Fixing jig for laminate and method for manufacturing aluminum nitride single crystal substrate

Abstract

To suppress deviation from a target position in a thickness direction in separation of an aluminum nitride single crystal body.SOLUTION: A fixing jig used for separating an aluminum nitride single crystal body from a laminate includes a placing surface for placing an adhesion layer for bonding a laminate thereon, where the placing surface includes at least one recess part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to the separation of an aluminum nitride single crystal body from a laminate. [Background technology]

[0002] Aluminum-based group III nitride semiconductors made of aluminum nitride have a wide range of band gap energy values. These nitride semiconductors can be made into alloy semiconductors of any composition, and depending on the alloy composition, they can take on various band gap values.

[0003] Therefore, by using aluminum-based Group III nitride semiconductors, it is possible in principle to fabricate light-emitting devices that emit a wide range of light, from infrared to ultraviolet. In particular, light-emitting devices using aluminum-based Group III nitride semiconductors are capable of emitting light in short wavelengths, such as in the ultraviolet region.

[0004] Like conventional semiconductor light-emitting devices, light-emitting devices using aluminum-based Group III nitride semiconductors can be manufactured by sequentially stacking thin films of semiconductor single crystals (specifically, thin films that will become an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer) each having a thickness of about several microns on a substrate.Known methods for forming such thin films of semiconductor single crystals include crystal growth methods such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD).

[0005] In the manufacture of aluminum-based Group III nitride semiconductor light-emitting devices, sapphire substrates are generally used from the viewpoints of the substrate's crystalline quality, ultraviolet light transmittance, mass productivity, and cost. However, when an aluminum-based Group III nitride semiconductor light-emitting device is formed on a sapphire substrate, differences in lattice constant, thermal expansion coefficient, etc. between the sapphire substrate and the aluminum-based Group III nitrides that constitute each layer of the semiconductor light-emitting device cause crystal defects (misfit dislocations), cracks, etc., which cause a deterioration in the light-emitting performance of the device.

[0006] To solve these problems, it is desirable to use a substrate with a lattice constant and thermal expansion coefficient close to those of the aluminum-based Group III nitride semiconductor thin film that constitutes the device.Aluminum nitride single crystal substrates are suitable as substrates for growing aluminum-based Group III nitride semiconductor thin films.

[0007] To use aluminum nitride single crystal as a substrate, it is preferable that the single crystal have a certain thickness (for example, 10 μm or more) from the viewpoint of mechanical strength. The MOCVD method is suitable for producing aluminum nitride single crystal substrates because it allows faster crystal growth than the MBE method. Furthermore, hydride vapor phase epitaxy (HVPE) and physical vapor transport (PVT) are known as growth methods for aluminum nitride single crystal that allow even faster crystal growth than the MOCVD method.

[0008] Wafers are obtained by cutting an aluminum nitride single crystal grown on a base substrate into plates, and aluminum nitride single crystal substrates are obtained by polishing the wafers to remove damaged layers on the surface. A wire saw is commonly used as a means for separating (cutting, slicing) an aluminum nitride single crystal into plates (see Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2016 / 076270 Brochure Summary of the Invention [Problem to be solved by the invention]

[0010] However, when cutting aluminum nitride single crystals with a wire saw, deviation from the target position in the thickness direction occurs. Also, although crystal orientation is an important factor in the manufacture of semiconductor devices, cut bodies with significant deviation in crystal orientation can be produced.

[0011] Therefore, an object of the present disclosure is to suppress deviation from the target position and deviation in the orientation in the thickness direction when separating an aluminum nitride single crystal body. [Means for solving the problem]

[0012] As a result of extensive research, the inventors have found that when an aluminum nitride single crystal body is fixed to a fixing jig with an adhesive for separation (cutting, slicing) of the aluminum nitride single crystal body, the thickness of the adhesive between the aluminum nitride single crystal body and the mounting surface of the fixing jig causes deviation from the target position. They have also found that variations in the thickness of the adhesive layer within the surface lead to deviations in the crystal orientation, and have completed the technology of the present disclosure by providing specific means for solving this problem.

[0013] One aspect of the present disclosure is a fixture used when separating an aluminum nitride single crystal body from a laminate, the fixture comprising a mounting surface on which an adhesive layer that bonds the laminate is placed, the mounting surface having at least one recess.

[0014] An adhesive layer may be provided on the mounting surface, and the recess may be formed at a position where at least a portion of the recess overlaps with the laminate in a plan view when the laminate is adhered to the adhesive layer.

[0015] Another aspect of the present disclosure is a method for producing an aluminum nitride single crystal substrate, comprising: a preparation step of preparing a laminate including an aluminum nitride single crystal body; a placement step of placing the laminate on a placement surface of a fixing jig via an adhesive layer formed by an adhesive; and a separation step of separating the aluminum nitride single crystal body from the laminate adhered to the adhesive layer, wherein the placement step comprises guiding a portion of the adhesive present between the placement surface and the laminate to a position lower than the placement surface in the thickness direction of the fixing jig.

[0016] In the separation step, the aluminum nitride single crystal may be cut into plates from the laminate using a wire saw.

[0017] In the separation step, a buffer layer can be formed on the side surface of the aluminum nitride single crystal body, and then the buffer layer and the wire saw can be brought into contact with each other before cutting the aluminum nitride single crystal body. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to suppress the degree of deviation from the target separation position and deviation in the crystal orientation of the aluminum nitride single crystal body in the thickness direction of the aluminum nitride single crystal body. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the flow of the method S10 for manufacturing an aluminum nitride single crystal substrate. [Figure 2] FIG. 2(a) is a plan view of the laminate 10, and FIG. 2(b) is a front view of the laminate 10. As shown in FIG. [Figure 3] 3A and 3B are diagrams illustrating the placing step S12, in which FIG. 3A is a plan view and FIG. 3B is a front view. [Figure 4] FIG. 4(a) is a plan view of the fixing jig 20A, and FIG. 4(b) is a front view of the fixing jig 20A. [Figure 5] FIG. 5(a) is a plan view of the fixing jig 20B, and FIG. 5(b) is a front view of the fixing jig 20B. [Figure 6]FIG. 6(a) is a plan view of the fixture 20C, and FIG. 6(b) is a front view of the fixture 20C. [Figure 7] FIG. 7(a) is a plan view of the fixing jig 20D, and FIG. 7(b) is a front view of the fixing jig 20D. [Figure 8] FIG. 8 is a diagram illustrating the separation step S13. [Figure 9] 9A and 9B are diagrams for explaining the separation step S13, in which FIG. 9A is a plan view and FIG. 9B is a front view. [Figure 10] FIG. 10 is a diagram illustrating the positions at which the height of the aluminum nitride single crystal was measured. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1. Manufacturing method for aluminum nitride single crystal substrate A method S10 for manufacturing an aluminum nitride single crystal substrate according to one embodiment of the present disclosure includes a preparation step S11, a placement step S12, and a separation step S13, as shown in Fig. 1. Each step will be described below. Note that in the explanation of the steps, an example of a fixing jig will also be described.

[0021] 1.1. Preparation process S11 In the preparation step S11, a laminate including an aluminum nitride single crystal (AIN single crystal) to be separated (cut, sliced) is prepared. FIG. 2(a) is a plan view schematically illustrating a laminate 10 including an aluminum nitride single crystal body, and FIG. 2(b) is a front view of the laminate 10. As shown in FIGS. 2(a) and 2(b), the laminate 10 has a first surface 10a and a second surface 10b opposite to the first surface 10a. There is a thickness between the first surface 10a and the second surface 10b, and a side surface 10c is formed so as to connect the outer periphery of the first surface 10a and the outer periphery of the second surface 10b. As can be seen from FIGS. 2(a) and 2(b), the laminate 10 in this embodiment is disk-shaped. The thickness of the laminate 10 is not particularly limited, but taking into consideration the cutting allowance by the wire saw, the thickness of the aluminum nitride single crystal layer is preferably 500 μm or more, and more preferably 800 μm or more.

[0022] The laminate 10 may be a single layer of aluminum nitride single crystal as shown in Figures 2(a) and 2(b), or may be a laminate in which an aluminum nitride single crystal is laminated on another substrate.

[0023] 1.2. Placement step S12 In the placing step S12, the laminate 10 including the aluminum nitride single crystal produced in the preparing step S11 is placed on the placing surface of the fixing jig 20 via an adhesive layer 11 formed with an adhesive. That is, as shown in the plan view of Fig. 3(a) and the front view of Fig. 3(b), the laminate 10 is fixed by placing it on the fixing jig 20 via the adhesive layer 11 with the second surface 10b of the laminate 10 facing the placing surface 20a of the fixing jig 20.

[0024] 1.2.1.Adhesive layer Any known adhesive can be used for the adhesive layer 11, and there is no limitation on the adhesive that can be used, but examples include epoxy-based, cyanoacrylate-based, urea resin-based, melamine resin-based, phenolic resin-based, resorcinol resin-based, vinyl acetate resin-based, isocyanate-based, silicone resin-based, modified silicone resin-based, urethane resin-based, acrylic resin-based, polyester-based, polyethylene-based, etc.

[0025] There are two types of adhesives: those that use a chemical reaction as the driving force for adhesion, such as epoxy and cyanoacrylate adhesives, and those that use thermoplastic resins such as polyester and polyethylene. Of these, epoxy adhesives, which use a chemical reaction as the driving force for adhesion, are particularly easy to obtain and inexpensive, have little volume change before and after the reaction, and can be cured stably. Epoxy adhesives are preferred because the resin hardness after the reaction is high, making them useful for stable cutting.

[0026] There are various types of epoxy adhesives, including two-component, one-component, and heat-curing types. Two-component adhesives are more useful because they can be handled at room temperature and are inexpensive. Among the two-component adhesives, Nikka Seiko's Q Bond and U Bond are useful.

[0027] Although there is no limitation on the viscosity of the adhesive, the kinematic viscosity is preferably 0.01 cSt or more and 10,000 cSt or less, more preferably 0.1 cSt or more and 1,000 cSt or less, even more preferably 0.4 cSt or more and 100 cSt or less, and most preferably 0.8 cSt or more and 10 cSt or less.

[0028] When applying adhesive, it is necessary to keep the surface of the fixture clean before application. If it is not clean, the adhesive's fixing ability may decrease, or the adhesive surface may become tilted due to the inclusion of foreign matter. Effective methods for keeping the surface of the fixture clean include removing foreign matter with a blower, wiping with a clean wipe, and removing organic matter with chemicals such as acetone or alcohol.

[0029] Tools that can be used to apply the adhesive include spatulas, dispensers, bar coaters, and the like, without limitation. When using an adhesive that hardens over time, such as a typical two-component epoxy adhesive, the viscosity may change between mixing and bonding, so it is best to monitor the time to avoid variations and complete the work within a certain time. When using thermoplastic resins, it is preferable to perform bonding when the temperature is uniform. Therefore, it is preferable to monitor the temperature using a rod thermometer, thermocouple, radiation thermometer, etc. Compared to metals, which are generally used in fixing jigs, resins have low thermal conductivity and tend not to heat up as easily.

[0030] When placing a laminate on the adhesive layer, it is preferable to apply an appropriate pressure to the laminate after placement. Applying pressure causes excess adhesive layer to flow from the outer periphery of the laminate or through holes in the fixing jig, resulting in uniform adhesion. There is no limit to the pressure to be applied, but the pressure is preferably 0.001 MPa to 1 MPa, more preferably 0.002 MPa to 0.5 MPa, or even more preferably 0.0025 MPa to 0.05 MPa. The time for which pressure is applied is optional, but it is preferable to keep it constant. The time for which pressure is applied is preferably 5 seconds to 24 hours, more preferably 20 seconds to 1 hour, or 1 minute to 10 minutes. It is preferable to apply pressure to the entire surface of the laminate simultaneously. If there is a flow path that guides part of the applied adhesive to a position lower than the mounting surface in the thickness direction of the fixture, excess adhesive can be efficiently removed.

[0031] When curing adhesives, it is necessary to select the appropriate curing method depending on the type of adhesive being used. For example, with a typical two-component epoxy adhesive, the curing process progresses over time, so it is necessary to allow an appropriate amount of time. With heat-curing adhesives, a certain temperature must be applied. Also, with thermoplastic resins, it is necessary to confirm that the adhesive has cooled sufficiently and that the temperature has dropped.

[0032] 1.2.2. Fixture In this step, in the process of placing the laminate on the mounting surface of the fixing jig, a portion of the adhesive present between the mounting surface and the laminate is guided (moved) away from between the mounting surface and the laminate in the thickness direction (vertical direction) of the fixing jig to a position lower than the mounting surface. This adjusts the amount of adhesive remaining between the mounting surface and the laminate, thinning the adhesive layer 11 and making it possible to suppress displacement of the aluminum nitride single crystal body from the target position when it is separated from the laminate 10 in the separation step S13 described below. The present invention efficiently guides excess adhesive between the laminate and the fixing jig, thereby enabling precise fixing and cutting of the laminate. The details of how the amount of adhesive remaining between the mounting surface and the laminate is adjusted by guiding (moving) a portion of the adhesive between the mounting surface and the laminate in the thickness direction (vertical direction) of the fixing jig away from the gap between the mounting surface and the laminate and guiding (moving) it to a position lower than the mounting surface are unclear, but the inventors speculate as follows: Frictional stress occurs between the adhesive, the laminate, and the fixing jig according to Newton's law of viscosity. With a conventional fixing jig, the adhesive is guided to the outer edge of the laminate, and guiding requires a workload proportional to the frictional stress and the distance the adhesive travels. Providing an opening shortens the distance the adhesive travels, reducing the workload. As a result, the adhesive layer becomes thinner, enabling more precise fixing.

[0033] The means for guiding the adhesive in this manner is not particularly limited, but one specific embodiment is to provide a recess on the mounting surface side of the fixing jig 20. The form of the fixing jig will be described below.

[0034] 1.2.2a. Fixture 20A 4 shows a diagram for explaining the fixing jig 20A. To distinguish it from other types of fixing jigs, it is written as fixing jig 20A, but the fixing jig 20A can be used as the fixing jig 20 described above. Fig. 4(a) is a plan view of fixing jig 20A, and Fig. 4(b) is an A-A' cross-sectional view of fixing jig 20A. As can be seen from Fig. 4, fixing jig 20A has mounting surface 21A and rear surface 22A on the opposite side, with a thickness between mounting surface 21A and rear surface 22A, and side surface 23A formed to bridge the outer periphery of mounting surface 21A and the outer periphery of rear surface 22A. In this embodiment, fixing jig 20A is disk-shaped, but it does not necessarily have to be disk-shaped.

[0035] The fixing jig 20A has a plurality of holes 24A formed in the mounting surface 21A as recesses opening into the mounting surface 21A. In this embodiment, the holes 24A are through-holes that penetrate the mounting surface 21A and the back surface 22A in the thickness direction. However, they do not necessarily have to be through-holes; they may be non-through-holes (recesses) opening into the mounting surface 21A. When the holes are not through-holes, the depth of the holes need only be large enough to allow the amount of adhesive to be removed when adjusting the amount of adhesive remaining between the mounting surface and the laminate to be transferred into the holes. However, it is preferable that the holes have at least one through-hole that leads to the outside. This is because the through-holes allow the adhesive to be efficiently guided. Furthermore, some adhesives, such as epoxy adhesives, require a dedicated stripping solution to be used for peeling from the jig. The through-holes allow the stripping solution to penetrate effectively, enabling efficient peeling.

[0036] In this embodiment, when viewed from above, the fixing jig 20A has one hole 24A at its center, and multiple holes 24A arranged on two concentric circles around the center. Four holes 24A are arranged at 90° intervals on the concentric circle closer to the center, and eight holes 24A are arranged at 45° intervals on the concentric circle farther from the center.

[0037] The holes 24A are arranged at positions where the holes 24A overlap the stack 10 when viewed from above in a position where the stack 10 is placed on the placement surface 21A. It is not necessary for all the holes 24A to overlap, but it is preferable that all the holes 24A overlap the stack 10 when viewed from above. Furthermore, it is preferable that the holes 24A are arranged in point symmetry with respect to the center point of the fixing jig 20A.

[0038] The size and number of holes 24A are not particularly limited, but it is preferable that the opening ratio, which is the ratio of the total opening area of ​​holes 24A to the area of ​​mounting surface 21A, be 10% or more. Holes with a sufficient opening area can efficiently guide the adhesive. Furthermore, a smaller adhesive area reduces the load associated with peeling. It is more preferable that the opening ratio be 20% or more, and even more preferable that the opening ratio be 30% or more. It is preferable that the opening area of ​​the holes be 60% or less of the total area of ​​the laminate. If the area is too small, the laminate will not be sufficiently bonded. It is more preferable that the opening ratio be 50% or less, and even more preferable that the opening ratio be 40% or less.

[0039] The holes are preferably arranged so as to be as uniform as possible within the contact surface between the laminate and the fixture. Specifically, the holes are preferably arranged so that the opening length thereof is as uniform as possible within the contact surface between the laminate and the fixture. Here, "opening length" refers to the shorter of b or c, where b is the distance from any point where the laminate and the fixture contact each other to the nearest hole opening and c is the distance to the nearest outer periphery of the laminate.

[0040] Specific examples are listed using Figure 4. Focusing on an arbitrary first point P1, if the distance to the opening of the nearest hole 24A (the opening located at the top right of the concentric circle furthest from the center in the illustration) is taken as b1 and the distance to the nearest outer periphery of the laminate is taken as c1, then since c1 > b1, the opening length at the first point P1 is b1. Next, if we focus on an arbitrary second point P2 located closer to the outer periphery of the laminate than the first point P1, if the distance to the opening of the nearest hole 24A (the opening located two places to the right from the top on the concentric circle farthest from the center as shown) is b2 and the distance to the nearest outer periphery of the laminate is c2, then since b2 > c2, the opening length at the second point P2 is c2. When the opening length is defined as above, the longest opening length among the opening lengths at any point on the mounting surface is defined as the maximum opening length. In the example shown in Fig. 4, the opening length at the illustrated first specific point Q1 is the maximum opening length L1. In the example shown in Fig. 4, the first specific point Q1 is the center point of the openings of three holes 24A, consisting of the openings of two adjacent holes 24A on a concentric circle far from the center and the opening of one hole 24A on the concentric circle closer to the center and located closest to the two holes 24A.

[0041] An increase in the maximum opening length L1 leads to an increase in the distance the adhesive travels, resulting in a thicker adhesive layer for the same amount of work, and greater variation in the thickness of the adhesive layer. Therefore, the maximum opening length L1 is preferably 20 mm or less. The opening length L1 is more preferably 10 mm or less, and even more preferably 5 mm or less, or 2 mm or less. If the maximum opening length L1 is too short, the load on the laminate increases, which may lead to damage to the laminate. Furthermore, the adhesive area between the laminate and the fixing jig decreases, which may result in insufficient fixing. The maximum opening length L1 is preferably 0.5 mm or more, and more preferably 1 mm or more, or 2 mm or more.

[0042] The openings of the holes are preferably arranged so that the opening lengths are as uniform as possible within the contact surface between the laminate and the fixture. To achieve this arrangement, the openings are preferably arranged so as to be point symmetric or line symmetric. The number and size of the holes in the fixing jig of this embodiment are arbitrary, but it is preferable to make the opening length as small as possible. Specifically, it is preferable to increase the number of through holes, such as hole 24A in FIG. 4, and uniformly arrange them over the entire surface that contacts the laminate and the fixing jig to make the opening length small. In such a shape, the number of holes is preferably four or more, and more preferably 13 or more. In this case, the size of the holes is preferably 1 mm or more and 10 mm or less in diameter, and preferably 2 mm or more and 6 mm or less.

[0043] In this embodiment, the shape of the hole 24A in plan view is circular, but is not limited to this and may be other shapes (triangle, square, other polygonal shapes, and ellipse).

[0044] The material constituting the fixture 20A is not particularly limited, but is preferably a metal from the viewpoint of strength, etc. Examples of metals include stainless steel, copper, iron, etc. When using an oxidizable material such as copper or iron, it is preferable to perform a plating process to suppress changes in size and shape due to oxidation. Any material can be used for plating, but nickel plating is preferable from the viewpoint of versatility.

[0045] 1.2.2b. Fixture 20B 5 shows a diagram for explaining the fixing jig 20B. To distinguish it from other types of fixing jigs, it is written as fixing jig 20B, but the fixing jig 20B can be used as the fixing jig 20 described above. Fig. 5(a) is a plan view of fixing jig 20B, and Fig. 5(b) is a B-B' cross-sectional view of fixing jig 20B. As can be seen from Fig. 5, fixing jig 20B has mounting surface 21B and rear surface 22B on the opposite side, with a thickness between mounting surface 21B and rear surface 22B, and side surface 23B formed to bridge the outer periphery of mounting surface 21B and the outer periphery of rear surface 22B. In this embodiment, fixing jig 20B is disk-shaped, but it does not necessarily have to be disk-shaped.

[0046] Fixing jig 20B has a plurality of holes 24B formed in mounting surface 21B as recesses opening into mounting surface 21B. In this embodiment, holes 24B are through holes that penetrate through mounting surface 21B and back surface 22B in the thickness direction, but they do not necessarily have to be through holes and may be non-through holes (depressions) that open in mounting surface 21B. When holes are not through holes, the depth of the holes only needs to have a volume that allows the amount of adhesive that should be removed to be moved into the holes when the amount of adhesive remaining between the mounting surface and the laminate is adjusted.

[0047] In this embodiment, hole 24B is a hole whose shape is surrounded by arcs belonging to two concentric circles (outer arc 24Ba, inner arc 24Bb) when viewed in a plane of fixing jig 20B, and two straight lines (24Bc) connecting the ends of the arcs, and four holes of the same shape are arranged at 90° intervals around the center.

[0048] The holes 24B are arranged at positions that overlap the stack 10 when viewed from above with the stack 10 placed on the placement surface 21B. It is not necessary for all the holes 24B to overlap, but it is preferable that all the holes 24B be positioned so as to overlap the stack 10 when viewed from above. Furthermore, it is preferable that the holes 24B are arranged in point symmetry with respect to the center point of the fixing jig 20B.

[0049] The size and number of holes 24B are not particularly limited, but it is preferable that the opening ratio, which is the ratio of the total area of ​​the openings of holes 24B to the area of ​​the mounting surface 21B, be 10% or more. Having holes with a sufficient opening area allows the adhesive to be guided efficiently. Also, reducing the adhesive area reduces the load when peeling. It is more preferable that it be 20% or more, and even more preferable that it be 30% or more. It is preferable that the opening area be 60% or less of the total area of ​​the laminate. If the area is too small, the laminate will not be sufficiently bonded. It is more preferable that it be 50% or less, and even more preferable that it be 40% or less.

[0050] In the example shown in FIG. 5, the opening length at the specific point Q2 shown in the figure is the opening maximum length L2. The maximum opening length L2 is preferably 20 mm or less. It is more preferable that the opening length L2 is 10 mm or less, and even more preferable that it is 5 mm or less, or 2 mm or less. If the maximum opening length is too short, the load on the laminate increases, which may lead to damage to the laminate. Furthermore, the adhesive area between the laminate and the fixing jig decreases, which may result in insufficient fixing. It is preferable that the maximum opening length L2 is 0.5 mm or more, and more preferably 1 mm or more, or 2 mm or more.

[0051] The number and size of holes in the fixing jig of the present invention are arbitrary, but it is preferable to make the opening length small. Specifically, it is preferable to increase the number of through holes having a cross-sectional shape such as hole 24B in Fig. 5, uniformly arrange them over the entire surface that contacts the laminate and the fixing jig, and make the opening length small. In the case of such a shape, it is preferable that the number of holes is four or more. In this case, the size of the holes is 150 mm2 or less. 2 More than 250mm 2 It is preferable that:

[0052] The material constituting the fixture 20B is not particularly limited, but is preferably a metal from the viewpoint of strength, etc. Examples of metals include stainless steel, copper, iron, etc. When using an oxidizable material such as copper or iron, it is preferable to perform a plating process to suppress changes in size and shape due to oxidation. Any material can be used for plating, but nickel plating is preferable from the viewpoint of versatility.

[0053] 1.2.2c. Fixture 20C 6 shows a diagram for explaining the fixing jig 20C. To distinguish it from other types of fixing jigs, it is written as fixing jig 20C, but the fixing jig 20C can be used as the fixing jig 20 described above. Fig. 6(a) is a plan view of fixing jig 20C, and Fig. 6(b) is a CC' cross-sectional view of fixing jig 20C. As can be seen from Fig. 6, fixing jig 20C has mounting surface 21C and rear surface 22C on the opposite side, with a thickness between mounting surface 21C and rear surface 22C, and side surface 23C formed to bridge the outer periphery of mounting surface 21C and the outer periphery of rear surface 22C. In this embodiment, fixing jig 20C is disk-shaped, but it does not necessarily have to be disk-shaped.

[0054] Fixing jig 20C has hole 25C in the center of mounting surface 21C and multiple holes 24C around it as recesses opening into mounting surface 21C. In this embodiment, holes 24C and 25C are through holes that penetrate through mounting surface 21C and back surface 22C in the thickness direction, but they do not necessarily have to be through holes and may be non-through holes (depressions) that open into mounting surface 21C. When the holes are not through holes, the depth of the holes only needs to have a volume that allows the amount of adhesive that should be removed to be moved into the holes when adjusting the amount of adhesive remaining between the mounting surface and the laminate.

[0055] In this embodiment, the hole 24C can be considered to be the same as the hole 24B of the fixing jig 20B described above.

[0056] On the other hand, the hole 25C is provided in the center of the placement surface 21C and has a circular shape in a plan view, but is not limited to this and may have other shapes (triangle, square, other polygonal shapes, and ellipse).

[0057] The holes 24C and 25C are arranged in positions where the holes 24C and 25C overlap the laminate 10 when viewed from above in a position where the laminate 10 is placed on the placement surface 21C. It is not necessary for all the holes 24C and 25C to overlap the laminate 10, but it is preferable that all the holes 24C and 25C are positioned so as to overlap the laminate 10 when viewed from above. Furthermore, it is preferable that the holes 24C are arranged symmetrically with respect to the center point of the fixing jig 20C.

[0058] There are no particular limitations on the size or number of holes 24C or the size of holes 25C, but it is preferable that the opening ratio, which is the ratio of the total area of ​​the openings of holes 24C and 25C to the area of ​​the mounting surface 21C, be 10% or more. Having openings of sufficient area allows the adhesive to be guided efficiently. Furthermore, reducing the adhesive area reduces the load during peeling. It is more preferable that the opening area be 20% or more, and even more preferable that it be 30% or more. It is preferable that the opening area be 60% or less of the total area of ​​the laminate. If the area is too small, the laminate will not be sufficiently bonded. It is more preferable that the opening area be 50% or less, and even more preferable that it be 40% or less.

[0059] In the example shown in FIG. 6, the opening length at the specific point Q3 shown in the figure is the opening maximum length L3. In the example shown in FIG. 6, the specific point Q3 is a point located at the corner of the outermost portion (on the outer periphery side of the laminated body) of the hole 24C provided around the mounting surface 21. The maximum opening length L3 is preferably 20 mm or less. The opening length L3 is more preferably 10 mm or less, and even more preferably 5 mm or less, or 2 mm or less. If the maximum opening length is too short, the load on the laminate increases, which may lead to damage to the laminate. Furthermore, the adhesive area between the laminate and the fixing jig decreases, which may result in insufficient fixing. The maximum opening length L3 is preferably 0.5 mm or more, and more preferably 1 mm or more, or 2 mm or more.

[0060] The number and size of the holes in the fixing jig of this embodiment are arbitrary, but it is preferable to make the opening length small. Specifically, it is preferable to increase the number of through holes shaped as represented by hole 24C in Fig. 6, uniformly arrange them over the entire surface that contacts the laminate and the fixing jig, and make the opening length small. In the case of such a shape, it is preferable that the number of holes is four or more. In this case, the size of hole 24C provided around the mounting surface 21 is 150 mm2 in area. 2 More than 250mm 2The size of the hole 25C provided in the center is preferably smaller than the size of the hole 24C, specifically, the area is 5 mm 2 More than 20mm 2 It is preferable that:

[0061] The material constituting the fixing jig 20C is not particularly limited, but is preferably a metal from the viewpoint of strength, etc. Examples of metal include stainless steel and copper.

[0062] 1.2.2d. Fixture 20D 7 shows a diagram for explaining the fixing jig 20D. To distinguish it from other types of fixing jigs, it is written as fixing jig 20D, but the fixing jig 20D can be used as the fixing jig 20 described above. Fig. 7(a) is a plan view of fixing jig 20D, and Fig. 7(b) is a D-D' cross-sectional view of fixing jig 20D. As can be seen from Fig. 7, fixing jig 20D has mounting surface 21D and rear surface 22D on the opposite side, with a thickness between mounting surface 21D and rear surface 22D, and side surface 23D formed to bridge the outer periphery of mounting surface 21D and the outer periphery of rear surface 22D. In this embodiment, fixing jig 20D is disk-shaped, but it does not necessarily have to be disk-shaped.

[0063] Fixing jig 20D has holes 24D formed in the center and near the outer periphery of mounting surface 21D as recesses opening into mounting surface 21D, and groove 25D is formed in a spiral shape in plan view connecting these two holes 24D. In this embodiment, the hole 24D is a through hole that penetrates through the mounting surface 21D and the back surface 22D in the thickness direction, but it does not necessarily have to be a through hole and may be a non-through hole (recess) that opens on the mounting surface 21D. Also, the hole 24D does not have to be provided. In this embodiment, groove 25D is a groove that has an opening in mounting surface 21D and extends in a spiral shape around central hole 24D to outer peripheral hole 24D. In this embodiment, groove 25D does not reach rear surface 22D in the depth direction, but this is not limited thereto and grooves that reach the rear surface may also be used.

[0064] The hole 24D has a circular shape in plan view, but is not limited to this and may have other shapes (triangle, square, other polygonal shapes, and ellipse).

[0065] The holes 24D and grooves 25D are arranged in positions that overlap the laminate 10 when viewed from above in a position where the laminate 10 is placed on the placement surface 21D. It is not necessary for all of the holes 24D and grooves 25D to overlap the laminate 10, but preferably all of the holes 24D and grooves 25D are positioned so as to overlap the laminate 10 when viewed from above.

[0066] There are no particular limitations on the size and number of holes 24D, the groove width of groove 25D, or the number of spiral turns, but it is preferable that the opening ratio, which is the ratio of the total opening area of ​​holes 24D and grooves 25D to the area of ​​mounting surface 21D, be 10% or more. Having openings with sufficient area allows the adhesive to be guided efficiently. Also, reducing the adhesive area reduces the load during peeling. It is more preferable that it be 20% or more, and even more preferable that it be 30% or more. It is preferable that the opening area be 60% or less of the total area of ​​the laminate. If the area is too small, the laminate will not be sufficiently bonded. It is more preferable that it be 50% or less, and even more preferable that it be 40% or less.

[0067] When arranging holes 24D so that the opening length is uniform, it is preferable to arrange the holes in a circle at equal intervals, or to arrange the holes in a shape that keeps the spacing between holes constant, as typified by Archimedes' spiral. In the case of the Archimedes' spiral, since there is only one hole, the number of required through-holes is reduced, allowing for greater design freedom compared to when each hole is independent, such as when the holes are arranged in a circle and evenly spaced (see Figure 4). Furthermore, when the holes are arranged in a circle and evenly spaced, the opening length depends on both distance b and distance c, so the design must be tailored to the size of the laminate, which depends on distance c. In the case of the Archimedes' spiral, if the diameter of the spiral expands to a size equal to or greater than the diameter of the laminate, it is clear that the distance c to the outer periphery of the laminate will always be smaller than the distance b to the opening. A fixture with such a shape is preferable because it can be used universally and does not require redesign even when the area or shape of the laminate changes. When an Archimedes spiral hole is provided, it is preferable that the hole has through holes at two locations, the start point and the end point.

[0068] In the case of the Archimedes' spiral shown in FIG. 7, the maximum opening length L4 can be defined as the distance between adjacent grooves 25 in the radial direction of the fixing jig 20D. The maximum opening length L4 is preferably 20 mm or less. The opening length is more preferably 10 mm or less, and even more preferably 5 mm or less, or 2 mm or less. If the maximum opening length is too short, the load on the laminate increases, which may lead to damage to the laminate. Furthermore, the adhesive area between the laminate and the fixing jig decreases, which may result in insufficient fixation. The maximum opening length L4 is preferably 0.5 mm or more, and more preferably 1 mm or more, or 2 mm or more.

[0069] The Archimedes spiral can be expressed by the polar coordinate equation r = aθ. Here, r is the distance from the center point of the fixture 20D to the center of the groove 25D in the width direction, θ is the angle between the line segment connecting the center point of the fixture 20D and the center of the groove 25D in the width direction and the reference line (which is the horizontal direction in the example shown in FIG. 7), and a is a coefficient. In the shape of this embodiment, a is preferably 0.5 to 10, more preferably 1 to 5, and more preferably 1.5 to 3. In this case, if the width of the spiral is d, d is preferably 0.5 mm to 10 mm, more preferably 1 mm to 5 mm, and even more preferably 1.5 mm to 3 mm. The ratio of a to d is preferably d / a = 0.3 to 3, more preferably 0.5 to 2, 0.8 to 1.5, or 0.95 to 1.1. The Archimedes spiral can be enlarged as far as the size of the jig allows, but if the diameter of the spiral is enlarged to a size equal to or larger than the diameter of the laminate, the distance c to the outer periphery of the laminate will always be smaller than the distance b to the opening, and any laminate smaller than this can be used in this embodiment and is more suitable.

[0070] The material constituting the fixture 20D is not particularly limited, but is preferably a metal from the viewpoint of strength, etc. Examples of metals include stainless steel, copper, and iron. When using an oxidizable material such as copper or iron, it is preferable to perform a plating process to prevent changes in size and shape due to oxidation. Any material can be used for plating, but nickel plating is preferable from the viewpoint of versatility.

[0071] 1.2.3.Laminate arrangement As described above, in this step, the laminate 10 is fixed to the mounting surface of the fixing jig 20 via the adhesive layer 11. At this time, unnecessary adhesive is moved to the recesses (holes or grooves of various shapes) provided in the fixing jig 20, as described above. To achieve this, a pressing force can be applied between the laminate 10 and the fixing jig 20. This allows for smooth movement of the adhesive. The specific pressing force is not particularly limited, but is adjusted so that an adhesive layer 11 of an appropriate thickness is formed between the laminate 10 and the mounting surface of the fixing jig 20. If the adhesive layer 11 is too thick, the aluminum nitride single crystal body will deviate significantly from the target separation (cutting) position. On the other hand, if the adhesive layer 11 is too thin, the fixation will be weak and unstable, which may prevent proper separation (cutting). The specific thickness of the adhesive layer is not particularly limited, but is preferably 0.1 μm to 50 μm. It is more preferably 0.5 μm to 30 μm, or 1 μm to 10 μm.

[0072] 1.3.Separation process In the separation step S13, the aluminum nitride single crystal is separated from the laminate 10 that has been prepared in the placement step S12 and placed on the fixing jig 20 via the adhesive layer 11. The separation method is not particularly limited, but may be, for example, cutting with a wire saw. That is, as shown in Fig. 8, the aluminum nitride single crystal is separated by moving a wire saw 12 from the side surface 10c of the laminate 10 along the first surface 10a and the second surface 10b as indicated by the straight arrows in Fig. 8.

[0073] In addition to the above, the separation step S13 can be configured as follows: Fig. 9 shows explanatory diagrams, in which Fig. 9(a) is a plan view and Fig. 9(b) is a front view. 9, a buffer layer 13 may be formed on the side surface 10c of the laminate 10 before cutting with the wire saw 12, and then the buffer layer 13 may be brought into contact with the wire saw 12 before cutting the aluminum nitride single crystal of the laminate 10. This can further prevent the wire saw 12 from shifting out of position.

[0074] The material that constitutes the buffer layer 13 can be any of a variety of adhesives, including epoxy and cyanoacrylate adhesives, and thermoplastic resins, such as polyester and polyethylene. A different resin may be used for the adhesive layer, but it is preferable to use the same material for ease of use. Glass, aluminum oxide, or other particles may be mixed into the resin to increase its hardness. Nikka Seiko's Q Bond and U Bond are useful materials for the buffer layer.

[0075] 9, the buffer layer 13 is disposed around the entire periphery of the side surface 10c of the laminate 10, but this is not necessarily limited to this, and it is sufficient if it can suppress misalignment of the wire saw 12. For this reason, it is preferable that the buffer layer 13 be disposed at least in the portion of the side surface 10c that the wire saw 12 first touches. Furthermore, although not shown in the drawings, aluminum nitride single crystals may have convex polycrystals called crowns on their periphery depending on the crystal growth conditions. For such aluminum nitride single crystals with crowns on their periphery, it is more preferable to remove the crowns by cutting, polishing, or grinding the periphery, and then apply the method according to the above-described embodiment. In other words, the effects of the present invention are more pronounced for aluminum nitride single crystals that do not have crowns on their periphery.

[0076] 2. Effects etc. According to the present disclosure, in the process of placing the laminate on the mounting surface of the fixing jig, a portion of the adhesive present between the mounting surface and the laminate can be guided from between the mounting surface and the laminate in the thickness direction (vertical direction) of the fixing jig to a recess and to a position lower than the mounting surface. This adjusts the amount of adhesive remaining between the mounting surface and the laminate, reduces the thickness of the adhesive layer, and suppresses displacement of the aluminum nitride single crystal body from the target position when it is separated from the laminate in the separation step.

[0077] 3. Working Example As examples, fixing jigs were fabricated in imitation of the above-described fixing jigs 20A, 20B, 20C, and 20D, and as comparative examples, fixing jigs without recesses on the mounting surface were fabricated and tested.

[0078] The dimensions of each fixture were a rectangular parallelepiped with a width of 70 mm, a length of 100 mm, and a height of 20 mm.

[0079] The adhesive used to form the adhesive layer was the aforementioned Q Bond or U Bond manufactured by Nikka Seiko.

[0080] 3.1. Example A In Example A, a laminate 10 was prepared by laminating an aluminum nitride single crystal by the HVPE method on an AlN substrate produced by the PVT method. The laminate had a diameter of 2 inches and a thickness of 1400 μm. Hereinafter, the laminate 10 will also be referred to as "aluminum nitride single crystal." The off-angle of the aluminum nitride single crystal was measured. The heights of fixtures 20A, 20B, and 20C, as well as the fixture of the comparative example, were measured using a micrometer and used as the origin. The aluminum nitride single crystal was placed on the fixture, and the height of the nitride single crystal was measured at the locations indicated by the black circles in Figure 10 (a total of 17 locations, including the center point, eight locations spaced 5 mm apart on the left and right of the center point on a line segment passing through the center of the aluminum nitride single crystal, and eight locations spaced 5 mm apart above and below the center point on a line segment perpendicular to the line segment). Similar measurements were performed at different measurement points to measure the in-plane height distribution of the aluminum nitride single crystal. After cleaning the fixture and the surface of the laminate with acetone, an adhesive was applied to the mounting surface of the fixture, and the second surface of the fabricated laminate was placed and pressed against it. The pressing was performed at a pressure of 0.05 MPa for 1 minute. After leaving the fixture for 24 hours to allow the adhesive layer to solidify, the thicknesses of the laminate and adhesive layer were measured using a micrometer. Similar measurements were performed at different measurement points, and the average thickness and standard deviation of the adhesive layer were calculated by calculating the difference from the height of the laminate before and after bonding. The off-angle of the aluminum nitride single crystal after cutting was measured, and the difference from before cutting was calculated to calculate the difference in off-angle before and after cutting. The results are shown in Table 1.

[0081] [Table 1]

[0082] As can be seen from Table 1, compared to the fixing jigs of the comparative example, fixing jigs 20A, 20B, and 20C were able to reduce the adhesive layer thickness, which makes it possible to suppress displacement of the aluminum nitride single crystal mass from the target position when it is separated from the laminate in the separation step.

[0083] 3.2. Example B In Example B, a laminate was prepared by laminating an aluminum nitride single crystal on a sapphire substrate by the HVPE method. The size of the laminate was 2 inches in diameter and 1400 μm in thickness. Adhesive was applied to the mounting surface of each of fixtures 20A, 20B, 20C, 20D, and the comparative fixture, and the second surface of the laminate was placed on it and pressed. In this example, the pressing force was varied and pressed for 1 minute at that pressure. The thickness of the adhesive layer between the second surface of the laminate and the mounting surface of the fixture was then measured. The results are shown in Table 2.

[0084] [Table 2]

[0085] As can be seen from Table 2, even when the pressing force was changed, fixing jigs 20A, 20B, 20C, and 20D were able to reduce the adhesive layer thickness compared to the fixing jig of the comparative example. Furthermore, the standard deviation was reduced, indicating that the in-plane variation in adhesive layer thickness was reduced. It was also confirmed that the difference in off-angle before and after cutting was also reduced. [Explanation of symbols]

[0086] 10 Laminate 11 Adhesive layer 12 Wire Saw 13 Buffer layer 20 Fixture 20A Fixture 20B Fixture 20C Fixture 20D Fixture

Claims

[Claim 1] a preparation step of preparing a laminate including an aluminum nitride single crystal body; a placing step of placing the laminate on a placing surface of a fixing jig via an adhesive layer formed by an adhesive; A method for manufacturing an aluminum nitride single crystal substrate, comprising: a separation step of separating the aluminum nitride single crystal body from the laminate bonded onto the adhesive layer, the placing step includes guiding a portion of the adhesive present between the placement surface and the laminate to a position lower than the placement surface in a thickness direction of the fixing jig, In the separating step, the aluminum nitride single crystal body is cut into a plate shape from the laminate using a wire saw; In the separation step, a buffer layer is formed on the side surface of the aluminum nitride single crystal body, and then the buffer layer is brought into contact with a wire saw before cutting the aluminum nitride single crystal body. A method for manufacturing an aluminum nitride single crystal substrate.

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