JP4513480B2 - Method for manufacturing gallium nitride crystal and method for manufacturing gallium nitride substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a gallium nitride crystal and a method for manufacturing a gallium nitride 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 single 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 free-standing GaN crystal. When a GaN crystal is grown on a GaAs substrate, a nitride deposit adheres to the outer periphery of the GaN crystal and the GaAs substrate. Even if the GaAs substrate is removed by wet etching after the GaN crystal is grown, the protrusions protruding outward from the outer periphery of the GaN crystal remain. Therefore, the shape processing of the GaN crystal can be performed only after the protrusions are removed. However, in order to remove the protruding deposits, it is necessary to perform processing manually. What is required is to further improve the productivity in producing a gallium nitride substrate by efficiently removing nitride deposits on the outer circumference of the GaN 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. This relaxes the stress and prevents the GaN film from cracking. 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-mentioned matters. Gallium nitride crystals for producing a gallium nitride substrate and nitride deposits formed on the outer periphery of the substrate are efficiently removed, and gallium nitride is obtained. It is an object of the present invention to provide a method for producing a crystal body and a method for producing a gallium nitride substrate.

One aspect of the present invention relates to a method of manufacturing a gallium nitride crystal. This method is a method of manufacturing a gallium nitride crystal for producing a gallium nitride substrate on a substrate made of a material different from gallium nitride by vapor deposition, and the substrate and the nitridation by the growth. A nitride deposit is formed on the side surface of the gallium crystal. In this method, (a) a composite including the substrate, the gallium nitride crystal, and the nitride deposit is rotated around a predetermined axis, and an outer peripheral portion of the nitride deposit is ground by machining. Leaving a first inner peripheral portion of the nitride deposit on the side surface of the gallium nitride crystal and a second inner peripheral portion of the nitride deposit on the side surface of the substrate; ) After the machining, the step of removing the substrate by etching to form a wall of the second inner peripheral portion extending from the first inner peripheral portion along the edge of the gallium nitride crystal body (C) after removing the substrate, removing the second inner peripheral portion of the nitride deposit; and (d) removing the wall of the second inner peripheral portion and then nitriding The first inner peripheral portion of the deposit is removed by machining to remove the gallium nitride crystal It provided that step. After grinding the outer peripheral portion of the nitride deposit, the inner peripheral portion of the nitride deposit and the gallium nitride crystal are sized to fit in a cylinder having a predetermined diameter, and the predetermined diameter is It is larger than the diameter of the substrate by a value in the range of 1 mm to 4 mm.

According to this method, since the outer peripheral portion of the nitride deposit is removed prior to peeling the substrate from the gallium nitride crystal, the nitride deposit can be removed by outer peripheral processing, and then the substrate can be removed by etching.
In the method of the present invention, the thickness of the gallium nitride crystal is larger than the thickness of the substrate .

  In the method of the present invention, after grinding the outer peripheral portion of the nitride deposit, the inner peripheral portion of the nitride deposit and the gallium nitride crystal are sized to fit in a cylinder having a predetermined diameter, The predetermined diameter is preferably larger than the diameter of the substrate by a value in the range of 1 mm to 4 mm.

  According to this method, the gallium nitride crystal is formed on a substantially disk-shaped substrate. If the diameter is in the above range, misalignment in the outer periphery processing step can be allowed.

  In the method of the present invention, after grinding the outer peripheral portion of the nitride deposit, the inner peripheral portion of the nitride deposit and the gallium nitride crystal are sized to fit in a cylinder having a predetermined diameter, The predetermined diameter is preferably larger than the diameter of the substrate by a value in the range of 1 mm to 3 mm.

  According to this method, the gallium nitride crystal is formed on a substantially disk-shaped substrate. If the diameter is in the above range, misalignment in the outer periphery processing step can be allowed.

  In the method of the present invention, in the machining, the nitride deposit is removed using a grindstone while rotating the gallium nitride crystal around a predetermined axis.

  Gallium nitride crystals are formed on a substantially disk-shaped substrate. According to this method, nitride deposits can be removed while rotating the gallium nitride crystals around a predetermined axis.

Another aspect of the present invention relates to a method of manufacturing a gallium nitride substrate. This method is a method of manufacturing a gallium nitride substrate from a gallium nitride crystal grown by vapor deposition on a substrate made of a material different from gallium nitride, and the substrate and the gallium nitride crystal are grown by the growth. Nitride deposits are formed on the side surfaces. In this method, (a) a composite including the substrate, the gallium nitride crystal, and the nitride deposit is rotated around a predetermined axis, and an outer peripheral portion of the nitride deposit is ground by machining. Leaving a first inner peripheral portion of the nitride deposit on the side surface of the gallium nitride crystal and a second inner peripheral portion of the nitride deposit on the side surface of the substrate; ) After the machining, the step of removing the substrate by etching to form a wall of the second inner peripheral portion extending from the first inner peripheral portion along the edge of the gallium nitride crystal body (C) after removing the substrate, removing the second inner peripheral portion of the nitride deposit; and (d) removing the wall of the second inner peripheral portion and then nitriding The first inner peripheral portion of the deposit is removed by machining to remove the gallium nitride crystal Comprises that the step and the step of preparing one or more gallium nitride substrate from (e) the gallium nitride crystal. After grinding the outer peripheral portion of the nitride deposit, the inner peripheral portion of the nitride deposit and the gallium nitride crystal are sized to fit in a cylinder having a predetermined diameter, and the predetermined diameter is It is larger than the diameter of the substrate by a value in the range of 1 mm to 4 mm.

  According to this method, since the outer peripheral portion of the nitride deposit is removed before the substrate is peeled from the gallium nitride crystal, the substrate can be removed by etching after the outer peripheral portion of the nitride deposit is removed by outer peripheral processing. . Thereafter, the second inner peripheral portion of the nitride deposit is removed. Therefore, a gallium nitride crystal can be produced with high productivity.

  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 gallium nitride crystal for producing a gallium nitride substrate and a nitride deposit formed on the side surface of the substrate are efficiently removed to produce a gallium nitride crystal. And a method of manufacturing a gallium nitride substrate are provided.

  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, embodiments of the method for producing a gallium nitride crystal body and a gallium nitride substrate of the present invention will be described with reference to the accompanying drawings. In this method, a gallium nitride 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.

FIG. 1 shows a film forming apparatus for vapor phase epitaxy such as HVPE used for epitaxial growth. A cylindrical heater 2 is provided around the vertical reactor 1. There are source gas inlets 3 and 4 on the upper wall 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 reaction furnace 1 through a gas inlet 3. Opposite the inlet 3 is a gallium (Ga) source 5 in which metallic gallium is accommodated. Since the melting point of metallic gallium is low, when heated by the heater 2, a Ga melt 6 is formed. When HCl touches 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 G ₂ of gallium chloride and the carrier gas H ₂ is provided. A mixed gas G _{3 of} ammonia (NH ₃ ) + hydrogen (H ₂ ) is introduced into the reaction furnace 1 through the introduction port 4. A thick gallium nitride film for producing a gallium nitride substrate 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 able to rotate and lift. 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. Gallium nitride is deposited on the main surface of the substrate 9. The remaining raw material gas and the reaction product gas mixed gas G ₄ are discharged through the exhaust gas outlet 10. The GaN crystal produced by the HVPE method is undoped and exhibits n conductivity type. The carrier concentration is, for example, about 1 × 10 ¹⁸ 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 gallium nitride 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. The nitride deposit 26 has an outer peripheral portion 26a that is ground in the next outer peripheral processing step, and an inner peripheral portion 26b that remains even after the outer peripheral processing step.

  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 26c, and the composite 20 is reduced to a dimension D2 (<D1). For example, the outer periphery of the composite 20 is ground to a diameter of 54 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 deposit remains on the side surfaces of the gallium nitride crystal body 24 and the substrate 9. By this step, the outer peripheral portion 26a of the nitride deposit 26 is removed, and the inner peripheral portion 26b is left. For the following explanation, the nitride deposit 26a left on the side surface 24a of the gallium nitride crystal body 24 is referred to as the first inner peripheral portion 26d, and the nitride deposit left on the side surface 9a of the substrate 9 is referred to. 26a is referred to as the second inner peripheral portion 26e.

  As shown in FIG. 2C, after the outer periphery processing, the substrate 9 is removed from the gallium nitride crystal body 24 in the composite 20a. This removal is performed by etching to form a composite 20c. In this embodiment, since the substrate 9 is made of a gallium arsenide semiconductor, the substrate 9 can be selectively removed by wet etching using an etchant such as aqua regia. The composite 20c includes a first inner peripheral portion 26d left on the side surface 24a of the gallium nitride crystal body 24, and a second inner peripheral portion 26e extending from the first inner peripheral portion 26d. The second inner peripheral portion 26 e is a wall provided along the edge of the gallium nitride crystal body 24, and the height of this wall is approximately the thickness of the substrate 9.

  Next, the second inner peripheral portion 26e is removed from the composite 20c. By this step, the wall extending along the edge of the gallium nitride crystal 24 is removed from the composite 20c.

FIG. 3A shows the composite 20d in which the second inner peripheral portion 26e is removed from the nitride deposit 26c. The composite 20d is attached to the outer peripheral processing device 32 so as to be rotatable around a predetermined axis Bx. The outer periphery processing device 32 includes a grindstone 38 for machining the outer periphery of the composite 20d. The grindstone 38 is brought into contact with the outer periphery of the composite 20c while rotating the composite 20d around the predetermined axis Bx. When the grindstone 38 is moved at an appropriate feed speed, the outer periphery of the composite 20d is ground. The nitride deposit 26 is gradually removed, and the first inner peripheral portion 26d of the nitride deposit 26a is completely removed. For example, the outer periphery of the composite 20 is ground to a diameter of 50 millimeters using the outer periphery processing device 32. By this step, as shown in FIG. 3B, a gallium nitride crystal 25 processed to have a predetermined diameter is formed.
As shown in FIG. 4A, the gallium nitride crystal 25 is processed to have a desired diameter, and the gallium nitride crystal 25 is sliced and polished, as shown in FIG. 4B. As described above, one or a plurality of gallium nitride wafers 25a to 25d are processed.

Example 1
GaN was grown on a 50 mmφ GaAs substrate. A growth deposit is deposited on the side surface of the gallium nitride crystal on the GaAs substrate, and the outer diameter of the composite becomes 58 mmφ. When the GaAs substrate is removed by etching, the outer peripheral projection remains. It takes 50 to 80 minutes to remove this manually. This processing is desired to be improved in terms of production efficiency. Since the amount of deposits on the outer periphery is larger in the initial stage and is accumulated in a bell shape, the time required for the subsequent processing can be reduced by performing the outer periphery processing in advance and cutting off the end portion of the bell-shaped end. The growth deposit is ground until the outer diameter is 54 mm. The time required for the peripheral processing is approximately 40 minutes. Since the peripheral portion of the bell-shaped end portion was reduced by about half by this outer peripheral processing, the processing of the protruding portion after the GaAs substrate was removed by etching was completed in about 25 minutes, and the processing time could be shortened. Although the finished GaN crystal was a perfect circle, it was misaligned by about 1.5 mm and was decentered from the original product part.

(Example 2)
The outer diameter was processed to 51 mm by the same method. It took about 70 minutes to process the outer periphery. In addition, it took about 5 minutes to manually process the protrusions after removing the GaAs substrate. The misalignment is about 0.9 mm.

FIG. 5 is a diagram showing eccentricity in the outer periphery processing. After crystal growth, the gallium nitride composite has a distorted cylindrical shape whose outer diameter is not necessarily uniform over the entire outer periphery, although the level is not visually observable. Therefore, it is not easy to accurately center (determine the center of the circle) when finishing the outer periphery into a circle. Without centering accuracy, the product part that is a perfect circle is decentered, and the part that should be the product may be scraped off. In consideration of the centering error, it is necessary to finish the outer peripheral machining size slightly larger. In order to accurately collect a circular wafer from a product portion, the following process is desirable from the viewpoint of quality assurance.
(1) In the outer periphery machining, the size is cut slightly larger than the final diameter.
(2) The GaAs substrate is removed by etching.
(3) The remaining bell-shaped projection is scraped off by machining.
As shown in FIG. 5, the current misalignment accuracy was investigated. The average value of centering in 12 times of grinding is 1.25 mm, and the standard deviation is 0.371. In the peripheral processing performed before etching the substrate,
The 1 sigma value is 1.621 mm (1.25 + 0.371), and the 2 sigma is 1.991 mm (1.25 + 2 × 0.371).

  In the outer peripheral grinding step performed prior to the etching of the substrate, the diameter of the ground composite is preferably larger than the diameter of the substrate by a value in the range of 1 mm to 4 mm. If the upper limit is 4 mm, misalignment of 2 sigma can be allowed.

  As a result of further devising the centering method, such as a method for obtaining the apparent center using a circular jig circumscribing the gallium nitride composite, the above 2 sigma is about 1.5 mm, which is performed prior to the etching of the substrate. In the outer periphery grinding step, it is preferable that the diameter of the ground composite is larger than the diameter of the substrate by a value in the range of 1 mm to 3 mm.

  In any case, the lower limit is ideally 0 mm, but the lower limit is set to 1 mm. If it is this lower limit, the gallium nitride crystal will not be cut in the outer periphery grinding step, and gallium nitride crystal will not be damaged unexpectedly.

  In the embodiment of the present invention described above, the side surface of the gallium nitride crystal for manufacturing the gallium nitride substrate and the nitride deposit formed on the side surface of the substrate are efficiently removed to manufacture the gallium nitride crystal. And a method of manufacturing a gallium nitride substrate are provided.

(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 maximum outer diameter of the composite is about 58 mm. Although the shape of the growth deposit is various, as shown in FIG. 6A, 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. 6 (B), the growth deposit (end-spreading portion) adhering to the side surface of the GaAs substrate remains in a protruding shape. . 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 the method described in the present embodiment, the time required for this processing can be shortened as much as possible to increase the productivity. 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.

FIG. 1 shows a film forming apparatus for vapor phase epitaxy such as HVPE used for epitaxial growth. 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 is a drawing showing a process of removing nitride deposits by outer periphery processing. FIG. 3B is a drawing showing a gallium nitride crystal produced according to an embodiment of the present invention. 4 (A) and 4 (B) are drawings showing a process of manufacturing a gallium nitride wafer from a gallium nitride crystal. FIG. 5 is a diagram showing eccentricity in the outer periphery processing. 6 (A) to 6 (C) are drawings showing a manufacturing method for etching a composite.

Explanation of symbols

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, 25 ... Gallium nitride crystal, 26 ... Nitride deposit, 26a ... Outer periphery of nitride deposit, 26b ... Inner circumference of nitride deposit, 26d ... Gallium nitride Inner peripheral part on crystal, 26e ... Inner peripheral part on substrate, 28 ... Grinding wheel, 24a-24d ... Gallium nitride wafer

Claims (5)

A method of manufacturing a gallium nitride crystal for forming a gallium nitride substrate on a substrate made of a material different from gallium nitride by vapor deposition, wherein the growth of the substrate and the gallium nitride crystal is performed by the growth. Nitride deposits are formed on the sides,
The composite including the substrate, the gallium nitride crystal, and the nitride deposit is rotated around a predetermined axis, and the outer peripheral portion of the nitride deposit is ground by machining to thereby form the gallium nitride crystal. Leaving a first inner periphery of the nitride deposit on the side and leaving a second inner periphery of the nitride deposit on the side of the substrate;
Removing the substrate by etching after the machining and forming a wall of the second inner peripheral portion extending from the first inner peripheral portion along an edge of the gallium nitride crystal; ,
Removing the second inner periphery of the nitride deposit after removal of the substrate;
Removing the second inner peripheral wall and then removing the first inner peripheral portion of the nitride deposit by machining to obtain the gallium nitride crystal.
After grinding the outer periphery of the nitride deposit, the inner periphery of the nitride deposit and the gallium nitride crystal are sized to fit within a cylinder with a predetermined diameter,
The predetermined diameter is larger than the diameter of the substrate by a value in the range of 1 mm to 4 mm. The method of claim 1, wherein the thickness of the gallium nitride crystal is greater than the thickness of the substrate. After grinding the outer periphery of the nitride deposit, the inner periphery of the nitride deposit and the gallium nitride crystal are sized to fit within a cylinder with a predetermined diameter,
The method according to claim 1, wherein the predetermined diameter is larger than the diameter of the substrate by a value in a range of 1 mm to 3 mm. The said machining process removes the said nitride deposit using a grindstone, rotating the said gallium nitride crystal | crystallization around a predetermined axis | shaft, The Claim 1 characterized by the above-mentioned. Way. A method of manufacturing a gallium nitride 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. A nitride deposit is formed,
The composite including the substrate, the gallium nitride crystal, and the nitride deposit is rotated around a predetermined axis, and the outer peripheral portion of the nitride deposit is ground by machining to thereby form the gallium nitride crystal. Leaving a first inner periphery of the nitride deposit on the side and leaving a second inner periphery of the nitride deposit on the side of the substrate;
Removing the substrate by etching after the machining and forming a wall of the second inner peripheral portion extending from the first inner peripheral portion along an edge of the gallium nitride crystal; ,
Removing the second inner periphery of the nitride deposit after removal of the substrate;
After removal of the wall of the second inner peripheral portion, a step of the inner peripheral portion of the first nitride deposits is removed by machining to obtain the gallium nitride crystal,
Producing one or more gallium nitride substrates from the gallium nitride crystal,
After grinding the outer periphery of the nitride deposit, the inner periphery of the nitride deposit and the gallium nitride crystal are sized to fit within a cylinder with a predetermined diameter,
The predetermined diameter is larger than the diameter of the substrate by a value in the range of 1 mm to 4 mm.

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