JP2011219311A - Apparatus and method for manufacturing compound semiconductor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for manufacturing a compound semiconductor crystal that manufacture a compound semiconductor crystal by improving the accuracy of pressure control of gas inside a crystal growth chamber.SOLUTION: The apparatus for manufacturing the compound semiconductor crystal includes a gas supply section 101, the crystal growth chamber 110, a gas exhausting section 120, and pressure control sections 130 and 140. Gas is supplied from the gas supply section 101 to the crystal growth chamber 110. The gas exhausting section 120 exhausts gas from the crystal growth chamber 110. The pressure control sections 130 and 140 are connected to at least one of a part between the gas supply section 101 and crystal growth chamber 110 and a part between the crystal growth chamber 110 and gas exhausting section 120, and are opened to at least one of the crystal growth chamber 110 and the gas supply section 101 and gas exhausting section 120, thereby changing the pressure intermittently.

Description

  The present invention relates to a compound semiconductor crystal manufacturing apparatus and a compound semiconductor crystal manufacturing method.

  Compound semiconductor crystals such as gallium nitride (GaN) are very useful as materials for forming semiconductor devices such as light-emitting elements, electronic elements, and semiconductor sensors. In order to grow such a compound semiconductor crystal, conventionally, for example, a flux method has been proposed (for example, Patent Document 1).

  The crystal growth apparatus disclosed in Patent Document 1 adjusts the pressure of a reaction vessel (crystal growth chamber), a first gas supply device filled with nitrogen gas equal to or higher than the pressure in the reaction vessel, and the pressure of the nitrogen gas. And a pressure adjusting mechanism. The pressure adjustment mechanism has a pressure sensor and a pressure adjustment valve. Patent Document 1 discloses that a group III nitride crystal is grown using this crystal growth apparatus.

JP 2001-64097 A

  In the crystal growth apparatus and crystal growth method disclosed in Patent Document 1, the nitrogen gas pressure in the reaction vessel is adjusted using one pressure adjustment valve. As a result of intensive studies by the present inventors, it has been found that if the pressure of a gas such as nitrogen gas is controlled using one pressure regulating valve disclosed in Patent Document 1, the pressure of the gas in the reaction vessel cannot be precisely controlled. It was.

  17 and 18 are diagrams illustrating a configuration example of the crystal growth apparatus disclosed in Patent Document 1. FIG. With reference to FIG. 17 and FIG. 18, the subject of patent document 1 is demonstrated in detail below.

  In Patent Document 1, as shown in FIG. 17, the first cylinder 210 of the first gas supply device 220 is always filled with gas so as to be equal to or higher than the pressure inside the reaction vessel 201. It is described that the pressure is regulated via the pressure regulating valve 208 (Claim 1 of Patent Document 1 and paragraphs 0023-0025 and the like). From this, the pressure regulating valve 208 is not fully opened so that the pressure inside the first cylinder 210 and the pressure inside the reaction vessel 201 are equal, and the pressure regulating valve is generally Since the opening degree of the valve is adjusted according to the set pressure, the adjustment is made continuously. In such a mechanism, since the accuracy of the opening of the pressure regulating valve directly determines the accuracy of pressure control, precise control of the pressure inside the reaction vessel 201 is very difficult.

  In Patent Document 1, as shown in FIG. 18, when the second gas supply device 230 is prepared, in the flux method, dangerous substances such as Na (sodium) are diffused into the first cylinder 210. It is described that the effect of preventing can be expected (paragraph 0038 of Patent Document 1). However, the second cylinder 212 of the second gas supply device 230 is always filled with gas so as to be equal to or higher than the pressure inside the reaction vessel 201, and the pressure is adjusted via the pressure regulating valve 208 therebetween. It is described that it is adjusted (Claim 2 of Patent Document 1 and paragraph 0034). Therefore, the pressure regulating valve 208 is not fully opened so that the pressure inside the second cylinder 212 is equal to the pressure inside the reaction vessel 201, and the pressure regulating valve is generally Since the opening degree of the valve is adjusted according to the set pressure, the adjustment is made continuously. In such a mechanism, since the accuracy of the opening of the pressure regulating valve directly determines the accuracy of pressure control, precise control of the pressure inside the reaction vessel 201 is still very difficult.

  As described above, the controllability of the pressure inside the reaction vessel 201 in Patent Document 1 is that the pressure before and after the pressure regulating valve 208 is always different. Depends on accuracy. According to the inventor's further trial, even if various devices are used, the accuracy is at most within 10% of the set pressure inside the reaction vessel 201, for example, less than 1%. Currently, it is difficult to obtain a highly accurate pressure control valve.

  The present inventor actually tried to grow a GaN crystal by a flux method with such a device configuration using the pressure regulating valve 208. As a result, the controllability of the internal pressure is as large as ± 10% with respect to the set pressure, and there are cases where crystals do not grow. It was found that there was a quality problem. The pressure controllability necessary for stable crystal growth is generally required to be highly accurate. For example, an accuracy of 0.1 MPa to 0.01 MPa is realized with respect to a set pressure of a reaction vessel of 10 MPa. The pressure control mechanism is preferably less than 1%, and more preferably less than 0.1% with respect to the set pressure inside the reaction vessel. Thus, it is desirable that the compound semiconductor crystal manufacturing apparatus is capable of highly accurate pressure control.

  Further, in the device configuration of Patent Document 1 shown in FIG. 17 and FIG. 18, due to the problem of controllability of the opening degree of the pressure regulating valve 208 that continuously regulates pressure, it is often completely closed when it should be closed. Therefore, there is a possibility that a phenomenon of so-called “outflow” may occur in which a gas with a small flow rate is not passed. In this case, not only the controllability of the pressure is deteriorated, but there is a possibility that the equipment may be in a dangerous state such that the pressure inside the heated reaction vessel 201 rises above a desired pressure and bursts. This danger can occur in the same manner even if the pressure regulating valve 208 of Patent Document 1 is changed to a mass flow controller and an attempt is made to control the pressure inside the reaction vessel 201 by precise flow rate control. Thus, also from the viewpoint of controllability and safety, the compound semiconductor crystal manufacturing apparatus is equipped with a device that continuously adjusts the pressure or flow rate, such as a pressure adjustment valve and a mass flow controller, to the valve that supplies gas to the reaction vessel. Instead of using it, it is desirable to use a valve such as a stop valve that can reliably open or close intermittently.

  Further, in the apparatus configuration of Patent Document 1 shown in FIGS. 17 and 18, for example, when the reaction vessel 201 is heated by the heating device 205, the reaction vessel 201 is not subjected to the pressure regulating valve 208 but according to Boyle-Charles' law. The internal pressure rises and exceeds the desired pressure. After that, the pressure adjustment valve 208 cannot adjust the pressure to the reduced pressure side, and the internal pressure of the reaction vessel 201 greatly exceeds the design, and the reaction vessel The equipment may be in a dangerous state, such as 201 bursting. Thus, from the viewpoint of controllability and safety, it is desirable that the compound semiconductor crystal manufacturing apparatus can perform both pressurization and decompression by the pressure control mechanism connected to the reaction vessel.

  Further, the pressure regulating valve 208 found in the device configuration of Patent Document 1 is a very expensive device such that the price is generally 10 times or more that of a stop valve. Although it is premised on ensuring safety and controllability, considering the industrial application, it is desirable to use equipment that is as cheap as possible for the compound semiconductor crystal manufacturing apparatus.

  Accordingly, an object of the present invention is to provide a compound semiconductor crystal manufacturing apparatus and a compound semiconductor crystal manufacturing method for manufacturing a compound semiconductor crystal by improving the pressure control accuracy of the gas inside the crystal growth chamber. .

  The compound semiconductor crystal manufacturing apparatus of the present invention includes a gas supply unit, a crystal growth chamber, a gas discharge unit, and a pressure control unit. The crystal growth chamber is supplied with gas from a gas supply unit. The gas discharge unit discharges gas from the crystal growth chamber. The pressure control unit is connected to at least one of the gas supply unit and the crystal growth chamber and between the crystal growth chamber and the gas discharge unit, and at least the crystal growth chamber, the gas supply unit, and the gas discharge unit. On the other hand, the pressure changes intermittently by being opened respectively.

  The method for producing a compound semiconductor crystal of the present invention includes a step of supplying gas from the gas supply unit to the crystal growth chamber, and a step of discharging gas from the crystal growth chamber to the gas discharge unit. At least one of the gas supply step and the gas discharge step is connected to at least one of the gas supply unit and the crystal growth chamber, and between the crystal growth chamber and the gas discharge unit, and the crystal growth chamber The pressure inside the crystal growth chamber is controlled using a pressure control unit that changes pressure intermittently by being opened to at least one of the gas supply unit and the gas discharge unit.

  According to the compound semiconductor crystal manufacturing apparatus and the manufacturing method of the present invention, at the time of supplying the gas, the gas from the gas supply unit is temporarily held in the pressure control unit so that the pressure is different from the pressure of the crystal growth chamber, The gas can be supplied to the crystal growth chamber. When the gas is supplied to the crystal growth chamber, the pressure in the pressure control unit and the pressure in the crystal growth chamber are temporarily equal. The supply amount of gas from the pressure control unit to the crystal growth chamber at one time is equal to or less than the amount (number of moles) held in the pressure control unit. The amount (number of moles) of gas held in the pressure control unit is proportional to the pressure of the pressure control unit and the volume of the pressure control unit, and inversely proportional to the absolute temperature of the pressure control unit. For this reason, by arbitrarily setting the pressure, volume and temperature of the pressure control unit, the amount of gas supplied from the pressure control unit to the crystal growth chamber can be freely controlled, and the gas inside the crystal growth chamber can be controlled. The accuracy of pressure rise can be increased freely. By repeating this, it is possible to control the pressure of the gas inside the crystal growth chamber with improved accuracy during the process of supplying the gas.

  In the process of discharging gas, the pressure of the pressure control unit is set to a pressure different from the pressure inside the crystal growth chamber, and then the pressure of the crystal growth chamber and the pressure control unit are temporarily equal to each other. As described above, the gas from the crystal growth chamber is discharged to the pressure control unit and held by the pressure control unit. Next, the gas can be discharged from the pressure control unit to the gas discharge unit such that the pressure of the pressure control unit and the pressure of the gas discharge unit are equal. The maximum amount of gas discharged from the crystal growth chamber to the pressure control unit is less than the amount (number of moles) held in the pressure control unit. The amount (number of moles) of gas held in the pressure control unit is proportional to the pressure of the pressure control unit and the volume of the pressure control unit, and inversely proportional to the absolute temperature of the pressure control unit. Therefore, by arbitrarily setting the pressure, volume and temperature of the pressure control unit, the amount of gas discharged from the crystal growth chamber to the pressure control unit can be freely controlled, and the gas inside the crystal growth chamber can be controlled. The accuracy of pressure reduction can be increased freely. By repeating this, it is possible to improve the accuracy and control the pressure of the gas inside the crystal growth chamber during the process of discharging the gas.

  Thus, by using the pressure control unit that can freely control the supply amount or discharge amount of gas per operation in at least one of the step of supplying gas and the step of discharging gas, the crystal growth chamber The compound semiconductor crystal is manufactured by freely improving the accuracy of internal gas pressure control.

  Here, “the pressure changes intermittently when opened with the crystal growth chamber” means that when the pressure control unit is opened with the crystal growth chamber, the pressure of the pressure control unit and the pressure of the crystal growth chamber The gas flows so that is equal. The above "at least one of the gas supply unit and the gas discharge unit, the pressure changes intermittently by being opened" means that when the pressure control unit is opened to at least one of the gas supply unit or the gas discharge unit, It means that the gas flows so that at least one of the pressure of the pressure control unit, the pressure of the gas supply unit, and the pressure of the gas discharge unit becomes equal.

  Preferably, in the compound semiconductor crystal manufacturing apparatus, the pressure control unit is connected between the gas supply unit and the crystal growth chamber, and between the crystal growth chamber and the gas discharge unit.

  Preferably, in the compound semiconductor crystal manufacturing method, in the gas supplying step and the gas discharging step, the pressure inside the crystal growth chamber is controlled using a pressure control unit.

  Accordingly, the pressure control unit can be used in both the gas supply step and the gas discharge step, so that the pressure of the gas supply unit or the gas discharge unit, the internal volume or temperature of the pressure control unit, etc. By appropriately setting the above, it is possible to freely improve the accuracy of the pressure control of the gas inside the crystal growth chamber and manufacture the compound semiconductor crystal.

  In the compound semiconductor crystal manufacturing apparatus, in the pressure control unit, a control unit that controls a pressure between the gas supply unit and the crystal growth chamber, and a control unit that controls a pressure between the crystal growth chamber and the gas discharge unit And may be the same.

  In the compound semiconductor crystal manufacturing method, in the step of supplying gas and the step of discharging gas, a control unit that controls the pressure between the gas supply unit and the crystal growth chamber, and the crystal growth chamber and the gas discharge unit The pressure inside the crystal growth chamber may be controlled using a pressure control unit that is the same as the control unit that controls the pressure in between.

  Thereby, the pressure control part in the process of supplying gas and the pressure control part in the process of exhausting gas can be shared. For this reason, since the component of a crystal manufacturing apparatus can be reduced, cost can be reduced and a compound semiconductor crystal can be manufactured.

  In the compound semiconductor crystal manufacturing apparatus, the pressure control unit preferably includes a control unit having two valves and a pipe partitioned by the valves.

  Preferably, in the method for producing a compound semiconductor crystal, at least one of the gas supply step and the gas discharge step uses a pressure control unit including a control unit having two valves and a pipe partitioned by the valves. The pressure inside the crystal growth chamber is controlled.

  The valve does not have to be capable of continuously adjusting the opening, but is preferably one that can be reliably opened and closed intermittently. By such opening / closing operation of the valve, the gas can be reliably held in the piping partitioned by the valve. For this reason, the precision of the pressure fluctuation of the gas inside a crystal growth chamber can be raised more.

  In the compound semiconductor crystal manufacturing apparatus, preferably, the pressure control unit includes a control unit having three or more valves and a pipe partitioned into two or more regions by the valves.

  Preferably, in the compound semiconductor crystal manufacturing method, at least one of the step of supplying gas and the step of discharging gas includes a control unit having three or more valves and pipes partitioned into two or more regions by the valves. Is used to control the pressure inside the crystal growth chamber.

  By opening and closing the valve, gas can be held in two or more regions in the piping partitioned by the valve. The two or more regions can be controlled to different pressures. For this reason, the precision of the pressure control of the gas inside a crystal growth chamber can be raised more.

  Preferably, the compound semiconductor crystal manufacturing apparatus further includes a connection pipe connecting the crystal growth chamber and the pressure control unit, and a buffer pipe provided in the connection pipe, and the buffer pipe has a volume different from that of the connection pipe. Have a volume.

  Preferably, in the compound semiconductor crystal manufacturing method, at least one of the gas supply step and the gas discharge step is provided in a connection pipe connecting the crystal growth chamber and the pressure control unit, and has a volume different from that of the connection pipe. The internal pressure of the crystal growth chamber is controlled using the buffer pipe.

  The amount of change in pressure inside the crystal growth chamber can be further optimized by the buffer pipe. For this reason, the precision of the pressure fluctuation of the gas inside a crystal growth chamber can be raised more.

  Preferably, the compound semiconductor crystal manufacturing apparatus further includes a heating unit that heats the pressure control unit.

  In the method for producing a compound semiconductor crystal, preferably, the pressure control unit is heated in at least one of the step of supplying gas and the step of discharging gas.

  Thereby, the number of moles of the gas held by the pressure control unit can be adjusted. For this reason, the precision of the pressure fluctuation of the gas inside a crystal growth chamber can be raised more.

  Preferably, in the above-described compound semiconductor crystal manufacturing apparatus and manufacturing method, a command unit for controlling the pressure of the crystal growth chamber is provided, and a pressure control program preset in the command unit and a pressure value from the pressure gauge are provided. In response, a command is issued from the command unit to the pressure control unit.

  As a result, the pressure control and temperature control necessary for crystal growth can be performed at the same time, and a command can be issued to the pressure control unit so as to obtain the best pressure controllability according to the pressure value from the pressure gauge. .

  According to the compound semiconductor crystal manufacturing apparatus and the compound semiconductor crystal manufacturing method of the present invention, it is possible to improve the pressure control accuracy of the gas inside the crystal growth chamber and manufacture the compound semiconductor crystal.

It is a schematic diagram which shows schematically the manufacturing apparatus of the compound semiconductor crystal in Embodiment 1 of this invention. It is a schematic diagram which shows schematically the starting state of one operation | movement of the pressure control part at the time of pressurizing the inside of a crystal growth chamber in the manufacturing method of the compound semiconductor crystal in Embodiment 1 of this invention. It is a schematic diagram which shows roughly the completion | finish state of one operation | movement of the pressure control part at the time of pressurizing the inside of a crystal growth chamber in the manufacturing method of the compound semiconductor crystal in Embodiment 1 of this invention. It is a figure which shows roughly the control action in the manufacturing method of the compound semiconductor crystal in Embodiment 1 of this invention. It is a schematic diagram which shows schematically the manufacturing apparatus of the compound semiconductor crystal in Embodiment 2 of this invention. It is a schematic diagram which shows schematically the manufacturing apparatus of the compound semiconductor crystal in Embodiment 3 of this invention. It is a schematic diagram which shows schematically the manufacturing apparatus of the compound semiconductor crystal in Embodiment 4 of this invention. It is a schematic diagram which shows roughly the starting state of one operation | movement of the pressure control part at the time of pressurizing the inside of a crystal growth chamber in the manufacturing method of the compound semiconductor crystal in Embodiment 4 of this invention. It is a schematic diagram which shows roughly the completion | finish state of one operation | movement of the pressure control part at the time of pressurizing the inside of a crystal growth chamber in the manufacturing method of the compound semiconductor crystal in Embodiment 4 of this invention. It is a figure which shows the pressure of the gas inside the crystal growth chamber at the time of pressurization in an Example. It is a figure which shows the amount of pressure changes of the gas inside the crystal growth chamber at the time of pressurization in an Example. It is a figure which shows the pressure of the gas inside the crystal growth chamber at the time of pressure reduction in an Example. It is a figure which shows the amount of pressure changes of the gas inside the crystal growth chamber at the time of pressure reduction in an Example. It is a figure which shows the temperature and pressure in the crystal growth chamber in an Example. It is a figure which shows the microscope picture of the crystal surface after the crystal growth in an Example. It is another figure which shows the microscope picture of the crystal surface after the crystal growth in an Example. It is a figure which shows the structural example of the crystal growth apparatus of patent document 1. FIG. It is another figure which shows the structural example of the crystal growth apparatus of patent document 1. FIG.

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

(Embodiment 1)
With reference to FIG. 1, the manufacturing apparatus of the compound semiconductor crystal in this Embodiment is demonstrated. As shown in FIG. 1, the compound semiconductor crystal manufacturing apparatus according to the present embodiment includes a gas supply unit 101, pipes 102 and 103, a crystal growth chamber 110, a gas discharge unit 120, and pressure control units 130 and 140. And a pressure reducing valve 150, a pressure gauge 151, and a command unit 160.

  The gas supply unit 101 supplies gas to the crystal growth chamber 110. The gas supplied by the gas supply unit 101 includes, for example, a raw material of the compound semiconductor crystal to be manufactured. The gas supply unit 101 is held at a higher pressure than the inside of the crystal growth chamber 110. The gas supply unit 101 is, for example, a nitrogen gas cylinder.

  The pipe 102 connects the gas supply unit 101 and the pressure control unit 130 and causes the gas to flow inside. The pipe 103 connects the pressure control units 130 and 140 and the crystal growth chamber 110 to flow gas inside.

  The crystal growth chamber 110 is supplied with gas from the gas supply unit 101. The crystal growth chamber 110 is supplied with gas so as to have a desired pressure, and grows a compound semiconductor crystal therein. The crystal growth chamber 110 includes a heating unit 111 and a reaction vessel 112 in the case of a liquid phase growth method such as a flux method. The heating unit 111 heats the gas 113 supplied from the gas supply unit 101 and the pressure-controlled gas 114 and the solvent 113 containing the raw material. The reaction vessel 112 holds the solvent 113 and the seed substrate 115 inside.

  The gas discharge unit 120 discharges gas from the crystal growth chamber 110 to the outside of the manufacturing apparatus. The gas exhaust unit 120 is at a lower pressure than the crystal growth chamber 110, for example, atmospheric pressure. When the gas discharge unit 120 is set to atmospheric pressure, it may be opened to the atmosphere as long as there are no safety or environmental problems with the components of the exhaust gas.

  The pressure control units 130 and 140 are connected between the gas supply unit 101 and the crystal growth chamber 110 and between the crystal growth chamber 110 and the gas discharge unit 120. The pressure control units 130 and 140 are intermittently changed in pressure by being opened to the crystal growth chamber 110 and at least one of the gas supply unit 101 and the gas discharge unit 120, respectively.

  The pressure control unit 130 includes two valves 131 and 132 and a pipe 133 partitioned by the two valves 131 and 132. The pressure control unit 140 includes two valves 141 and 142 and a pipe 143 partitioned by the two valves 141 and 142. The valves 131, 132, 141, 142 can be opened and closed, respectively. By opening the valves 131 and 142, the pressure inside the piping 133 and the piping 143 partitioned by the valves 131 and 132 and the valves 141 and 142 can be made different from the pressure inside the crystal growth chamber 110, respectively. Alternatively, by opening the valves 132 and 141, respectively, the crystal growth chamber 110, the pipe 133, and the pipe 143 can be opened, and the pressure can be made equal to the pressure inside the crystal growth chamber 110. The pipes 133 and 143 can be closed by valves 131, 132, 141, and 142.

  A heating unit (not shown) for heating the pressure control units 130 and 140 may be arranged. In this case, the heating unit can heat the pipes 133 and 143, for example. The number of moles of gas inside the pipes 133 and 143 can also be adjusted by the heating unit.

  The pressure reducing valve 150 reduces the pressure of the gas supplied from the gas supply unit 101. The pressure gauge 151 measures the pressure inside the crystal growth chamber 110. Alternatively, when the pressure of the gas supplied from the gas supply unit 101 is insufficient, a compressor is provided at this location instead of the pressure reducing valve 150, and the pressure of the gas supplied from the gas supply unit 101 is increased. Also good.

  The command unit 160 commands the opening / closing of the valves 131, 132, 141, 142 according to the pressure value from the pressure gauge 151 in order to control the pressure in the crystal growth chamber 110.

  Then, the manufacturing method of the compound semiconductor crystal in this Embodiment is demonstrated. The manufacturing method of the compound semiconductor crystal in the present embodiment is performed using the manufacturing apparatus shown in FIG.

  First, gas is supplied from the gas supply unit 101 to the crystal growth chamber 110. The pressure of the gas derived from the gas supply unit 101 is adjusted to P1 (P1 is higher than the pressure of the crystal growth chamber 110) by the pressure reducing valve 150, and flows into the pressure control unit 130 via the pipe 102. The gas that has flowed into the pressure control unit 130 is supplied to the crystal growth chamber 110.

  At this time, the pressure inside the crystal growth chamber 110 is controlled using the pressure control unit 130 connected between the gas supply unit 101 and the crystal growth chamber 110. In the present embodiment, the pressure inside the crystal growth chamber 110 is controlled using a pressure control unit 130 having two valves 131 and 132 and a pipe 133 partitioned by the two valves 131 and 132.

  Specifically, as shown in FIG. 2, the valve 131 is opened and the valves 132, 141, 142 are closed. In this state, the gas whose pressure is adjusted to P1 is supplied to the pipe 133. As a result, the pipe 133 is filled with the gas having the pressure P1, the volume V1, and the temperature T1. At this time, pressure T 130 (in this embodiment, pipe 133) may be heated to further adjust temperature T1.

  Thereafter, as shown in FIG. 3, the valve 131 is closed and the valve 132 is opened. Thereby, since the gas having the pressure P1, the volume V1, and the temperature T1 is supplied to the crystal growth chamber 110 through the pipe 103, the pressure inside the crystal growth chamber 110 can be increased.

  In one operation of the pressure control unit 130 (operation from the start state in FIG. 2 to the end state in FIG. 3), T1 and TA are respectively expressed as absolute temperatures (unit K) from the law of mass conservation and the gas state equation. (P1 × V1) / (R × T1) + (P2 × VA) / (R × TA) = (P3 × V1) / (R × T1) + (P3 × VA) / (R × TA) A relationship is established. Therefore, in one operation of the pressure controller 130, the pressure inside the crystal growth chamber 110 increases from P2 to P3. On the other hand, the pressure inside the pressure control unit 130 decreases from P1 to P3. As described above, not all the gas inside the pressure control unit 130 is pushed out toward the crystal growth chamber 110. By opening the valve 132, the gas flows so that the pressure inside the pressure control unit 130 and the pressure inside the crystal growth chamber 110 are equal to P3 which is the pressure between P1 and P2, respectively. This contributes to precise control of the pressure inside the crystal growth chamber 110. Thereafter, the valve 132 is closed.

  Then, by repeating the above steps intermittently, every time the pressure control unit 130 operates, a part of the gas having the pressure P1, the volume V1, and the temperature T1 is crystallized according to the above relational expression. Since it can be supplied to the growth chamber 110, accuracy can be improved and the pressure inside the crystal growth chamber 110 can be increased. For one operation of the pressure control unit 130, based on the pressure inside the crystal growth chamber 110 measured by the pressure gauge 151, the command unit 160 controls the opening and closing of the valves 131 and 132 and the time for opening the valves 131 and 132. May be.

  When the inside of the crystal growth chamber 110 reaches a desired pressure, a compound semiconductor crystal is grown. For example, the seed substrate 115 is disposed inside the reaction vessel 112, and a solvent 113 containing a metal that is a raw material is accommodated in the reaction vessel 112. The solvent 113 is heated by the heating unit 111 to be liquefied. Then, the gas supplied from the pressure control unit 130 is dissolved in the solvent 113. Thereby, the solvent in which the gas is dissolved can be brought into contact with the seed substrate 115. In this state, a compound semiconductor crystal is grown on the seed substrate 115 by adjusting the pressure of the gas supplied from the pressure controller 130.

  Even during crystal growth, when the pressure decreases, the pressure inside the crystal growth chamber 110 may be increased using the pressure control unit 130. In this case, the command unit 160 may be used to control the pressure inside the crystal growth chamber 110.

  Next, in order to cool and depressurize the inside of the crystal growth chamber 110, the gas is discharged from the crystal growth chamber 110 to the gas discharge unit 120. At this time, the pressure inside the crystal growth chamber 110 is controlled using the pressure control unit 140 connected between the crystal growth chamber 110 and the gas discharge unit 120. In the present embodiment, the pressure inside the crystal growth chamber 110 is controlled using the pressure control unit 140 having two valves 141 and 142 and a pipe 143 partitioned by the valves 141 and 142.

  Specifically, the valves 131, 132, 142 are closed and the valve 141 is opened. In this state, the gas discharged from the crystal growth chamber 110 is supplied to the pipe 143. In this case, the pipe 143 is filled with a gas having a high pressure. At this time, the pressure control unit 140 (in this embodiment, the pipe 143) may be heated to adjust the number of moles of gas to be filled.

  Thereafter, the valve 141 is closed and the valve 142 is opened. Thereby, since the gas with which the piping 143 was filled is discharged | emitted by the gas discharge part 120, the pressure inside the crystal growth chamber 110 can be made low. Since the gas from the crystal growth chamber 110 can be gradually reduced by one operation of the pressure control unit 140, the accuracy can be improved and the pressure can be lowered by intermittently repeating the above steps. it can. In addition, about one operation | movement of the pressure control part 140, based on the pressure in the crystal growth chamber 110 measured by the pressure gauge 151, the instruction | command part 160 controls the time of opening and closing of the valves 141 and 142, and its opening time. May be. Further, the pressure of the gas discharge unit 120 may be atmospheric pressure, or may be controlled to an arbitrary pressure lower than the pressure inside the crystal growth chamber 110.

  Next, the compound semiconductor crystal is taken out from the crystal growth chamber 110. A compound semiconductor crystal can be manufactured by performing the above process.

  In this embodiment, in the step of supplying gas and the step of discharging gas, connection is made between the gas supply unit 101 and the crystal growth chamber 110, and between the crystal growth chamber 110 and the gas discharge unit 120. The pressure inside the crystal growth chamber 110 is controlled using the pressure control units 130 and 140. However, in the present invention, in at least one of the step of supplying gas and the step of discharging gas, the gas supply unit 101 and the crystal growth chamber 110 and the crystal growth chamber 110 and the gas discharge unit 120 are connected. The pressure inside the crystal growth chamber 110 may be controlled using the pressure control units 130 and 140 connected to at least one of them.

  Further, in the present embodiment, a liquid phase growth method such as a flux method has been described as an example of a method for growing a compound semiconductor crystal, but a crystal growth method that requires precise pressure control is widely applicable, and gas Alternatively, a melt growth method that is a liquid phase growth method that does not directly become a crystal raw material, or a vapor phase growth method such as an MOCVD (Metal Organic Chemical Vapor Deposition) method may be applied.

  Further, in the present embodiment, the gas supplied from the gas supply unit 101 has been described by taking a gas containing a raw material as an example, but the gas supplied from the gas supply unit 101 includes a raw material such as a carrier gas. It does not have to be.

  As described above, according to the compound semiconductor crystal manufacturing apparatus and method in the present embodiment, the pressure control unit 130, 140 causes the pressure change in the crystal growth chamber 110 to be in a state as shown in FIG. Can be. In FIG. 4, an arrow indicates a time change and a pressure change due to one operation of the pressure control units 130 and 140, a solid line indicates a set pressure, and a dotted line indicates a temperature. Further, e (time) to f (time) is a step of increasing the pressure inside the crystal growth chamber 110, f (time) to g (time) is a step of crystal growth, and g (time) to h ( Time) is a step of decreasing the pressure inside the crystal growth chamber 110.

  Specifically, at the time of supplying the gas, the gas from the gas supply unit 101 is temporarily held in the pressure control unit 130 (in this embodiment, the pipe 133) so that the pressure is higher than the pressure in the crystal growth chamber 110. Then, the gas can be supplied to the crystal growth chamber 110. In the one-time gas supply from the pressure control unit 130 to the crystal growth chamber 110, the pressure P1, the volume V1, and the temperature T1 of the pressure control unit 130 are appropriately selected, and the crystal is obtained by one operation of the pressure control unit 130. By reducing the number of moles of gas supplied to the growth chamber 110, it is possible to reduce the pressure change caused by the single operation of the pressure control unit 130. Moreover, the time change by one operation | movement of the pressure control part 130 can be decreased by shortening the time which the valves 131 and 132 open and close for one supply of gas. As a result, the arrows in FIG. 4 become shorter, and the accuracy of the pressure increase of the gas inside the crystal growth chamber 110 can be improved. By repeating this, as shown in FIG. 4, the temperature of the crystal growth chamber 110 is increased from c (° C.) to d (° C.) and the pressure is increased from time e (time) to f (time). It can rise little by little (stepwise) from a (MPa) to b (MPa). For this reason, according to the set pressure, the accuracy can be improved and the pressure of the gas inside the crystal growth chamber 110 can be increased.

  In the process of discharging the gas, the gas from the crystal growth chamber 110 is temporarily held in the pressure control unit 140 (in this embodiment, the pipe 143), which is lower than the pressure in the crystal growth chamber 110, and the gas Can be discharged from the gas discharge unit 120. By discharging the gas once from the crystal growth chamber 110 to the pressure controller 140, the accuracy of the pressure reduction of the gas inside the crystal growth chamber 110 can be increased. By repeating this, as shown in FIG. 4, the temperature of the crystal growth chamber 110 is lowered from d (° C.) to c (° C.) during the time g (hour) to h (hour), and the pressure is changed. It can descend little by little (stepwise) from b (MPa) to a (MPa). For this reason, according to the set pressure, the accuracy can be improved and the pressure of the gas inside the crystal growth chamber 110 can be lowered.

  As described above, by using the pressure control units 130 and 140 in at least one of the gas supply step and the gas discharge step, the pressure control accuracy of the gas inside the crystal growth chamber 110 is improved and the compound is improved. Semiconductor crystals can be manufactured.

  Thus, the compound semiconductor crystal manufacturing apparatus and method in the present embodiment can improve pressure control accuracy, so that sudden nucleation and non-uniform growth are unlikely to occur, and in-plane growth rate and crystal quality are reduced. Is made uniform. For this reason, it is possible to produce a compound semiconductor crystal having a flat or homogeneous growth surface. Further, since nucleation is less likely to occur unevenly in the plane, a compound semiconductor crystal having a small dislocation density distribution can be manufactured. Furthermore, such a high-quality compound semiconductor crystal can be manufactured at a reduced cost.

  In particular, the compound semiconductor crystal manufacturing apparatus and method in the present embodiment are suitably used for the flux method. The flux method is a system in which gas, liquid, and solid coexist, and in the liquid, an alkali metal such as Na as a flux (solvent) or a constituent element of a crystal to be grown as a self-flux (for example, Ga), etc. May be put in. In such a system, the dissolved amount of the gas phase component in the liquid phase is basically proportional to the partial pressure of the gas phase component according to Henry's law. The amount of dissolution and the temperature of the liquid phase determine the crystal growth rate and the degree of supersaturation that affects nucleation. Therefore, according to the manufacturing apparatus and the manufacturing method capable of improving the accuracy of pressure control as in this embodiment, a homogeneous compound semiconductor crystal can be manufactured.

  The compound semiconductor crystal manufactured in the compound semiconductor crystal manufacturing apparatus and manufacturing method in the present embodiment is not particularly limited, but a nitride crystal is preferably manufactured, and GaN (gallium nitride), AlN (aluminum nitride), InN ( It is more preferable to produce indium nitride) or the like. This is because nitrogen is difficult to dissolve in the solvent 113, but by improving the accuracy of pressure control, the nitrogen can be precisely controlled and dissolved in the solvent 113 at each temperature by a necessary amount.

(Embodiment 2)
With reference to FIG. 5, the compound semiconductor crystal manufacturing apparatus in the present embodiment will be described. As shown in FIG. 5, the compound semiconductor crystal manufacturing apparatus in the present embodiment basically has the same configuration as the compound semiconductor crystal manufacturing apparatus in the first embodiment shown in FIG. The control unit that controls the pressure between the supply unit 101 and the crystal growth chamber 110 is different from the control unit that controls the pressure between the crystal growth chamber 110 and the gas discharge unit 120.

  Specifically, as shown in FIG. 5, in this embodiment, the pressure is between the gas supply unit 101 and the crystal growth chamber 110 and between the crystal growth chamber 110 and the gas discharge unit 120. A control unit 130 is arranged.

  Then, the manufacturing method of the compound semiconductor crystal in this Embodiment is demonstrated. The manufacturing method of the compound semiconductor crystal in the present embodiment basically has the same configuration as the manufacturing method of the compound semiconductor crystal of the first embodiment, but in the step of supplying gas and the step of discharging gas The pressure control unit 130 is the same as the control unit that controls the pressure between the gas supply unit 101 and the crystal growth chamber 110 and the control unit that controls the pressure between the crystal growth chamber 110 and the gas discharge unit 120. Is used to control the pressure inside the crystal growth chamber 110. Specifically, in the step of discharging the gas, the valve 121 is opened and the pressure inside the crystal growth chamber 110 is controlled using the pressure control unit 130.

  As described above, according to the compound semiconductor crystal manufacturing apparatus and method of the present embodiment, since the pressure control unit 130 is used in both the gas supply process and the gas discharge process, the crystal The compound semiconductor crystal can be manufactured by improving the control accuracy of the gas pressure inside the growth chamber 110.

(Embodiment 3)
With reference to FIG. 6, the manufacturing apparatus of the compound semiconductor crystal in this Embodiment is demonstrated. As shown in FIG. 6, the compound semiconductor crystal manufacturing apparatus in the present embodiment basically has the same configuration as the compound semiconductor crystal manufacturing apparatus in the first embodiment shown in FIG. The control units 130 and 140 are divided into two or more regions by three or more valves 131, 132, 134, 141, 142, and 144 and the three or more valves 131, 132, 134, 141, 142, and 144. It differs in that it has piping 133, 135, 143, 145 to be used.

  Specifically, the pressure control unit 130 includes three valves 131, 132, and 134, a pipe 133 that is partitioned by the valves 131 and 132, and a pipe 135 that is partitioned by the valves 132 and 134. Yes. The pressure control unit 140 includes three valves 141, 142, 144, a pipe 143 partitioned by the valves 141, 142, and a pipe 145 partitioned by the valves 141, 144.

  Then, the manufacturing method of the compound semiconductor crystal in this Embodiment is demonstrated. The manufacturing method of the compound semiconductor crystal in the present embodiment basically has the same configuration as the manufacturing method of the compound semiconductor crystal of the first embodiment, but the process of supplying gas and the process of discharging gas At least one of the three or more valves 131, 132, 134, 141, 142, 144, and the pipe 133 that is partitioned into two or more regions by the three or more valves 131, 132, 134, 141, 142, 144 , 135, 143, and 145 are used to control the pressure inside the crystal growth chamber 110 using the pressure control units 130 and 140.

  Specifically, in the step of supplying gas, when increasing the pressure inside the crystal growth chamber 110, first, among the three valves 131, 132, 134, the valves 132, 134 are closed and the valve 131 is opened. . Thereafter, the valve 132 is opened. Finally, the valves 131 and 132 are closed. Thereby, it is possible to fill the pipes 133 and 135 with a gas whose pressure has been increased. At this time, the internal volumes of the pipes 133 and 135 may be the same or different.

  Thereafter, when the valves 131 and 132 are kept closed and the valve 134 is opened, the gas filled in the pipe 135 flows into the crystal growth chamber 110. Thereafter, when the valve 131 is kept closed and the valves 132 and 134 are opened, the gas filled in the pipe 133 flows into the crystal growth chamber 110. Finally, the valves 131, 132, 134 are closed. By repeating such an operation, the pressure inside the crystal growth chamber 110 can be increased stepwise.

  Further, in the step of supplying gas, when the controllability is further improved and the pressure in the crystal growth chamber 110 is increased, first, the valve 132, 134 among the three valves 131, 132, 134 is closed, and the valve 131 is set. Open. Thereafter, the valve 131 is closed and then the valve 132 is opened. Finally, the valve 132 is closed. As a result, the pipes 133 and 135 can be filled with a gas whose pressure has been increased, and the pressure charged in the pipes 133 and 135 is lower than the pressure controlled by the pressure reducing valve 150. At this time, the internal volumes of the pipes 133 and 135 may be the same or different.

  Thereafter, when the valves 131 and 132 are kept closed and the valve 134 is opened, the gas filled in the pipe 135 flows into the crystal growth chamber 110. Thereafter, when the valve 131 is kept closed and the valves 132 and 134 are opened, the gas filled in the pipe 133 flows into the crystal growth chamber 110. Finally, the valves 131, 132, 134 are closed. By repeating such an operation, the pressure inside the crystal growth chamber 110 can be increased step by step. Such an operation is preferably used when precise control of pressure is particularly desired in the crystal growth process.

  The above operation of the pressure control unit 130 is repeated until the inside of the crystal growth chamber 110 reaches a desired pressure.

  In the process of exhausting gas, when the pressure inside the crystal growth chamber 110 is lowered, first, among the three valves 141, 142, 144, the valves 141, 142 are closed and the valve 144 is opened. Thereby, the gas from the crystal growth chamber 110 is filled in the pipe 145. Thereafter, when the valve 141 is opened while the valve 142 is closed, the gas from the crystal growth chamber 110 is also filled into the pipe 143. In this state, when the valves 141 and 144 are closed and the valve 142 is opened, the gas filled in the pipe 143 is discharged from the gas discharge unit 120 to the outside. When the valve 144 is closed and the valve 141 is opened, the gas filled in the pipe 145 is also discharged from the gas discharge unit 120. As a result, the pressure inside the crystal growth chamber 110 can be lowered stepwise.

  Further, in the process of exhausting gas, when the controllability is further improved and the pressure inside the crystal growth chamber 110 is lowered, first, among the three valves 141, 142, 144, the valves 141, 142 are closed, Open 144. Thereby, the gas from the crystal growth chamber 110 is filled in the pipe 145. After that, when the valve 144 is opened after the valve 144 is closed and the valve 142 is closed, a part of the gas filled in the pipe 145 is also filled into the pipe 143 and filled into the pipes 145 and 143. The gas pressure is lower than the pressure in the crystal growth chamber 110. In this state, when the valves 141 and 144 are closed and the valve 142 is opened, the gas filled in the pipe 143 is discharged from the gas discharge unit 120 to the outside. Finally, the valves 141, 142, 144 are closed. By repeating such an operation, the pressure inside the crystal growth chamber 110 can be lowered step by step. Such an operation is preferably used when precise control of pressure is particularly desired in the crystal growth process.

  The operation of the pressure control unit 130 is repeated until the inside of the crystal growth chamber 110 reaches a desired pressure.

  In one operation of the pressure control units 130 and 140, there is a case where only one of the two or more pipes 133, 135, 143, and 145 is filled with gas other than the case described above. Also good.

  In addition, the single operation of the pressure control units 130 and 140 is not limited to the opening / closing order of the valves, and the pressure inside the crystal growth chamber 110 may be controlled by another order.

  As described above, according to the compound semiconductor crystal manufacturing apparatus and method of the present embodiment, the valves 131, 132, 134, 141 are opened and closed by the opening / closing operations of the valves 131, 132, 134, 141, 142, 144. , 142, 144 can hold the gas in the pipes 133, 135, 143, 145. The pressures in the pipes 133, 135, 143, and 145 can be controlled to different pressures. For this reason, the precision of the pressure rise of the gas inside the crystal growth chamber 110 can be improved more.

(Embodiment 4)
With reference to FIG. 7, the compound semiconductor crystal manufacturing apparatus in the present embodiment will be described. As shown in FIG. 7, the compound semiconductor crystal manufacturing apparatus in the present embodiment has basically the same configuration as the compound semiconductor crystal manufacturing apparatus in the first embodiment shown in FIG. The difference is that a buffer pipe 170 having a volume different from the volume 103 is further provided. In the present embodiment, a buffer pipe 170 is disposed between the pressure control units 130 and 140 and the crystal growth chamber 110.

  Then, the manufacturing method of the compound semiconductor crystal in this Embodiment is demonstrated. The manufacturing method of the compound semiconductor crystal in the present embodiment basically has the same configuration as the manufacturing method of the compound semiconductor crystal in the first embodiment, but the process of supplying gas and the process of discharging gas At least one of the pressures inside the crystal growth chamber 110 is controlled by using a buffer pipe 170 provided in the pipe 103 connecting the crystal growth chamber 110 and the pressure control units 130 and 140 and having a volume different from that of the pipe 103. It is different in point.

  Specifically, in the step of supplying gas, when increasing the pressure inside the crystal growth chamber 110, first, as shown in FIG. 8, the valve 131 is opened and the valves 132, 141, 142 are closed. The pipe 133 is filled with a gas having a pressure P1, a volume V1, and a temperature T1. Next, as shown in FIG. 9, the valve 131 is closed and the valve 132 is opened. As a result, the gas having the pressure P1, the volume V1, and the temperature T1 is filled in the pipe 103 and the buffer pipe 170 and supplied to the crystal growth chamber 110.

  In this one operation, from the law of conservation of mass and the equation of state of gas, (P1 × V1) / (R × T1) + (P2 × VB) / (R × TB) + (P2 × VA) / (R The relationship of × TA) = (P3 × V1) / (R × T1) + (P3 × VB) / (R × TB) + (P3 × VA) / (R × TA) is established. Therefore, when the pressure inside the crystal growth chamber 110 increases from P2 to P3 in one operation of the pressure controller 130, the pressure inside the crystal growth chamber 110 can also be adjusted by the buffer pipe 170. For example, from the relational expression, the difference between the pressure P2 and the pressure P3 decreases as the volume VB of the buffer pipe increases, so that the pressure inside the crystal growth chamber 110 can be changed step by step.

  Similarly, when the pressure inside the crystal growth chamber 110 is lowered in the step of exhausting the gas, the pressure inside the crystal growth chamber 110 can be adjusted by the buffer pipe 170 as well.

  As described above, according to the compound semiconductor crystal manufacturing apparatus and method in the present embodiment, the amount of change in the pressure inside the crystal growth chamber 110 can be further optimized by the buffer pipe 170. For this reason, the accuracy of the pressure fluctuation of the gas inside the crystal growth chamber 110 can be further increased.

  In the present embodiment, at least one of the gas supply step and the gas discharge step is connected between at least one of the gas supply unit and the crystal growth chamber and between the crystal growth chamber and the gas discharge unit. The effect of controlling the pressure inside the crystal growth chamber using a pressure control unit that can be controlled to a pressure different from the pressure inside the crystal growth chamber was investigated.

(Invention Example 1)
In Example 1 of the present invention, gas was supplied to the crystal growth chamber 110 using the compound semiconductor crystal manufacturing apparatus in Embodiment 1 shown in FIG. First, in order to examine the basic accuracy of the pressure control of this manufacturing apparatus, the temperature of the crystal growth chamber 110 and the pressure control units 130 and 140 are all set to room temperature, and the pressure increase and decrease rates of the crystal growth chamber 110, and The amount of pressure change in the crystal growth chamber 110 in each operation of the pressure control units 130 and 140 was examined.

  Specifically, first, nitrogen gas was flowed from the gas supply unit 101 to the crystal growth chamber 110 as a gas to the pressure control unit 130 and further supplied to the crystal growth chamber 110. At this time, the pressure inside the crystal growth chamber 110 was increased to around 10 MPa as follows using the pressure control unit 130 having the two valves 131 and 132 and the pipe 133 partitioned by the valves 131 and 132.

  The pressure of the gas discharged from the gas supply unit 101 was 14.7 MPa, and the pressure was reduced to 11.0 MPa by the pressure reducing valve 150. The volume of the pipe 133 was 1.7 cc. The volume of the crystal growth chamber 110 was 500 cc. Moreover, the temperature of the crystal growth chamber 110 was room temperature before pressurization, and was also room temperature after pressurization.

  The increase in the pressure in the crystal growth chamber 110 was as follows. That is, as shown in FIG. 2, the gas was supplied to the pipe 133 with the valve 131 opened and the valves 132, 141, 142 closed. Thereafter, as shown in FIG. 3, the valve 131 was closed, the valve 132 was opened, and the gas filled in the pipe 103 was supplied to the crystal growth chamber 110. This operation was repeated intermittently to increase the pressure inside the crystal growth chamber 110. The results are shown in FIG. 10 and FIG. FIG. 10 shows the pressure with respect to the elapsed time in the step of increasing the pressure. FIG. 11 shows the pressure change amount with respect to the elapsed time in the step of increasing the pressure. In FIG. 11, the solid line is a value obtained by approximating the amount of pressure change of Example 1 of the present invention to a square.

  As shown in FIG. 10, according to the manufacturing apparatus and manufacturing method of Example 1 of the present invention, the inside of the crystal growth chamber could be increased to 10 MPa within 41 minutes.

  Moreover, as shown in FIG. 11, the amount of pressure change in the pressurizing process of Example 1 of the present invention was made substantially the same as the theoretical value. Furthermore, when the pressure inside the crystal growth chamber 110 is increased to 10 MPa, the amount of change in pressure per operation is 0.002 MPa at the smallest and 0.01 MPa even at the largest, and the inside of the crystal growth chamber 110 is increased. The pressure of was found to be very stable.

  Next, in order to depressurize the inside of the crystal growth chamber 110, gas is supplied from the crystal growth chamber 110 to the gas exhaust portion 120 using the pressure control unit 140 connected between the crystal growth chamber 110 and the gas exhaust portion 120. Was discharged. The pressure control unit 140 has two valves 141 and 142 and a pipe 143 partitioned by the two valves 141 and 142. The volume of the pipe 143 was 1.7 cc. In addition, the temperature of the crystal growth chamber 110 was room temperature before decompression, and the temperature after decompression was also room temperature.

  The pressure drop in the crystal growth chamber 110 was as follows. That is, with the valves 131, 132, 142 closed and the valve 141 opened, the pipe 143 was filled with the gas discharged from the crystal growth chamber 110. Thereafter, the valve 141 was closed, the valve 142 was opened, and the gas filled in the pipe 143 was discharged to the gas discharge unit 120. This operation was repeated intermittently to reduce the pressure inside the crystal growth chamber 110 from 10 MPa. The results are shown in FIGS. In addition, FIG. 12 shows the pressure with respect to elapsed time in the process of decreasing the pressure. FIG. 13 shows the pressure change amount with respect to the elapsed time in the step of decreasing the pressure. In FIG. 13, the solid line is a value obtained by approximating the amount of pressure change of Example 1 of the present invention to a square.

  As shown in FIG. 12, according to the manufacturing apparatus and manufacturing method of Example 1 of the present invention, the pressure inside the crystal growth chamber after the elapse of 60 minutes could be lowered to 0.56 MPa or less.

  Moreover, as shown in FIG. 13, it was able to be substantially the same as the theoretical value. Furthermore, it was found that the pressure change amount per operation was −0.002 MPa in the smallest case and −0.01 MPa even in the largest case, and the pressure inside the crystal growth chamber 110 was very stable.

(Invention Example 2)
In Example 2 of the present invention, crystal growth of GaN, which is a compound semiconductor, was performed by a flux method (solution growth method) using the compound semiconductor crystal manufacturing apparatus in Embodiment 1 shown in FIG. In Invention Example 2, the pressure and temperature of the crystal growth chamber 110 are set to predetermined crystal growth conditions, the reaction vessel 112 is a pBN crucible, the solvent 113 is metal gallium, the gas 114 is nitrogen gas, and the seed substrate 115 is 1 A GaN seed substrate having a square shape with a side of 10 mm and a thickness of 400 μm was used. Crystal growth of GaN was performed on the GaN seed substrate 115 by reacting liquid metal gallium with nitrogen gas dissolved in liquid metal gallium.

  Specifically, simultaneously with the start of the temperature increase inside the crystal growth chamber 110, nitrogen gas was flowed as a gas from the gas supply unit 101 to the pressure control unit 130 and further supplied to the crystal growth chamber 110. At this time, the pressure inside the crystal growth chamber 110 was increased from 0 MPa to 9 MPa using the pressure control unit 130 having two valves 131 and 132 and a pipe 133 partitioned by the valves 131 and 132. FIG. 14 shows the temperature and pressure conditions in the crystal growth chamber 110 in this crystal growth. In FIG. 14, the horizontal axis indicates time (unit: time (hrs)), 0 hrs indicates the start of operation, and 236 hrs indicates the end of operation. Moreover, in FIG. 14, a solid line shows a pressure and a dotted line shows temperature.

  The pressure of the gas discharged from the gas supply unit 101 was 14.7 MPa, and the pressure was reduced to 11.0 MPa by the pressure reducing valve 150. The volume of the pipe 133 was 1.7 cc. The volume of the crystal growth chamber 110 was 500 cc. The temperature of the crystal growth chamber 110 was room temperature when the pressure was 0 MPa before the pressure of the crystal growth chamber 110 was increased, and was 900 ° C. when the pressure was 9 MPa after the pressure of the crystal growth chamber 110 was increased. This pressure increase and temperature increase were each 18 hours.

  The pressure in the crystal growth chamber 110 was increased as follows. As shown in FIG. 2, the gas was supplied to the pipe 133 with the valve 131 opened and the valves 132, 141, 142 closed. Thereafter, as shown in FIG. 3, the valve 131 was closed, the valve 132 was opened, and the gas filled in the pipe 103 was supplied to the crystal growth chamber 110. Finally, the valve 132 was closed. The time during which the valves 131 and 132 were opened was 1 second, and the time during which all the valves were closed was 0.5 seconds. Therefore, the time required for these series of operations is a total of 3 seconds. By repeating this series of operations intermittently by the command unit 160, the pressure in the crystal growth chamber 110 was gradually increased. The repetition interval of the series of operations is such that the pressure inside the crystal growth chamber 110 rises linearly from 0 MPa to 9 MPa in 18 hours from the command unit 160 according to the pressure inside the crystal growth chamber 110 at that time. Controlled. Thereafter, a crystal growth time for maintaining the temperature of the crystal growth chamber 110 at 900 ° C. and the pressure at 9 MPa was set for 200 hours. During this crystal growth time, the nitrogen gas as the gas 114 is dissolved in the metal gallium as the solvent 113, reaches the GaN seed substrate as the seed substrate 115, and grows as a GaN crystal. Nitrogen gas consumed with crystal growth during the crystal growth time is supplied from the pressure control unit 130 according to a command from the command unit 160, and the pressure during the crystal growth time is kept constant.

  In Example 2 of the present invention, when the pressure of the crystal growth chamber 110 is increased and the pressure inside the crystal growth chamber 110 during the crystal growth time for maintaining the pressure is controlled to a desired value regardless of the temperature of the crystal growth chamber 110. Furthermore, the amount of change in pressure per operation was 0.004 MPa at the smallest and 0.01 MPa even at the largest. This is within the accuracy of 0.04% to 0.1% of the pressure inside the crystal growth chamber 110 during the crystal growth time, and the pressure inside the crystal growth chamber 110 is both when the pressure rises and when the pressure is maintained. It was possible to control it very precisely.

  Next, in order to depressurize the inside of the crystal growth chamber 110, the pressure control unit 140 is connected between the crystal growth chamber 110 and the gas discharge unit 120 and can be controlled to a pressure different from the pressure inside the crystal growth chamber 110. Was used to discharge gas from the crystal growth chamber 110 to the gas discharge unit 120. The pressure controller 140 intermittently changes its pressure by being opened to the crystal growth chamber 110 and at least one of the gas supply unit 101 and the gas discharge unit 120. The pressure control unit 140 includes two valves 141 and 142 and a pipe 143 partitioned by the two valves 141 and 142, and the volume of the pipe 143 is 1.7 cc. The temperature of the crystal growth chamber 110 was 900 ° C. before the pressure reduction, and the temperature after the pressure reduction was room temperature.

  The pressure drop in the crystal growth chamber 110 was as follows. With the valves 131, 132, 142 closed and the valve 141 opened, the pipe 143 was filled with the gas discharged from the crystal growth chamber 110. Thereafter, the valve 141 was closed, the valve 142 was opened, and the gas filled in the pipe 143 was discharged to the gas discharge unit 120. Finally, valve 142 was closed. These series of operations were repeated intermittently to reduce the pressure inside the crystal growth chamber 110 from 9 MPa.

  In Example 2 of the present invention, the pressure in the crystal growth chamber 110 can be controlled to a desired value in a desired time even when the pressure drops and even if the temperature of the crystal growth chamber 110 changes. The amount of pressure change per hit was −0.004 MPa at the smallest, and −0.01 MPa even at the largest. This is within the accuracy of 0.04% to 0.1% of the pressure inside the crystal growth chamber 110 during the crystal growth time, and the pressure inside the crystal growth chamber 110 is very precise even when the pressure drops. Could be controlled.

  After the pressure inside the crystal growth chamber 110 becomes 0 MPa and the temperature reaches room temperature, the seed substrate 115 (GaN seed substrate) and the GaN crystal grown thereon are taken out from the reaction vessel 112 and immersed in aqua regia to obtain a solvent. After removing 113 (metal gallium), the surface shape of the GaN crystal grown on the seed substrate 115 was observed with a Nomarski microscope. In addition, the dislocation density on the surface was evaluated based on the density of etch pits appearing by etching.

As a result, as shown in FIG. 15, the surface of the GaN crystal grown on the seed substrate 115 is very flat and shows that it has been stably and two-dimensionally grown on the entire surface by observation with a Nomarski microscope. A plurality of almost parallel growth stripes were observed. Further, when the surface dislocation density was observed by etching with a mixed solution of phosphoric acid and sulfuric acid, etch pits were estimated to be 10 ⁵ pieces / cm ² or less, and it was confirmed that crystals with a low dislocation density were growing. . FIG. 15 is a Nomarski micrograph of a 100 μm square field of the crystal of Example 2 of the present invention.

  In the inventive example 2, since the grown crystal is flat and the dislocation density is low, it is considered that the controllability of the pressure inside the crystal growth chamber 110 was sufficiently good. Further, when it is desired to precisely control the pressure, the pressure of the gas discharged from the gas supply unit 101 is reduced to a pressure lower than the current 11 MPa by the pressure reducing valve 150, the volume of the pipe 133 is further reduced, or FIG. P2 (before the operation of the pressure control unit) and P3 (after the operation of the pressure control unit) in the relational expression derived from the law of conservation of mass and the equation of state of the gas by providing the buffer pipe 170 described in FIG. By reducing the pressure difference, it is possible to control freely and precisely.

(Comparative example)
In Example 2 of the present invention, a pressure control valve is used instead of the pressure control unit 130, and a stop valve (valve) that can be opened and closed is used instead of the pressure control unit 140, and the pressure control valve is controlled by the command unit 160. The GaN crystal was grown under the same conditions. As a result, although the pressure inside the crystal growth chamber could be increased to 9 MPa, the pressure of the crystal growth time (200 hours) to be maintained at 9 MPa varied between 8.8 MPa and 9.1 MPa. As compared with Example 2 of the present invention, the controllability of pressure was 10 times or more worse.

  After the completion of the crystal growth time, the temperature of the crystal growth chamber 110 is reduced to room temperature, the internal nitrogen gas is discharged, and then the seed substrate 115 (GaN seed substrate) and the GaN crystal grown thereon are taken out from the reaction vessel 112. After removing the solvent 113 (metal gallium) by immersion in aqua regia, the surface shape of the GaN crystal growing on the seed substrate 115 was observed with a Nomarski microscope. The dislocation density on the surface was evaluated by cathodoluminescence.

As a result, random growth fringes were observed on the surface of the GaN crystal growing on the seed substrate 115 by Nomarski microscope observation, as shown in FIG. The surface dislocation density was estimated to be 10 ⁷ to 10 ⁸ pieces / cm ² by etching with a mixed solution of phosphoric acid and sulfuric acid, and it was confirmed that crystals with a high dislocation density were growing. . Due to poor controllability of nitrogen gas pressure during the crystal growth time, the nitrogen concentration in the solution becomes unstable, and nucleation of GaN crystals tends to occur randomly on the surface of the GaN seed substrate. As a result of the growth, random growth streaks indicating that the crystal growth has progressed so that the nuclei coalesce can be seen, and the crystal misorientation occurred at the coalescence part, and the dislocation density increased. Conceivable. FIG. 16 is a Nomarski micrograph of a 100 μm square field of view of the comparative crystal.

  As described above, at least one of the gas supply step and the gas discharge step is connected to at least one of the gas supply unit and the crystal growth chamber, and between the crystal growth chamber and the gas discharge unit, and the crystal. It was confirmed that the gas pressure inside the crystal growth chamber can be controlled with high accuracy by using a pressure control unit that can be controlled to a pressure different from the pressure inside the growth chamber. At this time, since it is not necessary to use a pressure control valve that continuously adjusts the pressure, it is possible to reduce the cost of the equipment of the manufacturing apparatus, and it is possible to open and close the valve reliably and safely. A compound semiconductor crystal can be manufactured.

  Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to appropriately combine the features of the embodiments and examples. The embodiments and examples 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 embodiments and examples described above but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  101 gas supply unit, 102, 103, 133, 135, 143, 145 piping, 110 crystal growth chamber, 111 heating unit, 112 reaction vessel, 113 solvent, 114 gas, 115 seed substrate, 120 gas discharge unit, 130 pressure control unit 121, 131, 132, 134, 141, 142, 144 valve, 150 pressure reducing valve, 151 pressure gauge, 160 command section, 170 buffer piping.

Claims (14)

A gas supply unit;
A crystal growth chamber to which gas is supplied from the gas supply unit;
A gas discharge unit for discharging gas from the crystal growth chamber;
Connected to at least one of the gas supply section and the crystal growth chamber and between the crystal growth chamber and the gas discharge section, and the crystal growth chamber, the gas supply section, and the gas discharge section An apparatus for producing a compound semiconductor crystal, comprising at least one of the first and second pressure control units that change pressure intermittently when opened.   2. The compound semiconductor crystal manufacturing apparatus according to claim 1, wherein the pressure control unit is connected between the gas supply unit and the crystal growth chamber and between the crystal growth chamber and the gas discharge unit. .   In the pressure control unit, the control unit for controlling the pressure between the gas supply unit and the crystal growth chamber and the control unit for controlling the pressure between the crystal growth chamber and the gas discharge unit are the same. The apparatus for producing a compound semiconductor crystal according to claim 2.   The said pressure control part is a manufacturing apparatus of the compound semiconductor crystal of any one of Claims 1-3 which has two valves and piping divided by the said valve.   The said pressure control part is a manufacturing apparatus of the compound semiconductor crystal of any one of Claims 1-3 which has three or more valves and piping divided into two or more area | regions by the said valve. A connection pipe connecting the crystal growth chamber and the pressure control unit;
A buffer pipe provided on the connection pipe;
The said buffer piping is a manufacturing apparatus of the compound semiconductor crystal of any one of Claims 1-5 which has a volume different from the volume of the said connection piping.   The apparatus for manufacturing a compound semiconductor crystal according to claim 1, further comprising a heating unit that heats the pressure control unit. Supplying gas from the gas supply unit to the crystal growth chamber;
And a step of discharging gas from the crystal growth chamber to a gas discharge portion,
At least one of the step of supplying the gas and the step of discharging the gas is connected to at least one between the gas supply unit and the crystal growth chamber and between the crystal growth chamber and the gas discharge unit. And a pressure control unit that changes pressure intermittently by being opened to each of the crystal growth chamber and at least one of the gas supply unit and the gas discharge unit. A method for producing a compound semiconductor crystal, wherein the pressure of the semiconductor is controlled.   The method for producing a compound semiconductor crystal according to claim 8, wherein in the step of supplying the gas and the step of discharging the gas, the pressure inside the crystal growth chamber is controlled using the pressure control unit.   In the step of supplying the gas and the step of discharging the gas, a control unit that controls a pressure between the gas supply unit and the crystal growth chamber, and a pressure between the crystal growth chamber and the gas discharge unit The method for producing a compound semiconductor crystal according to claim 9, wherein the pressure inside the crystal growth chamber is controlled using the pressure controller that is the same as the controller that controls the temperature.   At least one of the step of supplying the gas and the step of discharging the gas controls the pressure inside the crystal growth chamber using the pressure control unit having two valves and a pipe partitioned by the valve. The manufacturing method of the compound semiconductor crystal of any one of Claims 8-10.   At least one of the step of supplying the gas and the step of discharging the gas, the crystal growth using the pressure control unit having three or more valves and a pipe partitioned into two or more regions by the valves. The manufacturing method of the compound semiconductor crystal of any one of Claims 8-11 which controls the pressure inside a chamber.   At least one of the step of supplying the gas and the step of discharging the gas is provided in a connection pipe that connects the crystal growth chamber and the pressure control unit, and a buffer pipe having a volume different from that of the connection pipe is used. The method for producing a compound semiconductor crystal according to claim 8, wherein a pressure inside the crystal growth chamber is controlled.   The at least one of the step of supplying the gas and the step of discharging the gas controls the pressure inside the crystal growth chamber by heating the pressure control unit. A method for producing a compound semiconductor crystal.