperature correlation diagram PT3. This is a button for designating one of the region REG13 in the temperature / temperature correlation diagram PT1, the region REG23 in the pressure / temperature correlation diagram PT2, and the region REG33 in the pressure / temperature correlation diagram PT3. The input button 307 is a pressure / temperature correlation diagram. PT1 region REG14, pressure / temperature correlation diagram PT2 region REG24 and pressure / temperature A button for designating one of the areas REG34 of Sekizu PT3.

  When the input buttons 301 and 304 are continuously pressed, the region REG11 of the pressure / temperature correlation diagram PT1 is designated. Then, when any one of the regions REG12, REG13, REG14 of the pressure / temperature correlation diagram PT1 and the regions REG21, REG22, REG23, REG24, REG31, REG32, REG33, REG34 of the pressure / temperature correlation diagram PT2, PT3 is designated. One of the buttons 301 to 303 and one of the input buttons 304 to 307 are continuously pressed.

  When a plurality of areas included in the pressure / temperature correlation diagrams PT1 to PT3 are designated, any one of the input buttons 301 to 303 and a plurality of the input buttons 304 to 307 are continuously pressed. Various modes are set for growing a GaN crystal according to the order of pressing a plurality of buttons among the input buttons 304 to 307.

  For example, when sequentially specifying the region REG13, the region REG11, and the region REG12, after pressing the input button 301, the input button 306, the input button 304, and the input button 305 are sequentially pressed.

  When the input buttons 301 to 307 are pressed, signals SG1 to SG7 are generated and output to the CPU 304, respectively. The signal SG1 is a signal for setting the mixing ratio r to “0.4”, the signal SG2 is a signal for setting the mixing ratio r to “0.7”, and the signal SG3 is a mixing ratio r. This is a signal for setting r to “0.95”.

  The signal SG4 is a signal for designating one of the regions REG11, REG21, REG31, the signal SG5 is a signal for designating any of the regions REG12, REG22, REG32, and the signal SG6 is The signal SG7 is a signal for designating any of the regions REG13, REG23, REG33, and the signal SG7 is a signal for designating any of the regions REG14, REG24, REG34.

  Table 1 shows signals SG1 to SG7, mixing ratios r = 0.4, 0.7, 0.95 and regions REG11, REG12, REG13, REG14; REG21, REG22, REG23, REG24; REG31, REG32, REG33, REG34. The correspondence relationship is shown.

  The mixing ratios r = 0.4, 0.7, 0.95 are respectively associated with the signals SG1 to SG3, the signal SG4 is associated with the regions REG11, REG21, REG31, and the signal SG5 is associated with the regions REG12, Associated with REG22 and REG32, signal SG6 is associated with regions REG13, REG23, and REG33, and signal REG7 is associated with regions REG14, REG24, and REG34.

  CPU 308 holds Table 1 and receives signals SG1 to SG3, and detects mixing ratios r = 0.4, 0.7, and 0.95 with reference to Table 1, respectively. When the CPU 308 receives the signal SG4 after receiving the signal SG1, the CPU 308 detects the region REG11 with reference to Table 1, and receives the signal SG4 after receiving the signal SG2, and then the region with reference to Table 1. After detecting REG21 and receiving signal SG3, when receiving signal SG4, region REG31 is detected with reference to Table 1.

  Further, when receiving the signal SG5 after receiving the signal SG1, the CPU 308 detects the signal REG12 with reference to Table 1, and receives the signal SG5 after receiving the signal SG2, and then receives the signal SG5 with reference to Table 1. When REG22 is detected and signal SG3 is received and then signal SG5 is received, signal REG32 is detected with reference to Table 1.

  Further, when receiving the signal SG6 after receiving the signal SG1, the CPU 308 detects the signal REG13 with reference to Table 1, and receives the signal SG6 after receiving the signal SG2, and then receives the signal SG6 with reference to Table 1. After detecting REG23 and receiving the signal SG3, when receiving the signal SG6, the signal REG33 is detected with reference to Table 1.

  Further, when receiving the signal SG7 after receiving the signal SG1, the CPU 308 detects the signal REG14 with reference to Table 1, and receives the signal SG7 after receiving the signal SG2, and then referring to Table 1. When the signal SG7 is received after the REG24 is detected and the signal SG3 is received, the signal REG34 is detected with reference to Table 1.

  FIG. 21 is a diagram showing the relationship between the mixing ratio r and the pressure / temperature correlation diagram. Referring to FIG. 21, pressure / temperature correlation diagrams PT1 to PT3 are associated with mixing ratios r = 0.4, 0.7, and 0.95, respectively. The memory 309 stores the pressure / temperature correlation diagrams PT1 to PT3 in association with the mixture ratios r = 0.4, 0.7, and 0.95, respectively. Since the pressure / temperature correlation diagrams PT1 to PT3 shown in FIG. 21 are the pressure / temperature correlation diagrams PT1 to PT3 shown in FIG. 4, the memory 309 stores the pressure / temperature correlation diagrams PT1 to PT1. PT3 is stored in association with the mixing ratios r = 0.4, 0.7, and 0.95, respectively.

  Referring to FIG. 20 again, CPU 308 continuously receives any of signals SG1 to SG3 and at least one of signals SG4 to SG7. First, a case where CPU 308 continuously receives signal SG1 and signal SG6 will be described.

  When the CPU 308 continuously receives the signal SG1 and the signal SG6, the CPU 308 detects the mixing ratio r (= 0.4) and the region REG13 specified by the signal SG1 with reference to Table 1, and the detected mixing ratio r The pressure / temperature correlation diagram PT1 corresponding to (= 0.4) is read from the memory 309.

  As described above, since the memory 309 stores the pressure / temperature correlation diagrams PT1 to PT3 in association with the mixing ratios r = 0.4, 0.7, and 0.95, the CPU 308 stores the mixing ratio r. The pressure / temperature correlation diagram PT1 corresponding to = 0.4 can be read from the memory 309.

  Then, since the CPU 308 detects the region REG13 according to the signal SG6, the CPU 308 detects a desired pressure and a desired temperature included in the region REG13 of the read pressure / temperature correlation diagram PT1. For example, the CPU 308 detects 5.05 MPa and 725 ° C. as the desired pressure and desired temperature from the region REG13 of the pressure / temperature correlation diagram PT1.

  Then, CPU 308 generates control signal CTL5 for setting the mixing ratio r = 0.4, which is the detected mixing ratio of metal Na and metal Ga in mixed melt 290, and outputs it to heating device 350.

The relationship between the temperature of the temperature and the metal melt 340 in the melt mixture 290, the relationship between the vapor pressure _{P Na} and the vapor pressure _{P Na-Ga} is determined, the relationship between the vapor pressure _{P Na} and the vapor pressure _{P Na-Ga} As described above, the amount of metal Na in the mixed melt 290 and the metal melt 350 is maintained, the metal Na moves from the metal melt 340 to the mixed melt 290, or from the mixed melt 290 to the metal melt. Metal Na moves to the liquid 340 (see FIG. 19). The movement of metal Na referred to here is vapor phase transport.

And when the temperature of the mixed melt 290 is 725 ° C., the temperature of the metal melt 340 is measured in advance when the mixing ratio r in the mixed melt 290 becomes 0.4, 0.7, 0.95. Then, based on the temperature T4 received from the temperature sensor 351, the CPU 308 adds the current mixing ratio r _NOW in the mixed melt 290 and the mixing ratio r _DIR specified by the signal SG1 in the mixed melt 290. The temperature T _DIR of the metal melt 340 for setting the mixing ratio r can be detected.

  FIG. 22 is a diagram showing the relationship between the temperature of the metal melt 340 and the mixing ratio r. In FIG. 22, the horizontal axis represents the temperature of the mixed melt 340, and the vertical axis represents the mixing ratio r. A curve k15 shows the relationship between the mixing ratio r and the temperature of the metal melt 340 when the temperature of the mixed melt 290 is 725 ° C.

Referring to FIG. 22, when the temperature of the metal melt 340 is T _Na 1 (> 600 ° C.), the mixing ratio r in the mixed melt 290 is set to 0.4, and the temperature of the metal melt 340 is set. Is T _Na 2 (> T _Na 1), the mixing ratio r in the mixed melt 290 is set to 0.7, and the temperature of the metal melt 340 is T _Na 3 (T _Na 2 <T _Na 3 <950 ° C.), the mixing ratio r in the mixed melt 290 is set to 0.95.

If the temperature T4 received from the temperature sensor 351 is T _Na 2 + β ° C., the CPU 308 indicates that the temperature of the metal melt 340 is T _Na 2 and the current mixing ratio r _NOW in the mixed melt 290 is 0.7. Detect something. Since the mixing ratio r _DIR specified by the signal SG1 is 0.4, the CPU 308 determines that the temperature of the metal melt 340 for setting the mixing ratio in the mixed melt 290 to the mixing ratio r _DIR is T _Na. 1 is detected.

Then, the CPU 308 generates a control signal CTL5 for setting the temperature of the heater of the heating device 350 to T _Na 1 + β ° C. and outputs it to the heating device 350.

  Further, the CPU 308 detects 5.05 MPa and 950 ° C. as the desired pressure and desired temperature included in the region REG13 of the pressure / temperature correlation diagram PT1, and therefore the temperature of the mixed melt 290 (= crucible 10 and reaction vessel 20). Control signals CTL1 and CTL2 for setting the temperature of 950 ° C. to be output to the heating devices 70 and 80, respectively, and a control signal CTL3 for setting the pressure of the space 23 to 5.05 MPa. Output to the pressure regulator 130.

Then, heating device 350 sets the temperature of metal melt 340 to T _Na 1 in accordance with control signal CTL5 from CPU 308 of control device 300A. Thus, the mixing ratio r in the mixed melt 290 is set to “0.4”.

  Further, the heating devices 70 and 80 set the temperature of the mixed melt 290 to 950 ° C. according to the control signals CTL1 and CTL2 from the CPU 308 of the control device 300A. Furthermore, the pressure regulator 130 sets the pressure of the space 23 to 5.05 MPa in accordance with the control signal CTL3 from the CPU 308 of the control device 300A.

  As a result, crystal growth of the GaN crystal is performed using the desired pressure and desired temperature included in the region REG13 of the pressure / temperature correlation diagram PT1.

  Next, the case where CPU 308 receives signal SG1, signal SG4, and signal SG5 successively in sequence will be described.

  When the CPU 308 sequentially receives the signal SG1, the signal SG4, and the signal SG5 sequentially, the CPU 308 detects the mixing ratio r (= 0.4) and the regions REG11, REG12 designated by the signal SG1, with reference to Table 1, The pressure / temperature correlation diagram PT1 corresponding to the detected mixing ratio r (= 0.4) is read from the memory 309.

  CPU 308 detects desired pressure Pf1 and desired temperature Tf1 included in region REG11 of pressure / temperature correlation diagram PT1, and desired pressure Pf2 and desired temperature Tf2 included in region REG12.

  Then, the CPU 308 generates the control signal CTL5 for setting the mixing ratio r in the mixed melt 290 to “0.4” and outputs it to the heating device 350 by the method described above, and the temperature of the mixed melt 290 is determined. Is generated and output to the heating devices 70 and 80, respectively, and a control signal CTL3 for setting the pressure of the space 23 to the pressure Pf1 is generated. Output to the pressure regulator 130.

The heating device 350 sets the temperature of the metal melt 340 to T _Na 1 according to the control signal CTL5 from the CPU 308 of the control device 300A. Thus, the mixing ratio r in the mixed melt 290 is set to “0.4”.

  Further, the heating devices 70 and 80 set the temperature of the mixed melt 290 to Tf1 according to the control signals CTL1 and CTL2 from the CPU 308 of the control device 300A. Further, the pressure regulator 130 sets the pressure of the space 23 to Pf1 in accordance with the control signal CTL3 from the CPU 308 of the control device 300A.

  Thus, the GaN crystal is dissolved using a desired pressure and a desired temperature included in the region REG11 of the pressure / temperature correlation diagram PT1.

  Thereafter, the CPU 308 generates control signals CTL1 and CTL2 for setting the temperature of the mixed melt 290 to a desired temperature Tf2 and outputs them to the heating devices 70 and 80, respectively, and sets the pressure in the space 23 to the pressure Pf2. Control signal CTL3 is generated and output to the pressure regulator 130.

  Then, the heating devices 70 and 80 set the temperature of the mixed melt 290 to Tf2 in accordance with the control signals CTL1 and CTL2 from the CPU 308 of the control device 300A. Further, the pressure regulator 130 sets the pressure of the space 23 to Pf2 in accordance with the control signal CTL3 from the CPU 308 of the control device 300A.

  As a result, crystal growth of the GaN crystal from the seed crystal is performed using the desired pressure and desired temperature included in the region REG12 of the pressure / temperature correlation diagram PT1.

  Note that the CPU 308 also sets the mixing ratio r in the mixed melt 290 to the specified mixing ratio according to the same operation as described above even when a signal pattern different from the above-described signal pattern is received from the input buttons 301 to 307. In addition, a desired pressure and a desired temperature included in each region of the pressure / temperature correlation diagrams PT1 to PT3 are set.

  Further, the CPU 308 holds the relationship between the temperature of the metal melt 340 and the mixing ratio r shown in FIG. 22 with respect to desired temperatures included in each region of the pressure / temperature correlation diagrams PT1 to PT3.

  FIG. 23 is a flowchart in the second embodiment for explaining a method for producing a GaN crystal. The flowchart shown in FIG. 23 is the same as the flowchart shown in FIG. 8 except that steps S51 to S54 are added between step S5 and step S6 of the flowchart shown in FIG.

Referring to FIG. 23, when step S1 to step S5 described above are executed, CPU 308 determines whether or not to change the mixing ratio in mixed melt 290 (step S51). More specifically, whether CPU308, the mixing ratio _{r DIR} specified by any of the signals SG1~SG3 is depending on whether different from the current mixture ratio _{r the NOW,} changing the mixing ratio of the molten mixture 290 Determine whether.

  When it is determined in step S51 that the mixing ratio in the mixed melt 290 is to be changed, the mixing ratio r in the mixed melt 290 is changed in the range of 0.4, 0.7, 0.95 by the method described above ( Step S52).

  Then, the pressure / temperature correlation diagram corresponding to the changed mixing ratio is selected from the pressure / temperature correlation diagrams PT1 to PT3 as a predetermined pressure / temperature correlation diagram (step S53).

  Thereafter, the pressure of the space 23 and the temperature of the crucible 10 are respectively set to the desired pressure and the desired temperature included in the selected pressure / temperature correlation diagram (step S54). And a series of operation | movement transfers to step S5, and step S5, S51-S54 mentioned above is repeatedly performed until it determines with not changing the mixing ratio in the mixed melt 290 in step S51.

  And if it determines with not changing the mixing ratio in the mixed melt 290 in step S51, a series of operation | movement will transfer to step S6 mentioned above.

  The loop of steps 5, S51 to S54 in the flowchart shown in FIG. 23 changes the mixing ratio in the mixed melt 290, and the pressure / temperature correlation diagram corresponding to the changed mixing ratio (of the pressure / temperature correlation diagrams PT1 to PT3). Any one) is used to grow a GaN crystal.

  FIG. 24 is another schematic cross-sectional view of the crystal growth apparatus according to the third embodiment. The crystal growth apparatus according to the third embodiment may be a crystal growth apparatus 100C shown in FIG. Referring to FIG. 24, crystal growth apparatus 100C according to the third embodiment is different from crystal growth apparatus 100B shown in FIG. 18 in bellows 40, support device 50, pipe 200, thermocouple 210, vertical mechanism 220, and vibration application device 230. A detection device 240, a gas supply pipe 250, a flow meter 260, a gas cylinder 270, and a temperature control device 280 are added.

  In crystal growth apparatus 100C, temperature sensor 71 outputs detected temperature T1 to temperature control apparatus 280 and control apparatus 300A, and temperature sensor 81 outputs detected temperature T2 to temperature control apparatus 280 and control apparatus 300A. Output.

  The bellows 40, the support device 50, the pipe 200, the thermocouple 210, the vertical mechanism 220, the vibration application device 230, the vibration detection device 240, the gas supply pipe 250, the flow meter 260, the gas cylinder 270, and the temperature control device 280 are described in the first embodiment. As described above.

  FIG. 25 is a flowchart for explaining an operation of manufacturing a GaN crystal using the crystal growth apparatus 100C shown in FIG. The flowchart shown in FIG. 25 is the same as the flowchart shown in FIG. 17 except that steps S51 to S54 are added between step S5B and step S6 of the flowchart shown in FIG.

  Referring to FIG. 25, when steps S1, S2, S2A, S3, S4, S4A, S5, S5A, and S5B described above are executed, steps S51 to S54 described in FIG. 23 are sequentially executed. Then, after step S54, the series of operations proceeds to step S5.

  The loop of steps 5, S5A, S5B, S51 to S54 in the flowchart shown in FIG. 25 changes the mixing ratio in the mixed melt 290 while the seed crystal 6B is in contact with the mixed melt 290, and the changed mixing. This is a loop for growing a GaN crystal from a seed crystal using a pressure / temperature correlation diagram (any of pressure / temperature correlation diagrams PT1 to PT3) corresponding to the ratio.

  As described above, according to the third embodiment, the mixing ratio r of the metal Na and the metal Ga in the mixed melt 290 is automatically changed to the mixing ratio specified by the signals SG1 to SG3, and the changed mixing is performed. A GaN crystal is grown or dissolved using a pressure / temperature correlation diagram corresponding to the ratio. Therefore, the GaN crystal can be grown by controlling the mixing ratio r, pressure and temperature.

In the third embodiment, the pipe 320 and 330, the metal melt 340, the control signal CTL5 for changing the mixing ratio of the molten mixture 290 as the mixture ratio _{r DIR} specified by the signal SG1~SG3 CPU 308 that generates and outputs to heating device 350, and heating device 350 that sets the temperature of metal melt 340 to a temperature that sets the mixing ratio in mixed melt 290 to mixing ratio r _DIR in response to control signal CTL5 Constitutes "mixing ratio changing means".

Further, the CPU 308 that reads out the pressure / temperature correlation diagram corresponding to the mixing ratio r _DIR specified by the signals SG1 to SG3 from the memory 309 constitutes “selecting means”.

  Further, the pipe 320 constitutes an “external container”, and the spaces 331 and 322 constitute an “external container space”.

Furthermore, the CPU308 outputs to the heating unit 350 generates a control signal CTL5 for varying the mixing ratio _{r DIR} specified mixing ratio in the melt mixture 290 by a signal SG1 to SG3, in response to the control signal CTL5, The heating device 350 that sets the temperature of the metal melt 340 to the temperature at which the mixing ratio in the mixed melt 290 is set to the mixing ratio _rDIR constitutes a “vapor pressure controller”.

  FIG. 26 is another perspective view of the melt holding member according to the present invention. FIG. 27 is a cross-sectional view for explaining a method of fixing the melt holding member 400 shown in FIG. Referring to FIG. 26, the melt holding member 400 includes a stopper 401 and a plurality of convex portions 402. The stopper 401 has a cylindrical shape whose diameter changes in the length direction DR3. Each of the plurality of convex portions 402 has a substantially hemispherical shape and has a diameter of several tens of μm. The plurality of convex portions 402 are randomly formed on the outer peripheral surface 401 </ b> A of the stopper 401. However, the interval between two adjacent convex portions 402 is set to several tens of μm.

  Referring to FIG. 27, melt holding member 400 is fixed in pipe 30 by support members 403 and 404. More specifically, the melt holding member 400 is fixed by being sandwiched between a support member 403 whose one end is fixed to the inner wall of the pipe 30 and a support member 404 whose one end is fixed to the inner wall of the pipe 30. Is done.

  In this case, the convex portion 402 of the melt holding member 400 may be in contact with the pipe 30 or may not be in contact therewith. When the melt holding member 400 is fixed so that the convex portion 402 does not contact the pipe 30, the interval between the convex portion 402 and the pipe 30 is set to an interval that can hold the metal melt 190 by the surface tension of the metal melt 190. The melt holding member 400 is fixed by the support members 403 and 404 by setting.

  Since the metal Na put in the pipe 30 is solid before the heating of the crucible 10 and the reaction container 20 is started, the nitrogen gas supplied from the gas cylinder 140 is connected to the space 23 in the reaction container 20 and the pipe 30. Can be diffused through the melt holding member 400.

  Then, heating of the crucible 10 and the reaction vessel 20 is started, and when the temperature of the pipe 30 is raised to 98 ° C. or higher, the metal Na put in the pipe 30 is melted into the metal melt 190, and nitrogen The gas is confined in the space 23.

  The melt holding member 400 holds the metal melt 190 by the surface tension of the metal melt 190 so that the metal melt 190 does not flow out into the space 31.

  Further, the metal melt 190 and the melt holding member 400 confine nitrogen gas and metal Na vapor evaporated from the metal melt 190 and the mixed melt 290 in the space 23 as the growth of the GaN crystal proceeds. As a result, further evaporation of the metal Na from the mixed melt 290 can be suppressed, and fluctuations in the quantitative ratio between the metal Na and the metal Ga due to evaporation of the metal Na in the mixed melt 290 can be suppressed. When the nitrogen gas in the space 23 decreases as the growth of the GaN crystal progresses, the pressure P1 in the space 23 becomes lower than the pressure P2 in the space 31, and the melt holding member 400 is in the space 31. The nitrogen gas is passed in the direction of the reaction vessel 20 and supplied to the space 23 via the metal melt 190.

  Thus, the melt holding member 400 acts in the same manner as the melt holding member 60 described above. Therefore, the melt holding member 400 is used in the crystal growth apparatuses 100, 100A, 100B, and 100C in place of the melt holding member 60.

  In the above description, the melt holding member 400 has been described as having the convex portion 402, but the melt holding member 400 may not have the convex portion 402. In this case, the melt holding member 400 is fixed to the inner wall of the pipe 30 by the support members 403 and 404 so that the distance between the stopper 401, the reaction vessel 20 and the pipe 30 is several tens of μm.

  Then, the interval between the melt holding member 400 (including the case where the convex portion 402 is provided and the case where the convex portion 402 is not included; hereinafter the same) and the pipe 30 is determined according to the temperature of the melt holding member 400. You may be made to do. In this case, when the temperature of the melt holding member 400 is relatively high, the distance between the melt holding member 400 and the pipe 30 is set to be relatively small. When the temperature of the melt holding member 400 is relatively low, the distance between the melt holding member 400 and the pipe 30 is set to be relatively large.

  The distance between the melt holding member 400 capable of holding the metal melt 190 by the surface tension and the pipe 30 varies depending on the temperature of the melt holding member 400. Therefore, the distance between the melt holding member 400 and the pipe 30 is changed according to the temperature of the melt holding member 400 so that the metal melt 190 can be reliably held by the surface tension.

  The temperature control of the melt holding member 400 is performed by the heating device 80.

  When the melt holding member 400 is used, the gas cylinder 140, the pressure regulator 130, the gas supply pipes 90 and 110, the valve 121, the piping 30, the melt holding member 400, and the metal melt 190 constitute a “gas supply device”. To do.

  FIG. 28 is still another perspective view of the melt holding member according to the present invention. Referring to FIG. 28, the melt holding member 410 includes a plug 411 in which a plurality of through holes 412 are formed. The plurality of through holes 412 are formed along the length direction DR2 of the plug 411. Each of the plurality of through holes 412 has a diameter of several tens of μm (see FIG. 28A).

  In the melt holding member 410, at least one through hole 412 may be formed.

  The melt holding member 420 includes a plug 421 in which a plurality of through holes 422 are formed. The plurality of through holes 422 are formed along the length direction DR2 of the plug 421. Each of the plurality of through holes 422 has diameters r1, r2, and r3 that are changed in a plurality of stages in the length direction DR2. Each of the diameters r1, r2, and r3 is determined within a range where the metal melt 190 can be held by surface tension, and is determined within a range of several μm to several tens of μm, for example (see FIG. 28B).

  In the melt holding member 420, at least one through hole 422 may be formed. The diameter of the through hole 422 may be changed to at least two. Further, the diameter of the through hole 422 may be continuously changed in the length direction DR2.

  The melt holding member 410 or 420 is used in place of the melt holding member 60 of the crystal growth apparatus 100, 100A, 100B, 100C.

  In particular, when the melt holding member 420 is used in place of the melt holding member 60, a plurality of crystal growth apparatuses 100, 100A, 100B, and 100C can be used without precisely controlling the temperature of the melt holding member 420. Since the metal melt 190 can be held by the surface tension of the metal melt 190 by any of the diameters changed to the steps, a GaN crystal having a large size can be formed without precisely controlling the temperature of the melt holding member 420. Can be manufactured.

  When the melt holding member 410 or 420 is used, the gas cylinder 140, the pressure regulator 130, the gas supply pipes 90 and 110, the valve 121, the piping 30, the melt holding member 410 or 420, and the metal melt 190 are “gas supply”. Device ".

  Furthermore, in the present invention, a porous plug or a backflow prevention valve may be used instead of the melt holding member 60. The porous plug is made of a sintered body obtained by sintering stainless steel powder, and has a structure in which many pores of several tens of μm are formed. Therefore, the porous plug can hold the metal melt 190 by the surface tension of the metal melt 190 in the same manner as the melt holding member 60 described above.

  The backflow prevention valve in the present invention includes both a spring-type backflow prevention valve used for a low temperature portion and a piston type backflow prevention valve used for a high temperature portion. This piston-type backflow prevention valve means that when the pressure P2 in the space 31 is higher than the pressure P1 in the space 23, the piston moves upward along a pair of guides due to the differential pressure between the pressure P2 and the pressure P1. It moves and supplies nitrogen gas in the space 31 to the space 23 through the metal melt 190. When P1 ≧ P2, the backflow prevention valve of the type in which the piston closes the connecting portion between the reaction vessel 20 and the pipe 30 by its own weight. It is. Therefore, this check valve can be used even in a high temperature part.

  In the above-described embodiment, the crystal growth temperature has been described as being 725 ° C. or 950 ° C. However, the present invention is not limited to this, and the crystal growth temperature may be 600 ° C. or higher. The nitrogen gas pressure may be any pressure that allows growth by the present crystal growth method in a pressurized state of 0.4 MPa or more. That is, the upper limit is not limited to 5.05 MPa in the present embodiment, and may be a pressure of 5.05 MPa or more.

  Further, in the above description, it has been described that metal Na and metal Ga are put in the crucible 10 in an Ar gas atmosphere, and metal Na is put in the pipe 30 or 320 in the Ar gas atmosphere. First, metal Na and metal Ga may be put in the crucible 10 in a gas atmosphere other than Ar gas such as He, Ne, and Kr, or in a nitrogen gas atmosphere, and metal Na may be put in the pipe 30 or 320. What is necessary is just to put metal Na and metal Ga into the crucible 10 and put the metal Na into the pipe 30 or 320 in an inert gas or nitrogen gas atmosphere. In this case, the inert gas or nitrogen gas has a moisture content of 1 ppm or less and an oxygen content of 1 ppm or less.

  Furthermore, although it has been described that the metal mixed with the metal Ga is Na, in the present invention, the present invention is not limited to this, and alkali metals such as lithium (Li) and potassium (K), or magnesium (Mg), calcium ( Alkaline earth metals such as Ca) and strontium (Sr) may be mixed with metal Ga to form mixed melt 290. And those in which these alkali metals are dissolved constitute an alkali metal melt, and those in which these alkaline earth metals are dissolved constitute an alkaline earth metal melt.

  Furthermore, instead of nitrogen gas, a compound containing nitrogen as a constituent element such as sodium azide and ammonia may be used. These compounds constitute nitrogen source gas.

  Further, a group III metal such as boron (B), aluminum (Al), and indium (In) may be used instead of Ga.

  Therefore, the crystal growth apparatus or manufacturing method according to the present invention generally manufactures a group III nitride crystal using a mixed melt of an alkali metal or alkaline earth metal and a group III metal (including boron). Anything is acceptable.

  The group III nitride crystal manufactured using the crystal growth apparatus or manufacturing method according to the present invention is used for manufacturing a group III nitride semiconductor device such as a light emitting diode, a semiconductor laser, a photodiode, and a transistor.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

The present invention is applied to a crystal growth apparatus for growing a group III nitride crystal by controlling the mixing ratio, gas pressure and temperature .

It is a schematic sectional drawing of the crystal growth apparatus by Embodiment 1 of this invention. It is a perspective view of the melt holding member shown in FIG. It is a top view which shows the attachment state to piping of a melt holding member. It is a figure which shows the pressure / temperature correlation diagram which prescribes | regulates the relationship between the pressure and temperature when growing a GaN crystal with respect to the mixing ratio of metal Na and metal Ga. It is a timing chart of the temperature of a crucible and a reaction container. It is a schematic diagram which shows the state in a crucible and reaction container between two timing t1, t2 shown in FIG. FIG. 2 is a schematic diagram of a GaN crystal grown or dissolved using the crystal growth apparatus shown in FIG. 1. 4 is a flowchart in the first embodiment for explaining a method of manufacturing a GaN crystal. FIG. 9 is a flowchart for explaining detailed operation of step S4 shown in FIG. 8 when a GaN crystal is grown using a desired pressure and a desired temperature included in a plurality of regions of the pressure / temperature correlation diagram. FIG. 9 is another flowchart for explaining the detailed operation of step S4 shown in FIG. 8 when a GaN crystal is grown using a desired pressure and a desired temperature included in a plurality of regions of the pressure / temperature correlation diagram. . 6 is a schematic cross-sectional view of a crystal growth apparatus according to a second embodiment. FIG. It is an enlarged view of the support apparatus, piping, and thermocouple which are shown in FIG. It is the schematic which shows the structure of the up-and-down mechanism shown in FIG. It is a timing chart of a vibration detection signal. It is another timing chart of the temperature of a crucible and a reaction container. It is a figure which shows the relationship between the temperature of a seed crystal, and the flow volume of nitrogen gas. 12 is a flowchart for explaining an operation of manufacturing a GaN crystal using the crystal growth apparatus shown in FIG. 6 is a schematic cross-sectional view of a crystal growth apparatus according to a third embodiment. FIG. It is a conceptual diagram for demonstrating the method to control the mixing ratio of metal Na and metal Ga in a mixed melt. It is a block diagram which shows the structure of a part of control apparatus shown in FIG. It is a figure which shows the relationship between a mixing ratio and a pressure / temperature correlation diagram. It is a figure which shows the relationship between the temperature of a metal melt, and a mixing ratio. It is a flowchart in Embodiment 2 for demonstrating the manufacturing method of a GaN crystal. FIG. 10 is another schematic cross-sectional view of the crystal growth apparatus according to the third embodiment. 25 is a flowchart for explaining an operation of manufacturing a GaN crystal using the crystal growth apparatus shown in FIG. It is another perspective view of the melt holding member by this invention. It is sectional drawing for demonstrating the fixing method of the melt holding member shown in FIG. FIG. 10 is still another perspective view of the melt holding member according to the present invention.

Explanation of symbols

  1-3 gas-liquid interface, 4 nitrogen gas, 5 metal Na vapor, 6-9, 9A GaN crystal, 6B seed crystal, 10 crucible, 11, 20B bottom surface, 20 reaction vessel, 20A outer peripheral surface, 21 body portion, 22 lid Part, 23, 31, 321, 322, 331 space, 30, 200, 320, 330 piping, 30A inner wall, 40 bellows, 50 support device, 60, 400, 410, 420 melt holding member, 61, 401, 411 421 plug, 62, 402 convex portion, 63 gap, 70, 80, 350, 360, 370 heating device, 71, 81, 351 temperature sensor, 90, 110, 250 gas supply pipe, 100, 100A, 100B, 100C crystal growth Equipment, 120, 121, 160 Valve, 130 Pressure regulator, 140, 270 Gas cylinder, 150 Exhaust pipe, 170 True Empty pump, 180 Pressure sensor, 190, 340 Metal melt, 201 Air hole, 210 Thermocouple, 220 Vertical mechanism, 221 Concavity and convexity member, 222 Gear, 223 Shaft member, 224 Motor, 225 Control unit, 230 Vibration application device, 240 Vibration detection device, 280 temperature control device, 290 mixed melt, 300, 300A control device, 301-307 input button, 308 CPU, 309 memory, 310 pressure sensor.

Claims (7)

It is determined according to the mixing ratio indicating the amount ratio of the alkali metal to the total amount of the alkali metal and the group III metal, and defines the relationship between the pressure and the temperature when the group III nitride crystal is grown or dissolved. A crystal growth apparatus for growing a group III nitride crystal using a pressure / temperature correlation diagram,
A crucible for holding a mixed melt containing the alkali metal and the group III metal at a predetermined mixing ratio;
A gas supply device for supplying a nitrogen source gas to a container space in contact with the mixed melt in the crucible and setting a gas pressure in the container space to a predetermined pressure;
A heating device for setting the temperature of the mixed melt to a predetermined temperature;
The container at a desired pressure and a desired temperature included in a predetermined pressure / temperature correlation diagram determined according to the predetermined mixing ratio from a plurality of pressure / temperature correlation diagrams provided corresponding to the plurality of mixing ratios A control device that controls the gas supply device and the heating device to set the gas pressure of the nitrogen source gas in the space and the temperature of the mixed melt, respectively;
With
The plurality of pressure / temperature correlation diagrams are:
FIG. 4 is a pressure / temperature correlation diagram suitable for crystal growth of the group III nitride crystal from a seed crystal and column III-shaped crystal growth of the group III nitride crystal, and was determined according to a first mixing ratio. A first pressure / temperature correlation diagram;
A pressure / temperature correlation diagram suitable for crystal growth of the group III nitride crystal having a plate shape, and a second pressure determined in accordance with a second mixing ratio larger than the first mixing ratio / Temperature correlation diagram,
A pressure / temperature correlation diagram suitable for crystal growth of the group III nitride crystal from the seed crystal, and a third pressure determined in accordance with a third mixing ratio that is larger than the second mixing ratio / Temperature correlation diagram,
Including
The predetermined pressure / temperature correlation diagram is selected according to the determination of the predetermined mixing ratio from the first to third pressure / temperature correlation diagrams,
In the case where the group III nitride crystal having the plate shape is grown, the control device is configured to set the second desired pressure and the second desired temperature included in the second pressure / temperature correlation diagram to the second desired temperature. Controlling the gas supply device and the heating device to set the gas pressure of the nitrogen source gas in the container space and the temperature of the mixed melt, respectively.
Crystal growth equipment. A support device for supporting the seed crystal composed of the group III nitride crystal in an interface between the container space and the mixed melt or in the mixed melt;
In the case where the group III nitride crystal is grown from the seed crystal, the control device is configured to bring the container space to a third desired pressure and a third desired temperature included in the first pressure / temperature correlation diagram. Or controlling the gas supply device and the heating device so as to set the gas pressure of the nitrogen source gas and the temperature of the mixed melt respectively, or a fourth desired value included in the third pressure / temperature correlation diagram The gas supply device and the heating device are controlled so as to set the gas pressure of the nitrogen source gas and the temperature of the mixed melt in the container space to the pressure and the fourth desired temperature, respectively. The crystal growth apparatus described in 1. Each of the first to third pressure / temperature correlation diagrams is:
A first region for dissolving the group III nitride crystal;
A second region for crystal growth of the group III nitride crystal from the seed crystal;
A third region for crystal growth of the group III nitride crystal having the columnar shape;
A fourth region for crystal growth of the group III nitride crystal having the plate shape,
In the predetermined pressure / temperature correlation diagram selected from the first to third pressure / temperature correlation diagrams in accordance with the determination of the predetermined mixing ratio, the control device includes the first to fourth regions. The gas supply device and the heating device are controlled so as to set the gas pressure of the nitrogen source gas and the temperature of the mixed melt in the container space to a desired pressure and a desired temperature included in at least one region, respectively. The crystal growth apparatus according to claim 1. A mixing ratio changing means for changing a mixing ratio of the alkali metal and the group III metal in the mixed melt in a range of the plurality of mixing ratios;
Selecting means for selecting a pressure / temperature correlation diagram corresponding to the mixing ratio changed by the mixing ratio changing unit as the predetermined pressure / temperature correlation diagram from the plurality of pressure / temperature correlation diagrams;
The control device sets the gas pressure of the nitrogen source gas and the temperature of the mixed melt in the container space to a desired pressure and a desired temperature included in the pressure / temperature correlation diagram selected by the selection means, respectively. The crystal growth apparatus according to claim 1, wherein the gas supply apparatus and the heating apparatus are controlled to do so.   The crystal growth apparatus according to claim 4, wherein the mixing ratio changing unit changes the mixing ratio by controlling supply / stop of the alkali metal to the mixed melt. The mixing ratio changing means includes
An external container for holding an alkali metal melt in contact with the external container space communicating with the container space;
Supply / stop of the alkali metal is controlled by changing a relative relationship between the first vapor pressure of the alkali metal evaporated from the alkali metal melt and the second vapor pressure of the alkali metal evaporated from the mixed melt. The crystal growth apparatus according to claim 5, comprising a vapor pressure controller.   The crystal growth apparatus according to claim 6, wherein the vapor pressure controller changes a relative relationship between the first vapor pressure and the second vapor pressure by changing a temperature of the alkali metal melt.

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