Manufacturing method and heat treatment method of p-type gallium nitride semiconductor

Abstract

The present invention relates to a method for manufacturing a p-type gallium nitride semiconductor and a heat treatment method. The present invention provides a technology capable of activating a p-type dopant with high efficiency. Magnesium is injected into a gallium nitride (GaN) substrate as a p-type dopant. The GaN substrate is preheated by irradiating light from a halogen lamp in an atmosphere containing nitrogen and hydrogen, and then heated to a high temperature in a very short time by flash irradiation from a flash lamp. By heating the GaN substrate in an atmosphere containing nitrogen and hydrogen, the nitrogen that has been separated can be replenished to prevent nitrogen deficiency. Moreover, the GaN substrate can be heated while hydrogen is supplied to the GaN substrate. Furthermore, the crystal defects existing in the GaN substrate can be repaired. As a result, the p-type dopant injected into the GaN substrate can be activated with high efficiency.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a p-type gallium nitride semiconductor and a heat treatment method for activating a p-type dopant injected into a gallium nitride (GaN) substrate. Background Art

[0002] Gallium nitride compounds have attracted attention as light-emitting elements that emit blue light, and are also expected to be basic materials for power devices used for power conversion. For example, Patent Document 1 discloses a method for producing a gallium nitride compound semiconductor by activating impurities added to a gallium nitride compound.

[0003] [Background Technology Literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2007-42898 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] As disclosed in Patent Document 1, for n-type gallium nitride semiconductors, by making the gallium nitride compound contain silicon (Si) or the like as an n-type dopant, the dopant can be relatively easily activated, thereby obtaining a high-quality n-type gallium nitride semiconductor. On the other hand, for p-type gallium nitride semiconductors, by simply making the gallium nitride compound contain magnesium (Mg) or the like as only a p-type dopant, it is impossible to produce a semiconductor of the same high quality as an n-type gallium nitride semiconductor. The reason for this is that the activation rate of the p-type dopant in the gallium nitride compound is low.

[0008] The present invention has been developed in view of the above-mentioned problems, and an object of the present invention is to provide a technology capable of activating a p-type dopant with high efficiency.

[0009] [Technical means to solve the problem]

[0010] To solve the above-mentioned problem, the invention of technical solution 1 is a method for manufacturing a p-type gallium nitride semiconductor, which is characterized by comprising: an injection step of injecting a p-type dopant into a gallium nitride substrate; and a heating step of irradiating a flash of light to the substrate with an irradiation time of less than 1 second in an atmosphere containing nitrogen and hydrogen to heat the substrate.

[0011] Furthermore, the invention according to claim 2 is the method for manufacturing a p-type gallium nitride-based semiconductor according to the invention according to claim 1 , wherein the atmosphere containing nitrogen and hydrogen is an ammonia atmosphere.

[0012] Furthermore, the invention according to claim 3 is the method for manufacturing a p-type gallium nitride-based semiconductor according to the invention according to claim 1 , wherein the atmosphere containing nitrogen and hydrogen is a nitrogen-hydrogen mixed atmosphere.

[0013] Moreover, the invention of technical solution 4 is a heat treatment method, which is characterized by comprising: a carrying-in process, in which a gallium nitride substrate injected with a p-type dopant is carried into a chamber; an atmosphere forming process, in which an atmosphere containing nitrogen and hydrogen is formed in the chamber; and a light irradiation process, in which a flash of light is irradiated to the substrate with an irradiation time of less than 1 second to heat the substrate.

[0014] Furthermore, the invention according to claim 5 is a heat treatment method according to the invention according to claim 4 , wherein the atmosphere containing nitrogen and hydrogen is an ammonia atmosphere.

[0015] Furthermore, the invention of claim 6 is a heat treatment method according to the invention of claim 4, wherein the atmosphere containing nitrogen and hydrogen is a nitrogen-hydrogen mixed atmosphere.

[0016] [Effects of the Invention]

[0017] According to the invention of technical solutions 1 to 3, in an atmosphere containing nitrogen and hydrogen, a gallium nitride substrate injected with a p-type dopant is irradiated with a flash for an irradiation time of less than 1 second to heat the substrate. Therefore, while suppressing the deficiency of nitrogen from the substrate, hydrogen is supplied to the substrate to perform a heat treatment, thereby activating the p-type dopant with high efficiency.

[0018] According to the invention of technical solutions 4 to 6, in an atmosphere containing nitrogen and hydrogen, a gallium nitride substrate injected with a p-type dopant is irradiated with a flash for an irradiation time of less than 1 second to heat the substrate. Therefore, while suppressing the deficiency of nitrogen from the substrate, hydrogen is supplied to the substrate to perform a heat treatment, thereby activating the p-type dopant with high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a longitudinal sectional view showing the structure of a heat treatment apparatus used when carrying out the heat treatment method of the present invention.

[0020] Figure 2 It is a perspective view showing the overall appearance of the holding portion.

[0021] Figure 3 This is a top view of the base.

[0022] Figure 4 is a cross-sectional view of the base.

[0023] Figure 5 It is a top view of the transfer mechanism.

[0024] Figure 6 It is a side view of the transfer mechanism.

[0025] Figure 7 It is a top view showing the arrangement of a plurality of halogen lamps.

[0026] Figure 8 This is a flowchart showing the procedure of the method for manufacturing a p-type gallium nitride-based semiconductor according to the present invention.

[0027] Fig. 9 This is a diagram showing a state where a GaN substrate is placed on a placing plate. DETAILED DESCRIPTION

[0028] Below, refer to the attached Figure 1 Embodiments of the present invention will be described in detail.

[0029] First, a heat treatment apparatus for carrying out the heat treatment method of the present invention will be described. Figure 1 It is a longitudinal sectional view showing the structure of a heat treatment apparatus 1 used when carrying out the heat treatment method of the present invention. Figure 1 The heat treatment apparatus 1 is a flash lamp annealing apparatus that heats a gallium nitride substrate (GaN substrate) W by flash irradiating the GaN substrate W. Figure 1 In the following drawings, the size or number of each component is exaggerated or simplified as necessary for easy understanding.

[0030] The heat treatment apparatus 1 includes: a chamber 6 for accommodating a GaN substrate W, a flash heating unit 5 having a plurality of flash lamps FL built therein, and a halogen heating unit 4 having a plurality of halogen lamps HL built therein. The flash heating unit 5 is provided on the upper side of the chamber 6, and the halogen heating unit 4 is provided on the lower side. In addition, the heat treatment apparatus 1 includes a holding unit 7 for holding the GaN substrate W in a horizontal position inside the chamber 6, and a transfer mechanism 10 for transferring the GaN substrate W between the holding unit 7 and the outside of the apparatus. Furthermore, the heat treatment apparatus 1 includes a control unit 3, which controls the halogen heating unit 4, the flash heating unit 5, and each operating mechanism provided in the chamber 6, and performs heat treatment of the GaN substrate W.

[0031] The chamber 6 is formed by installing chamber windows made of quartz on the upper and lower parts of a cylindrical chamber side portion 61. The chamber side portion 61 has a substantially cylindrical shape with upper and lower openings, and an upper chamber window 63 is installed at the upper opening to be closed, and a lower chamber window 64 is installed at the lower opening to be closed. The upper chamber window 63 constituting the top wall of the chamber 6 is a disk-shaped member formed of quartz, and functions as a quartz window that allows the flash emitted from the flash heating unit 5 to pass through the chamber 6. In addition, the lower chamber window 64 constituting the bottom plate of the chamber 6 is also a disk-shaped member formed of quartz, and functions as a quartz window that allows the light from the halogen heating unit 4 to pass through the chamber 6.

[0032] Moreover, a reflection ring 68 is installed on the upper part of the inner wall surface of the chamber side portion 61, and a reflection ring 69 is installed on the lower part. Both the reflection rings 68 and 69 are formed in a circular ring shape. The upper reflection ring 68 is installed by embedding from the upper side of the chamber side portion 61. On the other hand, the lower reflection ring 69 is installed by embedding from the lower side of the chamber side portion 61 and fixing it with screws omitted from the figure. In other words, the reflection rings 68 and 69 are both installed in the chamber side portion 61 so as to be freely loaded and unloaded. The inner space of the chamber 6, that is, the space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side portion 61 and the reflection rings 68 and 69 is defined as a heat treatment space 65.

[0033] By installing the reflection rings 68 and 69 on the chamber side portion 61, a recessed portion 62 is formed on the inner wall surface of the chamber 6. That is, the recessed portion 62 is formed to be surrounded by the central portion of the inner wall surface of the chamber side portion 61 where the reflection rings 68 and 69 are not installed, the lower end surface of the reflection ring 68, and the upper end surface of the reflection ring 69. The recessed portion 62 is formed in a circular ring shape along the horizontal direction on the inner wall surface of the chamber 6 and surrounds the holding portion 7 holding the GaN substrate W. The chamber side portion 61 and the reflection rings 68 and 69 are formed of a metal material (for example, stainless steel) having excellent strength and heat resistance.

[0034] Furthermore, a transport opening (furnace port) 66 for carrying GaN substrates W into and out of the chamber 6 is provided on the chamber side portion 61. The transport opening 66 can be opened and closed by the gate valve 185. The transport opening 66 is connected to the outer peripheral surface of the recess 62. Therefore, when the gate valve 185 opens the transport opening 66, the GaN substrate W can be carried into and out of the heat treatment space 65 through the transport opening 66 through the recess 62. Furthermore, when the gate valve 185 closes the transport opening 66, the heat treatment space 65 in the chamber 6 becomes a closed space.

[0035] Furthermore, a through hole 61a is bored in the chamber side portion 61. A radiation thermometer 20 is installed at the portion where the through hole 61a is provided on the outer wall surface of the chamber side portion 61. The through hole 61a is a cylindrical hole for guiding infrared light emitted from the lower surface of a mounting plate 91 held on a base 74 described below to the radiation thermometer 20. The through hole 61a is provided so as to be inclined relative to the horizontal direction in such a manner that the axis of the through hole 61a intersects with the main surface of the base 74. A transparent window 21 is installed at the end of the through hole 61a facing the heat treatment space 65, and the transparent window 21 contains a barium fluoride material that allows infrared light in a wavelength range that can be measured by the radiation thermometer 20 to pass through.

[0036] Moreover, a gas supply hole 81 for supplying a processing gas to the heat treatment space 65 is provided at the upper portion of the inner wall of the chamber 6. The gas supply hole 81 is provided at a position higher than the recess 62 and can be provided at the reflection ring 68. The gas supply hole 81 is connected to a gas supply pipe 83 via a buffer space 82 formed in an annular shape inside the side wall of the chamber 6. The gas supply pipe 83 is connected to a processing gas supply source 85. Moreover, a valve 84 is inserted in the middle of the path of the gas supply pipe 83. When the valve 84 is opened, the processing gas is fed from the processing gas supply source 85 to the buffer space 82. The processing gas flowing into the buffer space 82 flows in a diffused manner in the buffer space 82 where the fluid resistance is smaller than that of the gas supply hole 81, and is supplied to the heat treatment space 65 from the gas supply hole 81. As the processing gas, for example, ammonia (NH3) or a nitrogen-hydrogen mixed gas which is a mixed gas of hydrogen (H2) and nitrogen (N2) can be used. Furthermore, the processing gas supply source 85 may supply nitrogen gas, which is an inert gas, to the heat treatment space 65 .

[0037] On the other hand, a gas exhaust hole 86 for exhausting the gas in the heat treatment space 65 is provided at the lower part of the inner wall of the chamber 6. The gas exhaust hole 86 is provided at a lower position than the recess 62, and may also be provided at the reflection ring 69. The gas exhaust hole 86 is connected to the gas exhaust pipe 88 via a buffer space 87 formed in an annular shape inside the side wall of the chamber 6. The gas exhaust pipe 88 is connected to the exhaust portion 190. Moreover, a valve 89 is inserted in the middle of the path of the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is discharged from the gas exhaust hole 86 through the buffer space 87 to the gas exhaust pipe 88. In addition, the gas supply hole 81 and the gas exhaust hole 86 may be provided in a plurality along the circumferential direction of the chamber 6, or may be slit-shaped. Moreover, the processing gas supply source 85 and the exhaust portion 190 may be a mechanism provided in the heat treatment device 1, or may be an entity of a factory for providing the heat treatment device 1.

[0038] A gas exhaust pipe 191 for exhausting the gas in the heat treatment space 65 is also connected to the front end of the transfer opening 66. The gas exhaust pipe 191 is connected to the exhaust unit 190 via a valve 192. By opening the valve 192, the gas in the chamber 6 is exhausted through the transfer opening 66.

[0039] Figure 2 : is a perspective view showing the overall appearance of the holding part 7. The holding part 7 is composed of a base ring 71, a connecting part 72 and a base 74. The base ring 71, the connecting part 72 and the base 74 are all formed of quartz. In other words, the holding part 7 is formed of quartz as a whole.

[0040] The base ring 71 is a quartz member in an arc shape with a portion of the ring missing. The missing portion is provided to prevent interference between the transfer arm 11 of the transfer mechanism 10 described below and the base ring 71. The base ring 71 is supported on the wall surface of the chamber 6 by being placed on the bottom surface of the recess 62 (see Figure 1 A plurality of connection parts 72 (four in this embodiment) are provided vertically on the upper surface of the base ring 71 along the circumferential direction of the annular shape. The connection part 72 is also a quartz member and is fixed to the base ring 71 by welding.

[0041] The base 74 is supported by four connection parts 72 provided on the base ring 71 . Figure 3 is a top view of the base 74. Furthermore, Figure 4 74. The susceptor 74 includes a holding plate 75, a guide ring 76, and a plurality of support pins 77. The holding plate 75 is a substantially circular flat plate-shaped member formed of quartz. The diameter of the holding plate 75 is larger than the diameter of the GaN substrate W. In other words, the holding plate 75 has a larger plane size than the GaN substrate W.

[0042] A guide ring 76 is provided on the peripheral edge of the upper surface of the holding plate 75. The guide ring 76 is a plate having a thickness larger than that of the mounting plate 91 (see Fig. 9 ) is a circular ring-shaped component with an inner diameter larger than the diameter of the mounting plate 91. For example, when the diameter of the mounting plate 91 is φ300 mm, the inner diameter of the guide ring 76 is φ320 mm. The inner periphery of the guide ring 76 is set as an inclined surface that expands upward from the retaining plate 75. The guide ring 76 is formed of the same quartz as the retaining plate 75. The guide ring 76 can be welded to the upper surface of the retaining plate 75, or fixed to the retaining plate 75 by a separately processed pin or the like. Alternatively, the retaining plate 75 and the guide ring 76 can be processed into an integral component.

[0043] The area on the upper surface of the holding plate 75 that is closer to the inner side than the guide ring 76 is set as a planar holding surface 75a for holding the mounting plate 91 on which the GaN substrate W is mounted. A plurality of support pins 77 are erected on the holding surface 75a of the holding plate 75. In the present embodiment, a total of 12 support pins 77 are erected at intervals of 30° along a circumference that is concentric with the outer circumference of the holding surface 75a (the inner circumference of the guide ring 76). The diameter of the circle in which the 12 support pins 77 are arranged (the distance between the opposing support pins 77) is smaller than the diameter of the mounting plate 91. If the diameter of the mounting plate 91 is φ300 mm, the diameter of the circle is φ270 mm to φ280 mm (φ270 mm in the present embodiment). Each support pin 77 is formed of quartz. The plurality of support pins 77 can be set on the upper surface of the holding plate 75 by welding, or can be processed integrally with the holding plate 75.

[0044] return Figure 2The four connecting parts 72 erected on the base ring 71 and the peripheral part of the holding plate 75 of the base 74 are fixed by welding. That is, the base 74 and the base ring 71 are fixedly connected by the connecting parts 72. The holding part 7 is installed in the chamber 6 by supporting the base ring 71 of the holding part 7 on the wall surface of the chamber 6. When the holding part 7 is installed in the chamber 6, the holding plate 75 of the base 74 is in a horizontal posture (a posture in which the normal line is consistent with the vertical direction). That is, the holding surface 75a of the holding plate 75 is a horizontal plane.

[0045] The carrier plate 91 on which the GaN substrate W is placed is held in a horizontal position on the base 74 of the holding portion 7 installed in the chamber 6. At this time, the carrier plate 91 is supported by 12 support pins 77 vertically arranged on the holding plate 75 and is held on the base 74. More strictly speaking, the upper ends of the 12 support pins 77 are in contact with the lower surface of the carrier plate 91 to support the carrier plate 91. The heights of the 12 support pins 77 (the distance from the upper ends of the support pins 77 to the holding surface 75a of the holding plate 75) are uniform, so the carrier plate 91 can be supported in a horizontal position by the 12 support pins 77.

[0046] The mounting plate 91 is supported by the plurality of support pins 77 at a fixed interval from the holding surface 75a of the holding plate 75. The thickness of the guide ring 76 is greater than the height of the support pins 77. Therefore, the guide ring 76 prevents the mounting plate 91 supported by the plurality of support pins 77 from being displaced in the horizontal direction.

[0047] Moreover, if Figure 2 and Figure 3 As shown, an opening 78 is formed through the top and bottom of the holding plate 75 of the base 74. The opening 78 is provided for the radiation thermometer 20 to receive the radiation light (infrared light) emitted from the lower surface of the mounting plate 91. That is, the radiation thermometer 20 receives the light emitted from the lower surface of the mounting plate 91 through the opening 78 and the transparent window 21 installed in the through hole 61a of the chamber side 61, and measures the temperature of the mounting plate 91. Furthermore, four through holes 79 are drilled in the holding plate 75 of the base 74, through which the lift pins 12 of the transfer mechanism 10 described below pass to transfer the mounting plate 91.

[0048] Figure 5 1 is a top view of the transfer mechanism 10. Figure 6 1 is a side view of the transfer mechanism 10. The transfer mechanism 10 includes two transfer arms 11. The transfer arms 11 are configured to be in an arc shape along the substantially annular recess 62. Two lift pins 12 are vertically provided on each transfer arm 11. The transfer arms 11 and the lift pins 12 are formed of quartz. Each transfer arm 11 is configured to be rotatable by a horizontal moving mechanism 13. The horizontal moving mechanism 13 enables a pair of transfer arms 11 to be in a transfer action position ( Figure 5 The solid line position) and the retreat position ( Figure 5 As the horizontal moving mechanism 13, each transfer arm 11 can be rotated separately by an independent motor, or a link mechanism can be used to rotate a pair of transfer arms 11 in conjunction with one motor.

[0049] Furthermore, the pair of transfer arms 11 are moved up and down together with the horizontal moving mechanism 13 by the lifting mechanism 14. When the lifting mechanism 14 raises the pair of transfer arms 11 to the transfer operation position, a total of four lift pins 12 are inserted through the through holes 79 (see Figure 2 , 3 ), the upper end of the lift pin 12 protrudes from the upper surface of the base 74. On the other hand, when the lifting mechanism 14 lowers the pair of transfer arms 11 in the transfer action position, pulls the lift pin 12 out of the through hole 79, and the horizontal moving mechanism 13 moves the pair of transfer arms 11 in an open manner, each transfer arm 11 moves to the retreat position. The retreat position of the pair of transfer arms 11 is directly above the base ring 71 of the holding portion 7. The base ring 71 is placed on the bottom surface of the recess 62, and therefore, the retreat position of the transfer arm 11 becomes the inner side of the recess 62. In addition, an exhaust mechanism (not shown) is also provided near the portion of the transfer mechanism 10 where the drive portion (the horizontal moving mechanism 13 and the lifting mechanism 14) is provided, and is configured to exhaust the atmosphere around the drive portion of the transfer mechanism 10 to the outside of the chamber 6.

[0050] return Figure 1 The flash heating unit 5 disposed above the chamber 6 is composed of a light source including a plurality of (30 in the present embodiment) xenon flash lamps FL on the inner side of a housing 51, and a reflector 52 disposed so as to cover the upper side of the light source. In addition, a light irradiation window 53 is installed at the bottom of the housing 51 of the flash heating unit 5. The light irradiation window 53 constituting the bottom plate of the flash heating unit 5 is a plate-shaped quartz window formed of quartz. By disposing the flash heating unit 5 above the chamber 6, the light irradiation window 53 and the upper chamber window 63 are opposed to each other. The flash lamp FL irradiates flash light from above the chamber 6 through the light irradiation window 53 and the upper chamber window 63 to the heat treatment space 65.

[0051] The plurality of flash lamps FL are rod-shaped lamps each having a long cylindrical shape, and are arranged in a plane in such a manner that the long side directions of the flash lamps FL are parallel to each other along the main surface of the GaN substrate W held by the holding portion 7 (i.e., along the horizontal direction). Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane. The area where the plurality of flash lamps FL are arranged is larger than the plane size of the GaN substrate W.

[0052] The xenon flash lamp FL includes: a cylindrical glass tube (discharge tube) in which xenon gas is sealed, and an anode and a cathode connected to a capacitor are arranged at both ends; and a trigger electrode is attached to the outer circumference of the glass tube. Since xenon gas is an electrical insulator, even if there is charge stored in the capacitor, the electricity does not flow into the glass tube under normal conditions. However, when a voltage is applied to the trigger electrode and the insulation is broken, the electricity stored in the capacitor flows into the glass tube instantly, and light is released by the excitation of the atoms or molecules of the xenon gas at this time. In this xenon flash lamp FL, the following characteristics are provided: since the electrostatic energy stored in the capacitor in advance is converted into an extremely short light pulse of 0.1 milliseconds to 100 milliseconds, it can emit extremely strong light compared to a continuously lit light source such as a halogen lamp HL. In other words, the flash lamp FL is a pulse light lamp that emits light instantly in an extremely short time of less than 1 second. In addition, the light emission time of the flash lamp FL can be adjusted according to the coil constant of the lamp power supply that supplies power to the flash lamp FL.

[0053] Furthermore, the reflector 52 is provided above the plurality of flash lamps FL so as to cover the entirety of the plurality of flash lamps FL. The basic function of the reflector 52 is to reflect the flash emitted from the plurality of flash lamps FL to the heat treatment space 65. The reflector 52 is formed of an aluminum alloy plate, and its surface (the surface facing the flash lamp FL side) is roughened by sandblasting.

[0054] The halogen heating unit 4 disposed below the chamber 6 has multiple (40 in this embodiment) halogen lamps HL built inside the housing 41. The halogen heating unit 4 irradiates the heat treatment space 65 with light from below the chamber 6 through the lower chamber window 64 using the multiple halogen lamps HL to heat the GaN substrate W.

[0055] Figure 7 It is a top view showing the arrangement of a plurality of halogen lamps HL. 40 halogen lamps HL are arranged in two layers, upper and lower. 20 halogen lamps HL are arranged in the upper layer close to the holding portion 7, and 20 halogen lamps HL are arranged in the lower layer farther from the holding portion 7 than the upper layer. Each halogen lamp HL is a rod-shaped lamp having a long cylindrical shape. The 20 halogen lamps HL in both the upper and lower layers are arranged in parallel with each other in the direction of their respective long sides along the main surface of the GaN substrate W held by the holding portion 7 (that is, in the horizontal direction). Therefore, the planes formed by the arrangement of the halogen lamps HL in both the upper and lower layers are horizontal planes.

[0056] Moreover, if Figure 7As shown, the upper and lower layers have a higher density of halogen lamps HL in the area opposite to the peripheral portion than in the area opposite to the central portion of the mounting plate 91 held by the holding portion 7. That is, in both the upper and lower layers, the spacing of the halogen lamps HL in the peripheral portion is shorter than in the central portion where the lamps are arranged. Therefore, more light can be irradiated to the peripheral portion of the mounting plate 91, which is prone to temperature drop when heated by light irradiation from the halogen heating portion 4.

[0057] Furthermore, the lamp group including the halogen lamps HL in the upper layer and the lamp group including the halogen lamps HL in the lower layer are arranged in a lattice-like manner, that is, a total of 40 halogen lamps HL are arranged in a manner such that the long sides of the 20 halogen lamps HL arranged in the upper layer and the long sides of the 20 halogen lamps HL arranged in the lower layer are orthogonal to each other.

[0058] The halogen lamp HL is a filament-type light source that emits light by energizing the filament disposed inside a glass tube to incandescently heat the filament. A gas formed by introducing a trace amount of halogen elements (iodine, bromine, etc.) into an inert gas such as nitrogen or argon is sealed inside the glass tube. By introducing the halogen element, the breakage of the filament can be suppressed, and the temperature of the filament can be set to a high temperature. Therefore, the halogen lamp HL has a longer service life than a conventional incandescent bulb and is characterized by being able to continuously irradiate strong light. In other words, the halogen lamp HL is a continuously lit lamp that emits light continuously for at least 1 second. Moreover, the halogen lamp HL is a rod-shaped lamp, so it has a long service life, and by arranging the halogen lamp HL in the horizontal direction, the radiation efficiency to the upper mounting plate 91 becomes excellent.

[0059] Furthermore, a reflector 43 ( Figure 1 ). The reflector 43 reflects the light emitted from the plurality of halogen lamps HL toward the heat treatment space 65 side.

[0060] The control unit 3 controls the various action mechanisms provided in the heat treatment device 1. The hardware structure of the control unit 3 is the same as that of a general computer. That is, the control unit 3 includes a CPU (Central Processing Unit) as a circuit for performing various calculations, a ROM (Read Only Memory) as a read-only memory for storing basic programs, a RAM (Random Access Memory) as a read-write free memory for storing various information, and a magnetic disk that stores control software or data in advance. The CPU of the control unit 3 performs processing in the heat treatment device 1 by executing a specific processing program.

[0061] In addition to the above-mentioned configuration, the heat treatment apparatus 1 is also provided with various cooling structures to prevent the halogen heating unit 4, the flash heating unit 5, and the chamber 6 from being overheated due to the heat energy generated from the halogen lamp HL and the flash lamp FL during the heat treatment of the GaN substrate W. For example, a water cooling pipe (not shown) is provided on the wall of the chamber 6. Furthermore, the halogen heating unit 4 and the flash heating unit 5 are provided with an air cooling structure for exhausting heat by forming an air flow inside. Furthermore, air is also supplied to the gap between the upper chamber window 63 and the lamp irradiation window 53 to cool the flash heating unit 5 and the upper chamber window 63.

[0062] Next, a method for producing a p-type gallium nitride-based semiconductor according to the present invention will be described. Figure 8 This is a flowchart showing the sequence of the method for manufacturing a p-type gallium nitride semiconductor of the present invention. First, magnesium (Mg) is implanted as a p-type dopant into the GaN substrate W to be processed using a known ion implantation method (step S1). The implantation of the p-type dopant is performed using an ion implantation device different from the heat treatment device 1. In addition, the implantation conditions (doping amount, implantation energy, etc.) of the p-type dopant are not particularly limited and can be set to appropriate values. In addition, it can also be a so-called high-temperature implantation in which the temperature of the GaN substrate W when the p-type dopant is implanted is set to a high temperature.

[0063] The GaN substrate W to be processed is a circular plate-shaped gallium nitride wafer with a diameter of about 50 mm (2 inches), which is significantly smaller than a typical silicon semiconductor wafer (diameter 300 mm). Therefore, in this embodiment, the GaN substrate W is placed on a mounting plate 91 and processed using the heat treatment apparatus 1. Fig. 9 : is a diagram showing a state where a GaN substrate W is placed on a mounting plate 91. The mounting plate 91 is a member in the shape of a circular plate with a diameter of 300 mm. The mounting plate 91 is formed, for example, of silicon carbide (SiC). A circular recess with a diameter of about 50 mm is provided in the central portion of the upper surface of the mounting plate 91, and the GaN substrate W is placed in an embedded manner in the recess. Then, the GaN substrate W placed on the mounting plate 91 is heat-treated by the heat treatment device 1. The size of the mounting plate 91 is about the same as that of a typical silicon semiconductor wafer, and therefore, the heat treatment device 1 for processing silicon semiconductor wafers can be used to perform heat treatment on the GaN substrate W. Below, the heat treatment of the GaN substrate W in the heat treatment device 1 is described. The processing sequence of the heat treatment device 1 described below is performed by the control unit 3 controlling each action mechanism of the heat treatment device 1.

[0064] First, the GaN substrate W placed on the mounting plate 91 is carried into the chamber 6 of the heat treatment apparatus 1 (step S2). Specifically, the gate valve 185 is opened, the transport opening 66 is opened, and the mounting plate 91 on which the GaN substrate W is placed is carried into the heat treatment space 65 in the chamber 6 through the transport opening 66 by a transport robot outside the apparatus. At this time, the valve 84 may be opened to supply nitrogen gas into the chamber 6, so that the nitrogen gas flows out from the transport opening 66, and the introduction of external gas accompanying the carrying of the GaN substrate W is suppressed to a minimum.

[0065] The loading plate 91 carried in by the transfer robot enters the position just above the holding portion 7 and stops. Then, the pair of transfer arms 11 of the transfer mechanism 10 horizontally move from the retracted position to the transfer operation position and rise, whereby the lift pins 12 pass through the through holes 79 and protrude from the upper surface of the holding plate 75 of the base 74 to receive the loading plate 91 carrying the GaN substrate W. At this time, the lift pins 12 rise to a position higher than the upper ends of the support pins 77.

[0066] After the carrier plate 91 on which the GaN substrate W is placed is placed on the lift pins 12, the transport robot withdraws from the heat treatment space 65 and closes the transport opening 66 by the gate valve 185. Then, the carrier plate 91 is handed over from the transfer mechanism 10 to the base 74 of the holding portion 7 by the pair of transfer arms 11 descending, and is held from below in a horizontal posture. The carrier plate 91 is supported by a plurality of support pins 77 vertically provided on the holding plate 75 and is held on the base 74. The carrier plate 91 is held on the holding portion 7 with the surface of the GaN substrate W implanted with the p-type dopant facing the top surface. A specific gap is formed between the back surface (the surface on the opposite side to the side on which the GaN substrate W is placed) of the carrier plate 91 supported by the plurality of support pins 77 and the holding surface 75a of the holding plate 75. The pair of transfer arms 11 descending below the base 74 are retracted to the retracted position, that is, the inside of the recess 62, by the horizontal moving mechanism 13.

[0067] Moreover, after the transfer opening 66 is closed by the gate valve 185 and the heat treatment space 65 becomes a closed space, an atmosphere containing nitrogen and hydrogen is formed in the chamber 6 (step S3). Here, the atmosphere containing nitrogen and hydrogen in the present invention refers to nitrogen and hydrogen as elements. That is to say, the atmosphere containing nitrogen and hydrogen does not necessarily need to contain molecular nitrogen (N2) and hydrogen (H2). In this embodiment, the valve 84 is opened to supply ammonia (NH3) as a processing gas from the processing gas supply source 85 to the heat treatment space 65. Ammonia contains nitrogen and hydrogen as elements. Moreover, the valve 89 is opened to discharge the gas in the chamber 6 from the gas exhaust hole 86. As a result, the processing gas supplied from the upper part of the heat treatment space 65 in the chamber 6 flows downward and is discharged from the lower part of the heat treatment space 65, and the chamber 6 is replaced by an ammonia atmosphere. The ammonia concentration in the ammonia atmosphere formed in the chamber 6 can be set to an appropriate value, for example, it can also be 100%. Furthermore, in order to improve the replacement efficiency, the pressure in the chamber 6 may be temporarily reduced to a pressure lower than the atmospheric pressure, and then ammonia may be supplied into the chamber 6 .

[0068] After the ammonia atmosphere is formed in the chamber 6, the 40 halogen lamps HL of the halogen heating unit 4 are lit at the same time to start preheating (auxiliary heating) (step S4). The halogen light emitted from the halogen lamp HL passes through the lower chamber window 64 and the base 74 formed by quartz, and irradiates the lower surface of the mounting plate 91 on which the GaN substrate W is mounted. Since the mounting plate 91 is formed of SiC, it absorbs the light emitted from the halogen lamp HL well and heats up. Then, the GaN substrate W is preheated by heat conduction from the heated mounting plate 91. In addition, the transfer arm 11 of the transfer mechanism 10 has retreated to the inner side of the recess 62, so it does not hinder the heating by the halogen lamp HL.

[0069] When the halogen lamp HL is preheated, the temperature of the mounting plate 91 on which the GaN substrate W is mounted is measured by the radiation thermometer 20. That is, the radiation thermometer 20 receives infrared light radiated from the lower surface of the mounting plate 91 held on the base 74 through the opening 78 through the transparent window 21, and measures the temperature of the mounting plate 91 during heating. The measured temperature of the mounting plate 91 is transmitted to the control unit 3. The control unit 3 controls the output of the halogen lamp HL while monitoring whether the temperature of the mounting plate 91, which is heated by the light irradiation from the halogen lamp HL, reaches the target temperature T1. That is, the control unit 3 feedback controls the output of the halogen lamp HL based on the measured value of the radiation thermometer 20 so that the temperature of the mounting plate 91 reaches the target temperature T1. The target temperature T1 is not less than 900°C and not more than 1000°C.

[0070] After the temperature of the mounting plate 91 reaches the target temperature T1, the control unit 3 adjusts the output of the halogen lamp HL so that the temperature of the mounting plate 91 is maintained at the target temperature T1. Specifically, at the time point when the temperature of the mounting plate 91 measured by the radiation thermometer 20 reaches the target temperature T1, the control unit 3 adjusts the output of the halogen lamp HL so that the temperature of the mounting plate 91 is substantially maintained at the target temperature T1. The mounting plate 91 is maintained at the target temperature T1 by irradiation with light from the halogen lamp HL, and thus the GaN substrate W is uniformly preheated by heat conduction from the mounting plate 91.

[0071] At a specific time point after the temperature of the mounting plate 91 reaches the target temperature T1, the surface of the GaN substrate W is flash-irradiated from the flash lamp FL of the flash heating unit 5 (step S5). At this time, part of the flash emitted from the flash lamp FL is directed directly into the chamber 6, and the other part is temporarily reflected by the reflector 52 and then directed into the chamber 6, and the GaN substrate W is flash-heated by these flash irradiations.

[0072] Flash heating is performed by irradiating a flash light from a flash lamp FL, so the surface temperature of the GaN substrate W can be raised in a short time. That is, the flash irradiated from the flash lamp FL is an extremely short and strong flash in which the electrostatic energy pre-stored in the capacitor is converted into an extremely short light pulse and the irradiation time is about 0.1 milliseconds to 100 milliseconds. Then, due to the flash irradiation from the flash lamp FL, the surface of the GaN substrate W injected with the p-type dopant is instantly heated to the processing temperature T2 and then rapidly cooled. The processing temperature T2 is higher than the target temperature T1 and is above 1400°C. By instantly heating the surface of the GaN substrate W to the processing temperature T2, the injected p-type dopant is activated. In addition, the time required for the dopant activation is extremely short, so even a short-time flash heating is sufficient to activate the dopant.

[0073] It is known that when gallium nitride is heated to a high temperature, nitrogen is relatively easy to be released. Therefore, attempts have been made to prevent nitrogen release by, for example, providing a capping layer on the surface of gallium nitride. In the present embodiment, the surface of the GaN substrate W is flash-heated from the target temperature T1 to the processing temperature T2 by irradiating the GaN substrate W with a flash having an extremely short irradiation time, so that the time for the GaN substrate W to reach a high temperature is short, thereby suppressing such nitrogen release to a minimum. Furthermore, even if nitrogen is slightly released, since the GaN substrate W is flash-heated from the target temperature T1 to the processing temperature T2 in an ammonia atmosphere (that is, in an atmosphere containing nitrogen), the released nitrogen can be replenished from the atmosphere while performing the heat treatment. As a result, without providing a capping layer, etc., it is possible to prevent the GaN substrate W from being deficient in nitrogen, thereby improving the activation efficiency of the p-type dopant.

[0074] Furthermore, in this embodiment, since the GaN substrate W is flash-heated in an ammonia atmosphere (that is, in an atmosphere containing hydrogen), the heat treatment can be performed while hydrogen is supplied to the GaN substrate W. Thus, the p-type dopant implanted into the GaN substrate W can be activated efficiently.

[0075] Furthermore, in this embodiment, the surface of the GaN substrate W is heated to a high temperature of 1400° C. or higher by flash heating. This repairs the crystal defects of the GaN substrate W generated during dopant implantation, thereby improving the activation efficiency of the p-type dopant.

[0076] After the p-type dopant is activated by flash heating, the atmosphere in the chamber 6 is replaced (step S6). Specifically, the valve 84 is closed, and the valve 89 is opened to exhaust the ammonia atmosphere in the chamber 6. After the pressure in the chamber 6 is reduced to less than the atmospheric pressure, the valve 84 is opened to supply nitrogen into the chamber 6. Thus, the ammonia atmosphere in the chamber 6 is replaced with a nitrogen atmosphere as an inert gas.

[0077] Thereafter, since the halogen lamp HL is also extinguished, the GaN substrate W and the mounting plate 91 are rapidly cooled. The temperature of the mounting plate 91 during cooling is measured by the radiation thermometer 20, and the measurement result is transmitted to the control unit 3. The control unit 3 monitors whether the temperature of the mounting plate 91 is cooled to a specific temperature based on the measurement result of the radiation thermometer 20. Then, after the temperature of the mounting plate 91 is cooled to below a specific temperature, the pair of transfer arms 11 of the transfer mechanism 10 are horizontally moved from the retreat position to the transfer action position again and then rise, whereby the lift pins 12 protrude from the upper surface of the base 74, and the mounting plate 91 carrying the heat-treated GaN substrate W is received from the base 74. Next, the transport opening 66 closed by the gate valve 185 is opened, and the mounting plate 91 carried on the lift pins 12 is carried out by the transport robot outside the device, thereby completing the heating treatment of the GaN substrate W in the heat treatment device 1 (step S7).

[0078] In this embodiment, flash irradiation is performed in an atmosphere containing nitrogen and hydrogen to flash heat the surface of the GaN substrate W injected with a p-type dopant to a high temperature of 1400°C or higher. This can prevent the GaN substrate W from lacking nitrogen during the heat treatment. Moreover, the heat treatment can be performed while hydrogen is supplied to the GaN substrate W. Furthermore, the crystal defects existing in the GaN substrate W can be repaired. Then, as a result of the above, the p-type dopant injected into the GaN substrate W can be activated with high efficiency, so that a high-quality p-type gallium nitride semiconductor can be manufactured.

[0079] Furthermore, a process such as forming a cap layer to prevent nitrogen from being released from the GaN substrate W is not necessary, and thus the manufacturing cost can be reduced.

[0080] The above has been described the embodiment of the present invention, but the present invention can be modified in various ways other than the above within the scope of the gist thereof. For example, in the above embodiment, the flash heating of the GaN substrate W is performed in an ammonia atmosphere, but the present invention is not limited to this, and the flash heating of the GaN substrate W can also be performed by irradiating a flash in a nitrogen-hydrogen mixed atmosphere which is a mixed gas of hydrogen and nitrogen. The nitrogen-hydrogen mixed atmosphere is also an atmosphere containing nitrogen and hydrogen as elements. Therefore, by irradiating a flash in the nitrogen-hydrogen mixed atmosphere and flash heating the GaN substrate W, the same effect as in the above embodiment can be obtained, so that the p-type dopant can be activated with high efficiency. In addition, the maximum hydrogen concentration in the nitrogen-hydrogen mixed gas is 4%. In short, the GaN substrate W can be heated by irradiating a flash in an atmosphere containing nitrogen and hydrogen.

[0081] Furthermore, the size of the GaN substrate W is not limited to a diameter of about 50 mm, and may be, for example, a diameter of about 100 mm (4 inches).

[0082] Furthermore, the material of the mounting plate 91 is not limited to silicon carbide, and may be silicon (Si), for example. However, if the GaN substrate W is heated to a high temperature of 1400°C or higher during flash heating, there is a concern that the silicon (melting point 1414°C) mounting plate 91 may melt, so the mounting plate 91 is preferably formed of silicon carbide (melting point 2730°C).

[0083] Furthermore, in the above-described embodiment, the flash heating unit 5 is provided with 30 flash lamps FL, but the present invention is not limited thereto, and the number of flash lamps FL can be set to any number. Furthermore, the flash lamps FL are not limited to xenon flash lamps, and can also be krypton flash lamps. Furthermore, the number of halogen lamps HL provided in the halogen heating unit 4 is not limited to 40, and can be set to any number.

[0084] Moreover, in the above-described embodiment, a filament-type halogen lamp HL is used as a continuous-lighting lamp that emits light continuously for more than 1 second to preheat the GaN substrate W, but this is not limited to this. A discharge-type arc lamp (such as a xenon arc lamp) may be used instead of the halogen lamp HL as a continuous-lighting lamp for preheating.

[0085] [Explanation of symbols]

[0086] 1 Heat treatment device

[0087] 3. Control Unit

[0088] 4 Halogen heating unit

[0089] 5 Flash heating unit

[0090] 6 Chamber

[0091] 7. Maintaining part

[0092] 10 Transfer mechanism

[0093] 65 Heat treatment space

[0094] 74 Base

[0095] 75 Holding Plate

[0096] 77 Support pin

[0097] 85 Process gas supply source

[0098] 91 Loading Plate

[0099] FL Flash

[0100] HL halogen lamp

[0101] W GaN substrate

Claims

1. A method for manufacturing a p-type gallium nitride semiconductor, characterized in that have: an implantation step of implanting p-type dopants into the gallium nitride substrate; and The heating step comprises irradiating the substrate with a flash of light for an irradiation time of 0.1 milliseconds to less than 1 second in an atmosphere containing nitrogen and hydrogen to heat the substrate, thereby replenishing nitrogen released from the gallium nitride substrate from the atmosphere.

2. The method for manufacturing a p-type gallium nitride-based semiconductor according to claim 1, wherein The atmosphere containing nitrogen and hydrogen is an ammonia atmosphere.

3. The method for manufacturing a p-type gallium nitride-based semiconductor according to claim 1, wherein The atmosphere containing nitrogen and hydrogen is a nitrogen-hydrogen mixed atmosphere.

4. A heat treatment method, characterized in that have: A loading step is to load the gallium nitride substrate implanted with p-type dopants into the chamber; an atmosphere forming step of forming an atmosphere containing nitrogen and hydrogen in the chamber; and The light irradiation step irradiates the substrate with a flash of light for an irradiation time of 0.1 milliseconds or longer and less than 1 second to heat the substrate, thereby replenishing nitrogen released from the gallium nitride substrate from the atmosphere.

5. The heat treatment method according to claim 4, wherein The atmosphere containing nitrogen and hydrogen is an ammonia atmosphere.

6. The heat treatment method according to claim 4, wherein The atmosphere containing nitrogen and hydrogen is a nitrogen-hydrogen mixed atmosphere.

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