JP2009161430A - Method for manufacturing gallium nitride independent substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a gallium nitride independent substrate by efficiently removing a nitride deposit formed on the outer periphery of a GaN crystal and a GaAs substrate. <P>SOLUTION: This method for manufacturing the gallium nitride independent substrate comprises manufacturing the substrate from a gallium nitride crystal 24 grown by chemical vapor deposition on a substrate 9 composed of a material different from gallium nitride. As the crystal grows, a nitride deposit 26 is formed on a side face of the gallium nitride crystal 24 and the substrate 9. This method comprises the steps of removing the nitride deposit 26 by peripheral processing and, after the peripheral processing, separating the substrate 9 from the gallium nitride crystal 24 to make the substrate 9 and the gallium nitride crystal 24 independent to each other. When separating the substrate 9 from the gallium nitride crystal 24, the substrate 9 is separated from the gallium nitride crystal 24 by applying force to the boundary between the gallium nitride crystal 24 and the substrate 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a gallium nitride independent substrate.

  Reference 1 (Japanese Patent Laid-Open No. 2000-12900) describes a GaN single crystal substrate. A mask having a staggered window or a stripe window is formed on a GaAs (111) substrate, a GaN buffer layer is formed at a low temperature by the HVPE method or the MOC method, and a GaN epitaxial layer is formed thick at a high temperature by the HVPE method. Remove the substrate. Using a GaN free-standing film as a seed crystal, GaN is thickened by the HVPE method to make a GaN ingot. This is cut by a slicer to make a transparent and colorless GaN wafer with little warpage.

  Document 2 (Japanese Patent Laid-Open No. 2002-284600) describes a method for manufacturing a gallium nitride crystal substrate and a gallium nitride crystal substrate. A metal film is deposited on a single crystal sapphire substrate, a substrate on which a single crystal gallium nitride film is grown on a sapphire substrate, or a starting substrate made of a single crystal semiconductor crystal substrate. By forming the laminated substrate in which the gallium nitride film is deposited on the metal film, the grown gallium nitride film and the starting substrate can be easily separated.

  Document 3 (Japanese Patent Laid-Open No. 2003-168820) describes a peeling method in which a crystal layer formed on a substrate is irradiated with light for peeling. In this peeling method, light is irradiated in a line shape. At this time, the crystal layer can be peeled from the substrate without generating cracks by setting the light irradiation width to be equal to or smaller than the thickness of the crystal layer.

Japanese Patent Laid-Open No. 2000-12900 JP 2002-284600 A JP 2003-168820 A

  In manufacturing a gallium nitride independent substrate, a GaN film is grown on a GaAs substrate, and then GaAs is removed by etching to form a self-standing GaN single crystal. When growing a GaN crystal on a GaAs substrate, a nitride deposit adheres to the outer periphery of the GaN single crystal and the GaAs substrate. Even if the GaAs substrate is removed by wet etching after growing the GaN single crystal, protrusions protruding outside the outer periphery of the GaN single crystal remain. Therefore, the shape processing of the GaN single crystal cannot be performed unless the protrusion is removed. However, in order to remove the protruding deposits, it is necessary to perform processing manually. What is required is to further improve productivity by efficiently removing nitride deposits on the outer periphery of the GaN single crystal and GaAs substrate.

As already described, in Document 2, a GaN film is grown on an sapphire substrate via an aluminum vapor deposition film, and the aluminum vapor deposition film is dissolved by etching (HCl + H ₂ O ₂ ) to obtain a self-standing GaN film. In Document 3, a GaN film is grown on a sapphire substrate, and the sapphire substrate is irradiated linearly with a laser beam to peel off the GaN film. Stress is relieved to prevent cracking of the GaN film. These techniques are different from removing nitride deposits on the periphery of a GaN single crystal and GaAs substrate.

  The present invention has been made in view of the above matters, and provides a method for manufacturing a gallium nitride independent substrate by efficiently removing nitride deposits formed on the outer periphery of a GaN crystal body and a GaAs substrate. The purpose is to do.

  The present invention relates to a method of manufacturing a gallium nitride independent substrate. This method is a method of manufacturing a gallium nitride independent substrate from a gallium nitride crystal grown by a vapor deposition method on a substrate made of a material different from gallium nitride, and the substrate and the gallium nitride crystal are grown by the growth. A nitride deposit is formed on the side of the body. The method includes (a) a step of removing the nitride deposit by peripheral processing, and (b) exfoliating the substrate from the gallium nitride crystal after the peripheral processing, so that the substrate and the gallium nitride crystal are separated. And making the bodies independent of each other. In the step of making the gallium nitride crystals independent of each other, a force is applied to the boundary between the gallium nitride crystal and the substrate to peel the substrate from the gallium nitride crystal.

  One aspect of the present invention relates to a method of manufacturing a gallium nitride independent substrate. This method is a method of manufacturing a gallium nitride independent substrate from a gallium nitride crystal grown by a vapor deposition method on a substrate made of a material different from gallium nitride, and the substrate and the gallium nitride crystal are grown by the growth. A nitride deposit is formed on the side of the body. The method includes (a) a step of removing the nitride deposit by peripheral processing, and (b) exfoliating the substrate from the gallium nitride crystal after the peripheral processing, so that the substrate and the gallium nitride crystal are separated. And making the bodies independent of each other.

  According to this method, since the nitride deposit is removed prior to peeling the substrate from the gallium nitride crystal, the nitride deposit can be removed by outer periphery processing.

  In the method of the present invention, in the step of removing the nitride deposit by outer periphery processing, it is preferable to remove the nitride deposit using a grindstone while rotating the gallium nitride crystal around a predetermined axis. .

  According to this method, the gallium nitride crystal is formed on a substantially disk-shaped substrate. Therefore, the nitride deposit can be removed while rotating the gallium nitride crystal around a predetermined axis.

  In the method of the present invention, the step of removing by peripheral processing includes (a1) a first step of processing the nitride deposit using a first grindstone having a first rigidity, and (a2) the first step. And a second step of processing the nitride deposit using a second grindstone having a second rigidity after the first step, wherein the first rigidity is higher than the second rigidity. preferable.

  According to this method, the inner peripheral region is closer to the gallium nitride crystal that is the product than the outer peripheral region of the nitride deposit. Therefore, the grindstone used in each of the inner peripheral area and the outer peripheral area is changed to reduce damage to the product.

  In the method of the present invention, in at least one of the first and second steps, the nitride may be produced while swinging one of the gallium nitride crystal and the grindstone along the predetermined axis with respect to the other. It is preferable to remove the deposit by outer periphery processing.

  According to this method, since the width of the grindstone is larger than the thickness of the gallium nitride crystal, the entire surface of the grindstone can be used evenly by rocking.

  In the method of the present invention, the step of removing by outer periphery processing includes an initial step and a finishing step, and it is preferable that the feed rate of the grindstone in the initial step is different from the feed rate of the grindstone in the finishing step. According to this method, the inner peripheral region is closer to the gallium nitride crystal that is the product than the outer peripheral region of the nitride deposit. Therefore, the feed rate used in the inner peripheral area and the outer peripheral area is changed to reduce damage to the product.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, a method for manufacturing a gallium nitride independent substrate by efficiently removing nitride deposits formed on the outer periphery of a GaN crystal body and a GaAs substrate is provided.

FIG. 1 shows a film forming apparatus for vapor phase growth method such as HVPE method used for epitaxial growth in an embodiment of the present invention. FIG. 2A is a drawing showing a peripheral processing apparatus that performs a step of removing nitride deposits by peripheral processing. FIG. 2B is a drawing showing a step of removing nitride deposits. FIG. 2C is a drawing showing a process of peeling the substrate from the gallium nitride crystal. FIG. 3A shows an independent gallium nitride crystal from which nitride deposits have been removed. FIG. 3B is a drawing showing a gallium nitride wafer formed from a gallium nitride crystal. FIG. 4A and FIG. 4B are drawings showing an outer periphery processing step according to the second embodiment. FIG. 5A and FIG. 5B are drawings showing the outer periphery machining process according to the third embodiment. FIG. 6A and FIG. 6B are drawings showing the outer periphery processing step according to the fourth embodiment. FIG. 7A to FIG. 7C are drawings showing a manufacturing method for etching a composite.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, an embodiment according to a method of manufacturing a gallium nitride independent substrate of the present invention will be described with reference to the accompanying drawings. In this method, a gallium nitride independent substrate is manufactured from a gallium nitride crystal grown by vapor deposition on a substrate made of a material different from gallium nitride. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1 shows a film forming apparatus for vapor phase epitaxy such as HVPE used for epitaxial growth in an embodiment of the present invention. A cylindrical heater 2 surrounds the vertically long reactor 1. There are source gas inlets 3 and 4 at the top of the reactor 1. A mixed gas G 1 of hydrogen chloride (HCl) as a source gas and hydrogen (H 2) as a carrier gas is introduced into the reactor 1 through a gas inlet 3. Opposite the inlet 3 is a gallium (Ga) source 5. Since metallic gallium is contained and the melting point of metallic gallium is low, it becomes Ga melt 6 when heated by heater 2. When HCl is blown onto the Ga melt, a reaction occurs in which 2Ga + 6HCl generates 2GaCl ₃ + 3H ₂ to generate gallium chloride (GaCl ₃ ). In the space in the reactor 1, a mixed gas G2 of gallium chloride and the carrier gas H ₂ is provided. A mixed gas G3 of ammonia (NH ₃ ) + hydrogen (H ₂ ) is introduced into the reaction furnace 1 through the inlet 4. Gallium nitride is deposited on the substrate 9 by the reaction of GaCl ₃ and NH _{3 in} the source gas.

The susceptor 7 is supported by a shaft 8 so as to be freely rotatable and raised / lowered. A substrate such as a GaAs substrate 9 is disposed on the susceptor 7. The GaAs substrate 9 has an inch size, for example, a substantially disk shape having a diameter of 2 inches. Product GaN is deposited on the main surface of the substrate 9. The remainder of the raw material gas and the mixed gas G4 of the reaction product gas are discharged through the exhaust gas outlet 10. A GaN crystal produced by the HVPE method exhibits an n conductivity type even if it is undoped. The carrier concentration is, for example, about 1 × 10 ¹⁶ cm ⁻³ . After the temperature of the film forming apparatus is lowered to room temperature, a complex composed of the GaAs substrate 9 and a GaN crystal grown on the substrate 9 is taken out. The thickness of the GaN crystal is larger than the thickness of the substrate 9.

  FIG. 2A shows an outer periphery processing apparatus that performs a step of removing nitride deposits by outer periphery machining. The composite 20 includes a GaAs substrate 9, a gallium nitride crystal 24 and a nitride deposit 26. For example, a cylindrical gallium nitride crystal body 24 is deposited on the disk-shaped substrate 9. Accompanying the growth of the gallium nitride crystal 24, a nitride deposit 26 is formed on the substrate 9 and the side surfaces 9 a and 24 a of the gallium nitride crystal 24. The nitride deposit 26 is a protrusion located outside the virtual cylinder having the diameter of the substrate 9. The composite 20 is attached to the outer peripheral processing device 22 so as to be rotatable around a predetermined axis Ax. The outer periphery processing device 22 includes, for example, a grindstone 28 as a grinding tool for machining the outer periphery of the composite 20. The complex 20 has a dimension indicated by the symbol D1.

  FIG. 2B is a drawing showing the outer periphery processing step. The grindstone 28 is brought into contact with the outer periphery of the composite 20 while rotating the composite 20 around a predetermined axis Ax. When the grindstone 28 is moved at an appropriate feed rate, the outer periphery of the composite 20 is ground. That is, the nitride deposit 26 is gradually removed. In FIG. 2B, the outer periphery of the composite 20 is ground to form a nitride deposit 26a, and the dimension D2 of the composite 20 is also reduced. For example, the outer periphery of the composite 20 is ground to a diameter of 50 millimeters using the outer periphery processing device 22. The protrusion is removed by this grinding. In the composite 20a shown in FIG. 2B, a slight amount of nitride deposits remain on the side surfaces of the gallium nitride crystal 24 and the substrate 9, but all of the nitride deposits are removed.

  As shown in FIG. 2C, the substrate 9 is mechanically peeled from the gallium nitride crystal body 24 in the composite 20b after the outer periphery processing. By this peeling, the substrate 9 and the gallium nitride crystal body 24 become independent from each other. The peeling can be performed as follows, for example. By removing the nitride deposit, the boundary between the gallium nitride crystal body 24 and the substrate 9 is exposed. By applying a force to this boundary, the composite 20 b is separated into the substrate 9 and the gallium nitride crystal 24. As a result, a gallium nitride crystal body 24 for forming a gallium nitride wafer is obtained.

  According to this method, since the nitride deposit 26 is removed before the substrate 9 is peeled from the gallium nitride crystal body 24, the nitride deposit 26 can be removed by outer peripheral processing.

  FIG. 3A shows an independent gallium nitride crystal with the nitride deposit removed and stripped. The gallium nitride crystal body 24 is processed to have a desired diameter. The gallium nitride crystal body 24 is sliced and polished, and as shown in FIG. 3B, one or more gallium nitride wafers 24a. To 24d.

Example 1
A composite in which a gallium nitride film of about 3 mm was stacked on a GaAs substrate having a diameter of 50 mm was prepared. Due to the nitride deposit, the outer diameter of the composite is 58 mm. After grinding at a peripheral speed of 2000 mm per minute with a resin bond grindstone (grindstone with diamond grains bonded by resin) # 600 and grinding from an outer diameter of 58 mmφ to 49.5 mmφ, the gallium nitride crystal is peeled off from the GaAs substrate. To do. The grinding time is 80 minutes.

  A composite having an outer diameter of 58 mm for the nitride deposit is processed using a metal bond straight grindstone (a grindstone obtained by baking diamond particles with a metal powder). The grinding time is 80 minutes. Although cracks were not observed at the initial stage of processing, several cracks were generated around the substrate when the processing was completed. In general, compared with a soft resin bond grindstone, the wear resistance is large and it is advantageous in terms of life, but the damage given to the product is large because of high rigidity. Vitrified grinding wheels (grinding stones in which diamond grains are baked and hardened with alumina) have a tendency similar to that of the metal bond grinding stone.

(Second Embodiment)
FIG. 4A and FIG. 4B are drawings showing an outer periphery processing step according to the second embodiment. As shown in FIG. 4A, in the outer periphery processing step, the composite 20 is processed using a first grindstone 29a having first rigidity. By this processing, the nitride deposit 26 of the composite 20 is ground into a nitride deposit 26b. Next, the nitride deposit 26b is processed using the second grindstone 29b having the second rigidity. By this processing, as shown in FIG. 4B, the nitride deposit 26b of the composite 20 is ground into a nitride deposit 26c. The first stiffness is higher than the second stiffness. Unlike the outer peripheral region of the nitride deposit, the inner peripheral region is adjacent to the gallium nitride crystal that is the product. Therefore, the grindstone used in each of the inner peripheral area and the outer peripheral area is changed to reduce damage to the product when necessary.

(Example 2)
A composite in which a gallium nitride film of about 3 mm was stacked on a GaAs substrate having a diameter of 50 mm was prepared. Due to the nitride deposit, the outer diameter of the composite is 58 mm. Grind the first 80 percent of the grinding with a vitrified wheel at a peripheral speed of 2000 mm / min. Next, the remaining 20 percent is ground at a peripheral speed of 2000 mm using a resin bond grindstone. The grinding time is 80 minutes. There are no cracks. After grinding to a desired dimension, the gallium nitride crystal is peeled from the GaAs substrate.

(Third embodiment)
FIG. 5A and FIG. 5B are drawings showing the outer periphery machining process according to the third embodiment. In the peripheral processing step, the nitride deposit 26 is removed by peripheral processing while swinging one of the gallium nitride crystal 24 and the grindstone 28 with respect to the other in part or all of the peripheral processing step. The grindstone 28 is supported by the rocking device 30 and is movable along a predetermined axis Ax.

  As shown in FIG. 5A, the grindstone 28 supported by the rocking device 30 uses the first area 28b of the grinding surface 28a. As the grindstone 28 moves in the direction indicated by the arrow M1, the area in contact with the nitride deposit 26d moves from the first area 28b to the second area 28c. As shown in FIG. 5B, when the grindstone 28 reaches the limit point by the swing device 30, the grindstone 28 moves in the reverse direction indicated by the arrow M2. By such movement, almost the entire grinding surface 28a is used. According to this method, since the thickness T1 of the grindstone 28 is larger than the thickness T2 of the gallium nitride crystal, the entire surface of the grindstone is evenly worn by swinging the grindstone.

(Example 3)
A composite in which a gallium nitride film of about 3 mm was stacked on a GaAs substrate having a diameter of 50 mm was prepared. Due to the nitride deposit, the outer diameter of the composite is 58 mm. Grind with a diamond straight grindstone (resin bond grindstone) # 600 at a peripheral speed of 2000 mm / min. The grindstone is evenly worn by swinging the grindstone in the thickness direction of the composite.

(Fourth embodiment)
FIG. 6A and FIG. 6B are drawings showing the outer periphery processing step according to the fourth embodiment. The outer periphery processing step includes an initial step shown in FIG. 6A and a finishing step shown in FIG. The feed speed of the grindstone 28 for grinding the nitride deposits 26f and 26g is changed by a feed device 32 that can be provided in the film forming device 22. The feed speed V1 of the grindstone 28 in the initial process is different from the feed speed V2 of the grindstone 28 in the finishing process. In the preferred embodiment, the feed rate V2 is less than the feed rate V1. For example, the feed rate V1 is preferably 3 mm / Hr to 7 mm / Hr, and the feed rate V2 is preferably 1 mm / Hr to 4 mm / Hr.

  According to this method, the inner peripheral region is closer to the gallium nitride crystal that is the product than the outer peripheral region of the nitride deposit. Therefore, the feed rate used in the inner peripheral area and the outer peripheral area is changed to reduce damage to the product.

Example 4
When the outer periphery of the composite having a diameter of 58 mmφ is processed at a processing feed rate of 5 mm / hrs and processed to 52 mmφ, the processing feed rate is changed to 2 mm / hrs and processed to 50 mmφ. There is no cracking.

  In the first to fourth embodiments described above, the nitride deposit 26 is removed before the substrate 9 is peeled off from the gallium nitride crystal body 24. Therefore, the nitride deposit 26 is removed by peripheral processing. Can do.

(Comparative example)
When the gallium nitride thick film 42 is grown on the GaAs substrate 40, a growth deposit 44 is inevitably formed on the outer periphery of a cylindrical gallium nitride crystal having a diameter of 50 mm, and the diameter of the composite becomes about 58 mm. Although the shape of the growth deposit is various, as shown in FIG. 7A, it becomes a shape spreading toward the substrate 9 from the gallium nitride crystal body 24. When the GaAs substrate is removed from this composite by etching with aqua regia etc., as shown in FIG. 7B, the growth deposit (end spread portion 44a) adhering to the side surface of the GaAs substrate remains in a protruding shape. To do. As it is, a wafer cannot be formed by processing the shape of the self-supported gallium nitride thick film. Therefore, as shown in FIG. 7C, it is necessary to remove the protrusions by pre-processing. This pre-processing is a work by human power and requires about 50 to 80 minutes. In order to further improve productivity, it is desirable to shorten this time. According to various methods described in the present embodiment, the time required for this processing can be shortened as much as possible, and the productivity can be increased. Further, by reducing the time for manual processing as much as possible, wafer breakage caused by a handling error or the like during manual processing can be reduced.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. If necessary, a mask having a predetermined pattern can be provided on the substrate prior to the formation of the gallium nitride crystal. In addition, the present invention can be applied to both a single crystal substrate and a composite substrate including a plurality of single crystals as a gallium nitride substrate. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

DESCRIPTION OF SYMBOLS 1 ... Reaction furnace, 2 ... Heater, 3, 4 ... Raw material gas inlet, 5 ... Gallium source, 6 ... Ga melt, 7 ... Susceptor, 9 ... Substrate, 10 ... Exhaust gas outlet, 20, 20a, 20b ... Composite, 22 ... Peripheral processing device, 24 ... Gallium nitride crystal, 26, 26a, 26b ... Nitride deposit, 28 ... Grinding stone, 24a, 24d ... Gallium nitride wafer, 29a, 29b ... Grinding stone, 30 ... Swing device 28a ... grinding surface, T1 ... thickness of grinding wheel, T2 ... thickness of gallium nitride crystal, 32 ... feed device, V1, V2 ... feed speed

Claims (7)

A method of manufacturing a gallium nitride independent substrate from a gallium nitride crystal grown by vapor deposition on a substrate made of a material different from gallium nitride, wherein the growth causes the substrate and the side surface of the gallium nitride crystal to be formed. Nitride deposits are formed on the
Removing the nitride deposit by peripheral processing;
Peeling the substrate from the gallium nitride crystal after the peripheral processing, and making the substrate and the gallium nitride crystal independent of each other,
The step of separating the gallium nitride crystals from the gallium nitride crystals by applying a force to the boundary between the gallium nitride crystals and the substrate in the step of making the gallium nitride crystals independent of each other. 2. The step of removing the nitride deposit by outer periphery processing, wherein the nitride deposit is removed using a grindstone while rotating the gallium nitride crystal around a predetermined axis. The method described in. The step of removing by peripheral processing is
A first step of processing the nitride deposit using a first grindstone having a first stiffness;
A second step of processing the nitride deposit using a second grindstone having a second rigidity after the first step;
The method of claim 2, wherein the first stiffness is higher than the second stiffness. In at least one of the first and second steps, the nitride deposit is formed by outer peripheral processing while either one of the gallium nitride crystal and the grindstone is swung along the predetermined axis with respect to the other. The method according to claim 3, wherein the method is removed. The step of removing by peripheral processing includes an initial step and a finishing step,
The method according to any one of claims 2 to 4, wherein a feed speed of the grindstone in the initial process is different from a feed speed of the grindstone in the finishing process. The method according to any one of claims 1 to 5, wherein the gallium nitride crystal has a thickness greater than a thickness of the substrate. 7. The substrate and the gallium nitride crystal are made independent of each other, and then the gallium nitride crystal is polished and sliced to be processed into one or more gallium nitride wafers. The method as described in any one of.

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