Method for grinding laminate, method for manufacturing polycrystalline substrate, and laminate

Abstract

To provide a method for grinding laminate, a method for manufacturing polycrystalline substrate, and laminate such that grinding powder is efficiently discharged when a laminate of a support substrate and a polycrystalline film is grounded, and then a grinding tool is suppressed from wearing to have a longer lifetime, so that costs can be reduced.SOLUTION: There is a method for grinding a laminate which has a support substrate for deposition and a polycrystalline film deposited by the chemical vapor deposition on a deposition target surface of the support substrate for deposition into the disk shape with a core drill. The method comprises: a discharge part forming stage of forming a grinding powder discharge part penetrating the laminate in a thickness direction at a part of a grinding target region to be ground with the core drill; and a grinding processing stage of grinding the grinding target region with the core drill after the discharge part forming stage to obtain a laminate in a disk shape, wherein the grinding powder discharge part is not formed inside the grinding target region in the discharge forming stage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for grinding a laminate, a method for manufacturing a polycrystalline substrate, and a laminate. [Background technology]

[0002] Silicon carbide (hereinafter sometimes referred to as "SiC") has a band gap about three times larger than silicon (hereinafter sometimes referred to as "Si") (about 3.8 eV for 4H-SiC, about 3.1 eV for 6H-SiC, about 1.1 eV for Si) and high thermal conductivity (about 5 W / cm K, about 1.5 W / cm K for Si). For this reason, single crystal silicon carbide has recently begun to be used as a substrate material for power devices.

[0003] For example, compared to conventionally used Si power devices, SiC power devices have a withstand voltage that is 5 to 10 times higher and an operating temperature that is several hundred degrees higher. In addition, they can reduce the power loss of the element to about 1 / 10, which is why they are being used in applications such as railway vehicle inverters.

[0004] Typically, silicon carbide single crystal substrates are produced by a vapor phase method called the sublimation recrystallization method (modified Lely process) (see, for example, Non-Patent Document 1), and are processed to the desired diameter and thickness.

[0005] The modified Lely process is a manufacturing method in which solid silicon carbide raw material (usually in powder form) is heated and sublimated at high temperatures (over 2,400°C). The sublimated silicon and carbon atoms are transported by diffusion through an inert gas atmosphere as vapor at 2,400°C, and become supersaturated on a seed crystal placed at a lower temperature than the raw material, where they recrystallize to grow a single crystal of silicon carbide in a lump.

[0006] However, this modified Lely process requires extremely high process temperatures of over 2,400°C, making it extremely difficult to control the temperature and convection during crystal growth, as well as control crystal defects. As a result, single-crystal silicon carbide substrates produced by this method can contain numerous crystal defects called micropipes and other crystal defects (stacking faults, etc.), making it extremely difficult to produce high-quality crystal substrates that can withstand electronic device use with a good yield.

[0007] As a result, high-quality silicon carbide single crystal substrates with few crystal defects that can be used for electronic devices are very expensive, and devices using such silicon carbide single crystal substrates are also expensive, which has hindered the widespread use of silicon carbide single crystal substrates.

[0008] In recent years, therefore, it has been proposed to prepare a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate, perform a process of bonding the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate, and then perform a process of thinning the silicon carbide single crystal substrate to produce a substrate in which a silicon carbide single crystal thin plate layer is formed on the silicon carbide polycrystalline substrate (see, for example, Non-Patent Document 2).

[0009] According to this manufacturing method, the thickness of the silicon carbide single crystal substrate can be reduced to a fraction or a few hundredths of that of the conventional method, and therefore the cost of the silicon carbide substrate can be significantly reduced compared to the conventional method in which the entire silicon carbide substrate is made of expensive, high-quality silicon carbide single crystal. In addition, since elements such as power devices can be formed on a high-quality silicon carbide single crystal layer with few crystal defects, the device performance and manufacturing yield can be significantly improved.

[0010] In the process of bonding such a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate, the silicon carbide polycrystalline substrate is required to be dense, highly pure, and highly flat, and therefore, a chemical vapor deposition method (hereinafter sometimes referred to as a "CVD method") is used to manufacture the silicon carbide polycrystalline substrate.

[0011] Patent Document 1 describes a method for producing a silicon carbide polycrystalline substrate using a chemical vapor deposition method (CVD method). According to this method, silicon carbide is precipitated on the surface of a graphite support substrate by the CVD method, and after forming a film of a desired thickness, the graphite support substrate is removed to obtain a silicon carbide polycrystalline substrate. The obtained silicon carbide polycrystalline substrate is denser and has a higher purity than silicon carbide polycrystalline substrates produced by sintering methods, and is also excellent in corrosion resistance, heat resistance, and strength properties. [Prior art documents] [Non-patent literature]

[0012] [Non-Patent Document 1] Yu. M. Tairov and VF Tsvetkov: J.of Cryst.Growth,43(1978)p.209 [Non-Patent Document 2] Journal of the Japan Society for Precision Engineering, 2017, Vol. 83, No. 9, pp. 833-836 [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 8-26714 Summary of the Invention [Problem to be solved by the invention]

[0014] Here, as an example of a method for producing a polycrystalline substrate by forming a polycrystalline film such as silicon carbide on a graphite support substrate and then removing the graphite support substrate, a conceivable method is to obtain a polycrystalline substrate by grinding a laminate of a graphite support substrate and a polycrystalline film obtained by forming a polycrystalline film into a desired size using a core drill, and then removing the graphite support substrate from the laminate.

[0015] When manufacturing a polycrystalline substrate by this method, particularly in the case of silicon carbide, which has high hardness, when grinding the laminate obtained by film formation to separate the disk-shaped laminate, grinding powder generated by grinding may become trapped between the grinding wheel and the laminate. If grinding is performed with grinding powder trapped between the grinding wheel and the laminate, the load on the grinding wheel increases, and grinding failure may occur due to wear of the grinding wheel, etc. Therefore, efforts have been made to improve the discharge of grinding powder generated by grinding by optimizing the grinding conditions and grinding wheel, using microbubbles (grinding water), etc., but the cost and processing time have been problems.

[0016] Also, for example, a disk-shaped laminate may be separated from a laminate of a polycrystalline film and a support substrate using a core drill grindstone. That is, as shown in Fig. 4, a laminate 300 (Fig. 4(A)) of a carbon film-forming support substrate 100 having a film-forming surface (front surface 110, back surface 120) fixed to a glass plate G and a silicon carbide polycrystalline film 200 is ground using a core drill C' to separate the laminate 300C (Fig. 4(B)). Furthermore, the disk-shaped laminate 300C is heated using an oven H or the like, and the film-forming support substrate 100 is burned off to obtain a polycrystalline substrate 200C.

[0017] In this method, the tip of the core drill where the abrasive grains are formed is flat, so there is a large grinding resistance against the laminate 300, which is the workpiece, and the discharge of cutting powder is very poor, which causes problems such as wear of the grinding stone and other grinding defects. For this reason, attempts have been made to improve the discharge efficiency of grinding powder by using a core drill C' with a slit S, as shown in Figure 5.

[0018] The core drill C' has a holder C2 that holds the shaft C1 and the grindstone C3', and the grindstone C3', and is not provided with a center drill or center pin so as not to drill a hole in the center of the disc-shaped laminate 300C. The thickness of the grindstone C3' can be about 0.4 mm to 1.0 mm. The grindstone C3' has four slits S, and grinding powder generated during grinding is taken into the grindstone C3' through the slits S, so that the grinding powder can be removed from the grinding area. Here, the width of the slits S can be about 5 mm to 20 mm.

[0019] However, even when using a core drill C' with a slit S, it was difficult to efficiently remove the grinding powder from the grinding point of the grinding wheel C3', and it was difficult to prevent the grinding powder from becoming caught between the grinding wheel and the substrate, which would increase the grinding load.

[0020] Therefore, the present invention focuses on the above-mentioned problems and aims to provide a method for grinding a laminate, a method for manufacturing a polycrystalline substrate, and a laminate, which can efficiently discharge grinding powder when grinding a laminate of a support substrate and a polycrystalline film, thereby suppressing wear on the grinding tool and reducing costs by extending the life of the grinding tool. [Means for solving the problem]

[0021] The method for grinding a laminate of the present invention is a method for grinding a laminate, which includes a film-formation support substrate and a polycrystalline film formed on a film-formation target surface of the film-formation support substrate by a chemical vapor deposition method, into a disk shape using a core drill, and includes a discharge portion forming step of forming a grinding powder discharge portion penetrating the laminate in the thickness direction in a part of the part to be ground that is ground with the core drill, and a grinding processing step of grinding the part to be ground with the core drill after the discharge portion forming step to obtain a disk-shaped laminate, and in the discharge portion forming step, the grinding powder discharge portion is not formed inside the part to be ground.

[0022] In the method for grinding a laminate of the present invention, the grinding powder discharge portion may be a through hole penetrating in the thickness direction of the laminate, or a slit penetrating in the thickness direction from a part of the area to be ground to the outer peripheral edge of the laminate.

[0023] In the method for grinding a laminate of the present invention, the core drill may have a single blade without a slit, and may not have a center pin or a center drill.

[0024] In the method for grinding a laminate of the present invention, the linear distance between two intersections where the outer periphery of the portion to be ground intersects with the grinding powder discharge portion may be 1.5 mm to 5 mm.

[0025] In the method for grinding a laminate of the present invention, the laminate may be provided with a plurality of the regions to be ground so as not to overlap each other.

[0026] The method for producing a polycrystalline substrate of the present invention includes a removing step of removing the film formation support substrate from the disk-shaped laminate obtained by the method for grinding a laminate of the present invention to obtain a polycrystalline substrate.

[0027] In the method for producing a polycrystalline substrate of the present invention, the polycrystalline substrate may be a silicon carbide polycrystalline substrate.

[0028] The laminate of the present invention is a laminate comprising a film-formation support substrate and a polycrystalline film formed by chemical vapor deposition on a film-formation target surface of the film-formation support substrate, and further comprising a grinding powder discharge portion formed in a part of the grinding target portion and penetrating the laminate in the thickness direction, wherein the grinding powder discharge portion is not formed inside the grinding target portion. Effect of the Invention

[0029] The method for grinding a laminate of the present invention can efficiently discharge grinding powder when grinding a laminate of a film formation support substrate and a polycrystalline film, suppress wear on the core drill, and reduce costs by extending the life of the core drill.

[0030] Furthermore, according to the method for manufacturing a polycrystalline substrate of the present invention, by grinding a laminate of a film-formation support substrate and a polycrystalline film using the method for grinding a laminate of the present invention, grinding powder can be efficiently discharged, wear on the core drill can be suppressed, and costs can be reduced by extending the life of the core drill.

[0031] The laminate of the present invention has a grinding powder discharge portion formed in a part of the area to be ground and penetrating the thickness direction of the laminate, so that grinding powder can be efficiently discharged when grinding a laminate of a film formation support substrate and a polycrystalline film, thereby suppressing wear on the core drill and reducing costs by extending the life of the core drill. [Brief description of the drawings]

[0032] [Figure 1] 1 is a plan view showing a laminate in a grinding method of a laminate according to an embodiment of the present invention; [Diagram 2] 3A to 3C are diagrams illustrating an example of steps of a method for grinding a laminate and a method for manufacturing a polycrystalline substrate according to the present embodiment. [Diagram 3] FIG. 11 is a plan view showing a modified example of the laminate of the present embodiment. [Figure 4] 1A to 1C are diagrams illustrating an example of a process for a conventional method for manufacturing a polycrystalline substrate. [Diagram 5] 5 is a diagram showing an example of a core drill used in the conventional method for producing a polycrystalline substrate shown in FIG. 4. [Figure 6] 3 is a diagram showing an example of a core drill used in the grinding method of the laminate of the present embodiment shown in FIG. 2. [Figure 7] FIG. 7(A) is an enlarged view of the area surrounded by dotted line P in FIG. 1(B), and FIG. 7(B) is an enlarged view of the area surrounded by dotted line Q in FIG. 1(B). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] A laminate, a grinding method for a laminate, and a manufacturing method for a polycrystalline substrate according to one embodiment of the present invention will be described with reference to Figures 1, 2, 6, and 7. The polycrystalline substrate of this embodiment is manufactured by grinding a laminate of a film-formation support substrate on which a polycrystalline film is to be formed and a polycrystalline film of silicon carbide, titanium nitride, aluminum nitride, titanium carbide, diamond-like carbon, or the like, formed by chemical vapor deposition on the film-formation target surface of the film-formation support substrate, into a disk shape using a core drill, and removing the film-formation support substrate from this disk-shaped laminate (disk-shaped laminate).

[0034] The laminate, the grinding method of the laminate, and the manufacturing method of the polycrystalline substrate of this embodiment are effective when a polycrystalline substrate is manufactured by forming a polycrystalline film having high hardness such as silicon carbide polycrystal, and therefore, in this embodiment, a case where a silicon carbide polycrystalline film is formed and a silicon carbide polycrystalline substrate is manufactured will be described as an example. The silicon carbide polycrystalline substrate manufactured by the method of this embodiment can be used as a substrate for a power device, for example, by bonding it to a silicon carbide single crystal substrate.

[0035] [Laminate grinding method and laminate] The grinding method for a laminate in this embodiment is a grinding method for a laminate 300 including a film-formation support substrate 100 and a silicon carbide polycrystalline film 200 formed by chemical vapor deposition on the film-formation target surface (front surface 110 and back surface 120 in FIG. 2(A)) of the film-formation support substrate 100, and includes a discharge portion forming step of forming a grinding powder discharge portion 330 penetrating the laminate 300 in the thickness direction in a part of a grinding target portion 310 to be ground by a core drill C, which is provided on the surface on which the silicon carbide polycrystalline film 200 is formed, and a grinding processing step of grinding the grinding target portion 310 by the core drill C after the discharge portion forming step, and separating an inner portion of the grinding target portion 310 to obtain a disk-shaped laminate (disk-shaped laminate 320). In addition, in the discharge portion forming step, the grinding powder discharge portion 330 is not formed inside the portion to be ground 310 so as not to grind the portion that will become the disk-shaped laminate 320.

[0036] The laminate of this embodiment is the laminate 300A shown in Fig. 1(B) and Fig. 2(B). The laminate 300A is a laminate including a film-formation support substrate 100 and a silicon carbide polycrystalline film 200 formed on the film-formation target surface of the film-formation support substrate 100 by chemical vapor deposition, and includes a grinding target portion 310 to be ground by a core drill C and a grinding powder discharge portion 330 formed in a part of the grinding target portion 310 and penetrating the thickness direction of the laminate 300A, and the grinding powder discharge portion 330 is not formed inside the grinding target portion 310.

[0037] As the film formation support substrate 100, a parallel plate-like one can be suitably used, that is, as shown in Fig. 2(A), a parallel plate whose film formation target surfaces correspond to a front surface 110 and a back surface 120. In this specification, the "parallel" in the parallel plate does not only mean strictly parallel, but also includes a case where there is an unavoidable error in creating the parallel surfaces of the film formation support substrate 100.

[0038] The thickness of the film formation support substrate 100 may be, for example, about 5 mm. The thickness of the silicon carbide polycrystalline film 200 formed on the film formation support substrate 100 is not particularly limited, and may be, for example, about 500 μm to 5 mm. The film formation support substrate 100 is formed larger than the polycrystalline substrate to be manufactured, and may have a diameter of 160 μm to 400 μm. For example, when a polycrystalline substrate with a diameter of 6 inches is obtained, the diameter may be about 160 mm.

[0039] As the film-formation support substrate 100, a carbon support substrate or a silicon support substrate can be used in consideration of the applicability to the film-formation conditions of the silicon carbide polycrystalline film 200 and the ease of removing the film-formation support substrate 100 from the disk-shaped laminate 320. In the following description, a manufacturing process in which a carbon support substrate is used as the film-formation support substrate 100 is exemplified.

[0040] Fig. 1(A) is a plan view of a laminate 300 of a film formation support substrate 100 and a silicon carbide polycrystalline film 200, and Fig. 2(A) is a cross-sectional view showing a cross section taken along line A in Fig. 1(A). The laminate 300 can be obtained by chemical vapor deposition, as described below. Film formation can be performed, for example, by using a film formation apparatus applicable to chemical vapor deposition, setting the temperature inside a film formation chamber holding the film formation support substrate 100 at about 1000°C to 1400°C, supplying raw material gases and the like into the film formation chamber, and forming the silicon carbide polycrystalline film 200 on the film formation target surfaces (front surface 110 and back surface 120) of the film formation support substrate 100.

[0041] The source gas is not particularly limited as long as it can form the silicon carbide polycrystalline film 200, and can be a Si-based source gas or a C-based source gas that is generally used for forming a silicon carbide polycrystalline film. For example, the Si-based source gas can be silane (SiH4), or a chlorine-based Si source-containing gas (chloride source) containing Cl having an etching effect, such as monochlorosilane (SiH3Cl), dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), or tetrachlorosilane (SiCl4). For example, a hydrocarbon such as methane (CH4), propane (C3H8), or acetylene (C2H2) can be used as the C-based source gas. In addition to the above, a method can also be used in which organic silicon compounds such as trichloromethylsilane (CH3Cl3Si), trichlorophenylsilane (C6H5Cl3Si), dichloromethylsilane (CH4Cl2Si), dichlorodimethylsilane ((CH3)2SiCl2), and chlorotrimethylsilane ((CH3)3SiCl) are subjected to reduction and pyrolysis in the gas phase.

[0042] In addition, as the carrier gas, a commonly used carrier gas can be used as long as the raw material gas can be expanded onto the film formation support substrate 100 without impeding the formation of the silicon carbide polycrystalline film 200. For example, H2 gas, which has excellent thermal conductivity and an etching effect on silicon carbide, can be used as the carrier gas. In addition, an impurity doping gas can be supplied as a third gas at the same time as the raw material gas and the carrier gas. For example, nitrogen (N2) can be used when the conductivity type of the silicon carbide polycrystalline substrate obtained by separating the silicon carbide polycrystalline film 200 from the film formation support substrate 100 is n-type, and trimethylaluminum (TMA) can be used when the conductivity type is p-type.

[0043] The above gases are appropriately mixed and supplied when forming the silicon carbide polycrystalline film 200. In addition, conditions such as the gas mixing ratio and supply amount may be changed during the film formation process depending on the desired properties of the silicon carbide polycrystalline film 200.

[0044] Furthermore, when depositing a film of a material other than silicon carbide, the deposition conditions such as gas, temperature, pressure, and time can be set according to the polycrystalline film to be deposited. When forming a titanium nitride polycrystalline film, TiCl4 gas, N2 gas, etc. can be used. When forming an aluminum nitride polycrystalline film, AlCl3 gas, NH3 gas, etc. can be used. When forming a titanium carbide polycrystalline film, TiCl4 gas, CH4 gas, etc. can be used. When forming a diamond-like carbon polycrystalline film, a hydrocarbon gas such as acetylene can be used.

[0045] 1(A) and 2(A), a laminate 300 is obtained, which includes a film-formation support substrate 100 and a silicon carbide polycrystalline film 200 formed by chemical vapor deposition on the film-formation target surface of the film-formation support substrate 100. The film formation of the silicon carbide polycrystalline film 200 on the film-formation support substrate 100 and the discharge portion forming step of the grinding method of the laminate of this embodiment may be performed continuously as one manufacturing process, or may be a discontinuous process, such as by purchasing the laminate.

[0046] (Discharge part forming process) The discharge part forming step is a step of forming a grinding dust discharge part 330 for discharging grinding dust in the laminate 300 of the film-forming support substrate 100 and the silicon carbide polycrystalline film 200. In the discharge part forming step, the grinding dust discharge part 330 is formed penetrating through a part of the grinding target part 310 to be ground by the core drill C in the thickness direction of the laminate 300. In addition, in order to maintain the shape of the disk-shaped laminate 320 obtained by separation, the grinding dust discharge part 330 is not formed inside the grinding target part 310. Here, FIG. 1(B) is a plan view showing the laminate 300A in which the grinding dust discharge part 330 is formed, and FIG. 2(B) is a cross-sectional view showing the cross section of the laminate 300A taken along line B in FIG. 1(B).

[0047] The grinding powder discharge part 330 is formed penetrating in the thickness direction of the laminate 300. The shape of the grinding powder discharge part 330 is not limited, but it can be a through hole 340 (for example, a circular shape in a plan view in this embodiment) in the thickness direction of the laminate 300, or a slit 350 penetrating in the thickness direction from a part of the grinding target part 310 to the outer periphery of the laminate 300. That is, both the through hole 340 and the slit 350 may be formed, or either one may be formed. In addition, the through hole 340, the slit 350, and the grinding powder discharge part 330 of another shape may be combined.

[0048] The through-hole 340 can be formed by using a drill or the like. The slit 350 can be formed by rotating a disk-shaped grindstone and grinding it against the thickness direction of the laminate 300. In this way, if the grinding powder discharge portion 330 is the through-hole 340 or the slit 350, the grinding powder discharge portion 330 can be formed by using a general-purpose processing tool.

[0049] 1(B) and 2(B), two through holes 340 and two slits 350 are formed as the grinding dust discharge portion 330. The grinding dust discharge portion 330 may be formed in one place, or may be formed in multiple places to more efficiently discharge the grinding dust.

[0050] Moreover, the width dimension of the grinding powder discharge portion 330 can be 5 mm or more. For example, when the grinding powder discharge portion 330 is a through hole 340, the diameter dimension of the through hole 340 can be 5 mm or more, and when the grinding powder discharge portion 330 is a slit 350, the width dimension of the slit 350 can be 5 mm or more.

[0051] The linear distance between the two intersections of the outer periphery 311 of the part to be ground 310 and the grinding powder discharge part 330 can be, for example, 1.5 mm to 5 mm. Here, Fig. 7(A) is an enlarged view showing the part surrounded by the dotted line P in Fig. 1(B), and Fig. 7(B) is an enlarged view showing the part surrounded by the dotted line Q in Fig. 1(B).

[0052] As shown in Fig. 7(A), when the grinding powder discharge section 330 is a through hole 340, the two intersections refer to two intersections R1 and R2 where the outer periphery 311 of the grinding target portion 310 intersects with the outer edge 341 of the through hole 340, and the linear distance L1 between the two intersections R1 and R2 can be set to, for example, 1.5 mm to 5 mm. As shown in Fig. 7(B), when the grinding powder discharge section 330 is a slit 350, the two intersections refer to two intersections R3 and R4 where the outer periphery 311 of the grinding target portion 310 intersects with the outer edge 351 of the slit 350, and the linear distance L2 between the two intersections R3 and R4 can be set to, for example, 1.5 mm to 5 mm. As a result, the area where the portion to be ground 310 and the grinding powder discharge section 330 are connected becomes sufficiently large, so that the grinding powder generated by grinding using the core drill can be efficiently discharged to the outside from the grinding powder discharge section 330.

[0053] Next, the procedure of the discharge part forming step will be described. First, the laminate 300 is fixed to the glass plate G using wax or the like. The laminate 300 fixed to the glass plate G is held by a processing device. The processing device is equipped with a drill for forming the through hole 340 or a disk-shaped grindstone for forming the slit 350. The processing device forms the through hole 340 and the slit 350 to obtain the laminate 300A shown in FIG. 1(B) and FIG. 2(B). At this time, the grinding powder discharge part 330 is integrally formed in the glass plate G to which the laminate 300 is fixed. The obtained laminate 300A is subjected to a grinding processing step.

[0054] Before forming the grinding powder discharge portion 330, the portion to be ground 310 may be slightly ground with a separation tool used in the grinding process in order to clarify the position of the portion to be ground 310.

[0055] (Grinding process) The grinding process is a process of obtaining a disk-shaped laminate 320 by separating the inside of the portion to be ground 310 from the laminate 300A. For example, a core drill C shown in FIG. 2(C) and FIG. 6 is used as a grinding tool. By using a core drill as a grinding tool, it is possible to efficiently grind into a circular shape. The outer diameter and inner diameter of the portion to be ground 310 can be set according to the size of the core drill C. For example, when obtaining a disk-shaped laminate 320 for manufacturing a 6-inch polycrystalline substrate using a core drill with a grindstone thickness of 0.5 mm and an inner diameter of the grindstone of 150.5 mm to 151 mm, the outer diameter of the portion to be ground 310 can be set to 151.5 mm to 152 mm.

[0056] FIG. 6(A) is a perspective view showing the entire core drill C, and FIG. 6(B) is a perspective view showing the core drill C from the grindstone C3 side. The core drill C has a holder C2 that holds the shaft C1 and the grindstone C3, and the grindstone C3. The core drill C has a single blade without a slit, and does not have a center pin, a center drill, or other members that may damage the disk-shaped laminate 320 so as not to make a hole in the center of the disk-shaped laminate 320. The thickness of the grindstone C3 can be about 0.4 mm to 1.0 mm. The abrasive grains fixed to the grindstone C3 can be those suitable for the object to be ground, and for example, diamond abrasive grains can be used.

[0057] Unlike the core drill C' shown in Fig. 5, the grinding wheel C3 of the core drill C does not have a slit formed thereon, but the core drill C' with a slit S formed thereon may be used in the grinding process of this embodiment. The use of a single-blade core drill C without a slit S is more suitable for the grinding process of this embodiment because the blade strength is increased due to the absence of the slit S, the rotation axis does not wobble during grinding, the grinding position does not shift, and grinding can be performed efficiently, and the grinding wheel has a larger area, which improves the durability of the grinding wheel. In particular, if the rotation axis wobble, the grinding target part 310 and the actually ground part may be misaligned, so it is preferable to suppress the wobble of the rotation axis.

[0058] When the part to be ground 310 is ground by the core drill C, the surface of the laminate 300A is ground to form grooves, and grinding powder is generated at the same time. In the conventional manufacturing process, the grinding powder generated by grinding can be caught between the grinding wheel and the laminate. If grinding is performed with the grinding powder caught between the grinding wheel and the laminate, the load on the grinding wheel increases, and grinding failures can occur due to wear of the grinding wheel, etc. In addition, wear of the grinding wheel can cause overload, which can stop the grinding device or increase the time and cost required to dress the abrasive grains on the worn grinding wheel.

[0059] In the method for grinding the laminate of this embodiment, the laminate 300A is formed with the grinding powder discharge portion 330 penetrating in the thickness direction, so that the grinding powder can be discharged to the outside of the laminate 300A. This prevents grinding with the grinding powder sandwiched between the grindstone C3 and the laminate 300A, suppresses wear of the core drill C, which is a grinding tool, and extends the life of the core drill C, thereby reducing costs.

[0060] Furthermore, since the laminate 300A of this embodiment is provided with a grinding powder discharge portion 330 formed in a part of the portion to be ground 310 and penetrating the thickness direction of the laminate 300A, grinding powder can be efficiently discharged when grinding the laminate 330A of the film-formation support substrate 100 and the silicon carbide polycrystalline film 200, and wear of the core drill C, which is the grinding tool, can be suppressed and costs can be reduced by extending the life of the core drill C.

[0061] [Method of manufacturing polycrystalline substrate] The method for manufacturing the polycrystalline substrate of this embodiment includes a removal step of removing the film formation support substrate 100 from the disk-shaped laminate (disk-shaped laminate 320) obtained by the laminate grinding method of the above-mentioned embodiment, to obtain a silicon carbide polycrystalline substrate 200B.

[0062] (Removal process) The removing step is a step of removing the film formation support substrate 100 from the disc-shaped laminate 320 separated from the laminate 300A.

[0063] When a carbon support substrate is used as the film formation support substrate 100 like the laminate 300A, the disc-shaped laminate 320 removed from the glass plate G is heated to several hundred degrees in an oxidizing gas atmosphere such as O2 or air to burn only the film formation support substrate 100, thereby removing it. For example, the oven H shown in Fig. 2(D) can be used to heat the disc-shaped laminate 320. The oven H has a heating chamber H2 surrounded by a heat-resistant wall H1.

[0064] By the removal step, a silicon carbide polycrystalline substrate 200B is obtained, as shown in FIG. 2(E).

[0065] In addition, when a silicon support substrate is used as the film formation support substrate, a silicon carbide polycrystalline substrate can be obtained by immersing the disk-shaped laminate in nitric hydrofluoric acid (a mixed acid of nitric acid and hydrofluoric acid) to dissolve only the silicon support substrate.

[0066] Furthermore, after the removal process, diameter / chamfering, thickness / flatness processing, and cleaning are performed as necessary. Diameter / chamfering is a process in which the outer periphery is ground using a diamond grinding wheel or the like to remove excess parts and adjust the diameter to the desired dimension, and the corners of the entire outer periphery of the silicon carbide polycrystalline substrate are rounded off. In addition, the thickness and flatness of the film-formed surface are adjusted by grinding and polishing to obtain a thickness and flatness suitable for applications such as manufacturing a bonded substrate with a silicon carbide single crystal substrate.

[0067] According to the method for manufacturing a polycrystalline substrate of this embodiment, by grinding the laminate 300A of the film-formation support substrate 100 and the silicon carbide polycrystalline film 200 using the method for grinding the laminate of the above-mentioned embodiment, grinding powder can be efficiently discharged, wear of the core drill C, which is the grinding tool, is suppressed, and costs can be reduced by extending the life of the core drill C.

[0068] It should be noted that the present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention, and modifications of the above-described embodiment are also included in the present invention.

[0069] For example, in the above-described method for grinding a laminate, a plurality of portions to be ground may be provided in the laminate so as not to overlap each other.

[0070] In the laminate 400A shown in FIG. 3, three grinding target portions 410 are provided so as not to overlap each other, and two through holes 430 and one slit 440 are formed as grinding powder discharge portions for each of the grinding target portions 410. By grinding the grinding target portions 410, three disk-shaped laminates 420 can be obtained. The number of grinding target portions provided in one laminate is not limited. For example, when a polycrystalline substrate having a diameter of 6 inches is manufactured using a laminate obtained by forming a polycrystalline film on a film-forming support substrate having a diameter of 380 mm, four disk-shaped laminates can be obtained. By providing a plurality of grinding target portions in one laminate so as not to overlap each other, manufacturing efficiency can be improved.

[0071] In addition, the best configuration, method, etc. for implementing the present invention are disclosed in the above description, but the present invention is not limited thereto. That is, the present invention has been mainly described with respect to a specific embodiment, but a person skilled in the art can make various modifications to the above-described embodiment in terms of shape, material, quantity, and other detailed configurations without departing from the scope of the technical idea and purpose of the present invention. Therefore, the description of the shape, material, etc. disclosed above that limits the present invention is illustrative and is not intended to limit the present invention, and therefore the description of the names of components that are free from some or all of the limitations on the shape, material, etc. is included in the present invention. [Explanation of symbols]

[0072] 100 Support substrate for film formation 200 Silicon carbide polycrystalline film 300 Laminate 300A, 400A laminate 310 Grinding target area 320 Disc-shaped laminate (disc-shaped laminate) 330 Grinding dust discharge section 340, 430 through hole 350, 440 slit 200B Silicon carbide polycrystalline substrate C Core Drill

Claims

1. A method for grinding a laminate, comprising grinding a laminate including a film-formation support substrate and a polycrystalline film formed on a film-formation target surface of the film-formation support substrate by a chemical vapor deposition method into a disk shape using a core drill, the method comprising the steps of: a discharge portion forming step of forming a grinding powder discharge portion penetrating the laminate in a thickness direction of the laminate in a part of a portion to be ground by the core drill; and a grinding process step of grinding the grinding target portion with the core drill after the discharge portion forming step to obtain a disk-shaped laminate, A method for grinding a laminate, wherein in the discharge portion forming step, the grinding powder discharge portion is not formed inside the portion to be ground.

2. 2. The method for grinding a laminate according to claim 1, wherein the grinding powder discharge portion is a through hole penetrating the thickness direction of the laminate, or a slit penetrating in the thickness direction from a portion of the portion to be ground to the outer peripheral edge of the laminate.

3. 3. The method for grinding a laminate according to claim 1, wherein the core drill has a single blade without a slit and does not have a center pin or a center drill.

4. 4. The method for grinding a laminate according to claim 1, wherein a straight-line distance between two intersections where an outer periphery of the portion to be ground intersects with the grinding powder discharge portion is 1.5 mm to 5 mm.

5. 5. The method for grinding a laminate according to claim 1, wherein the laminate has a plurality of the grinding target portions provided so as not to overlap each other.

6. A method for producing a polycrystalline substrate, comprising: a removing step of removing the film-formation support substrate from the disk-shaped laminate obtained by the method for grinding a laminate according to any one of claims 1 to 5, to obtain a polycrystalline substrate.

7. The method for producing a polycrystalline substrate according to claim 6 , wherein the polycrystalline substrate is a silicon carbide polycrystalline substrate.

8. A laminate including a film formation support substrate and a polycrystalline film formed on a film formation target surface of the film formation support substrate by a chemical vapor deposition method, The present invention includes a grinding target portion to be ground by a core drill, and a grinding powder discharge portion formed in a part of the grinding target portion and penetrating the laminate in a thickness direction, A laminate, wherein the grinding powder discharge portion is not formed inside the portion to be ground.

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