Carrier-assisted method for separating crystalline materials along laser-damaged regions.

Abstract

This invention provides a method for removing a portion of a crystalline material (e.g., SiC) substrate. [Solution] The method involves bonding the surface of a substrate 172 to a rigid support 176 (for example, with a thickness of >800 μm). A subsurface laser-damaged region 173 is provided at a certain depth relative to the surface within the substrate. The substrate may be bonded to the support 176 by an adhesive material 174 having a glass transition temperature greater than 25°C. The crystalline material is fractured along the subsurface laser-damaged region 173 to create a bonded assembly comprising the support and a portion of the crystalline material. The fracture of the crystalline material is facilitated by (i) applying a mechanical force in close proximity to at least one support edge to impart a bending moment to the support, (ii) cooling the support if the support has a larger coefficient of thermal expansion than the crystalline material, and / or (iii) applying ultrasonic energy to the crystalline material.

Description

Detailed description of the invention

[0001] [Description of related applications] This application claims priority to U.S. Patent Application No. 16 / 274,045 filed on 5 March 2019, U.S. Provisional Patent Application No. 62 / 803,333 filed on 8 February 2019, and U.S. Provisional Patent Application No. 62 / 786,335 filed on 29 December 2018, the entire disclosures of the said applications are thus incorporated herein by reference.

[0002] [Technical field] This disclosure relates to a method for processing crystalline materials, and more particularly to a carrier-assisted method for cutting or removing a relatively thin layer of crystalline material from a substrate such as a Boule or wafer with subsurface laser damage.

[0003] [background] Thin layers of crystalline materials are required as starting structures for fabricating various useful systems in a wide range of applications in microelectronics, optoelectronics, and microfabrication. Conventional methods for cutting thin layers (e.g., wafers) from large-diameter crystalline ingots of crystalline materials include the use of wire saws. Wire sawing techniques have been applied to various crystalline materials such as silicon, sapphire, and silicon carbide. Wire saw tools consist of extremely fine steel wires (typically less than 0.2 mm in diameter) that are passed through grooves in one or more guide rollers. Two slicing methods exist: free abrasive slicing and fixed abrasive slicing. Free abrasive slicing involves attaching a slurry (typically abrasive particles suspended in oil) to a steel wire moving at high speed, and the ingot is cut as the abrasive particles roll between the wire and the workpiece. Unfortunately, the environmental impact of the slurry cannot be ignored. To mitigate such effects, a wire with fixed diamond abrasive grains is sometimes used as a fixed abrasive slicing method, which requires only a water-soluble coolant (not a slurry). High-efficiency parallel slicing makes it possible to produce a large number of wafers in a single slicing procedure. Figure 1 shows a conventional wire saw tool 1, which includes a parallel wire section 3 that extends between rollers 4A-4C and is positioned to simultaneously saw the ingot 2 into multiple thin sections (e.g., wafers 8A-8G), each having a face substantially parallel to the end face 6 of the ingot 2. During the sawing process, the wire section 3, supported by rollers 4A-4C, can be pushed downward 5 toward a holder 7 located beneath the ingot 2. If the end face 6 is parallel to the crystallographic c-plane of the ingot 2, and the wire section 3 saws the ingot 2 parallel to the end face 6, then each resulting wafer 8A-8G will have an "on-axis" end face 6' parallel to the crystallographic c-plane.

[0004] It is also possible to produce micro-slope wafers (also known as off-cut or "off-axis") that have end faces that are not parallel to the crystallographic c-plane. Micro-slope wafers with a 4-degree offcut (e.g., of SiC) are often used as growth substrates for high-quality epitaxial growth of other materials (e.g., AlN and other Group III nitrides). Micro-slope wafers can be produced either by growing an ingot away from the c-axis (e.g., on a micro-slope species material) and sawing this ingot perpendicular to the ingot sidewall, or by starting the ingot from an on-axis species material and growing it and sawing this ingot at an angle away from the ingot sidewall perpendicular to the ingot sidewall.

[0005] Wire sawing of crystalline materials has several limitations. Kerf loss, based on the width of material removed with each cut, is unavoidable in saw cutting and represents a significant loss of crystalline material. The stress applied to the wafer by wire saw cutting is relatively high, resulting in non-zero bow and warp properties. Processing time for a single boule (or ingot) is very long, and events such as wire breakage can extend processing time and lead to unwanted material loss. Chipping and cracking on the cut surface of the wafer can reduce wafer strength. At the end of the wire sawing process, debris must be removed from the resulting wafer.

[0006] For silicon carbide (SiC), which has high wear resistance (and hardness comparable to diamond and boron nitride), wire sawing can require considerable time and resources, resulting in significant manufacturing costs. SiC substrates enable the fabrication of desirable power electronics devices, radio frequency devices, and optoelectronic devices. SiC appears in many different crystalline structures called polytypes, and certain polytypes (e.g., 4H-SiC and 6H-SiC) have a hexagonal structure.

[0007] Figure 2 is an oblique crystal plane view showing the coordinate system for hexagonal crystals such as 4H-SiC, where the c-plane (the (0001) plane, corresponding to the

[0001] (perpendicular) direction of epitaxial crystal growth) is perpendicular to both the m-plane ((1-100) plane) and the a-plane ((11-20) plane), the (1-100) plane is perpendicular to the [1-100] direction, and the (11-20) plane is perpendicular to the [11-20] direction. Figure 3 is a second oblique crystal plane view of the hexagonal crystal, showing a microslope 9 that is not parallel to the c-plane, where the vector 10 (orthogonal to the microslope 9) is tilted by an angle β away from the

[0001] direction, and the angle β is tilted (slightly) toward the [11-20] direction. Figure 4A is a perspective wafer orientation diagram showing the orientation of the beveled wafer 11A with respect to the c-plane ((0001) plane), where the vector 10A (orthogonal to the wafer plane 9A) is tilted by an angle β away from the

[0001] direction. This angle β is equal to the orthogonal tilt (or orientation shift angle) β that spans between the (0001) plane and the projection 12A of the wafer plane 9A. Figure 4B is a simplified cross-sectional view of the beveled wafer 11A superimposed on a portion of the ingot 14A (for example, an on-axis ingot having an end face 6A parallel to the (0001) plane) from which the beveled wafer 11A was defined. Figure 4B shows that the alignment of the wafer plane 9A of the beveled wafer 11A is shifted by an angle β from the (0001) plane.

[0008] Figure 5 includes an upper surface 26 (for example, parallel to the (0001) plane (c plane) and perpendicular to the

[0001] direction), and perpendicular to the (11-20) plane and parallel to the [11-20] direction (length L F This is a top plan view of an exemplary SiC wafer 25, with a substantially circular edge 27 (having a diameter D) as its lateral boundary, including a primary flat 28 (having a primary flat).

[0009] Due to the difficulties associated with the fabrication and processing of SiC, the cost of SiC device wafers is higher compared to wafers made from various other crystalline materials. Typical kerf loss resulting from SiC wire sawing can exceed approximately 250 microns per wafer, and the resulting wafer thickness from the wire sawing process is approximately 350 microns, which is not negligible considering that it is subsequently thinned (by grinding) to a final thickness of approximately 100 to 180 microns depending on the end application. Slicing wafers thinner than approximately 350 microns has not been practical until now, given the problems with wire sawing and device fabrication.

[0010] In an attempt to address the limitations associated with wire sawing, alternative techniques have been developed for removing thin layers of crystalline material from bulk crystals. One such technique is called controlled spaling. The technique works by growing a tensile stressor layer (e.g., nickel) on the surface of a substrate (e.g., Ge(001)), introducing cracks near the substrate edges, and mechanically guiding these cracks as a single fracture leading edge along the surface (e.g., using a flexible handle layer such as tape) (see Bedell et al., J. Phys. D: Appl. Phys. 46 (2013)). However, such techniques can result in the application of very high stresses and excessive bowing of the layer being removed. Another technique, involving the removal of silicon carbide layers from larger crystals, is described in Kim et al., "4H-SiC wafer slicing by using femtosecond laser double pulses," Optical Materials Express, p. 2450, vol. 7, no. 7 (2017). Such techniques involve forming a laser writing track by impacting silicon carbide with laser pulses to induce subsurface damage, then bonding the crystal to a locking jig and applying tensile force to cause fracturing along the subsurface damage zone. By using the laser to weaken specific areas of the material and then causing fracturing between these areas, the laser scanning time is reduced. However, there is doubt as to whether the above fracturing techniques can be applied to reliably remove thin wafers from an ingot without damaging them, and / or to industrial volumes. Another technique known in the art for causing fracturing along a laser-induced subsurface damage zone in crystalline materials involves applying ultrasonic energy to the crystalline material, but ultrasonic fracturing requires a higher degree of laser damage, and when applied to thin wafers, it may result in a higher wafer damage rate, so the reliability of obtaining thin wafers (e.g., less than 350 microns) in such a way has been questioned.

[0011] Another technique disclosed in U.S. Patent Application Publication 2010 / 0289189A1 involves applying a polymer layer (e.g., polydimethylsiloxane (PDMS)) onto a solid material and exposing the solid material and polymer layer (initially at a temperature below 300°C) to a temperature below room temperature (or below approximately -20°C). Such cooling causes the polymer layer to shrink, thereby inducing mechanical stress in the solid material, which in turn causes the material to fracture along a plane at a certain depth. PDMS is a crosslinked polymer, and its rigidity can be controlled by varying the crosslinking density (e.g., by changing the weight ratio of curing agent to prepolymer and by changing the curing conditions). The Young's modulus of PDMS has been reported to be in the range of less than approximately 4 MPa, even when efforts have been made to improve its mechanical properties. See, for example, Kim et al., J. Micromech. Microeng. 23 (2013) 095024.

[0012] Further techniques for removing thin layers of crystalline material from bulk crystals are disclosed in U.S. Patent Application Publication 2018 / 0126484A1. Laser radiation is applied to a solid-state material to create a desorption zone or a number of partial desorption zones, followed by the formation of a polymer receiving layer (e.g., PDMS), and then cooling (optionally combined with high-speed rotation) is performed to induce mechanical stress that separates the thin layer of solid-state material along the desorption zones from the rest of the material.

[0013] One drawback of these techniques utilizing polymer layer interface fracturing is that the resulting wafers may exhibit an undesirable high level of bowing. Another drawback of techniques utilizing polymer layer interface fracturing is that it requires considerable time (e.g., 30 minutes or more) to apply and cure the polymer layer on the solid material, and additional time is required to remove the polymer material from the resulting wafer. Another limitation of techniques requiring a polymer layer is that such a polymer layer may not be suitable to withstand subsequent wafer processing steps where precise dimensionality may be required.

[0014] Another technique for removing a thin layer of crystalline material from a bulk crystal is disclosed in U.S. Patent Application Publication 2018 / 0243944A1. A donor substrate is irradiated with laser radiation to indicate the crack path, a carrier substrate (i.e., having a thickness of less than 800 microns) is bonded to the donor substrate via a bonding layer, a stress generating layer (e.g., a PDMS layer) is provided on the carrier substrate, and when the stress generating layer is subjected to a thermal load (i.e., cooled with a coolant, particularly liquid nitrogen), stress is transmitted through the carrier substrate and bonding layer, generating stress in the donor substrate, resulting in the generation of a crack that propagates along the crack path, allowing the solid layer (and the carrier substrate bonded thereto) to be removed from the donor substrate. The donor substrate and carrier substrate are preferably made of the same material, but may be made of different materials. It appears that the maximum thickness of the carrier substrate must be limited in order for stress to be transmitted from the stress generating layer to the donor substrate. One limitation of the technique described above is that at least three layers must be provided to cover the donor substrate. Another limitation is that this technique appears to be limited to thermally induced cooling at very low temperatures (e.g., liquid nitrogen). Yet another limitation is that the maximum thickness of the support substrate cannot exceed 800 microns, which may limit the rigidity of the bonded assembly after separation from the donor substrate. Yet yet another limitation is that to reuse the support substrate, it is necessary to remove residual materials of different compositions (i.e., materials from the bonding layer and materials from the stress-generating layer) from both sides.

[0015] Therefore, in this field, there is still a search for improved methods for separating or removing relatively thin layers of crystalline material from a substrate, which address the problems associated with conventional methods.

[0016] [Overview of the prefecture] This disclosure relates to a method for processing crystalline materials, comprising bonding a support (e.g., a rigid support) to the surface of a crystalline material having subsurface laser damage to a non-zero depth relative to the surface, and then fracturing the crystalline material along the subsurface laser damage region, in various embodiments. Such fracturing yields a bonded assembly comprising the support and a portion of the crystalline material removed from the substrate. This fracturing is performed without requiring a separate stress-generating layer positioned to cover the support. The above steps can be repeated to form a wafer by successively removing thin layers of crystalline material from an ingot. In certain embodiments, the support may have crystalline properties. In certain embodiments, the rigid support can be bonded to the surface of the crystalline material by adhesive bonding, the rigid support may have a thickness greater than 800 microns, and the rigid support may have an elastic modulus of at least 20 GPa (or another threshold disclosed herein). In certain embodiments, the adhesive material has a glass transition temperature T greater than 25°C (or another threshold specified herein). g The crystalline material removed from the substrate is capable of embodying a wafer, and this portion is in a state where it can undergo further processing steps while being part of a bonded assembly. In certain embodiments, first and second rigid supports may be bonded to both sides of the substrate before crushing. In certain embodiments, crushing of the crystalline material may be facilitated by (i) applying a mechanical force (e.g., optionally localized to one or more locations) in close proximity to at least one edge of the support to impart a bending moment to at least a portion of the support, (ii) cooling the support if the support has a larger coefficient of thermal expansion than the crystalline material, and / or (iii) applying ultrasonic energy to the crystalline material.

[0017] In one embodiment, the disclosure relates to temporarily bonding a rigid support to the surface of a crystalline material using an intervening adhesive material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface, and the adhesive material has a glass transition temperature T greater than 25°C (or another threshold as specified herein). grelates to a method of processing a crystalline material, including temporarily joining, having a rigid carrier, an adhesive material, and a portion of the crystalline material removed from a substrate further comprising crushing the crystalline material along or adjacent to a subsurface laser damage region so as to obtain a joined assembly comprising .

[0018] In certain embodiments, the rigid carrier has a thickness greater than 800 microns, the rigid carrier has a modulus of elasticity of at least 20 GPa, and in the joined assembly, the portion of the crystalline material removed from the substrate has a thickness of at least 160 μm.

[0019] In certain embodiments, the adhesive material includes a thermoplastic material. In certain embodiments, the adhesive material has a glass transition temperature T of at least 35 °C, at least 50 °C, at least 60 °C, or another threshold specified herein. g having.

[0020] In certain embodiments, the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25 °C. In certain embodiments, the adhesive material has a modulus of elasticity of at least about 7 MPa when the adhesive material is at 25 °C.

[0021] In certain embodiments, the rigid carrier has a thickness greater than 800 microns; in certain embodiments, the rigid carrier has a modulus of elasticity of at least 20 GPa, at least 100 GPa, or another threshold specified herein; in certain embodiments, the rigid carrier includes a crystalline material.

[0022] In certain embodiments, the rigid carrier includes a first surface and a second surface opposite the first surface, the adhesive material is disposed in contact with the first surface, and the second surface contains no adhesive material and no stress generating material.

[0023] In certain embodiments, at 25°C, the coefficient of thermal expansion (CTE) of the rigid support is greater than that of the substrate. In certain embodiments, the fracturing includes cooling the rigid support to facilitate the fracturing of crystalline material along or adjacent to the subsurface laser-damaged region.

[0024] In certain embodiments, crushing includes applying ultrasonic energy to at least one of a rigid support or a substrate.

[0025] In certain embodiments, at least one of the maximum length or maximum width of at least a portion of the rigid support exceeds the corresponding maximum length or maximum width of the substrate. In certain embodiments, the substrate has a notch or flat along at least one edge of the substrate, and at least a portion of at least one edge of the rigid support extends laterally beyond the notch or flat. In certain embodiments, the crushing involves applying a mechanical force in close proximity to at least one edge of the rigid support, and the mechanical force is configured to impart a bending moment to at least a portion of the rigid support.

[0026] In certain embodiments, the crystalline material has a hexagonal structure, and the bending moment is oriented within ±5 degrees from the direction perpendicular to the <11-20> direction of the hexagonal structure.

[0027] In certain embodiments, the method further includes performing at least one additional processing step on a portion of the crystalline material while that portion of the crystalline material remains part of the joined assembly.

[0028] In certain embodiments, the method further includes bonding an additional rigid support to a second surface of the crystalline material opposite to the first surface, prior to the crushing.

[0029] In certain embodiments, the subsurface laser damage region comprises a plurality of substantially parallel subsurface laser damage lines.

[0030] In certain embodiments, the method further includes removing a portion of the crystalline material from the joined assembly.

[0031] In certain embodiments, the crystalline material includes SiC.

[0032] In certain embodiments, the method further includes roughening, textured, and / or etching (i) the first surface of the crystalline material, or (ii) at least one of the adjacent surfaces of the rigid support, before the temporary bonding of the rigid support to the first surface of the crystalline material using an adhesive material.

[0033] In certain embodiments, the crystalline material has a thickness of at least 500 microns before the crystalline material is fractured along or adjacent to the subsurface laser damage area.

[0034] In certain embodiments, a portion of the crystalline material removed from the substrate includes a self-supporting wafer configured to grow at least one epitaxial layer thereon. In certain embodiments, a portion of the crystalline material removed from the substrate includes a device wafer having at least one epitaxial layer grown thereon.

[0035] In another aspect, the present disclosure relates to a method for processing a crystalline material, comprising bonding a first crystalline support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface; bonding a second crystalline support to a second surface of the crystalline material; and, after the bonding step, crushing the crystalline material along or near the subsurface laser-damaged region so that a bonded assembly is obtained comprising the first crystalline support and a portion of the crystalline material removed from the substrate.

[0036] In certain embodiments, at least one of the first or second crystalline support has an elastic modulus of at least 100 GPa. In certain embodiments, at least one of the first or second crystalline support has a thickness greater than 800 microns.

[0037] In certain embodiments, at 25°C, the coefficient of thermal expansion (CTE) of the first crystalline support is greater than that of the substrate, and the fracturing includes cooling at least the first crystalline material support to facilitate the fracturing of the crystalline material along or adjacent to the subsurface laser-damaged region.

[0038] In certain embodiments, the fracture of a crystalline material along or adjacent to a subsurface laser-damaged area includes applying ultrasonic energy to at least one of a first crystalline support or substrate.

[0039] In certain embodiments, at least one of the maximum length or maximum width of at least a portion of the first crystal support exceeds the corresponding maximum length or maximum width of the substrate.

[0040] In certain embodiments, the substrate has a notch or flat along at least one edge of the substrate, and at least a portion of at least one edge of the first crystal support extends laterally beyond the notch or flat.

[0041] In certain embodiments, the fracture of the crystalline material along or adjacent to the subsurface laser damage region is achieved by applying a mechanical force in close proximity to at least one edge of the first crystalline support. The mechanical force is configured to impart a bending moment to at least a portion of the first crystalline support. In certain embodiments, the crystalline material has a hexagonal structure, and the bending moment is oriented within ±5 degrees from a direction perpendicular to the <11-20> direction of the hexagonal structure parallel to the surface of the substrate.

[0042] In certain embodiments, at least one of bonding a first crystal support to a first surface of a crystal material, or bonding a second crystal support to a second surface of a crystal material, includes anodic bonding.

[0043] In certain embodiments, at least one of joining a first crystal support to a first surface of a crystal material, or joining a second crystal support to a second surface of a crystal support, includes adhesive bonding using an adhesive material.

[0044] In certain embodiments, the adhesive material has a glass transition temperature T greater than 25°C. g It holds.

[0045] In certain embodiments, the first crystal support comprises a first surface and a second surface opposite to the first surface, the adhesive material is placed in contact with the first surface, and the second surface contains no adhesive material and no stress generating material.

[0046] In certain embodiments, the adhesive material includes a thermoplastic material.

[0047] In certain embodiments, the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25°C.

[0048] In certain embodiments, the adhesive material has an elastic modulus of at least about 7 MPa when the adhesive material is at 25°C.

[0049] In certain embodiments, the method further includes performing at least one additional processing step on a portion of the crystalline material while that portion of the crystalline material remains part of the joined assembly.

[0050] In certain embodiments, the subsurface laser damage region comprises a plurality of substantially parallel subsurface laser damage lines.

[0051] In certain embodiments, the method further includes removing a portion of the crystalline material from the joined assembly.

[0052] In certain embodiments, the crystalline material includes SiC.

[0053] In certain embodiments, the portion of crystalline material removed from the substrate comprises a self-supporting wafer configured to grow at least one epitaxial layer thereon. In certain embodiments, the portion of crystalline material removed from the substrate comprises a device wafer including at least one epitaxial layer grown thereon.

[0054] In another aspect, the present disclosure relates to a method for processing a crystalline material, comprising bonding a rigid support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface, and at least a portion of at least one edge of the rigid support extending laterally beyond at least one edge of the corresponding substrate. The method involves applying a bending moment to at least a portion of the rigid support and subsurface laser damage to obtain a bonded assembly comprising the rigid support and a portion of the crystalline material removed from the substrate. The method further includes applying a mechanical force in proximity to at least one edge of a rigid support in order to fracture the crystalline material along or near the damaged area.

[0055] In certain embodiments, applying a mechanical force in close proximity to at least one edge of a rigid support comprises applying the mechanical force locally at a single location in close proximity to at least one edge of the rigid support.

[0056] In certain embodiments, applying a mechanical force in proximity to at least one edge of the rigid support includes locally applying a mechanical force at a plurality of spatially isolated locations in proximity to at least one edge of the rigid support, and applying a counter-mechanical force at the central location of the rigid support.

[0057] In certain embodiments, at least a portion of at least one edge of the rigid support extends transversely across at least one edge of the corresponding substrate by at least about 100 microns, or at least about 500 microns (or any other distance threshold disclosed herein).

[0058] In certain embodiments, the substrate has a notch or flat along at least one edge of the substrate, and at least a portion of at least one edge of the rigid support extends laterally beyond the notch or flat.

[0059] In certain embodiments, the crystalline material has a hexagonal structure, and the bending moment is oriented within ±5 degrees from a direction perpendicular to the <11-20> direction of the hexagonal structure parallel to the surface of the substrate.

[0060] In certain embodiments, bonding a rigid support to the surface of a crystalline material includes adhesive bonding utilizing an adhesive material placed between the rigid support and the surface of the crystalline material.

[0061] In certain embodiments, the method further includes bonding an additional rigid support to a second surface of the crystalline material opposite the first surface before the application of mechanical force. In certain embodiments, the application of mechanical force includes applying a localized torsional force between the first rigid support and the additional rigid support in order to increase the separation between the first rigid support and the additional rigid support.

[0062] In certain embodiments, the portion of crystalline material removed from the substrate comprises a self-supporting wafer configured to grow at least one epitaxial layer thereon. In certain embodiments, the portion of crystalline material removed from the substrate comprises a device wafer including at least one epitaxial layer grown thereon.

[0063] In another aspect, the present disclosure relates to a method for processing a crystalline material, comprising bonding a rigid support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface, and the rigid support having a thickness greater than 850 microns and possessing at least one of the following features: (i) or (ii) the support comprises a crystalline support, or (ii) the support has an elastic modulus of at least 20 GPa; and crushing the crystalline material along or near the subsurface laser-damaged region to obtain a bonded assembly comprising the rigid support and a portion of the crystalline material removed from the substrate.

[0064] In certain embodiments, the rigid support includes a crystalline support. In certain embodiments, the support has an elastic modulus of at least 20 GPa, at least 100 GPa, or another threshold specified herein. In certain embodiments, bonding the rigid support to the crystalline material includes adhesive bonding utilizing an adhesive material placed between the rigid support and the crystalline material.

[0065] In certain embodiments, the adhesive material has a glass transition temperature T greater than 25°C. g In certain embodiments, the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25°C. In certain embodiments, the adhesive material has an elastic modulus of at least about 7 MPa when the adhesive material is at 25°C.

[0066] In certain embodiments, the rigid support comprises a first surface and a second surface opposite the first surface, the adhesive material is positioned in contact with the first surface, and the second surface contains no adhesive material and no stress generating material.

[0067] In certain embodiments, at 25°C, the coefficient of thermal expansion (CTE) of the rigid support is greater than that of the substrate.

[0068] In certain embodiments, the fracturing includes cooling at least a rigid support to facilitate the fracturing of crystalline material along or adjacent to the subsurface laser-damaged area.

[0069] In certain embodiments, crushing includes applying ultrasonic energy to at least one of a rigid support or a substrate.

[0070] In certain embodiments, at least one of the maximum length or maximum width of at least a portion of the rigid support exceeds the corresponding maximum length or maximum width of the substrate. In certain embodiments, the substrate has a notch or flat along at least one edge of the substrate, and at least a portion of at least one edge of the rigid support extends laterally beyond the notch or flat.

[0071] In certain embodiments, the crushing involves applying a mechanical force in close proximity to at least one edge of the rigid carrier, wherein the mechanical force is configured to impart a bending moment to at least a portion of the rigid carrier.

[0072] In certain embodiments, the crystalline material has a hexagonal structure, and the bending moment is oriented within ±5 degrees from a direction perpendicular to the <11-20> direction of the hexagonal structure.

[0073] In certain embodiments, the method further includes performing at least one additional processing step on a portion of the crystalline material while that portion of the crystalline material remains part of the joined assembly.

[0074] In certain embodiments, the method further includes bonding an additional rigid support to a second surface of the crystalline material opposite to the first surface, prior to the crushing. In certain embodiments, the method further includes removing a portion of the crystalline material from the bonded assembly.

[0075] In certain embodiments, the crystalline material includes SiC.

[0076] In certain embodiments, a portion of the crystalline material removed from the substrate comprises a self-supporting wafer configured to grow at least one epitaxial layer thereon.

[0077] In certain embodiments, a portion of the crystalline material removed from the substrate comprises a device wafer containing at least one epitaxial layer grown thereon.

[0078] In another embodiment, the present disclosure relates to grinding the edges of a thick wafer of crystalline material in order to eliminate non-perpendicular edge profiles and form perpendicular edge profiles, The wafer comprises a first surface, a second surface opposite the first surface, and at least one epitaxial layer grown on or over the first surface, wherein the first rigid support is temporarily bonded to the at least one epitaxial layer using an adhesive material disposed between the first rigid support and the at least one epitaxial layer, and the method comprises grinding and, after forming a vertical edge profile, irradiating the second surface of the thick wafer with laser radiation to form a subsurface laser damage region within the thick wafer.

[0079] In certain embodiments, the method further comprises bonding a second rigid support to a second surface of a thick wafer, and shattering the thick wafer along or near a subsurface laser-damaged region to obtain (i) a first bonded assembly comprising a first rigid support, an adhesive material, at least one epitaxial layer, and a first thin wafer separated from the thick wafer, and (ii) a second bonded assembly comprising a second rigid support and a second thin wafer separated from the thick wafer.

[0080] In certain embodiments, the method further includes bonding a first rigid support to the main surface of a crystalline material, wherein the crystalline material includes a substrate having an initial subsurface laser-damaged region at a certain depth relative to the main surface; crushing the crystalline material along or near the initial subsurface laser-damaged region so that an initial bonded assembly is obtained comprising the first rigid support and a portion of the crystalline material removed from the substrate; and removing a portion of the crystalline material from the first bonded assembly to produce a thick wafer, wherein the thick wafer includes a portion of the crystalline material.

[0081] In certain embodiments, the method further includes forming a non-perpendicular wafer edge of a thick wafer, and, after creating the non-perpendicular wafer edge, epitaxially growing at least one epitaxial layer on or covering a first surface of the thick wafer.

[0082] In certain embodiments, at least one of the first thin wafer or the second thin wafer has a thickness less than 250 microns. In certain embodiments, the crystalline material includes SiC.

[0083] In another aspect, the Disclosure relates to a method for processing a crystalline material wafer having a first surface having surface damage, wherein the first surface is bounded by an edge, and the method includes: grinding the first surface with at least one first grinding apparatus to remove a first portion of the surface damage; edge grinding the edge after grinding the first surface with at least one first grinding apparatus to form a chamfered or rounded edge profile; and grinding the first surface with at least one second grinding apparatus after edge grinding to remove a second portion of the surface damage to such an extent that the first surface is suitable for further processing by chemical mechanical planarization.

[0084] In certain embodiments, the method further includes processing the first surface by chemical planarization after grinding the first surface using at least one second grinding device, so that the first surface can be epitaxially grown on it with one or more layers of semiconductor material.

[0085] In certain embodiments, at least one first grinding apparatus comprises at least one grinding wheel having a grinding surface of less than 5000 grits (e.g., 1000 grits, 1400 grits, 2000 grits, 3000 grits, 4000 grits, etc.), and at least one second grinding apparatus comprises at least 5000 grits (e.g., 5000 grits) It comprises at least one grinding wheel having a grinding surface with a grit size of 7,000, 8,000, 10,000, 15,000, 20,000, 25,000, 30,000, etc.

[0086] In certain embodiments, grinding of a first surface using at least one first grinding device includes the removal of crystalline material with a thickness of 20 to 100 microns (e.g., 20 to 80 microns, 40 to 80 microns, 40 to 60 microns, etc.), and grinding of a second surface using at least one second grinding device includes the removal of crystalline material with a thickness of 3 to 15 microns (e.g., 5 to 10 microns).

[0087] In certain embodiments, surface damage includes laser damage and fracture damage.

[0088] In certain embodiments, the crystalline material includes a silicon carbide material, and the first surface includes a Si-terminated surface of the silicon carbide material.

[0089] In another aspect, the Disclosure relates to a method for processing a crystalline material wafer having a first surface having surface damage, wherein the first surface is bounded by an edge, and the method includes: grinding the first surface with at least one first grinding device to remove a first portion of the surface damage; grinding the first surface with at least one second grinding device to remove a second portion of the surface damage after grinding the first surface with at least one first grinding device, to a degree sufficient to make the first surface suitable for further processing by chemical mechanical planarization; forming a protective coating on the first surface after grinding the first surface with at least one second grinding device; edge grinding the edge to form a chamfered or rounded edge profile after growing sacrificial material on the first surface; and removing the protective coating from the first surface after edge grinding.

[0090] In certain embodiments, the method further includes processing the first surface by chemical planarization so that, after the removal of sacrificial material from the first surface, the first surface can be epitaxially grown on thereon.

[0091] In certain embodiments, at least one first grinding device comprises at least one grinding wheel having a grinding surface of less than 5000 grits, and at least one second grinding device comprises at least one grinding wheel having a grinding surface of at least 5000 grits.

[0092] In certain embodiments, grinding of a first surface using at least one first grinding device includes the removal of crystalline material with a thickness of 20 to 100 microns, and grinding of a second surface using at least one second grinding device includes the removal of crystalline material with a thickness of 3 to 15 microns.

[0093] In certain embodiments, the protective coating includes a photoresist.

[0094] In certain embodiments, surface damage includes laser damage and fracture damage.

[0095] In certain embodiments, the crystalline material includes a silicon carbide material, and the first surface includes a Si-terminated surface of the silicon carbide material.

[0096] In another aspect, the present disclosure relates to a crystalline material substrate supplied to a laser processing station, with a subsurface surface. The present invention relates to a material processing apparatus comprising: a laser processing station configured to form a laser damage region; a crushing station positioned to receive a crystalline material substrate processed by the laser processing station and configured to crush the crystalline material substrate along the subsurface laser damage region to form a crystalline material portion removed from the crystalline material substrate, wherein each crystalline material portion is subject to surface damage; a plurality of rough grinding stations arranged in parallel downstream of the crushing station and configured to remove a first portion of surface damage from a crystalline material portion, wherein at least the first and second rough grinding stations of the plurality are configured to operate simultaneously to remove a first portion of surface damage from different crystalline material portions; and at least one precision grinding station positioned downstream of the plurality of rough grinding stations and configured to remove a second portion of surface damage from a crystalline material portion to a degree sufficient to make at least one surface of each crystalline material portion suitable for further processing by chemical mechanical planarization.

[0097] In certain embodiments, the apparatus further comprises at least one chemical mechanical planarization station located downstream of at least one precision grinding station and configured to prepare at least one surface of each crystalline material portion for further processing by chemical mechanical planarization.

[0098] In certain embodiments, the apparatus further comprises at least one edge grinding station configured to grind the edges of each crystalline material portion in order to form a chamfered or rounded edge profile.

[0099] In certain embodiments, each rough grinding station comprises at least one grinding wheel having a grinding surface of less than 5000 grits, and at least one precision grinding station comprises at least one grinding wheel having a grinding surface of at least 5000 grits.

[0100] In certain embodiments, each rough grinding station is configured to remove crystalline material in thicknesses ranging from 20 to 100 microns from each crystalline material portion, while each precision grinding station is configured to remove crystalline material in thicknesses ranging from 3 to 15 microns from each crystalline material portion.

[0101] In certain embodiments, the laser processing station is configured to simultaneously form subsurface laser-damaged regions on multiple crystalline material substrates.

[0102] In other embodiments, any of the embodiments described above and / or any of the various distinct embodiments and features described herein may be combined to obtain additional advantages. Unless otherwise indicated herein, any of the various features and elements disclosed herein may be combined with one or more other disclosed features and elements.

[0103] Other aspects, features, and embodiments of this disclosure will be more readily apparent from the subsequent disclosure and the accompanying claims.

[0104] The accompanying drawings incorporated herein and forming part thereof illustrate several aspects of this disclosure and serve to illustrate the principles of this disclosure together with this description. [Brief explanation of the drawing]

[0105] [Figure 1] The figure includes a first frame providing a perspective view of an ingot being received by a conventional wire saw tool and subjected to a wire sawing process, and a second frame providing perspective views of a plurality of wafers obtained by the wire sawing process. [Figure 2] This is the first perspective crystal plane view showing the coordinate system for hexagonal crystals such as 4H-SiC. [Figure 3] This is a second perspective crystal plane view for hexagonal crystals, showing a microslope nonparallel to the c-plane. [Figure 4A] This is an oblique wafer orientation diagram showing the orientation of a slightly sloped wafer with respect to the c-plane. [Figure 4B] Figure 4A is a simplified cross-sectional view of a slightly sloped wafer superimposed on a portion of an ingot. [Figure 5] This is a top view of an example SiC wafer, with the superimposed arrows indicating the crystal orientation. [Figure 6A] This is a schematic side elevation view of an on-axis ingot of crystalline material. [Figure 6B] Figure 6A is a schematic side elevation view of the ingot rotated 4 degrees, with an overlapping pattern for cutting the end of the ingot. [Figure 6C] This is a schematic side elevation view of the ingot after the end has been removed to provide an end face that is not perpendicular to the c-direction. [Figure 7] This is a schematic perspective view of a movable laser tool configured to focus laser radiation into the interior of a crystalline material to create subsurface damage. [Figures 8A-8D] Figure 8D provides an exemplary laser tool movement path toward a crystalline material for forming subsurface damage within the crystalline material, and includes superimposed arrows indicating the orientation of the subsurface damage lines toward the [11-20] direction of the hexagonal structure of the crystalline material, with those lines also parallel to the surface of the crystalline material. [Figure 9]This is a schematic lateral cross-sectional view of an assembly, which includes a subsurface laser-damaged crystalline material substrate bonded to a rigid support using an intermediately placed adhesive material, and which includes an exposed adhesive lip around at least a portion of the peripheral edge of the crystalline material along the bonding surface with the rigid support. [Figure 10A] This is a schematic lateral cross-sectional view of a rigid carrier to which an adhesive material is bonded to the surface. [Figure 10B] Figure 10A is a schematic cross-sectional view of an assembly including a rigid support and adhesive material, bonded to a crystalline material substrate with a subsurface laser-damaged region adjacent to the adhesive material. The assembly is similar to that shown in Figure 9, but without the exposed adhesive lip. [Figure 10C] Figure 10B is a schematic cross-sectional view of the assembly, where the surface of the rigid support is positioned on a cooling device in the form of a water-cooled chuck. [Figure 10D] This is a schematic cross-sectional view of the majority of a crystalline substrate separated from a bonded assembly (on a water-cooled chuck), including the portion of crystalline material removed from the rigid support and substrate after fragmentation of the crystalline material along the subsurface laser-damaged region. [Figure 10E] Figure 10D is a schematic cross-sectional view of the joined assembly after removal from the water-cooled chuck, showing residual laser damage along the upper-facing surface. [Figure 10F] This is a schematic cross-sectional view of a portion of a crystalline material supported by a heated vacuum chuck, where the rigid support and adhesive material are laterally translated away from the crystalline material portion after the adhesive material has been thermally softened and released. [Figure 11] This is a schematic cross-sectional view of the assembly shown in Figure 10C, which is located on a cooling device in the form of a water-cooled chuck placed inside a tank of liquid refrigerant. [Figure 12] This is a perspective view of a cooling device, including a vacuum chuck positioned close to the bottom wall of a container designed to receive a liquid refrigerant (e.g., methanol or liquid nitrogen received from an evaporative cooling system). [Figures 13A-13E] This is a top view of a bonded assembly containing various shaped carriers bonded to a crystalline material substrate. [Figure 13F-13G] Figures 13D and 13E are schematic cross-sectional views of the joined assemblies, respectively. [Figure 14] This is a schematic cross-sectional view of a subsurface laser-damaged crystalline material bonded to a rigid support, with the crystalline material and support located in a liquid tank of an ultrasonic generator. [Figures 15A-15D] This is a schematic cross-sectional view illustrating a step for fracturing a subsurface laser-damaged crystalline material, which includes applying a mechanical force close to one edge of the support to impart a bending moment to at least a portion of the support. [Figure 16A] This is a schematic cross-sectional view of a device for fragmenting subsurface laser-damaged crystalline material bonded to a support by applying mechanical force along the edges on both sides of the support to impart bending moments to multiple parts of the support. [Figure 16B] This is a schematic cross-sectional view of a bonded assembly including a rigid support and a substrate, separated from a bulk crystalline material using the apparatus shown in Figure 16A. [Figures 17A-17D] This is a schematic cross-sectional view of the formation of subsurface laser damage on a crystalline material substrate by focusing laser radiation into the bare substrate, through the surface of a substrate supported by a carrier, through the carrier and adhesive layer into the substrate, and through the carrier into the substrate. [Figure 18A-18O] This is a schematic cross-sectional diagram illustrating the steps of a device wafer splitting process, according to which a thick wafer is crushed from a crystalline material, at least one epitaxial layer is grown on the thick wafer, and the thick wafer is crushed to form first and second bonded assemblies, each containing a carrier and a thin wafer separated from the thick wafer, the first bonded assembly containing at least one epitaxial layer as part of a functional semiconductor-based device. [Figure 19]This flowchart schematically illustrates each step of the process, from creating subsurface laser damage to bonding a rigid support to an ingot of crystalline material (e.g., SiC), then laser-cutting the bonded assembly containing the support and a portion of the crystalline material, to further processing the bonded assembly to form an epitaxial layer on a device wafer, and finally returning the ingot and rigid support to the beginning of the process. [Figure 20] Figure 19 is a schematic cross-sectional view of a portion of a crystalline material substrate showing subsurface laser damage, with superimposed dotted lines identifying expected kerf loss areas that may result from laser damage and subsequent surface processing (e.g., grinding and polishing). [Figure 21] This is a schematic diagram of a material processing apparatus according to one embodiment, which includes a laser processing station, a material crushing station, a plurality of parallel-arranged rough grinding stations, a precision grinding station, and a CMP station. [Figure 22] This is a schematic diagram of a material processing apparatus according to one embodiment, which is similar to the embodiment shown in Figure 21, but in which the edge grinding station is located between the precision grinding station and the rough grinding station. [Figure 23] This is a schematic diagram of a material processing apparatus according to one embodiment, which includes a laser processing station, a material crushing station, a plurality of parallel-arranged rough grinding stations, a precision grinding station, a surface coating station, an edge grinding station, a coating removal station, and a CMP station. [Figure 24A] This is a schematic lateral cross-sectional view of a first apparatus for holding an ingot having an end face not perpendicular to a side wall, according to one embodiment. [Figure 24B] This is a schematic lateral cross-sectional view of a second device for holding an ingot having an end face not perpendicular to a side wall, according to one embodiment. [Figure 25] This is a piecewise line graph plotting the linear thermal expansion coefficient of sapphire as a function of temperature. [Figure 26]This is a broken line graph for SiC, plotting the linear thermal expansion coefficient as a function of temperature. [Figure 27] This bar graph provides a comparison of the linear thermal expansion coefficients of various crystalline materials and metals. [Figure 28] This figure plots the elastic modulus (Young's modulus) values ​​of various materials classified into three groups: (1) metals and alloys, (2) graphite, ceramics, and semiconductors, and (3) polymers. [Modes for carrying out the invention]

[0106] In aspects of this disclosure, a support (e.g., a rigid support) is bonded to the surface of a crystalline material having subsurface laser damage to a certain depth, and the crystalline material is along the subsurface laser damage region A method for processing crystalline materials is provided, wherein a bonded assembly is provided comprising a portion of crystalline material that has been crushed and removed from a carrier and a substrate. This crushing is performed without requiring a separate stress-generating layer positioned to cover the carrier. The above steps can be repeated to form a wafer by successively removing thin layers of crystalline material from an ingot. In certain embodiments, the carrier comprises crystalline material. In certain embodiments, a rigid carrier can be bonded to the surface of the crystalline material by adhesive bonding, and the rigid carrier may have an elastic modulus of at least 20 GPa. The adhesive material has a glass transition temperature T greater than 25°C (or another threshold as specified herein). g The crystalline material removed from the substrate may be capable of embodying a wafer, and this portion is in a state where it can undergo further processing steps while being part of a joined assembly. In certain embodiments, the fragmentation of the crystalline material may be facilitated by (i) applying a mechanical force in close proximity to at least one edge of the carrier (e.g., optionally localized to one or more locations) to impart a bending moment to at least a portion of the carrier, (ii) cooling the carrier if the carrier has a larger coefficient of thermal expansion than the crystalline material, and / or (iii) applying ultrasonic energy to at least a portion of the joined assembly.

[0107] The embodiments described below represent the information necessary to enable a person skilled in the art to carry out the embodiments and indicate the best mode of carrying out the embodiments. A person skilled in the art will understand the concepts of this disclosure and recognize uses of these concepts that are not discussed in detail herein by reading the following description in conjunction with the figures in the accompanying drawings. It should be understood that these concepts and uses are within the scope of this disclosure and the accompanying claims.

[0108] Terms such as "first," "second," etc., may be used herein to describe various elements, but it should be understood that these elements are not limited by those terms. These terms are used solely to distinguish one element from another. For example, without departing from the scope of this disclosure, the first element may be called the second element, and similarly, the second element may be called the first element. As used herein, the term "and / or" includes any combination of one or more of the related enumerated things.

[0109] When an element, such as a layer, region, or substrate, is described as existing "on top of" or extending "upwards" from another element, it will be understood that the element may exist directly on or extend directly onto that other element, or there may be an intervening element. In contrast, when an element is described as existing "directly on top of" another element or extending "directly upwards" from another element, there is no intervening element. Again, when an element, such as a layer, region, or substrate, is described as existing "on top of" or extending "upwards" from another element, it will be understood that the element may exist directly on or extend directly onto that other element, or there may be an intervening element. In contrast, when an element is described as existing "directly on top of" another element or extending "directly onto" another element, there is no intervening element. Furthermore, when an element is described as being "connected" or "bonded" to another element, it will be understood that the element may be directly connected to or bonded to that other element, or there may be an intervening element. In contrast, when one element is described as being "directly connected" or "directly coupled" to another element, there is no intervening element.

[0110] In this specification, relative terms such as “below,” “up,” “top,” “upper,” “lower,” “horizontal,” or “vertical” may be used to describe the relationship between one element, layer, or region and another, as shown in the figures. It will be understood that these terms, and the terms discussed above, are intended to encompass various orientations of the device in addition to the orientation depicted in the figures.

[0111] The technical terms used herein are intended solely to describe specific embodiments and are not intended to limit the disclosure. Where used herein, the singular forms “a,” “an,” and “the” are intended to include the plural form unless the context explicitly indicates otherwise. It will be further understood that, where used herein, the terms “comprise,” “comprising,” “include,” and / or “including” indicate the presence of a mentioned feature, integer, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0112] Unless otherwise defined, all terms used herein (including technical and / or scientific terms) have the same meaning as those generally understood by those skilled in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted in a way that is consistent with their meaning in the context of this specification and the related art, and not in an idealized or overly formal sense unless expressly defined herein.

[0113] As used herein, “substrate” means a crystalline material such as an ingot or wafer that is divisible into at least two thinner portions having substantially the same lateral dimensions (e.g., diameter, or length and width) as the substrate, and has sufficient thickness to (i) be surface-processed (e.g., lapping and polishing) to support the epitaxial growth of one or more crystalline material layers, and optionally (ii) stand upright when separated from a rigid support. In certain embodiments, the substrate may have a substantially cylindrical shape and / or have a thickness substantially the same as at least one or more of the following thicknesses: 300 μm, 350 μm, 500 μm, 750 μm, 1 mm, 2 mm, 3 mm, 5 mm, 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, or more. In certain embodiments, the substrate may include a thicker wafer that is divisible into two thinner wafers. In certain embodiments, the substrate may be part of a thicker wafer on which one or more epitaxial layers (optionally coupled with one or more metal contacts) are disposed as part of a device wafer having a plurality of electrically operating devices. The device wafer may be divided according to aspects of the present disclosure to obtain a thinner device wafer and a second thinner wafer on which one or more epitaxial layers (optionally coupled with one or more metal contacts) may be subsequently formed. In certain embodiments, the substrate may have a diameter of 150 mm or more, or 200 mm or more.

[0114] The methods disclosed herein can be applied to a variety of crystalline materials, both single-crystal and polycrystalline. In certain embodiments, the methods disclosed herein can utilize cubic, hexagonal, and other crystalline structures and may apply to crystalline materials having on-axis and off-axis crystal orientations. In certain embodiments, the methods disclosed herein can be applied to semiconductor materials and / or wide-bandgap materials. Examples of materials, but not limited to, include Si, GaAs, and diamond. In certain embodiments, such methods may utilize single-crystal semiconductor materials having a hexagonal structure, such as 4H-SiC, 6H-SiC, or Group III nitride materials (e.g., GaN, AlN, InN, InGaN, AlGaN, or AlInGaN). While the various exemplary embodiments described below herein generally refer to SiC or specifically to 4H-SiC, it should be understood that any suitable crystalline material can be used. Among the various SiC polytypes, the 4H-SiC polytype is particularly attractive for power electronics devices due to its high thermal conductivity, wide bandgap, and isotropic electron mobility. Bulk SiC growth is on-axis (i.e., its This can be done without intentional angular deflection from the c-plane (suitable for forming undoped or semi-insulating materials), or off-axis (typically moving away from the growth axis, such as the c-axis, at a non-zero angle typically within a range of 0.5 to 10 degrees (or a lower range such as 2 to 6 degrees), which may be suitable for forming N-doped or highly conductive materials). The embodiments disclosed herein are applicable to on-axis and off-axis crystalline materials, as well as doped and unintentionally doped crystalline materials. The specific embodiments disclosed herein can utilize on-axis 4H-SiC, or micro-slope (off-axis) 4H-SiC with offcuts ranging from 1 to 10 degrees, or within a range of 2 to 6 degrees, or about 4 degrees.

[0115] Figures 6A and 6C schematically show on-axis and off-axis crystalline substrates in the form of ingots that may be used with the methods disclosed herein. Figure 6A is a schematic side elevation view of an on-axis ingot 15 of a crystalline material having a first end face 16 and a second end face 17 perpendicular to the c direction (i.e., the

[0001] direction of a hexagonal structure material such as 4H-SiC). Figure 6B is a schematic side elevation view of the ingot 15 of Figure 6A rotated by 4 degrees, with an overlapping pattern 18 (shown by dotted lines) for cutting and removing the ends of the ingot 15 adjacent to the end faces 16,17. Figure 6C is a schematic side elevation view of an off-axis ingot 15A formed from the ingot 15 of Figure 6B after the ends have been removed to provide new end faces 16A,17A that are not perpendicular to the c direction. When laser radiation to a first depth is supplied through the end face 16 of an ingot 15 to form subsurface laser damage, a carrier (not shown) is bonded to the end face 16, and the ingot 15 is fractured along the subsurface laser damage, after which an on-axis wafer may be formed. Conversely, when laser radiation to a first depth is supplied through the end face 16A of an off-axis ingot 15A to form subsurface laser damage, a carrier (not shown) is bonded to the end face 16A, and the ingot 15A is fractured along the subsurface laser damage, after which an off-axis wafer may be formed.

[0116] While various substrates, carriers, adhesives, and crushing techniques are disclosed herein, it should be understood that these crushing techniques can be used individually, or any combination of crushing techniques can be used simultaneously and / or sequentially, depending on the various combinations of substrates, carriers, and / or bonding methods, to achieve the desired separation.

[0117] [Carrier properties] The carriers disclosed herein are intended for use in various carrier-assisted methods for cleaving crystalline materials along subsurface laser-damaged regions. Given the various methods for cleaving (i.e., fracturing) crystalline materials disclosed herein, the desired carrier properties may vary depending on the specific fracturing method.

[0118] In various embodiments, we refer to carriers having rigid properties. In certain embodiments, at least the proximal portion, or all, of the crystalline material to be separated from the rigid carrier has an elastic modulus (also known as Young's modulus) of at least about 20 GPa, at least about 50 GPa, at least about 100 GPa, at least about 200 GPa, or at least about 300 GPa. For example, sapphire has an elastic modulus of 345 GPa. The elastic modulus is a mechanical property that serves as a measure of the rigidity of a solid material. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material in the linear modulus regime of uniaxial deformation.

[0119] We do not wish to be bound by any particular theory regarding the reasons for the improvement of the separation methods disclosed herein compared to conventional methods (e.g., using low-rigidity bonding surface materials such as PDMS or silicone and cryogenic fracturing), but rather the relatively high rigidity or stiffness When a support (i.e., a high modulus of elasticity) is bonded to the crystalline material to be fractured along the subsurface laser-damaged region, this support is thought to provide highly reproducible crystalline material separation results while simultaneously reducing wafer bowing and / or fracture. In addition to the mechanical aspects required for separation (e.g., by mechanical, CTE mismatch, and / or ultrasonic means), the support also provides mechanical support during and after separation. This is useful for post-separation processing because the separated crystalline material can be ground, polished, etc., while it remains attached to and supported by the rigid support. This avoids the need to bond the wafer to the rigid support after fracture in order to perform one or more post-separation processing steps.

[0120] When the rigid support is to be bonded to the substrate with an adhesive, in certain embodiments the support may generally include a wider range of materials, including semiconductors, inorganic materials, metals, metalloids, nonmetals, ceramics, crystalline materials (e.g., those with single-crystal or polycrystalline properties), amorphous materials, polymer materials, glass, and composite materials. In certain embodiments the support may include two or more materials bonded or joined together by various conventional means. Other materials that will be recognized by those skilled in the art may also be used.

[0121] When the rigid support is not limited to adhesive bonding to a substrate using an adhesive, a narrower range of support materials may be desirable. In certain embodiments, supports that are not necessarily adhesively bonded to the rigid support may include single-crystal materials (e.g., those with single-crystal or polycrystalline properties), semiconductor materials, ceramic materials, metalloids, inorganic materials, and composite materials.

[0122] In certain embodiments, the rigid support may have a thickness that is 1, 2, 3, 4, or 5 times greater than the depth of the subsurface laser damage of the crystalline material bonded to the rigid support. In various embodiments, the rigid support may have a thickness that is less than, equal to, or greater than the (pre-separation) thickness of the crystalline material bonded to the rigid support. In certain embodiments, the rigid support may have a thickness of at least 500 μm, greater than 800 μm, at least 850 μm, at least 900 μm, at least 1 mm, at least 1.5 mm, at least 2 mm, or at least 3 mm, with the above ranges optionally defined as upper bounds of 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. In certain embodiments, the rigid carrier may have a thickness in the range of 0.5 to 5 mm, or 0.5 to 3 mm, or 0.5 to 2 mm, or 0.8 to 5 mm, or 0.8 to 3 mm, or 0.8 to 2 mm, or 0.85 to 5 mm, or 0.9 to 5 mm, or 1 to 4 mm, or 1 to 3 mm, or 1 to 2 mm.

[0123] In certain embodiments, the rigid support may preferably have a lateral elongation (e.g., diameter, or length and width) that is at least the same as, or greater than, the corresponding dimensions of the substrate to which it is bonded. Giving the rigid support a diameter at least the same as (or greater than) the diameter of the crystalline substrate is considered to facilitate the initiation of fracturing during the various fracturing processes described herein.

[0124] In certain embodiments, at least one of the maximum lengths or widths of at least a portion of the rigid support exceeds the corresponding maximum length or width of the substrate. In certain embodiments, at least a portion of at least one edge of the rigid support may extend laterally beyond at least one edge of the corresponding substrate by at least about 100 microns, at least about 200 microns, at least about 500 microns, at least about 1 mm, or at least about 2 mm. Such a lateral overlap is particularly desirable in embodiments utilizing mechanical separation, because the overlap can receive at least a portion of a tool suitable for imparting a moment to initiate fracture to the rigid support. In certain embodiments, the substrate has a notch or along at least one edge of the substrate. The structure includes a flat, and at least a portion of the edge (or at least one edge) of the rigid support extends laterally beyond the notch or flat.

[0125] This specification discloses embodiments including single and dual carriers. As the substrate to be separated becomes thinner (e.g., less than approximately 5 mm thick), two carriers become practically necessary. The carrier located proximal to the subsurface laser damage region may be called the front carrier and is distinguished from the back carrier located distal to it. According to certain embodiments disclosed herein, the front carrier is specifically intended to facilitate the separation of crystalline material along or adjacent to the subsurface laser damage region. In contrast, the back carrier is not intended to facilitate the separation of the substrate during the shattering process. For this reason, if a CTE mismatch between the carrier and the substrate is used to facilitate the shattering of the substrate along the subsurface damage region, the back carrier may have a different CTE than the front carrier. In certain embodiments, the back carrier may have a lower CTE mismatch with respect to the substrate than the front carrier. In certain embodiments, the back carrier may be CTE matched or nearly CTE matched with respect to the substrate.

[0126] [CTE properties of support materials for crystalline materials] In certain embodiments, a rigid support having a first coefficient of thermal expansion, i.e., CTE1, is bonded or bonded to the surface of a subsurface laser-damaged crystalline material having a second coefficient of thermal expansion, i.e., CTE2, such that CTE1 > CTE2 at a desired temperature (e.g., 25°C) or over a desired temperature range. Subsequently, at least the support is cooled, causing the size of the support to shrink more rapidly than the crystalline material due to the CTE difference. Such differential shrinkage generates stress (e.g., shear stress) in the support and crystalline material, which in turn causes the crystalline material to fracture along the subsurface laser-damaged region. The inventors have extensively tested combinations of SiC substrates and sapphire supports, but those skilled in the art can easily determine other combinations of materials with CTE mismatch that are beneficial to the present disclosure.

[0127] To impart sufficient stress to the substrate, the CTE mismatched substrates according to the various embodiments disclosed herein can have rigidity as a characteristic, taking into account not only the mechanical properties of the carrier material (e.g., modulus of elasticity) but also the carrier thickness. In certain embodiments, the rigid carrier may have a thickness greater than 800 microns, at least 850 microns, at least 900 microns, at least 1 mm, at least 1.5 mm, or another threshold disclosed herein.

[0128] For various materials, the CTE can change with temperature. In the case of a rigid support having a CTE greater than that of a crystalline material, in certain embodiments, the rigid support may include a material having a CTE greater than that of a crystalline material at a desired temperature (e.g., at 25°C, 100°C, 200°C, 300°C, 0°C, and / or -100°C) or over a desired temperature range (e.g., the range from -100°C to 300°C, the range from -100°C to 200°C, the range from -100°C to 100°C, the range from 0°C to 200°C, the range from 50°C to 150°C, or any other suitable temperature range or lower range disclosed herein).

[0129] In certain embodiments, the size of the CTE of the rigid support (which will be positioned in close proximity to the subsurface damage region of the crystalline material substrate) is less than 5 times, about 4 times or less, about 3 times or less, about 2 times or less, and about 1.5 times or less than the CTE of the crystalline material substrate. In certain embodiments, the CTE of the rigid support is larger than the CTE of the crystalline material substrate by a factor ranging from about 1.25 to about 4. Some or all of the above-described CTE mismatch ratios are considered to be significantly smaller than the CTE mismatch ratios of materials used in conventional nickel-based or polymer-based spalling (separation) techniques (as described in the background section of this disclosure). For example, nickel or The CTE mismatch between nickel-containing metals (usable as carriers) and SiC (usable as crystalline materials) can be at least 5, and the CTE mismatch between polymers and SiC can be on the order of 10 to 100 or more.

[0130] While we have discussed rigid supports bonded to a crystalline material with subsurface damage and having a CTE greater than that of the crystalline material, in certain embodiments, the crystalline material with subsurface laser damage may be positioned between the first and second rigid supports. In such embodiments, the first rigid support is bonded to a first surface of the crystalline material adjacent to the subsurface laser damage, and the second rigid support is bonded to a second surface of the crystalline material distal to the subsurface laser damage and opposite the first surface. In certain embodiments, both the first and second rigid supports may have CTE values ​​greater than that of the crystalline material. In other embodiments, the first rigid support may have a CTE greater than that of the crystalline material, while the second rigid support may have a CTE less than or equal to that of the crystalline material. For example, in certain embodiments, the front support of a SiC substrate may be made of sapphire, which exhibits a large CTE mismatch with respect to SiC, while the back support may be made of SiC, which has no CTE mismatch with respect to the CTE support. Alternatively, the front support of the SiC wafer may be made of sapphire (which has a larger CTE than SiC), while the back support may be made of SiC (which does not have a CTE mismatch with the SiC wafer).

[0131] In certain embodiments that utilize CTE mismatch to facilitate fragmentation, it may be desirable to provide the minimum amount of CTE mismatch necessary to enable the desired separation in order to reduce bowing of the bonded assembly after separation (i.e., the carrier and the fragmented substrate portion bonded thereto). When using SiC substrates and sapphire carriers, bowing on the order of 200 microns has been observed for a 150 mm diameter SiC wafer. Bowing of such a level is within a range that can be easily addressed through grinding, which is due to both mechanical and grinding forces imposed by the vacuum chuck used during grinding, which plays a role in flattening the bonded assembly during processing. In contrast, excessive bowing is a major problem faced by prior art processes.

[0132] [Bonding or bonding of a support to a crystalline material] Various methods can be used to bond or bond a rigid support to the surface of a subsurface-damaged crystalline material in order to promote fracture along the subsurface damage. One method involves adhesive bonding, which may include applying an adhesive material to the proximal surface of the rigid support, making the adhesive adhere to the surface of the subsurface-laser-damaged crystalline material, and curing the adhesive (for example, by exposing the support / adhesive / crystalline material laminate to high temperature and pressure).

[0133] In certain embodiments, the bonding between a rigid carrier and a subsurface laser-damaged crystalline material is of transient properties, for example, by using an adhesive that attempts to maintain adhesion under certain conditions (e.g., room temperature) but exhibits reduced adhesion under removal conditions (e.g., a temperature sufficient to cause the adhesive to flow, and / or exposure to chemicals configured to weaken or decompose the adhesive). The use of a transient bonding medium makes it possible to bond the crystalline material to the carrier in order to allow for fracturing according to the methods disclosed herein (e.g., thermally induced fracturing at low temperatures, fracturing induced by the application of mechanical force, and / or fracturing induced by ultrasonic energy), and subsequently (optionally, after performing one or more other processing steps on the portion of the crystalline material while it is attached to the rigid carrier), the removed portion of the crystalline material bonded to the rigid carrier can be removed. The desirable properties of the adhesive material usable with the various embodiments of this disclosure may depend to some extent on the method used to induce the fracturing of the crystalline material.

[0134] Important parameters of a temporary bonding material can include (a) cohesive force, (b) adhesive strength, (c) elastic modulus, (d) glass transition temperature, and (e) thickness. A suitable temporary bonding material (e.g., a temporary adhesive) should have an appropriate combination of the above parameters to effectively transmit a separating force between the carrier and the crystal material to cause fracture along the subsurface damage region, and such an adhesive material should be easily removed, destroyed, or rendered inoperative (e.g., chemical decomposition, photodecomposition, thermal decomposition, etc.) under the specified conditions in that case, and preferably does not require excessive labor for residue removal.

[0135] Regarding the cohesive force, the desired adhesive material should have a sufficiently high cohesive force such that when subjected to the force necessary to fracture a crystal material with subsurface laser damage, the adhesive material maintains its integrity and is not broken. The adhesive strength of the adhesive material should be high enough to maintain adhesion to the surrounding material (e.g., the carrier or the crystal material) when the force required to fracture a crystal material with subsurface laser damage is applied to the adhesive material. Some adhesive materials exhibit a decrease in adhesive strength and cohesive strength at lower temperatures, and thus it is noted that it may be desirable to employ a fracturing technique involving a relatively warmer temperature in some cases.

[0136] Regarding the elastic modulus and thickness of the adhesive material, the desired adhesive material should function to appropriately transmit an appropriate amount of stress from the carrier to the crystal material without absorbing an excessive amount of the stress required to cause fracture of the crystal material by the adhesive material. This shows a tendency to prefer a relatively high-rate (i.e., relatively rigid) adhesive material that exists as a relatively thin layer to promote stress transmission while preventing stress absorption by the adhesive material.

[0137] Regarding the glass transition temperature (T g ), when utilizing the CTE mismatch between the carrier and the crystal material, T gThe smaller the value, the lower the temperature at which the support must be cooled to cause crystalline material fracture (e.g., spontaneous fracture) along the subsurface laser damage region. For example, T of adhesive material g If the temperature is 0°C and a temperature change of 70°C is desired to introduce sufficient stress, the carrier must be cooled to -70°C. Unfortunately, at very low temperatures, the adhesive material properties (including stress transfer efficiency) may deteriorate. Therefore, for use with embodiments of this disclosure, relatively higher T g Adhesive materials that exhibit a certain value may be preferable in some cases.

[0138] In certain embodiments, the adhesive material may include an adhesive suitable for high-temperature thermal compression adhesive bonding. In the case of high-temperature thermal compression bonding, a lower glass transition temperature (T) is used to avoid the bonding requirements becoming extremely high, and to prevent the assembly of separated crystalline material parts / rigid support from having excessive bow at room temperature. g ) is preferable. However, in certain embodiments, particularly when used in embodiments that utilize cooling in combination with a CTE mismatch of the substrate / support to cause crystalline material fracture, the T of the adhesive material g It shouldn't be too low, but the reason is, T g Materials with low T g This is because it can unintentionally absorb an excessive amount of stress due to CTE mismatch between the substrate and support before the transition occurs. The glass transition temperature of a polymer material is the temperature range in which the polymer transitions from a hard, glassy substance to a soft, rubbery substance.

[0139] In certain embodiments, the adhesive material may include an adhesive that can be cured with ultraviolet (UV) light. Such adhesives have a higher T gThis can be used because the adhesive bond can be formed at room temperature (e.g., about 25°C), thereby minimizing any residual stress in the resulting material separated at room temperature. In certain embodiments, UV-curable adhesive bonds can be formed above room temperature to generate a desired level of residual stress at room temperature, in embodiments that utilize cooling in combination with a CTE mismatch of the substrate / support to cause fracture of the crystalline material. In such embodiments, the support and the bonded thereto This residual stress can be desirable in some cases to reduce the temperature difference required to achieve separation due to CTE mismatch between the crystalline material portions.

[0140] Considering various adhesive bonding and / or curing processes, in certain embodiments that utilize cooling and CTE mismatch between the support and the crystalline material bonded thereto to cause fracture, the adhesive material has a glass transition temperature (T) of about 25°C, or greater than 25°C, greater than 50°C, greater than 75°C, greater than 100°C, or greater than 150°C. g ) may have. In certain embodiments, the above lower threshold can have upper thresholds of (appropriately) less than about 250°C, less than about 200°C, less than about 150°C, less than about 125°C, or less than about 100°C as boundary values. Furthermore, considering various adhesive bonding and / or curing processes, in certain embodiments, the adhesive material may have a melting point greater than 50°C, greater than 100°C, greater than 150°C, and greater than 200°C.

[0141] In certain embodiments, the adhesive material may include a thermoplastic adhesive. At least one thermoplastic adhesive has desirable mechanical and adhesive properties (relatively high T gThese adhesives may possess high elastic modulus, high cohesive force, high adhesive strength to desired carriers and crystalline materials, and hardness in a desired temperature range (e.g., close to room temperature), while still being easily removed when heated to high temperatures and / or exposed to solutions. Examples of adhesive materials that may be suitable for use with the methods disclosed herein include BrewerBOND® 220, WaferBOND® HT-10.10, and BrewerBOND® 305 thermoplastic adhesives, commercially available from Brewer Science, Inc. (Rolla, Missouri, USA), and Crystalbond® 509 thermoplastic adhesive, commercially available from Aremco Products (Valley Cottage, NY, USA). Selected thermal and mechanical properties for these adhesives are summarized in the table below.

[0142] [Table 1]

[0143] The table above shows the hardness values ​​of the first and second adhesive films provided by the manufacturer. These values ​​are typically expressed in Pascal (e.g., MPa or GPa) and established using the nano-indenter method, while the hardness value of the fourth adhesive is expressed as a durometer determined by the applicant using the Shore D method. The applicant calculated the modulus of elasticity of the fourth adhesive from the Shore D durometer value. Although there is no direct theoretical relationship between the Shore scale and Young's modulus, there are empirically derived mathematical formulas useful for conversion between them. Formulas used by the applicant (using Microsoft Excel) The formula is "EXP((Durometer+50)*0.0235-0.6403)", where Durometer refers to the Shore D durometer value. The Shore D durometer value of 73.2 for the fourth adhesive material (Crystalbond® 509) is between that of a durable truck tire (Shore D value of approximately 50) and a high-density polyethylene helmet (Shore D value of approximately 75). Furthermore, the Shore D durometer value of the fourth adhesive material is significantly higher than the Shore D durometer values ​​of 50.51 and 54.25 for the measured waxes (i.e., SHIFTWAX 7607, commercially available from Nichika Seiko Co., Ltd., and Galaxy Wax, commercially available from Galaxy Technologies, respectively), which the applicant has tested and determined to be unsuitable for inducing crystalline material fracture along the subsurface damage region using the thermally induced spontaneous separation method and the mechanically induced separation method described herein. In the wax material, separation was observed within the wax itself, and it was determined that the cohesive force was insufficient to induce fragmentation. This is consistent with online descriptions suggesting that the intermolecular attractive forces (London forces) of the wax are very weak and therefore do not hold other molecules very strongly.

[0144] Other adhesives, not limited to the thermoplastic materials described herein, may be used, as those skilled in the art will recognize after reviewing this disclosure. In certain embodiments, the adhesive material may have a glass transition temperature greater than 0°C, greater than 5°C, greater than 10°C, greater than 20°C, greater than 25°C, greater than 30°C, greater than 35°C, or any preferred higher threshold. In certain embodiments, the above lower threshold can be defined by upper thresholds of (as appropriate) less than about 250°C, less than about 200°C, less than about 150°C, less than about 125°C, or less than about 100°C. Such adhesive materials can avoid the need for cooling at extremely low temperatures (e.g., less than -75°C or less than -100°C, requiring liquid nitrogen or a similar refrigerant). When using liquid nitrogen to achieve very low temperatures below -100°C, the inventors have observed catastrophic failure of the adhesive depending on the exposure time when using the thermoplastic adhesive materials already disclosed herein. Such thermoplastic materials appear to develop cracks and crazing at very low temperatures, suggesting that extremely low temperatures (e.g., below -100°C) should be avoided.

[0145] One class of adhesive materials that requires cooling to extremely low temperatures is silicone (including PDMS), with a glass transition temperature (T) ranging from -110°C to -140°C. g ) has a range. Easy removal of silicone may be difficult. Silicone exhibits a very low modulus of elasticity above its glass transition temperature, but this modulus changes by several orders of magnitude to the GPa range when the material is cooled below its glass transition temperature. The inventors tested silicone as a bonding material between a SiC ingot and a sapphire support in an attempt to induce spontaneous fracturing along a subsurface laser damage region due to CTE mismatch by cooling the support to a temperature of approximately -110°C. Fracturing was not successfully achieved. The silicone material acted as a stress absorber during the cooling of the sapphire support, adhesive material, and SiC ingot, as well as the T of silicone. gIt has been theorized that the height of the CTE mismatch between the support and the crystalline material was insufficient when the temperature reached this level. The CTE mismatch between the sapphire support and the SiC ingot was large at room temperature, but at the low temperature of -110°C, the CTE mismatch decreased to a relatively small value. Nevertheless, even if it is hypothetically assumed that silicon exhibits effective stress transfer properties, it may still be beneficial to avoid ultra-low temperatures (e.g., liquid nitrogen temperature) when separating device wafers, as exposure to ultra-low temperatures can damage the device.

[0146] In certain embodiments, the adhesive material may include a chemically crosslinked adhesive such as epoxy. In certain embodiments, a reactive catalyst type may be used to bond a rigid support and a crystalline material substrate. A multi-component adhesive (e.g., a two-component epoxy) may be used.

[0147] A layer of adhesive material of any suitable thickness can be used, but in certain embodiments, the adhesive layer can be relatively thin (e.g., less than about 100 microns, less than about 50 microns, less than about 40 microns, less than about 30 microns, less than about 20 microns, or less than about 10 microns (the upper thresholds mentioned above are all optionally limited to lower thresholds of at least about 2 microns, at least about 5 microns, or at least about 10 microns as appropriate)). By providing a thin adhesive layer, a more direct transfer of shear stress between the rigid support and the crystalline material during crushing can be promoted, thereby reducing the force and time required to complete the crushing. However, the optimal adhesive thickness may depend on several factors, such as the elastic modulus of the adhesive, the joining method, the separation technique, etc.

[0148] Given the existence of various types of adhesives that can be used to bond a rigid support and a crystalline material, various adhesive bonding methods can be employed. In certain embodiments, thermal compression (including the application of compressive force at high temperatures) can be used. For example, a crystalline material substrate (e.g., 4HSiC) with a diameter of 150 mm fixed to a rigid support (e.g., single-crystal sapphire) with adhesive can be subjected to a force of 1800 to 3000 N while being exposed to a temperature of 180°C. In certain embodiments, compressive force can be applied while irradiating a UV-curable adhesive material between the rigid support and the crystalline material substrate with UV radiation. When a liquid or flowable bonding medium is used, in certain embodiments, when the bonding medium is compressed during bonding, it can partially climb the sidewalls of the crystalline material substrate (and along the proximal surface of the rigid support), resulting in the formation of a peripheral lip around at least part (or all) of the periphery of the crystalline material, such a peripheral lip may play a role in slightly increasing the bonding strength between the substrate and the support.

[0149] In certain embodiments, plasma-activated anodic bonding or any other suitable anodic bonding process can be used to bond the rigid support and the crystalline material substrate. Details relating to anodic bonding between the crystalline material substrate and the support are disclosed in U.S. Patent Application Publication No. 2016 / 0189954, the contents of which are incorporated herein by reference for all purposes.

[0150] In certain embodiments, to facilitate adhesion, the proximal surfaces of the rigid support and / or crystalline material may be roughened, textured, and / or surface activated in any preferred manner prior to bonding (e.g., including adhesive bonding). Examples of surface treatments that can be performed include, but are not limited to, micropatterning, mechanical abrasion, chemical etching, reactive ion etching, and plasma treatment. In certain embodiments, the rigid support may include single-crystal sapphire having a micropatterned surface.

[0151] In certain embodiments, the rigid support may include one or more features configured to facilitate debonding when it is desired to remove crystalline portions that are bonded to (already cut from) the support. Examples of such features include perforated and / or micropatterned surfaces that are located in close proximity to the proximal surface of the rigid support and / or provide holes or cavities that allow fluid communication with this proximal surface.

[0152] Various processes can be used to facilitate the debonding between the (already separated) crystalline material portion and the rigid support. In certain embodiments, thermal, mechanical, chemical, and / or optical debonding may be employed. In certain embodiments, debonding can be performed by thermal slide-off, which involves heating the adhesive-bonded assembly to a sufficient temperature while the rigid support is fixed in place (e.g., held by a vacuum chuck). This involves heating to a certain degree to soften and / or flow the adhesive material, and applying external shear stress to a portion of the crystalline material so that that portion can slide laterally from the rigid support. In certain embodiments, the adhesive may contain a UV-absorbing material, in which case irradiation of the adhesive after separation with UV radiation may be used to cause decomposition (e.g., by heating) of the adhesive between the crystalline material portion and the support in order to allow removal of the crystalline material portion. For chemical removal of the adhesive, any suitable chemical sufficient to reduce the adhesive strength and / or decompose the adhesive material may be used. When using chemical debonding, one or more access openings (e.g., perforations) may be provided in the support so that the chemical can come into contact with the adhesive material.

[0153] [Subsurface laser damage formation] In this technical field, tools for forming laser subsurface damage in crystalline materials are known and commercially available from various suppliers, such as DISCO Corporation (Tokyo, Japan). Such tools allow laser radiation to be focused into the interior of a crystalline material substrate, enabling lateral movement of the laser relative to the substrate. Typical laser damage patterns involve the formation of parallel lines spaced laterally apart from one another at a certain depth within the crystalline material substrate. Parameters such as focusing depth, laser power, translational velocity, and subsurface damage line spacing can be adjusted to impart laser damage, but adjusting certain factors involves trade-offs. Increasing the laser power tends to impart greater subsurface damage, which can improve the ease of fracturing (for example, by reducing the stress required to complete the fracturing), but greater subsurface damage results in greater surface irregularity along the surface exposed by the fracturing, which may require additional processing to smooth such a surface sufficiently for subsequent processing (for example, for integration into an electronic device). While reducing the lateral spacing between the laser damage lines below the surface can improve the ease of fragmentation, this also increases the number of translational paths between the substrate and the laser, thereby reducing the tool's throughput.

[0154] Figure 7 is a schematic perspective view of an example of a laser tool 29 configured to focus laser radiation into the interior of a crystalline material 30 to form subsurface damage 40. The crystalline material 30 includes an upper surface 32 and an opposite lower surface 34, and the subsurface damage 40 is formed inside the crystalline material 30 between the upper surface 32 and the lower surface 34. If the crystalline material contains SiC, the upper surface 32 through which the laser radiation passes and is guided may be the C-terminal surface. The laser radiation 36 is focused using a lens assembly 35 to form a focused beam 38, the focal point of which is inside the crystalline material 30. Such laser radiation 36 can be pulsed at any preferred frequency and beam intensity (typically in the range of nanoseconds, picoseconds, or femtoseconds) and has a wavelength less than the band gap of the crystalline material 30 so that the laser radiation 36 can be focused to a target depth below the surface of the crystalline material 30. At the focal point, the beam size and short pulse width result in an energy density high enough to produce a highly localized absorption that forms the subsurface damage. To adjust the focus of the concentrated beam 38 to a desired depth within the crystalline material 30, one or more properties of the lens assembly 35 can be modified. As schematically shown by the dotted line 44, a relative lateral movement (e.g., lateral translation) can be made between the lens assembly 35 and the crystalline material 30 to propagate the subsurface damage 40 in a desired direction. Such lateral movement may be repeated in various patterns, as shown in Figures 8A-8D.

[0155] Figures 8A–8D provide exemplary laser tool migration paths to a crystalline material for forming subsurface damage within the crystalline material. In certain embodiments, the laser tool portion (e.g., including a lens assembly) can be configured to move while the crystalline material remains stationary, but in other embodiments, the laser tool portion can be held in place, and the crystal The material is moved relative to the tool portion. Figure 8A shows a linear scanning motion 52 in the y direction suitable for forming a pattern of transversely spaced parallel lines of subsurface damage within a first crystalline material 50A. Figure 8B shows a linear scanning motion 52 in the y direction and a linear scanning motion 54 in the x direction suitable for forming a pattern of subsurface damage within a second crystalline material 50B in which a first group of transversely spaced parallel lines intersects a second group of transversely spaced parallel lines. Figure 8C shows a circular motion 56 within a third crystalline material 50C suitable for forming a pattern of concentric circles of subsurface damage. Figure 8D shows a linear scanning motion 56 in the y direction across (and beyond) the entire surface of the crystalline material 50D, sufficient to form parallel subsurface laser damage lines distributed across the crystalline material 50D, where these damage lines are perpendicular to the [11-20] direction of the hexagonal structure of the crystalline material 50D. If desired, other subsurface damage patterns (e.g., spiral, honeycomb, arrowhead, etc.) may be formed.

[0156] In certain embodiments, the crystalline material processing method disclosed herein may include some or all of the following items and / or steps: A second carrier wafer can be attached to the bottom surface of a crystalline material substrate (e.g., an ingot). The top surface of the crystalline material substrate is then ground or polished to an average surface roughness R of less than about 5 nanometers, for example, as preparation for a surface for transmitting laser energy. aThis is achieved. Next, laser damage can be applied to one or more desired depths within the crystalline material substrate, and the spacing and direction of the laser damage marks optionally depend on the crystal orientation of the crystalline material substrate. The first carrier is bonded to the top surface of the crystalline material substrate. The wafer to be obtained from the crystalline material substrate can be associated with an identification code or other information linked to the first carrier. Alternatively, before separation, laser marking can be applied to the wafer (not the carrier) to facilitate tracking of the wafer during and after fabrication. The crystalline material substrate is then crushed along the subsurface laser damage area (using one or more methods disclosed herein) to obtain a portion of the crystalline material substrate bonded to the first carrier and the remaining portion of the crystalline material substrate bonded to the second carrier. Both the removed portion and the remaining portion of the crystalline material substrate are smoothed and cleaned as necessary to remove any residual subsurface laser damage. The removed portion of the crystalline material substrate can be separated from the carrier. The process can then be repeated using the remaining portion of the crystalline material substrate.

[0157] Wire sawing of SiC wafers typically results in a kerf loss of at least about 250 microns per wafer, but the laser-assisted and carrier-assisted separation methods for SiC disclosed herein can achieve a kerf loss in the range of 80 to 140 microns per wafer.

[0158] Figure 9 is a schematic lateral cross-sectional view of an assembly 58, which includes a crystalline material substrate 60 with subsurface laser damage 66 bonded to a rigid support 72 by a layer of adhesive material 68 positioned in the middle. The assembly 58 is suitable for facilitating the removal of a portion of the crystalline material substrate 60 along the subsurface laser damage 66 by fracturing the crystalline material substrate 60 along the subsurface laser damage 66 using one or more of the methods disclosed herein. The crystalline material substrate 60 includes a first surface 62 adjacent to the adhesive material 68 and a second surface 64 opposite to it, with the subsurface laser damage 66 closer to the first surface 62 than to the second surface 64. The rigid support 72 also includes a first surface 73 adjacent to the adhesive material 68 and a second surface 74 opposite to the first surface 73. The adhesive material 68 extends between the first surface 62 of the crystalline substrate 60 and the first surface 73 of the rigid support 72. As shown, an exposed adhesive lip 70 is provided around at least a portion (or optionally all) of the peripheral edge of the crystalline material substrate 60 adjacent to the first surface 62 of the crystalline material substrate 60. In certain embodiments, the rigid support 72 comprises a material having a CTE greater than that of the crystalline material substrate 60 over a desired temperature range, and the crushing of the crystalline material 60 is performed by a low-temperature medium (e.g., The process can be initiated by cooling at least the rigid support 72 (or the support and substrate 60) by exposing it to a coolant or other conditions.

[0159] [Fracture of rigid supports with CTE mismatch between support / substrate due to cooling] Figures 10A to 10F illustrate steps of a semiconductor processing method according to one embodiment of the present disclosure, utilizing a rigid support with CTE mismatch bonded to a crystalline material. Figure 10A is a schematic lateral cross-sectional view of a rigid support 72 having a layer of adhesive material 68 bonded to a first surface 73 of the rigid support 72, and a second surface 74 opposite to the first surface 73. To promote better adhesion to the first surface 73, such surface may be etched (e.g., by reactive ion etching) before application of the adhesive material 68. The adhesive material 68 can be applied by any preferred method, such as spin coating, spraying, dipping, rolling, or similar.

[0160] Figure 10B is a schematic cross-sectional view of an assembly 58' including the rigid support 72 and adhesive material 68 of Figure 10A, bonded to a crystalline substrate 60 having a subsurface laser-damaged region 66. As shown, the rigid support 72 has a larger diameter or lateral extension than the crystalline substrate 60. The assembly 58' of Figure 10B is similar to that shown in Figure 9, except that it lacks the exposed adhesive lip shown in Figure 9. Continuing to refer to Figure 10B, the crystalline substrate 60 includes a first surface 62 adjacent to the adhesive material 68 and a second surface 64 on the opposite side, with the subsurface laser damage 66 being closer to the first surface 62 than to the second surface 64 of the substrate 60. The rigid support 72 also includes a first surface 73 adjacent to the adhesive material 68, with the adhesive material 68 extending between the first surface 62 of the crystalline substrate 60 and the first surface 73 of the rigid support 72. The adhesive material 68 can be cured according to the requirements of the selected bonding method (e.g., high-temperature thermal compression adhesive bonding, compression UV bonding, chemical reactive bonding, etc.). The second surface of the crystalline material substrate 60 is shown in a bare state, but in certain embodiments, a second support (not shown) may be bonded to the second surface 64 of the substrate 60 (either temporarily or permanently), in which case the second support is optionally less than or equal to the width of the substrate 60 and / or is CTE-matched with the substrate 60.

[0161] Figure 7C is a schematic cross-sectional view of the assembly of Figure 10B after the second surface 74 of the rigid support 72 is positioned on the support surface 78 of a cooling device in the form of a cooled chuck 76 configured to receive a coolant. Contact between the rigid support 72 and the cooled chuck 76 transfers heat from the rigid support 72 to the cooled chuck 76, thereby rapidly cooling the rigid support 72. During such a cooling process, the rigid support 72 shrinks laterally more than the crystalline material substrate 60, thereby exerting shear stress on the crystalline material substrate 60. Due to the presence of subsurface laser damage 66 near the adhesive layer 68 that bonds the rigid support 72 to the crystalline material substrate 60, the crystalline material is fractured along or near the subsurface laser damage region 66 by the shear stress exerted on the substrate 60.

[0162] In certain embodiments, the cooled chuck 76 has a diameter smaller than the diameter of the rigid support 72. It has been found that cooling of the assembly in Figure 10C is only necessary from the second surface 74 of the rigid support 72, and may only be necessary for the central portion of the rigid support 72 to create a temperature difference in both the lateral (i.e., from center to edge) and vertical (i.e., from crystalline material substrate 60 to rigid support 72) directions. Cooling liquid can be supplied to the cooled chuck 76, but the rigid support 72 does not need to reach liquid nitrogen temperature (-160°C) to successfully complete the thermally induced fracturing of the crystalline material substrate 60. Favorable separation results for fracturing a single SiC material supported by a crystalline sapphire substrate have been obtained using a cooled chuck maintained at -70°C. Such temperatures can be obtained from various coolants, such as liquid methanol (with a freezing point of -97°C) from a two-phase pump evaporative cooling system. Fluidity is maintained above ℃. Preferred separation results were also obtained by cooling the carrier, adhesive, and substrate in a freezer maintained at -20℃, in which case such a temperature can be maintained using a single-phase vaporization cooling system. The ability to use a single-phase vaporization cooling system or a two-phase pump-type vaporization cooling system instead of liquid nitrogen significantly reduces operating costs.

[0163] Figure 10D is a schematic cross-sectional view of the remaining portion of the crystalline material substrate 60A separated from the bonded assembly (on the water-cooled chuck 76), including the rigid support 72, the adhesive material 68, and the portion of crystalline material 80 removed from the rest of the substrate 60A, after the crystalline material has been fractured along the subsurface laser-damaged region. The remaining portion of the crystalline material substrate 60A is bounded by a new first surface 63 (with residual laser damage 66A) opposite the second surface 64. Correspondingly, the removed portion of crystalline material 80 is bounded by a new second surface 82 (with residual laser damage 66B) opposite the first surface 62. The bonded assembly 85, including the rigid support 72, the adhesive material 68, and the removed portion of crystalline material 80, can then be recovered from the cooled chuck 76.

[0164] Figure 10E is a schematic cross-sectional view of the joined assembly 85 of Figure 10D after recovery from the water-cooled chuck 76. By maintaining the portion of the removed crystalline material 80 attached to the rigid support 72, mechanical support for the portion of the removed crystalline material 80 is achieved, which is advantageous as it allows for the performance of one or more surface processing steps (e.g., grinding, polishing, etc.) on the new surface 82 to remove residual laser damage 66B and achieve a desired thickness of the crystalline material 80 (e.g., via grinding, and subsequent optional chemical mechanical planarization (CMP) steps and / or various polishing steps). In certain embodiments, laser damage removal and thinning may include a continuous grinding / polishing process with 2000-grit and 7000-grit polishing pads, as well as any suitable polishing and cleaning steps to prepare the new surface 82 for the next step (e.g., surface injection, laser marking (e.g., adjacent to the wafer flat), epitaxial layer formation, metallization, etc.).

[0165] Figure 10F is a schematic cross-sectional view of the removed portion 80 of the crystalline material supported by the upper surface 88 of a heated vacuum chuck 86, where the rigid carrier 72 and adhesive material 68 are laterally translated away from the removed portion 82 of the crystalline material after the high-temperature softening and release of the adhesive material 68. That is, the heated vacuum chuck 86 can be heated to a temperature sufficient to soften and / or flow the adhesive material 68 so that when an external shear stress is applied to the second surface 74 of the rigid carrier 72, the rigid carrier 72 can be laterally translated away from the removed portion 82 of the crystalline material that is temporarily held in place by the heated vacuum chuck 86. The operation of the heated vacuum chuck 86 may then be stopped, and the removed portion 82 of the crystalline material will embody a self-supporting material. If desired, all adhesive 68 residue can be removed and washed from the first surface 73 of the rigid carrier 72, and the rigid carrier 72 can be optionally reused for another crushing process. The removed crystalline material can then be used as a growth substrate for growing one or more epitaxial layers and conductive metal layers to form a device wafer, and the device wafer can be pulverized to form individual semiconductor devices.

[0166] In certain embodiments, a cooled chuck can be placed in a coolant tank (e.g., a tank of liquid nitrogen, or other coolant liquids such as methanol received from a pump-type evaporative cooling system) to induce thermally induced fracturing in a crystalline material substrate supported by a rigid support with appropriate CTE mismatch.

[0167] Figure 11 shows the coolant (for example, methanol received from a pump-type vaporization cooling system, Figure 10C is a schematic cross-sectional view of an assembly in the form of a cooled chuck 76A located in a cooling device (e.g., a liquid nitrogen tank) placed in a tank 79 of refrigerant. The adhesive material 68 is placed between a rigid support 72 and a crystalline material substrate 60 having a subsurface laser-damaged region 66, the subsurface laser-damaged region 66 being closer to the first surface 62 than to a second surface 64 on the opposite side of the substrate 60, and the first surface 62 being in contact with the adhesive material 68. The rigid support 72 includes a first surface 73 in contact with the adhesive material 68 and a second surface 74 on the opposite side that is positioned to be in contact with the support surface 78A of the cooled chuck 76A. The cooled chuck 76A has a diameter smaller than the diameter of the rigid support 72. The cooled chuck 76A is placed in a refrigerant tank (e.g., a liquid nitrogen tank) sufficient to lower the temperature of the cooled chuck 76A to or near the refrigerant temperature. In certain embodiments, the cooled chuck 76A and refrigerant tank 79 may be located in a closable insulating container (not shown) that can be selectively opened to allow a rigid carrier 72 having the attached adhesive material 68 and the crystalline material substrate 60 with subsurface laser damage 66 to be placed in contact with the cooled chuck 76A in order to rapidly break up a single crystalline material substrate 60 along the subsurface laser damage region 66.

[0168] Figure 12 is a perspective view of a cooling device 90, including a container 92 having cylindrical side walls 94 bounded by a bottom wall 96, on which a chuck 100 is supported by a thermally conductive spacer 98 (e.g., an aluminum rail) on the bottom wall 96. The chuck 100 is of a type that can apply sufficient suction force to the workpiece, but it is not necessary to provide vacuum suction functionality (provided by a suction port 102 configured to be connected to a vacuum source, and perforations 104 located along the upper surface 106 of the chuck) during the cooling process. During use, coolant can be supplied to the container 92 so as to contact the spacer 98, but not necessarily the entire width of the chuck 100 itself. Heat can be transferred from the chuck 100 to the coolant through the thermally conductive spacer 98. In experiments, the vacuum chuck 100 of the shown design was maintained at a temperature of around -70°C. The carrier side of the assembly 58', as shown in Figure 10B, can be placed on the upper surface 106 of the chuck so that the rigid carrier is cooled rapidly. Due to a CTE mismatch between the support and the crystalline material substrate bonded thereto, thermally induced fracturing is induced along the subsurface laser-damaged region. The inventors observed spontaneous separation of 4H-SiC at temperatures up to approximately -20°C using the thermoplastic adhesive disclosed herein, without mechanical intervention.

[0169] [Positioning of the support structure relative to the crystalline material] As previously noted, the rigid carrier may preferably have lateral dimensions (e.g., diameter, or length and width) that are at least the same as, or greater than, the corresponding dimensions of the substrate to which it is bonded, when used in conjunction with a method such as that disclosed herein. Figures 13A to 13E are top views of a bonded assembly, each containing carriers of various shapes bonded to a substrate of crystalline material, and Figures 13F and 13G provide side cross-sectional views of the bonded assembly shown in Figures 13D and 13E, respectively. Figure 13A shows a first bonded assembly 110, which contains a substantially circular substrate 112 having a flat 114 and a rounded portion 116 opposite the flat 114, the substrate 112 being bonded to a square-shaped carrier 118 that is substantially concentric with the substrate 112. Figure 13B shows a second joined assembly 120, which includes a substantially circular substrate 122 having a flat 124 and a rounded portion 126 opposite the flat 124, and the substrate 122 is bonded to a round carrier 128 that is substantially concentric with the substrate 122. Due to the presence of the flat 124, which locally reduces the diameter of the substrate 122, a larger boundary portion 129 of the carrier 128 is provided close to the flat 124. Figure 13C shows a third joined assembly 130, which includes a substantially circular substrate 132 having a flat 134 and a rounded portion 136 opposite the flat 134, and the substrate 132 is bonded to a round carrier 138 that is not concentric with the substrate 132, and the rounded portion 136 of the substrate 132 is substantially closer to the edge of the carrier 138 than the rest of the substrate 132. Even if flat 134 is not present, a larger boundary portion 139 of the carrier 138 will exist on the opposite side of the rounded portion 136. However, if flat 134 is present, the boundary portion 139 of the carrier 138 will be even larger than the boundary portion 129 shown in Figure 13B. As shown in Figure 13C, the presence of a locally enlarged boundary in one region and a locally smaller boundary in the opposite region may, in certain embodiments, be advantageous for enabling mechanical crushing of the substrate 132 bonded to the carrier 138, where the locally enlarged boundary accepts the presence of a prying tool (not shown), and the locally smaller boundary limits any overhang that might otherwise resist the tilting movement of the upper substrate (determined by the geometry of the separation device).

[0170] Figures 13D and 13F show a fourth bonded assembly 140 including a substantially circular substrate 142 having a flat 144 and a rounded portion 146 opposite the flat 144, the substrate 142 being bonded to a primarily circular carrier 148 substantially concentric with the substrate 142, the carrier 148 including a single laterally projecting tab portion 149 that provides a locally enlarged boundary close to the flat 144 of the substrate 142. The laterally projecting tab portion 149 of the carrier 148 can be aligned with the flat 144 to allow the application of localized mechanical forces such that a bending moment is applied that tends to initiate fracturing in a direction perpendicular to the flat 144. As shown in Figure 13F, a second carrier 148' of the same or different shape can be provided beneath the substrate 142, with the subsurface laser damage region 143 closer to the upper carrier 148. The presence of the protruding tab portion 149 makes it possible to insert a single prying tool (not shown) between the carriers 148, 148'.

[0171] Figures 13E and 13G show a fourth joined assembly 150, which includes a substantially circular substrate 152 having a flat 154 and a rounded portion 156 opposite the flat 154, the substrate 152 being joined to a primarily circular carrier 158 substantially concentric with the substrate 152, the carrier 158 including first laterally projecting tab portions 159A and second laterally projecting tab portions 159B on either side, which provide locally enlarged boundary areas, one of which is close to the flat 154 of the substrate 152. The laterally projecting tab portions 159A and 159B of the carrier 158 can be aligned with the flat 154 to allow the application of localized mechanical forces such that a bending moment is applied that tends to initiate fracturing in a direction perpendicular to the flat 154. As shown in Figure 13G, a second support 158' of the same or different shape can be provided beneath the substrate 152, with the subsurface laser damage region 153 being closer to the upper support 158. The presence of laterally protruding tab portions 159A and 159B allows for the insertion of a tool (not shown) between the supports 158 and 158' to apply mechanical force. Additional details regarding the application of mechanical force to initiate the fracture of the crystalline material along the subsurface laser damage region are discussed below in relation to Figures 15A–15D and 16A–16B.

[0172] Figures 13F and 13G show upper carriers 148, 158 and lower carriers 148' and 158' having lateral dimensions exceeding the lateral dimensions of substrates 142, 152, however, it should be understood that in certain embodiments, the lower carriers 148' and 158' may not be larger than the corresponding substrates 142, 152 (for example, to provide a base for resisting mechanical forces applied to the upper carriers 148, 158 when substrates 142, 152 are held by a vacuum chuck or other means).

[0173] [Fracture induced by ultrasonic energy] Another method for causing laser-induced fracture along a subsurface damage zone in a crystalline material bonded to a rigid support involves applying ultrasonic energy to the crystalline material while it is bonded. This includes applying the following. Figure 14 is a schematic cross-sectional view of an assembly 58A, which includes a crystalline material 60A with subsurface laser damage 66A' bonded to a rigid carrier 72A using an intervening adhesive material 68A, the assembly 58A being located in a liquid tank 165 of an ultrasonic generator device 160. The device further includes a container 162 located in contact with an ultrasonic generating element 164, the container 162 housing the liquid tank 165. The presence of the rigid carrier 72A can reduce or eliminate fracture of the crystalline material 60A when subjected to ultrasonic energy, especially if residual stress remains between the rigid carrier 72A and the crystalline material 60A before separation (e.g., due to CTE mismatch). Such residual stress can reduce the amount of ultrasonic energy required to initiate the fracture of the crystalline material, thereby reducing the likelihood of material fracture. In this regard, it should be noted that the combination of two or more fracturing techniques (e.g., CTE mismatch and ultrasonic-induced fracturing, or CTE mismatch and mechanical action-induced fracturing, or ultrasonic-induced and mechanical action-induced fracturing) is particularly intended. In certain embodiments, the liquid in the ultrasonic chamber can be cooled before or during the application of ultrasonic energy.

[0174] [Crushing induced by mechanical force] In certain embodiments, the fracture of a crystalline material bonded to a rigid support can be facilitated by the application of a mechanical force (e.g., localized to one or more locations, optionally) adjacent to at least one edge of the support. Such a force can impart a bending moment to at least a portion of the support, which is then transmitted to a subsurface laser-damaged region to initiate fracture.

[0175] As already noted herein, multiple crushing techniques can be used simultaneously or sequentially. In certain embodiments, CTE mismatch can be utilized in combination with mechanical force. When a large CTE mismatch exists between the substrate and the support and the temperature is sufficiently reduced, it may be necessary to use less (or zero) the required mechanical force to facilitate separation. Conversely, when the degree of CTE mismatch between the substrate and the support is low (or zero), the mechanical force required to complete the separation may be greater.

[0176] Exemplary embodiments of promoting the fracture of a crystalline material having subsurface damage bonded to a rigid support by the application of mechanical force are shown in Figures 15A-15D and 16A-16B.

[0177] Figures 15A–15D are schematic cross-sectional views illustrating the steps for fracturing a crystalline material substrate 142 with subsurface laser damage 143 by applying a mechanical force close to one edge of the carrier 148 to which the substrate 142 is bonded. These figures utilize the same bonded assembly 140 shown in Figures 13D and 13F. The bonded assembly includes a crystalline material substrate 142 having a subsurface laser damage region 143, bonded between rigid carriers 148, 148' (according to any bonding method disclosed herein). Each rigid carrier 148, 148' includes laterally projecting tab portions 149, 149' aligned with a flat 145 of the substrate 142, providing a locally enlarged boundary region defining a recess 141 into which a tool 166 can be inserted. Figure 15A shows the state before the tool 166 is inserted into the recess 141. Figure 15B shows the state after the tool 166 has been inserted into the recess, at which point the tool 166 is tilted upward, which causes a twisting force to act in a direction that promotes separation between the rigid supports 148 and 148', thereby causing a bending moment M to act on at least one support 148. In certain embodiments, the substrate 142 comprises a material having a hexagonal structure (e.g., 4H-SiC), and the bending moment M is oriented within ±5 degrees from the direction perpendicular to the [11-20] direction of the hexagonal structure (or, equivalently, within ±5 degrees from the direction parallel to the [1-100] direction). Such orientation of the bending moment M is particularly desirable when the substrate 142 comprises an off-axis (micro-slope) material. The orientation may be less important if the substrate 142 contains on-axis material. Figure 15C shows the state of the crystalline material substrate 142 after the initial fracturing along the subsurface laser-damaged region 143, in which case the upper portion 142A of the crystalline material remains bonded to the upper support 148, the lower portion 142B of the crystalline material remains bonded to the lower support 148', and the upper support 148 is tilted upward relative to the lower support 148'. Figure 15D shows the state after the fracturing is complete and the tool 166 has been removed, and such fracturing yields the first bonded assembly 168A (including the upper support 148 and the upper portion 142A of the crystalline material) separated from the second bonded assembly 168B (including the lower support 148' and the lower portion 142B of the crystalline material).

[0178] In certain embodiments, mechanical forces can be applied close to the edges on both sides of the rigid carrier to which the substrate is bonded in order to facilitate the fracture of a subsurface laser-damaged crystalline material bonded to a carrier. Figure 16A is a schematic cross-sectional view of a device 170 for fracture a crystalline material substrate 172 along a subsurface laser-damaged region 173 by applying mechanical forces along both edges of a rigid carrier 176 (bonded to a substrate 172 with adhesive material 174) to impart bending moments M1, M2 to multiple parts of the carrier 174. Beneath the substrate 172, a limiting element 171 (e.g., a vacuum chuck, a lower substrate, or other support) may be provided. The lateral elongation (e.g., diameter, or length and width) of the carrier 176 is greater than that of the substrate 172, and the carrier 176 forms laterally projecting lips 179A, 179A on both sides that are received by lifting members 175A, 175B. The central portion of the carrier 176 is restricted from being lifted by the limiting member 177 (for example, by being pressed downward). Vertical lifting forces are applied to the laterally protruding lips 179A and 179B by the lifting members 175A and 175B, and upward movement of the central portion of the carrier 176 is prevented by the limiting member 177, thereby applying bending moments M1 and M2 to both sides of the carrier 176. Such bending moments M1 and M2 are transmitted to the substrate 172 by the adhesive material 174, initiating the fracturing of the substrate 172 along the subsurface laser-damaged region 173. Subsequently, the limiting member 177 and the lifting members 175A and 175B can be released, and the fracturing can be completed. Figure 16B shows the state after the fracturing is complete, creating a joined assembly 178 including the rigid carrier 176, the adhesive material 174, and the crystalline material substrate portion 172A separated from the rest of the crystalline material 172. The exposed surfaces 173A, 173B of the crystalline material substrate portion 172A and the remaining portion of the crystalline material 172 may exhibit surface irregularities, which can be reduced by conventional surface processing steps (e.g., grinding, CMP, and / or polishing). In certain embodiments, such surface processing steps may be performed on the crystalline material substrate portion 172A, while such portion remains bonded to the rigid support 176.

[0179] Figures 15A–15D and 16A–16B provide examples of specific apparatus for facilitating the mechanical fracture of a substrate along a subsurface laser-damaged area, but it should be understood that other apparatus may be used to implement the methods disclosed herein, as those skilled in the art will recognize.

[0180] [Subsurface laser damage formation before or after carrier bonding] While forming subsurface laser damage in a crystalline substrate before bonding to a rigid support has already been described herein, in certain embodiments, a rigid support that is transparent to laser radiation of a desired wavelength may be bonded to the crystalline substrate before subsurface laser damage formation. In such embodiments, laser radiation can be transmitted through the rigid support into the interior of the crystalline substrate. Different support-substrate subsurface laser formation configurations are shown in Figures 17A to 17C. Figure 17A is a schematic diagram of laser radiation 181 focused through the surface of a bare substrate 182 to form subsurface laser damage 183 within the substrate 182, to which a rigid support may be attached after the formation of the subsurface laser damage. Figure 17B shows subsurface laser radiation within the substrate 182 Figure 17C is a schematic diagram of laser radiation 181 focused through the surface of substrate 182 to form the damage 183, substrate 182 is pre-bonded to rigid carrier 186 using adhesive material 184. Figure 17D is a schematic diagram of a laser beam 181 focused through the rigid support 186 into the substrate 182 (without an intervening adhesive layer) in order to form subsurface laser damage 183 within the substrate 182 which has been pre-bonded to the rigid support 186 (e.g., via anodic bonding or other adhesive-free means).

[0181] [Device / wafer splitting process] In certain embodiments, laser-assisted and carrier-assisted separation methods can be applied to a crystalline material after forming at least one epitaxial layer (and optionally at least one metallic layer) on it as part of a operable semiconductor-based device. Such device wafer splitting processes are particularly advantageous because they can increase the yield of crystalline material (and reduce waste) by greatly reducing the need to grind and remove the substrate material after device formation.

[0182] Figures 18A to 18O are schematic cross-sectional diagrams illustrating the steps of the device wafer splitting process, according to which a thick wafer is crushed from a crystalline material, at least one epitaxial layer is grown on the thick wafer, and the thick wafer is crushed to form first and second bonded assemblies, each containing a carrier and a thin wafer separated from the thick wafer, the first bonded assembly containing at least one epitaxial layer as part of a functional semiconductor-based device.

[0183] Figure 18A shows a crystalline material substrate 190 having a first surface 191 and a subsurface laser damage 193 positioned to a predetermined depth relative to the first surface. Figure 18B shows the substrate 190 of Figure 18A after adhesive material 194 has been added to cover the first surface 191. Figure 18C shows the item depicted in Figure 18B after a rigid carrier 196 has been bonded to the substrate 190 using the adhesive material 194. Figure 18D shows the item of Figure 18D after the substrate 190 has been fractured along the subsurface laser damage 193 (e.g., using one or more methods disclosed herein), resulting in the remaining portion of the substrate 190 separated from the bonded assembly, including the carrier 196, the adhesive material 194, and the crystalline material portion (e.g., a thick wafer) 192 removed from the substrate 190. In certain embodiments, the thick wafer 192 may have a thickness in the range of approximately 350 to 750 microns. The exposed surface 193A of the thick wafer 192 and the exposed surface 193B of the rest of the substrate 190 may exhibit surface irregularities, which can be reduced by surface processing steps such as grinding, CMP, polishing, etc. Figure 18E shows the thick wafer 192 after debonding and removal from the carrier 196, and the thick wafer 192 has a vertical edge profile. The vertical edge of the wafer is prone to fracturing during wafer handling, resulting in unacceptable edge chips and particles. To reduce the risk of breakage, the wafer edge can be edge-ground to create a non-vertical wafer edge with a chamfered or rounded edge. Figure 18F shows the thick wafer 192 supported by a turntable 198 adjacent to a rotary profile grinding tool 199 having a concave cutting surface 199A (e.g., impregnated with diamond particles) configured to impart a rounded edge profile 197 to the thick wafer 192. Figure 18G shows a thick wafer 192 after edge grinding (also known as edge profiling), which includes a rounded edge 197 that provides a boundary between the first wafer surface 201 and the second wafer surface 202. .

[0184] Figure 18H shows the items of Figure 18G after one or more epitaxial layers 203 have been grown on or covering the first surface 201 of a thick wafer 201. Due to the incompatibility of adhesives and epitaxy with high temperatures, the support shown in Figure 18D is absent. Figure 18I shows structural figure 18H after conductive (e.g., metallic) contacts 204 have been formed on the epitaxial layer 203 to form at least one operable semiconductor device, and the thick wafer 192 still has rounded edges 197. Conventionally, grinding is performed on a second surface 202 to thin the thick wafer 192 to a thickness suitable for the resulting device (e.g., 100 to 200 microns for a Schottky diode or MOSFET). The technique disclosed herein utilizes laser-assisted and support-assisted separation to reduce the need for wafer grinding and instead remove a portion of the thick wafer, surface finish it, and make it available for use in fabricating another operable semiconductor device.

[0185] The inventors found that the presence of rounded edges 197 on the thick wafer 192 hinders the control of the formation of subsurface laser damage adjacent to the edges 197, because the rounded profile negatively affects the control of laser focus and depth. To address this problem, the rounded edges 197 of the thick wafer 192 can be removed before further laser processing. Figure 18J shows the structure of Figure 18I being ground with an edge grinder 206 to remove the rounded edges 197 and to provide a substantially perpendicular edge 205 extending between the first surface 201 and the second surface 202 of the thick wafer 192, with the epitaxial layer 203 and contact 204 positioned on the first surface 201.

[0186] Figure 18K shows the structure of Figure 18J after adding a temporary adhesive material 207 covering the first surface 201, epitaxial layer 203, and contact 204 of the thick wafer 192 in preparation for receiving and bonding the first carrier. Figure 18L shows the structure of Figure 18K after adding the first carrier 208 to cover the temporary adhesive material 207 and after forming subsurface laser damage 209 within the thick wafer 192 by irradiating focused laser radiation through the second surface 202 of the thick wafer 192. Figure 18M shows the structure of Figure 18L after bonding the second rigid carrier 210 to the second surface 202 of the thick wafer 192 in proximity to the subsurface laser damage 209. For separation purposes, the second rigid carrier 210 acts as a front carrier intended to remove a portion (i.e., a layer) of the thick wafer 192.

[0187] Figure 18N shows the items of Figure 18M after the thick wafer 192 has been fractured along subsurface laser damage 209 by applying at least one of the fracturing steps disclosed herein to obtain a first bonded secondary assembly 212A and a second bonded secondary assembly 212B. The first bonded secondary assembly 212A includes a first thin wafer portion 192A (separated from the thick wafer 192 in Figure 18M), an epitaxial layer 203, contacts 204, a temporary adhesive material, and a first carrier 208. The second bonded secondary assembly 212B includes a second thin wafer portion 192B (separated from the thick wafer 192 in Figure 18M), and a second carrier 210. The exposed surfaces 209A of the thin wafer portion 192A and 209B of the thin wafer portion 192B may exhibit surface irregularities due to laser damage and / or fracturing, but these can be reduced by conventional surface processing steps (e.g., grinding, CMP, and / or polishing). Figure 18O shows a responsive semiconductor device 214 obtained from the first bonded subassembly 212A by removing the temporary adhesive 207 and the first carrier 208. Such a figure also shows the second thin wafer portion 192B being prepared for further processing (e.g., epitaxial growth). The second thin wafer portion 192B after the second carrier 210 has been removed in preparation.

[0188] [Examples of methods including the reuse of carrier wafers] Figure 19 is a flowchart illustrating the steps of the method according to this disclosure. Starting from the upper left, the laser 216 can focus its laser radiation below the first surface 222 of a thick crystalline material substrate 220 (e.g., a SiC ingot) to create a subsurface laser damage region 218. If the substrate 220 is a SiC material, the laser radiation is directed to the C-terminal surface of the SiC substrate 220. Subsequently, a carrier wafer 224 can be bonded to the first surface 222 of the crystalline material substrate 220, the carrier wafer 224 including a first surface 226 (proximal to the first surface 222 of the substrate 220) and a second surface 228 opposite the first surface 226 of the carrier wafer 224. Such bonding between the carrier wafer 224 and the crystalline material substrate 220 can be performed by any of the methods disclosed herein, such as adhesive bonding or anodic bonding. Subsequently, the crushing steps disclosed herein (e.g., cooling of the CTE mismatched carrier, application of ultrasonic energy, and / or application of mechanical force) are applied to crush the crystalline material 220 along the subsurface laser-damaged region 218 to separate the crystalline material portion 230, which is fixed to the carrier wafer 224, from the rest of the crystalline material substrate 220A. The newly exposed surface 232A of the rest of the crystalline material substrate 220A with residual laser damage is smoothed, cleaned, and returned to the beginning of the process (upper left in Figure 19). The newly exposed surface 234 of the removed crystalline material 230 is also smoothed while still attached to the carrier 224. Subsequently, the carrier wafer 224 can be separated from the removed portion of the crystalline material 230, and one or more layers can be epitaxially grown on the crystalline material 230 to form an epitaxial device 230', while the carrier wafer 224 is cleaned and returned to the beginning of the process (upper left of Figure 19) to allow for the removal of another relatively thin section of the crystalline material substrate 220.

[0189] Figure 20 is a schematic cross-sectional view of a portion of the crystalline material substrate (e.g., SiC ingot) 220 of Figure 19 showing subsurface laser damage 218, with the expected kerf-loss material region 240 identified by superimposed dotted lines. The expected kerf-loss material region 240 includes the laser damage 218, and further material 234 that will be mechanically removed (e.g., by grinding and polishing) from the underside 238 (e.g., Si-terminated surface) of the crystalline material portion 230 (e.g., SiC wafer) that will be separated from the substrate 220, and further material 236 that will be mechanically removed (e.g., by grinding and polishing) from the upper surface 232A (e.g., C-terminated surface) of the remaining portion 220A of the substrate 220. The underside 238 of the crystalline material portion 230 is opposite its upper surface 222. In certain embodiments, the entire kerf-loss material region may have a thickness in the range of 80 to 120 microns so that the SiC provides a substrate top surface 232A and a wafer bottom surface 238 sufficient for further processing.

[0190] [Material processing using multiple grinding stations / steps] In certain embodiments, crystalline materials subjected to laser processing and crushing can be further processed by a plurality of surface grinding steps to remove subsurface damage and edge grinding to impart a chamfered or rounded edge profile, in which case the order of the grinding steps is selected to minimize the possibility of imparting additional surface damage and to prepare the crystalline material wafer for chemical mechanical planarization, and / or a protective surface coating is employed. Such steps can be performed, for example, using a material processing apparatus according to the embodiments disclosed herein, in which case the exemplary apparatus includes a laser processing station, a crushing station, a plurality of rough grinding stations arranged in parallel downstream of the crushing station, and at least one fine grinding station located downstream of the rough grinding stations. When processing wafers cut by wire sawing, it is common to perform edge grinding before surface grinding or polishing to remove surface damage from the wire sawing. However, laser damage The inventors have found that combining edge grinding of a substrate (e.g., a wafer) with fracture damage increases the likelihood of crack formation in the substrate. While they do not wish to be bound by any specific theory regarding the reason for this phenomenon, it is believed that when edge grinding is performed before any surface treatment (grinding and / or polishing), the exposed cleavage planes resulting from surface fracture make the surface more susceptible to cracking. For this reason, it has been found that performing at least some surface treatment (e.g., grinding and / or polishing) before edge grinding is beneficial.

[0191] The rough grinding step (i.e., for removing laser and crushing damage along the crushed surface of the substrate portion and bulk substrate) has been found to take significantly longer to complete than the preceding laser processing and crushing steps, and significantly longer than the subsequent precision grinding step. For this reason, multiple rough grinding stations are provided in parallel to eliminate the bottleneck in the production of multiple wafers from bulk crystalline material (e.g., ingots). In certain embodiments, robotic handlers for controlling the loading and unloading of substrate portions may be located upstream and downstream of the multiple rough grinding stations. In certain embodiments, a carrier bonding station may be provided between the laser processing station and the crushing station, and a carrier removal station may be provided (either directly or indirectly) upstream of the edge grinding station. The carrier may preferably remain bonded to the substrate portion for at least some surface grinding steps to reduce the possibility of breakage, especially for thin substrate portions (e.g., wafers), but it is preferable that the carrier be removed before edge grinding (or before coating the wafer with a protective coating before edge grinding).

[0192] In certain embodiments, the carrier bonding station may use a carrier pre-coated with a temporary bonding medium, align and press the carrier against a substrate surface, and expose the bonding medium to the necessary conditions (e.g., heat and pressure) for bonding between the carrier and the substrate. Alternatively, the carrier bonding station may include a coating station that can be used to coat the carrier or substrate as required.

[0193] Figure 21 is a schematic diagram of a material processing apparatus 300 according to one embodiment, which includes a laser processing station 302, a carrier bonding station 303, a material crushing station 304, a plurality of parallel-arranged rough grinding stations 308A, 308B, a precision grinding station 312, a carrier removal station 313, and a CMP station 314. The laser processing station 302 includes at least one laser and a holder for at least one substrate arranged to receive at least one laser beam for forming subsurface laser damage in a crystalline material (e.g., an ingot). The carrier bonding station 303 is configured to bond the crystalline material (having subsurface laser damage) to at least one rigid carrier. The crushing station 304 is arranged to receive one or more assemblies (each containing a substrate bonded to a rigid carrier) from the carrier bonding station 303 and to crush at least one substrate along the subsurface laser damage area to remove substrate portions (which may be similar to wafers bonded to a carrier). Downstream of the crushing station 304, a first rough grinding station 308A and a second rough grinding station 308B are arranged in parallel, and a first robot handler 306 is provided to alternately feed the substrate portion (as part of the joined assembly) received from the crushing station 304 to either the first rough grinding station 308A or the second rough grinding station 308B. Downstream of the first rough grinding station 308A and the second rough grinding station 308B, a second robot handler 310 is provided to feed the roughly ground substrate portion (as part of the joined assembly) to the precision grinding station 312. Downstream of the precision grinding station 312, a carrier removal station 313 is provided, which separates the ground substrate portion from the carrier. It plays a role in this. Downstream of the carrier removal station 313 is a chemical mechanical planarization (CMP) station 314 for preparing the substrate portion for further processing such as cleaning and epitaxial growth. The CMP station 314 functions to remove damage remaining after precision grinding, while precision grinding itself removes damage remaining after rough grinding. In certain embodiments, each rough grinding station 308A, 308B comprises at least one grinding wheel having a grinding surface of less than 5000 grits, and the precision grinding station 312 comprises at least one grinding wheel having a grinding surface of at least 5000 grits. In certain embodiments, each rough grinding station 308A, 308B is configured to remove crystalline material with a thickness of 20 to 100 microns from a crystalline material portion (e.g., a wafer), and the precision grinding station 312 is configured to remove crystalline material with a thickness of 3 to 15 microns. In certain embodiments, each rough grinding station 308A, 308B and / or precision grinding station 312 may include multiple grinding substations, each substation having a grinding wheel with a different grit.

[0194] The apparatus according to the embodiment shown in Figure 21 can be modified to accommodate edge grinding for imparting rounded or chamfered edge profiles to crystalline substrate portions such as wafers. Such edge profiles reduce the risk of wafer edge breakage. Edge grinding may not be performed if the substrate portion is bonded to a carrier, and therefore the carrier removal station can be located (either directly or indirectly) upstream of the edge grinding station.

[0195] Figure 22 shows a material processing apparatus 320 according to one embodiment, which is similar to the embodiment in Figure 21 but incorporates an edge grinding station 332. The material processing apparatus 320 includes a laser processing station 322, a carrier bonding station 323, a material crushing station 324, a first robot handler 326, a plurality of parallel-arranged rough grinding stations 328A, 328B, a second robot handler 328, a carrier removal station 331, an edge grinding station 332, a precision grinding station 334, and a CMP station 336. The exemplary edge grinding station 332 may be positioned to grip the wafer between the upper and lower gripping portions of a turntable positioned in close proximity to a rotary grinding tool having a concave dueling surface (for example, as shown in Figure 18F). Gripping the wafer in this manner may cause undesirable damage to the wafer surface (e.g., the Si-terminated surface of a SiC wafer). For this reason, the edge grinding station 332 shown in Figure 22 is positioned upstream of the precision grinding station 334 so that any surface damage inflicted by the edge grinding station 332 can be removed by the precision grinding station 334. The precision grinding station 334 removes only a small thickness of the wafer, which may alter the rounded or chamfered edge profile created by the edge grinding station 332, but a sufficient amount of the rounded or chamfered edge profile remains to prevent wafer edge fracture.

[0196] A method for processing a crystalline material wafer having a first surface having surface damage can be performed using the apparatus 320 shown in Figure 22, wherein the first surface is bounded by an edge. The method includes grinding the first surface using at least one first grinding apparatus to remove a first portion of the surface damage; edge grinding the edge after grinding the first surface using at least one first grinding apparatus to form a chamfered or rounded edge profile; and grinding the first surface using at least one second grinding apparatus after edge grinding to remove a second portion of the surface damage to the extent that the first surface is suitable for further processing by chemical mechanical planarization. In a particular embodiment, the first grinding apparatus is a rough grinding station 328A, 3 This can be implemented in 28B, and edge grinding can be performed by an edge grinding station 332, and a second grinding device can be implemented in a precision grinding station 312. In certain embodiments, a carrier removal step can be performed after grinding the first surface using at least one first grinding device, and before edge grinding to form a chamfered or rounded edge profile.

[0197] In certain embodiments, protective surface coatings may be employed to reduce the likelihood of inflicting additional surface damage during edge grinding and to prepare the crystalline material wafer for chemical planarization. Such surface coatings may include photoresists or any other suitable coating materials and can be applied before edge grinding and removed after edge grinding.

[0198] Figure 23 is a schematic diagram of a material processing apparatus 340 according to one embodiment, which is similar to the embodiment in Figure 21, but with a surface coating station 354 incorporated between the precision grinding station 352 and the edge grinding station 356, and a coating removal station 358 incorporated between the edge grinding station 356 and the CMP station 360. The material processing apparatus 340 further includes a laser processing station 342, a material crushing station 344, a first robotic handler 346, a plurality of parallel-arranged rough grinding stations 348A, 348B, and a second robotic handler 348 upstream of the precision grinding station 352. The coating station 354 may be configured to apply a protective coating (e.g., photoresist) by methods such as spin coating, dip coating, spray coating, or similar. The protective coating should be thick and robust enough to absorb any damage that may be inflicted by the edge grinding station 365. In the case of SiC wafers, the Si-terminated surface may be coated with a protective coating because the Si-terminated surface is typically the surface on which epitaxial growth takes place. The coating removal station 358 may be configured to remove the coating by chemical, thermal, and / or mechanical means.

[0199] A method for processing a crystalline material wafer having a first surface having surface damage, wherein the first surface is bounded by an edge, can be performed using the apparatus 340 shown in Figure 23. The method includes grinding the first surface using at least one first grinding apparatus (e.g., rough grinding stations 348A, 348B) to remove a first portion of the surface damage; then grinding the first surface using at least one second grinding apparatus (e.g., precision grinding station 352) to remove a second portion of the surface damage to the extent sufficient to make the first surface suitable for further processing by chemical mechanical planarization; then forming a protective coating on the first surface (e.g., using a surface coating station 354); then grinding the edges (e.g., using an edge grinding station 356) to form a chamfered or rounded edge profile; and then removing the protective coating from the first surface (e.g., using a coating removal station). The first surface can then be processed by chemical planarization (e.g., by a CMP station 360), which prepares the first surface (e.g., the Si-terminated surface of the wafer) for subsequent processing such as surface cleaning and epitaxial growth.

[0200] In certain embodiments, the gripping device may be configured to hold an ingot having an end face that is not perpendicular to the side wall in order to enable laser processing of the end face to form subsurface damage. In certain embodiments, the gripping effector may be configured to follow an inclined side wall having a circular cross-section when viewed from above. In certain embodiments, the gripping effector may include a joint to allow the gripping effector to follow the inclined side wall.

[0201] Figure 24A is a schematic lateral cross-sectional view of a first gripping device 362 for holding an ingot 364 having end faces 366, 368 that are not perpendicular to the side wall 370, according to one embodiment. The upper end face 366 is positioned horizontally to receive a laser beam 376. A carrier 372 is attached to the lower end face 368, and a chuck 374 (e.g., a vacuum chuck) may hold the carrier 372. A gripping effector 378 having a non-perpendicular surface is provided for gripping the side wall 370 of the ingot 364, and the gripping effector 378 is positioned at angles A1, A2 that are not perpendicular to a horizontal operating rod 380. When the ingot 364 is held using the gripping device 362 as shown (e.g., near its bottom), the upper end face 366 and the upper portion of the side wall 370 become available for processing using the method disclosed herein.

[0202] Figure 24B is a schematic lateral cross-sectional view of a second gripping device 362' for holding an ingot 364' having end faces 366' and 368' that are not perpendicular to the side wall 370', according to one embodiment. The upper end face 366' is positioned horizontally to receive a laser beam 376, while a carrier 372' is attached to the lower end face 368', and the carrier 372' may be held by a chuck 374'. A gripping effector 378' having a non-perpendicular surface is provided to grip the side wall 370' of the ingot 364', and the gripping effector 378' is positioned at angles A1 and A2 that are not perpendicular to a horizontal operating rod 380'. A pivot joint 382' is provided between the operating rod 380' and the gripping effector 378', thereby facilitating automatic alignment between the gripping effector 378' and the side wall 370' of the ingot 364'.

[0203] Figure 25 is a line graph for sapphire plotting the linear thermal expansion coefficient as a function of temperature, with the plot of CTE parallel to the C-axis and the plot of CTE perpendicular to the C-axis of sapphire superimposed. Figure 26 is a line graph for SiC plotting the linear thermal expansion coefficient as a function of temperature, with the plot of CTE along the c-axis and the a-axis of SiC superimposed. Comparing Figures 25 and 26, the axial variation in CTE exhibited by sapphire (in Figure 25) is greater than that of SiC. It can be seen that sapphire has a larger CTE than SiC over a wide temperature range.

[0204] Figure 27 is a bar graph providing a comparison of the linear thermal expansion coefficients of various crystalline materials and metals, presumably observed at 25°C. It can be seen that the CTE of SiC is approximately 3, while the CTE of sapphire is approximately 7 (about 2.3 times larger). Although not shown in Figure 27, the CTE of PDMS polymer is 3.0 x 10⁻¹⁰ over a temperature range from -55 to 150°C. -4 It has been separately confirmed that it is / C. -6 The CTE value for / C is two orders of magnitude larger.

[0205] Figure 28 plots the elastic modulus (Young's modulus) values ​​of various materials classified into three groups: (1) metals and alloys, (2) graphite, ceramics, and semiconductors, and (3) polymers. Elastic modulus is a mechanical property that measures the rigidity of solid materials in the linear modulus regime of uniaxial deformation, and it defines the relationship between stress and strain in a material. As can be seen in Figure 28, metals and semiconductors exhibit elastic modulus values ​​at least an order of magnitude larger than those of polymers. Although the exact values ​​are not shown in Figure 28, it has been separately confirmed that sapphire has an elastic modulus of 345 GPa, while nickel has an elastic modulus of 190 GPa. In contrast, the polymer PDMS has an elastic modulus range between 0.57 MPa and 3.7 MPa, and this variation depends linearly on the amount of crosslinking agent present in the polymer.

[0206] The following embodiments disclose further, non-limiting embodiments of the present disclosure.

[0207] [Example 1] A single-crystal SiC substrate with a thickness of 640 μm and a diameter of 150 mm was used as the starting material. A 10 μm thick SiC epitaxial layer was grown on the first surface of the SiC substrate to obtain a 650 μm SiC structure. Laser radiation was focused to a depth of 240 μm from the SiC surface to create multiple substantially parallel subsurface laser damage lines at that depth. A single-crystal sapphire support was bonded to the second surface opposite the SiC substrate using WaferBOND® HT-10.10 thermoplastic adhesive (Brewer Science, Inc., Rolla, Missouri, USA), and adhesive curing was completed by applying a thermal compression process (including the application of a force of 1800 N and maintenance at 180°C). The sapphire support was brought into contact with a vacuum chuck cooled with liquid nitrogen and maintained at -70°C to perform thermal-induced fracturing. By crushing, a 240 μm thick portion of SiC (forming a bonded assembly) was obtained, which was fixed to a sapphire support, separated from a 410 μm thick portion of SiC. Residual laser damage on the 410 μm thick portion of SiC was removed by lapping and CMP to obtain a 350 μm thick SiC wafer ready for epitaxy. Separately, lapping and CMP were also performed on the bonded assembly containing the 240 μm thick SiC to reduce the thickness of this SiC to 180 μm. Subsequently, the support was removed from the bonded assembly, which involved a thermal slide-off process in which the support was brought into contact with a heated vacuum chuck to soften the adhesive, while lateral force was applied to the SiC. The resulting 180 μm thick SiC wafer has a SiC epitaxial layer at this point and is suitable for the fabrication of MOSFETs. As a result of this process, a 350 μm thick SiC wafer that is ready for epitaxy formation and a 180 μm thick SiC wafer that has a SiC epitaxial layer on its surface at this point are formed from a 640-micron thick SiC substrate used as the starting material.

[0208] [Example 2] A single-crystal SiC substrate with a thickness of 570 μm and a diameter of 150 mm was used as the starting material. A 2 μm thick SiC epitaxial layer was grown on the first surface of the SiC substrate to obtain a 572 μm SiC structure. Laser radiation was focused to a depth of 160 μm from the SiC surface to create multiple substantially parallel subsurface laser damage lines at that depth. Using the same bonding process as in Example 1, a single-crystal sapphire support was bonded to the second surface opposite the SiC substrate. The sapphire support was brought into contact with a vacuum chuck cooled with liquid nitrogen and maintained at -70°C to induce thermal fracturing. Fracturing yielded a 160 μm thick portion of SiC (forming a bonded assembly) fixed to the sapphire support, separated from a 412 μm thick portion of SiC. Residual laser damage on the 412 μm thick portion of SiC was removed by lapping and CMP to obtain a 350 μm thick SiC wafer ready for epitaxy. Separately, a bonded assembly containing 160 μm thick SiC was also subjected to lapping and CMP to reduce the thickness of this SiC to 100 μm. Subsequently, the support material was removed from the bonded assembly, which involved a thermal slide-off process in which the support material was brought into contact with a heated vacuum chuck to soften the adhesive, while a lateral force was applied to the SiC. The resulting 100 μm thick SiC wafer has a SiC epitaxial layer at this point and is suitable for the fabrication of RF devices. As a result of this process, a 350 μm thick SiC wafer with an epitaxy-ready layer and a 100 μm thick SiC wafer with a SiC epitaxial layer on its surface at this point are formed from a 570-micron thick SiC substrate used as the starting material.

[0209] [Example 3] As a starting material for producing SiC wafers with a thickness of 355 microns, a single-crystal SiC substrate (ingot) with a diameter of 150 mm and a thickness of over 10 mm is used. To form subsurface laser damage, laser radiation is directed through the C-terminated upper surface of the SiC substrate. A sapphire support is bonded to the upper surface of the SiC substrate using a thermoplastic adhesive material disclosed herein, and thermal-induced fracturing is performed to separate the upper (wafer) portion of SiC from the rest of the ingot. Both the Si-terminated surface of the separated wafer portion and the C-terminated surface of the rest of the ingot are roughly ground using a 2000-grit grinding wheel (e.g., a metal, glassy, ​​or resin-bonded grinding wheel) to remove all visible laser and fracturing damage. Subsequently, both the Si-terminated surface of the separated wafer portion and the C-terminated surface of the rest of the ingot are fine-ground to 7000 or more grits (e.g., up to 30,000 grits or more) (e.g., using a glassy grinding surface) to obtain a smoother surface, preferably with an average roughness (Ra) of less than 4 nm, more preferably in the range of 1-2 nmRa. The remaining portion of the ingot requires a smooth surface to avoid any impact on subsequent laser processing. The wafer is prepared for CMP and smooth enough to minimize the amount of CMP removal required, as CMP is generally a more expensive process. Typical material removal during precision grinding to remove all residual subsurface damage from rough grinding and any remaining laser damage (both visible and invisible to the naked eye) may be in the range of 5 to 10 microns. The remaining portion of the ingot is then returned to the laser for further processing, and the wafer is edge-ground and subjected to chemical mechanical planarization (CMP) to prepare it for epitaxial growth. Edge grinding can be performed between rough and precision grinding to avoid all risk of scratching the precision-ground Si surface. Material removal during CMP may be in the range of approximately 2 microns. The total material consumed from the substrate (ingot) may be less than 475 microns. If the final wafer thickness is 355 microns, the kerf loss is less than 120 microns.

[0210] Possible technical benefits obtained by one or more embodiments of the present disclosure include: reduced crystalline material kerf loss compared to wire sawing; reduced processing time and increased throughput of crystalline material wafers and resulting devices compared to wire sawing; reduced bowing of the resulting semiconductor wafers compared to conventional post-laser shredding methods; reduced need for liquid nitrogen consumption compared to conventional post-laser shredding methods; and improved ability to obtain crystalline thin layers with reduced need for thinning by abrasion (e.g., grinding).

[0211] Unless otherwise indicated herein, any of the various features and elements disclosed herein may be combined with one or more other disclosed features and elements.

[0212] Those skilled in the art will recognize improvements and modifications to preferred embodiments of this disclosure. All such improvements and modifications are deemed to fall within the scope of the concepts disclosed herein and in the following claims.

Claims

1. The method involves temporarily bonding a rigid support to a first surface of a crystalline material using an interposed adhesive material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface, and the adhesive material has a glass transition temperature T greater than 25°C. ｇ Having, to temporarily join, The crystalline material is fractured along or near the subsurface laser-damaged region so that a bonded assembly comprising the rigid carrier, the adhesive material, and the portion of the crystalline material removed from the substrate is obtained. A method for processing crystalline materials, including the method described above.

2. The rigid support has a thickness greater than 800 microns. The rigid carrier has an elastic modulus of at least 20 GPa, In the joined assembly, the portion of the crystalline material removed from the substrate has a thickness of at least 160 μm. The method for processing a crystalline material according to claim 1.

3. The method for processing a crystalline material according to claim 1 or 2, wherein the adhesive material includes a thermoplastic material.

4. The adhesive material has a glass transition temperature of at least 35°C T ｇ A method for processing a crystalline material according to any one of claims 1 to 3, comprising:

5. The method for processing a crystalline material according to any one of claims 1 to 4, wherein the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25°C.

6. The method for processing a crystalline material according to any one of claims 1 to 5, wherein the adhesive material has a thickness of less than approximately 50 microns.

7. The rigid support comprises a first surface and a second surface opposite to the first surface. The adhesive material is positioned in contact with the first surface. The second surface contains no adhesive material and no stress generating material. A method for processing crystalline material according to any one of claims 1 to 6.

8. The method for processing a crystalline material according to any one of claims 1 to 7, wherein the rigid support comprises a crystalline material.

9. At 25°C, the coefficient of thermal expansion (CTE) of the rigid support is greater than that of the substrate, and the fracturing includes cooling the rigid support to facilitate the fracturing of the crystalline material along or adjacent to the subsurface laser damage region. A method for processing a crystalline material according to any one of claims 1 to 8.

10. The crystalline material processing method according to any one of claims 1 to 8, wherein the crushing comprises applying ultrasonic energy to at least one of the rigid carrier or the substrate.

11. A method for processing a crystalline material according to any one of claims 1 to 8, wherein at least one of the maximum length or maximum width of at least a portion of the rigid carrier exceeds the corresponding maximum length or maximum width of the substrate, the crushing comprises applying a mechanical force in close proximity to at least one edge of the rigid carrier, and the mechanical force is configured to impart a bending moment to at least a portion of the rigid carrier.

12. A method for processing a crystalline material according to any one of claims 1 to 11, further comprising performing at least one additional processing step on the portion of the crystalline material while the portion of the crystalline material remains part of the joined assembly.

13. A method for processing a crystalline material according to any one of claims 1 to 8, further comprising bonding an additional rigid support to the second surface of the crystalline material opposite to the first surface before the crushing.

14. The crystalline material processing method according to any one of claims 1 to 13, wherein the crystalline material includes SiC.

15. A method for processing a crystalline material according to any one of claims 1 to 14, further comprising (i) roughening, texture, and / or etching at least one of the first surface of the crystalline material or (ii) an adjacent surface of the rigid support, before the temporary bonding of the rigid support to the first surface of the crystalline material using the adhesive material.

16. The method for processing a crystalline material according to any one of claims 1 to 15, wherein the portion of the crystalline material removed from the substrate comprises a self-supporting wafer configured to grow at least one epitaxial layer thereon.

17. The method for processing a crystalline material according to any one of claims 1 to 15, wherein the portion of the crystalline material removed from the substrate comprises a device wafer having at least one epitaxial layer grown thereon.

18. The bonding involves bonding a first crystal support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface. Bonding a second crystal support to the second surface of the crystalline material, After the bonding step, the crystalline material is fractured along or near the subsurface laser-damaged area so that a bonded assembly comprising the first crystal carrier and the portion of the crystalline material removed from the substrate is obtained. A method for processing crystalline materials, including the method described above.

19. The method for processing a crystalline material according to claim 18, wherein at least one of the following is bonding the first crystalline support to the first surface of the crystalline material, or bonding the second crystalline support to the second surface of the crystalline material, is anodic bonding.

20. The method for processing a crystalline material according to claim 18, wherein at least one of the following is bonding the first crystalline support to the first surface of the crystalline material, or bonding the second crystalline support to the second surface of the crystalline material, is adhesive bonding using an adhesive material.

21. The first crystal support comprises a first surface and a second surface opposite to the first surface, The adhesive material is positioned in contact with the first surface. The second surface contains no adhesive material and no stress generating material. The method for processing a crystalline material according to claim 20.

22. The adhesive material has the following characteristics (a) to (c): (a) the adhesive material contains a thermoplastic material, (b) the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25°C, or (c) the adhesive material has the following characteristics when the adhesive material is at 25°C A method for processing a crystalline material according to claim 20, comprising at least one of having an elastic modulus of at least about 7 MPa at some point.

23. The method of bonding a rigid support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface, the rigid support has a thickness greater than 850 microns, and the rigid support has at least one of the following features: (i) or (ii): the support comprises a crystalline support, or (ii) the support has an elastic modulus of at least 20 GPa. The crystalline material is fractured along or near the subsurface laser-damaged region so that a bonded assembly comprising the rigid carrier and the portion of the crystalline material removed from the substrate is obtained. A method for processing crystalline materials, including the method described above.

24. The method for processing a crystalline material according to claim 23, wherein the rigid support includes a crystalline support.

25. The method for processing a crystalline material according to claim 23 or 24, wherein the bonding of the rigid carrier to the crystalline material includes adhesive bonding using an adhesive material placed between the rigid carrier and the crystalline material.

26. The adhesive material has the following characteristics (a) to (d): (a) The adhesive material has a glass transition temperature T greater than 25°C. ｇ A method for processing a crystalline material according to claim 25, comprising at least one of the following: (b) the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25°C; (c) the adhesive material has an elastic modulus of at least about 7 MPa when the adhesive material is at 25°C; or (d) the adhesive material comprises a thermoplastic material.

27. A method for processing a crystalline material according to any one of claims 23 to 26, further comprising performing at least one additional processing step on the portion of the crystalline material while the portion of the crystalline material remains part of the joined assembly.

28. A method for processing a crystalline material according to any one of claims 23 to 26, further comprising bonding an additional rigid support to the second surface of the crystalline material opposite to the first surface before the crushing.

29. The bonding involves bonding a first crystal support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface. Bonding a second crystal support to the second surface of the crystalline material, After the bonding step, the crystalline material is fractured along or near the subsurface laser-damaged area so that a bonded assembly comprising the first crystal carrier and the portion of the crystalline material removed from the substrate is obtained. A method for processing crystalline materials, including the method described above.

30. The method for processing a crystalline material according to claim 29, wherein at least one of the first crystalline support or the second crystalline support has an elastic modulus of at least 100 GPa.

31. The crystal material processing method according to claim 29 or 30, wherein at least one of the first crystal support or the second crystal support has a thickness greater than 800 microns.

32. At 25°C, the thermal expansion coefficient (CTE) of the first crystal support is greater than that of the substrate. Large, The fracture includes cooling the first crystal support to facilitate the fracture of the crystalline material along or adjacent to the subsurface laser damage region. A method for processing a crystalline material according to any one of claims 29 to 31.

33. The method for processing a crystalline material according to any one of claims 29 to 32, wherein the crushing comprises applying ultrasonic energy to at least one of the first crystalline support or the substrate.

34. The crystal material processing method according to any one of claims 29 to 33, wherein at least one of the maximum length or maximum width of at least a portion of the first crystal support exceeds the corresponding maximum length or maximum width of the substrate.

35. The method for processing a crystal material according to claim 34, wherein the substrate has a notch or flat along at least one edge of the substrate, and at least a portion of at least one edge of the first crystal support extends laterally beyond the notch or flat.

36. The method for processing a crystalline material according to claim 34 or 35, wherein the crushing comprises applying a mechanical force in close proximity to at least one edge of the first crystalline support, the mechanical force being configured to impart a bending moment to at least a portion of the first crystalline support.

37. The aforementioned crystalline material includes a hexagonal structure. The bending moment is oriented within ±5 degrees from the direction perpendicular to the <11-20> direction of the hexagonal crystal structure. The method for processing crystalline material according to claim 36.

38. A method for processing a crystalline material according to any one of claims 29 to 37, wherein at least one of bonding the first crystalline support to the first surface of the crystalline material, or bonding the second crystalline support to the second surface of the crystalline material, includes anodic bonding.

39. A method for processing a crystalline material according to any one of claims 29 to 37, wherein at least one of the following is bonding the first crystalline support to the first surface of the crystalline material, or bonding the second crystalline support to the second surface of the crystalline material, is adhesive bonding using an adhesive material.

40. The aforementioned adhesive material has a glass transition temperature T greater than 25°C. ｇ A method for processing a crystalline material according to claim 39, comprising:

41. The first crystal support comprises a first surface and a second surface opposite to the first surface, The adhesive material is positioned in contact with the first surface. The second surface contains no adhesive material and no stress generating material. The method for processing a crystalline material according to claim 39.

42. The method for processing a crystalline material according to any one of claims 39 to 41, wherein the adhesive material includes a thermoplastic material.

43. The method for processing a crystalline material according to any one of claims 39 to 42, wherein the adhesive material has a Shore D durometer value of at least about 70 when the adhesive material is at 25°C.

44. The method for processing a crystalline material according to any one of claims 39 to 43, wherein the adhesive material has an elastic modulus of at least about 7 MPa when the adhesive material is at 25°C.

45. A method for processing a crystalline material according to any one of claims 29 to 44, further comprising performing at least one additional processing step on the portion of the crystalline material while the portion of the crystalline material remains part of the joined assembly.

46. The method for processing a crystalline material according to any one of claims 29 to 45, wherein the subsurface laser damage region comprises a plurality of substantially parallel subsurface laser damage lines.

47. A method for processing a crystalline material according to any one of claims 29 to 46, further comprising removing the portion of the crystalline material from the joined assembly.

48. The method for processing a crystalline material according to any one of claims 39 to 47, wherein the crystalline material includes SiC.

49. The method for processing a crystalline material according to any one of claims 39 to 48, wherein the portion of the crystalline material removed from the substrate comprises a self-supporting wafer configured to grow at least one epitaxial layer thereon.

50. The method for processing a crystalline material according to any one of claims 39 to 48, wherein the portion of the crystalline material removed from the substrate comprises a device wafer having at least one epitaxial layer grown thereon.

51. The bonding involves bonding a rigid support to a first surface of a crystalline material, wherein the crystalline material comprises a substrate having a subsurface laser-damaged region at a certain depth relative to the first surface, and at least a portion of at least one edge of the rigid support extends laterally beyond the corresponding at least one edge of the substrate. For the purpose of obtaining a joined assembly including the rigid support and the portion of the crystalline material removed from the substrate, a mechanical force is applied near at least one edge of the rigid support in order to apply a bending moment to at least a portion of the rigid support and to fracture the crystalline material along or near the subsurface laser damage region, A method for processing crystalline materials, including the method described above.

52. The method for processing a crystalline material according to claim 51, wherein applying a mechanical force in proximity to the at least one edge of the rigid carrier comprises applying the mechanical force locally at a single location in proximity to the at least one edge of the rigid carrier.

53. The method for processing a crystalline material according to claim 51, wherein applying a mechanical force in close proximity to the at least one edge of the rigid support comprises applying a mechanical force locally at a plurality of spatially isolated locations in close proximity to the at least one edge of the rigid support, and applying opposing mechanical forces at the central location of the rigid support.

54. The crystal material processing method according to any one of claims 51 to 53, wherein at least a portion of the at least one edge of the rigid carrier extends transversely by at least about 100 microns beyond the corresponding at least one edge of the substrate.

55. At least a portion of the at least one edge of the rigid carrier is the substrate A method for processing a crystalline material according to any one of claims 51 to 53, wherein the material extends laterally by at least about 500 microns beyond at least one corresponding edge.

56. The method for processing a crystalline material according to any one of claims 51 to 55, wherein the substrate has a notch or flat along the at least one edge of the substrate, and at least a portion of the at least one edge of the rigid carrier extends laterally beyond the notch or flat.

57. The aforementioned crystalline material includes a hexagonal structure. The bending moment is oriented within ±5 degrees from the direction perpendicular to the <11-20> direction of the hexagonal crystal structure. A method for processing a crystalline material according to any one of claims 51 to 56.

58. The method for processing a crystalline material according to any one of claims 51 to 57, wherein bonding the rigid carrier to the surface of the crystalline material includes adhesive bonding using an adhesive material disposed between the rigid carrier and the surface of the crystalline material.

59. A method for processing a crystalline material according to any one of claims 51 to 58, further comprising bonding an additional rigid support to a second surface of the crystalline material opposite to the first surface before the application of mechanical force.

60. The method for processing a crystalline material according to claim 59, wherein the application of mechanical force includes applying a localized twisting force between the first rigid support and the additional rigid support in order to increase the separation between the first rigid support and the additional rigid support.

61. The crystalline material processing method according to any one of claims 51 to 60, wherein the crystalline material includes SiC.

62. The method for processing a crystalline material according to any one of claims 51 to 61, wherein the portion of the crystalline material removed from the substrate comprises a self-supporting wafer configured to grow at least one epitaxial layer thereon.

63. The method for processing a crystalline material according to any one of claims 51 to 61, wherein the portion of the crystalline material removed from the substrate comprises a device wafer having at least one epitaxial layer grown thereon.

64. Grinding the edges of a thick wafer of crystalline material in order to eliminate non-perpendicular edge profiles and form perpendicular edge profiles, wherein the thick wafer comprises a first surface, a second surface opposite the first surface, and at least one epitaxial layer grown on or covering the first surface, and the first rigid carrier is temporarily bonded to the at least one epitaxial layer using an adhesive material disposed between the first rigid carrier and the at least one epitaxial layer. After the formation of the vertical edge profile, laser radiation is irradiated through the second surface of the thick wafer in order to form a subsurface laser damage region within the thick wafer. Methods that include...

65. The first rigid support is bonded to the main surface of the crystalline material, wherein the crystalline material includes a substrate having an initial subsurface laser damage region at a predetermined depth relative to the main surface. Joining and The crystalline material is fractured along or near the initial subsurface laser-damaged region so that an initial bonded assembly comprising the first rigid support and the portion of the crystalline material removed from the substrate is obtained, To produce the thick wafer, the removal of the portion of the crystalline material from the first bonded assembly, wherein the thick wafer includes the portion of the crystalline material, The method according to claim 64, further comprising:

66. Bonding the second rigid support to the second surface of the thick wafer, (i) a first bonded assembly comprising the first rigid carrier, the adhesive material, the at least one epitaxial layer, and a first thin wafer separated from the thick wafer, and (ii) a second bonded assembly comprising the second rigid carrier and a second thin wafer separated from the thick wafer, by fracturing the thick wafer along or near the subsurface laser damage region, The method according to claim 64 or 65, further comprising:

67. To form the non-vertical wafer edge of the thick wafer, After creating the non-perpendicular wafer edge, the at least one epitaxial layer is epitaxially grown on or covering the first surface of the thick wafer. The method according to claim 66, further comprising:

68. The crystal material processing method according to claim 66 or 67, wherein at least one of the first thin wafer or the second thin wafer has a thickness less than 250 microns.

69. The method for processing a crystalline material according to any one of claims 64 to 68, wherein the crystalline material includes SiC.

70. A method for processing a crystalline material wafer having a first surface with surface damage, wherein the first surface has an edge as its boundary, and the method is In order to remove the first portion of the surface damage, the first surface is ground using at least one first grinding device, After grinding the first surface using the at least one first grinding device, the edge is edge-ground to form a chamfered or rounded edge profile. A method comprising grinding the first surface using at least one second grinding device to remove, after the edge grinding, the second portion of the surface damage to such an extent that the first surface is suitable for further processing by chemical mechanical planarization.

71. The method according to claim 70, further comprising processing the first surface by chemical planarization after grinding the first surface using the at least one second grinding apparatus, so that one or more layers of semiconductor material can be epitaxially grown thereon.

72. The method according to claim 70 or 71, wherein the at least one first grinding device comprises at least one grinding wheel having a grinding surface of less than 5,000 grits, and the at least one second grinding device comprises at least one grinding wheel having a grinding surface of at least 5,000 grits.

73. The method according to any one of claims 70 to 72, wherein the grinding of the first surface using the at least one first grinding device includes the removal of the crystalline material to a thickness of 20 to 100 microns, and the grinding of the second surface using the at least one second grinding device includes the removal of the crystalline material to a thickness of 3 to 15 microns.

74. The method according to any one of claims 70 to 73, wherein the surface damage includes laser damage and fracture damage.

75. The method according to any one of claims 70 to 74, wherein the crystalline material comprises a silicon carbide material, and the first surface comprises a Si-terminated surface of the silicon carbide material.

76. A method for processing a crystalline material wafer having a first surface with surface damage, wherein the first surface has an edge as its boundary, and the method is In order to remove the first portion of the surface damage, the first surface is ground using at least one first grinding device, After grinding the first surface using the at least one first grinding device, the first surface is ground using at least one second grinding device to remove the second portion of the surface damage to a degree sufficient to make the first surface suitable for further processing by chemical mechanical planarization. After grinding the first surface using the at least one second grinding device, a protective coating is formed on the first surface. After growing the sacrificial material on the first surface, the edges are edge-ground to form a chamfered or rounded edge profile. A method comprising removing the protective coating from the first surface after the edge grinding.

77. The method according to claim 76, further comprising processing the first surface by chemical planarization after the removal of the sacrificial material from the first surface, so that one or more layers of semiconductor material can be epitaxially grown thereon.

78. The method according to claim 76 or 77, wherein the at least one first grinding device comprises at least one grinding wheel having a grinding surface of less than 5,000 grits, and the at least one second grinding device comprises at least one grinding wheel having a grinding surface of at least 5,000 grits.

79. The method according to any one of claims 76 to 78, wherein the grinding of the first surface using the at least one first grinding device includes the removal of the crystalline material to a thickness of 20 to 100 microns, and the grinding of the second surface using the at least one second grinding device includes the removal of the crystalline material to a thickness of 3 to 15 microns.

80. The method according to any one of claims 76 to 79, wherein the protective coating includes a photoresist.

81. The method according to any one of claims 76 to 80, wherein the surface damage includes laser damage and fracture damage.

82. The method according to any one of claims 76 to 81, wherein the crystalline material comprises a silicon carbide material, and the first surface comprises a Si-terminated surface of the silicon carbide material.

83. The laser processing station is configured to form a subsurface laser damage region on a crystalline material substrate supplied to the laser processing station, A crushing station is positioned to receive a crystalline material substrate processed by the laser processing station and is configured to crush the crystalline material substrate along the subsurface laser damage region in order to form a crystalline material portion removed from the crystalline material substrate, wherein each crystalline material portion is provided with surface damage. A plurality of rough grinding stations are arranged in parallel downstream of the crushing station and configured to remove a first portion of the surface damage from the crystalline material portion, wherein at least the first and second rough grinding stations of the plurality of rough grinding stations are configured to operate simultaneously to remove a first portion of the surface damage from different crystalline material portions, At least one precision grinding station is located downstream of the aforementioned plurality of rough grinding stations and is configured to remove a second portion of the surface damage from the crystalline material portion to an extent sufficient to make at least one surface of each crystalline material portion suitable for further processing by chemical mechanical planarization, A material processing apparatus equipped with the following features.

84. The material processing apparatus according to claim 83, further comprising at least one chemical mechanical planarization station located downstream of the at least one precision grinding station and configured to make at least one surface of each crystalline material portion suitable for further processing by chemical mechanical planarization.

85. The material processing apparatus according to claim 83 or 84, further comprising at least one edge grinding station configured to grind the edges of each crystalline material portion to form a chamfered or rounded edge profile.

86. The material processing apparatus according to any one of claims 83 to 85, wherein each rough grinding station comprises at least one grinding wheel having a grinding surface of less than 5,000 grits, and the at least one precision grinding station comprises at least one grinding wheel having a grinding surface of at least 5,000 grits.

87. The material processing apparatus according to any one of claims 83 to 86, wherein each rough grinding station is configured to remove crystalline material with a thickness of 20 to 100 microns from each crystalline material portion, and each precision grinding station is configured to remove crystalline material with a thickness of 3 to 15 microns from each crystalline material portion.

88. The material processing apparatus according to any one of claims 83 to 87, wherein the laser processing station is configured to simultaneously form subsurface laser damage regions on a plurality of crystalline material substrates.

Images