Silicon carbide substrate processing method based on back microgroove and gradient annealing and silicon carbide substrate

Abstract

The invention provides a silicon carbide substrate processing method based on back micro-grooves and gradient annealing and a silicon carbide substrate, through a non-uniformly distributed micro-groove structure, filling or injection is carried out in the micro-groove structure to form a modified layer, and a multi-section nonlinear gradient annealing process is carried out to deeply release harmful stress. The warping degree of the silicon carbide substrate is stably controlled below 50 microns, and the requirements of subsequent processes such as high-temperature epitaxy, photoetching and the like are met by actively inducing compensation stress in the microgroove to generate compensation stress opposite to the warping stress and performing stress distribution remodeling. The microgroove structure is arranged on the back face of the silicon carbide substrate, stress is guided to be released along a preset path, local stress concentration is avoided, and the residual stress gradient introduced by cutting, grinding and polishing is effectively restrained; regional selective stress release and compensation are realized by adopting a concentric annular groove with a gradually changing ring spacing or a spiral involute groove with a nonlinear screw pitch.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor material manufacturing, in particular to a silicon carbide substrate processing method based on back micro-groove and gradient annealing and a silicon carbide substrate. BACKGROUND

[0002] Silicon carbide (SiC) single crystal substrate, as the core material of the third generation of semiconductors, is widely used in high-voltage, high-frequency and high-temperature devices (such as electric vehicles and 5G communication) due to its high band gap, high thermal conductivity and high breakdown electric field. With the transition to large-size substrates of 6 inches (150 mm) or above, the warping problem caused by processing stress and thermal history has become a key bottleneck restricting yield and device performance. Especially in the post-processing stages such as cutting, grinding and polishing, if the substrate warping exceeds 50 μm, it will cause uneven epitaxial growth, lithography alignment failure and other problems, significantly increasing the manufacturing cost.

[0003] The main sources of post-processing stress are cutting stress, grinding stress, polishing stress, stress accumulation in each process, and thermal history difference. For example, in the cutting process, the linear saw or laser cutting introduces mechanical damage and residual stress at the edge and inside of the substrate. When removing the cutting damage layer by coarse grinding or fine grinding, a compression stress layer is formed near the surface due to abrasive impact and plastic deformation, and the stress distribution is uneven, resulting in edge effect. Frictional heat during chemical mechanical polishing may induce subsurface dislocation slip, causing stress redistribution. Temperature fluctuations in each processing step, especially cleaning, drying and detection, as well as possible intermediate annealing, cause different thermal cycles in different regions of the substrate, resulting in thermal stress.

[0004] In the prior art, the following methods are usually used to control warping, such as optimizing grinding or polishing parameters: adjusting pressure, speed, abrasive, etc., but the window is narrow, the effect is limited, and it is easily affected by batch fluctuations; conventional stress release annealing, constant temperature or simple linear cooling annealing at a fixed high temperature (such as 1300-1500℃), but it may not release deep and uneven stress sufficiently, and may introduce new thermal stress; back roughening or thinning, roughening the back surface or locally thinning by sandblasting, wet or dry etching to release stress, but the effect is uncontrollable, which may exacerbate the stress gradient and affect the mechanical strength and epitaxy / bonding. SUMMARY

[0005] To solve the above technical problems, the present application provides a silicon carbide substrate processing method based on back micro-groove and gradient annealing and a silicon carbide substrate.

[0006] In a first aspect, the present application provides a silicon carbide substrate processing method based on back micro-groove and gradient annealing, which is used for a silicon carbide substrate blank that has been cut and obtained a target thickness rough shape, and the method comprises the following steps: Step S1: A non-uniformly distributed microgroove structure is fabricated on the back side of a silicon carbide substrate using an ultraviolet nanosecond laser or a femtosecond laser; the depth of the microgroove structure is 8%-15% of the thickness of the silicon carbide substrate; the width of the microgroove structure is between 15μm and 40μm. Step S2: Fill the microgroove structure or inject low-energy nitrogen ions or nitrogen plasma into the inner wall and bottom wall of the microgroove structure to form a modified layer on the inner wall and bottom wall of the microgroove structure. Step S3: Place the silicon carbide substrate in a high-purity argon or vacuum environment and perform multi-stage nonlinear gradient annealing. Step S4: Perform chemical mechanical polishing on the front side of the silicon carbide substrate to obtain the target silicon carbide substrate.

[0007] In some embodiments of this application, in step S1, the microgroove structure includes multiple concentric annular grooves with a spacing between 80μm and 300μm, and the spacing between the rings gradually changes from the center to the edge.

[0008] In some embodiments of this application, in step S1, the microgroove structure is a spiral involute groove with its starting point at the center, and its pitch size is between 80μm and 300μm, and the pitch changes nonlinearly along the radial direction.

[0009] In some embodiments of this application, in step S2, the microgroove structure is filled using physical vapor deposition; the coefficient of thermal expansion of the filling material is less than that of silicon carbide.

[0010] In some embodiments of this application, the filler material may be tungsten or molybdenum.

[0011] In some embodiments of this application, after filling is completed, the back side of the silicon carbide substrate is chemically and mechanically polished to remove the filling material from the surface of the microgroove structure.

[0012] In some embodiments of this application, step S3, which involves performing multi-segment nonlinear gradient annealing, includes: Heating phase: Increase the temperature to the target temperature at a rate of 5-15℃ / min, where the target temperature is between 1650-1750℃; High-temperature insulation stage: Maintain at the target temperature for 60-90 minutes; Gradient cooling stage: Step A, reduce the temperature from the target temperature to 1500℃ at a rate of 8-12℃ / min; Step B, reduce the temperature from 1500℃ to 1200℃ at a rate of 1-2℃ / min; Step C, reduce the temperature from 1200℃ to 1000℃ at a rate of 3-5℃ / min. Low-temperature rapid cooling stage: Cool from 1000℃ to room temperature at a rate of natural cooling or greater than 20℃ / min.

[0013] In some embodiments of this application, multi-segment nonlinear gradient annealing is performed using a highly uniform tubular furnace or a dedicated annealing furnace.

[0014] In some embodiments of this application, the microgroove structure includes 3 to 10 concentric annular grooves, and the spacing between the rings gradually decreases from the center to the edge.

[0015] In a second aspect, this application provides a silicon carbide substrate prepared using the aforementioned silicon carbide substrate processing method based on backside microgrooves and gradient annealing, wherein a microgrooves structure is provided on the backside of the silicon carbide substrate; the microgrooves structure is filled with a filler material whose coefficient of thermal expansion is less than that of silicon carbide, or the inner wall and bottom wall of the microgrooves structure form a modified layer composed of low-energy nitrogen ions or nitrogen plasma.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: The silicon carbide substrate processing method and silicon carbide substrate based on back microgrooves and gradient annealing of this application, through non-uniformly distributed microgrooves structure, filling or injecting into the microgrooves structure to form a modified layer, and multi-segment nonlinear gradient annealing process, deeply releases harmful stress and actively induces compensation stress in the microgrooves, generating compensation stress opposite to the warping stress, and reshaping the stress distribution, so that the warping of the silicon carbide substrate is stably controlled below 50μm, which meets the requirements of subsequent processes such as high-temperature epitaxy and photolithography; by setting microgrooves structure on the back of the silicon carbide substrate, stress is guided to be released along a predetermined path, avoiding local stress concentration and effectively suppressing residual stress gradients introduced by cutting, grinding, and polishing; by using concentric annular grooves with gradient ring spacing or spiral involute grooves with nonlinear pitch, regional selective stress release and compensation are achieved.

[0017] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit this document. Attached Figure Description

[0018] The accompanying drawings, which form part of this document, are used to provide a further understanding of the document. The illustrative embodiments and descriptions herein are used to explain the document and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a flowchart of a silicon carbide substrate processing method based on backside microgrooves and gradient annealing provided in an exemplary embodiment of this application; Figure 2 This is a bottom view of a silicon carbide substrate provided in an exemplary embodiment of this application; Figure 3 This is a side view of a silicon carbide substrate provided in an exemplary embodiment of this application; Figure 4 This is a schematic diagram of the force distribution on a silicon carbide substrate provided in an exemplary embodiment of this application; Figure 5 This is a schematic diagram of the stress distribution of a silicon carbide substrate before processing, provided in an exemplary embodiment of this application; Figure 6 This is a schematic diagram of the stress distribution of a silicon carbide substrate after processing, provided in an exemplary embodiment of this application. Figure 7 This is a schematic diagram of stress region division of a silicon carbide substrate provided in an exemplary embodiment of this application; Figure 8 This is a schematic diagram of the distribution of the silicon carbide substrate microgroove structure provided in an exemplary embodiment of this application.

[0019] In the picture: 10. Silicon carbide substrate; 20. Microgroove structure; Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0020] Silicon carbide (SiC) single-crystal substrates, as a core material for third-generation semiconductors, are widely used in high-voltage, high-frequency, and high-temperature devices (such as electric vehicles and 5G communications) due to their high bandgap, high thermal conductivity, and high breakdown electric field. As the industry transitions to 6-inch (150mm) and larger substrate sizes, warpage caused by processing stress and thermal history has become a key bottleneck restricting yield and device performance. Especially in downstream processing stages such as dicing, grinding, and polishing, substrate warpage exceeding 50μm will lead to uneven epitaxial growth, photolithography alignment failures, and other problems, significantly increasing manufacturing costs.

[0021] The main sources of post-processing stress include cutting stress, grinding stress, polishing stress, stress accumulation from each process, and differences in thermal history. For example, during the cutting process, wire sawing or laser cutting introduces mechanical damage and residual stress at the edges and inside of the substrate. When removing the cutting damage layer during rough or fine grinding, a compressive stress layer is formed near the surface due to abrasive impact and plastic deformation, and the stress distribution is uneven, leading to edge effects. During chemical mechanical polishing, frictional heat may induce subsurface dislocation slip, resulting in stress redistribution. Temperature fluctuations in each processing step, especially during cleaning, drying, and inspection, as well as possible intermediate annealing, cause different areas of the substrate to experience different thermal cycles, generating thermal stress.

[0022] In existing technologies, warpage is typically controlled by methods such as optimizing grinding or polishing parameters by adjusting pressure, rotation speed, and abrasive. However, these methods have a narrow window, limited effectiveness, and are easily affected by batch fluctuations. Conventional stress-relief annealing, which involves isothermal or simple linear cooling annealing at a fixed high temperature (e.g., 1300-1500℃), can lead to insufficient release of deep, uneven stress and may introduce new thermal stress. Backside roughening or thinning, achieved through sandblasting, wet or dry etching to roughen or locally thin the backside to release stress, is also an option. However, the effect is uncontrollable and may exacerbate stress gradients, affecting mechanical strength and epitaxy / bonding.

[0023] Based on this, exemplary embodiments of this application provide a silicon carbide substrate processing method and a silicon carbide substrate based on backside microgrooves and gradient annealing. Through a non-uniformly distributed microgroove structure, filling or injecting into the microgroove structure to form a modified layer, and a multi-segment nonlinear gradient annealing process, harmful stress is deeply released, and compensating stress is actively induced within the microgrooves to generate compensating stress opposite to the warping stress, thus reshaping the stress distribution and stabilizing the warping of the silicon carbide substrate below 50 μm, meeting the requirements of subsequent processes such as high-temperature epitaxy and photolithography. By setting a microgroove structure on the backside of the silicon carbide substrate, stress is guided to be released along a predetermined path, avoiding local stress concentration and effectively suppressing residual stress gradients introduced by cutting, grinding, and polishing. Concentric annular grooves with gradually varying ring spacing or helical involute grooves with nonlinear pitch are used to achieve regionally selective stress release and compensation.

[0024] Example 1: An exemplary embodiment of this application provides a silicon carbide substrate processing method based on backside microgrooving and gradient annealing. The method is used for a silicon carbide substrate blank that has been cut and has obtained a preliminary target thickness. The silicon carbide substrate blank is typically 10 μm to 50 μm larger than the final thickness of the silicon carbide substrate to allow for sufficient processing margin. Preferably, this method is used for six-inch, i.e., 150 mm or larger silicon carbide single-crystal substrates, such as... Figure 1 As shown, the method includes the following steps: Step S1 involves fabricating a non-uniformly distributed microgroove structure 20 on the back side of the silicon carbide substrate 10 using an ultraviolet nanosecond laser or femtosecond laser. The use of ultraviolet nanosecond or femtosecond lasers enables micron-level processing with high precision, resulting in high dimensional accuracy of the microgroove structure 20. Simultaneously, the short pulse characteristics of the laser cause almost no heat diffusion, minimizing the laser-affected zone of the silicon carbide substrate 10 and preventing thermal damage to the substrate 10 caused by further processing. This avoids secondary stress concentration or deformation caused by localized high temperatures. The edges of the laser-processed microgroove structure 20 are smooth and free of significant defects. By setting the non-uniformly distributed microgroove structure 20, residual stress in different areas of the silicon carbide substrate 10 can be released in a targeted manner. For example, the microgroove structure 20 is densely arranged in high-stress areas at the edges, preventing uneven stress compensation. Preferably, the depth of the microgroove structure 20 is 8%-15% of the thickness of the silicon carbide substrate 10; preferably, the depth of the microgroove structure 20 is between 29 μm and 54 μm, ensuring effective stress release while avoiding excessive weakening of the substrate's mechanical strength; the width of the microgroove structure is between 15 μm and 40 μm, providing sufficient stress buffer space while maintaining the surface flatness of the silicon carbide substrate 10. The microgroove structure 20 guides the stress redistribution of the silicon carbide substrate 10, reducing the overall stress gradient of the silicon carbide substrate 10 and avoiding lattice mismatch problems during subsequent epitaxial growth. Through the synergistic effect of using laser processing for the microgroove structure 20 and its non-uniform distribution design, the inherent processing stress in different areas of the silicon carbide substrate 10 is effectively and specifically released without introducing new stress.

[0025] For example, the microgroove structure 20 includes a plurality of concentric annular grooves, such as Figure 2 and 3 As shown, the ring spacing between each pair of concentric annular grooves is between 80μm and 300μm, which can be adapted to ultraviolet nanosecond laser or femtosecond laser processing technology. Moreover, the ring spacing is gradually distributed from the center to the edge. In this way, the stress release rate of different regions of silicon carbide substrate 10 can be actively controlled. By gradually transitioning the stress, stress concentration points caused by abrupt interface are avoided, thus maintaining the bending strength of silicon carbide substrate 10.

[0026] Preferably, the microgroove structure 20 includes 3 to 10 concentric annular grooves, with the spacing between the rings gradually decreasing from the center to the edge. Compared to a uniform spacing design, when the ring spacing gradually changes from 300 μm at the center to 80 μm at the edge, the residual stress in the edge region will be significantly reduced. The concentric annular groove design can maintain thermal flow symmetry and avoid anisotropic deformation of the silicon carbide substrate 10. At the same time, the dense concentric annular grooves in the edge region can provide a higher density of stress release channels for the edge region, adapting to the high stress distribution in the edge region and suppressing edge warping at high temperatures.

[0027] Alternatively, the microgroove structure 20 can be a spiral involute groove with a starting point at the center, and its pitch is between 80 μm and 300 μm, with the pitch changing non-linearly in the radial direction. Preferably, the pitch gradually decreases from the starting point to the end point, with the pitch of the initial segment being greater than that of the epitaxial segment. For example, the pitch of the initial segment is 200 μm-300 μm, forming a low-density stress relief network in the central region to avoid excessively reducing the strength of the silicon carbide substrate 10; the pitch of the transition segment is 150 μm-200 μm, which can adapt to the changes in the radial thermal expansion coefficient of the silicon carbide substrate 10; and the pitch of the epitaxial segment is 80 μm-150 μm, forming a dense control network in the high-stress area at the edge to improve the residual stress relief efficiency.

[0028] The microgroove structure 20 with a spiral involute configuration has a continuous path, which can avoid stress abrupt interface and make stress redistribution more in line with the slip system characteristics of silicon carbide crystal; at the same time, the microgroove structure 20 is uninterrupted, which can realize continuous processing and reduce processing positioning time.

[0029] By using the microgroove structure 20 and the non-uniformly distributed spatial gradient stress regulation structure, the stress of the silicon carbide substrate 10 is effectively released from passive stress release to active stress compensation.

[0030] Step S2 involves filling the microgroove structure 20 or injecting low-energy nitrogen ions or nitrogen plasma into the inner and bottom walls of the microgroove structure 20, thereby forming a modified layer on the inner and bottom walls of the microgroove structure 20. For example, physical vapor deposition is used to fill the microgroove structure 20; the coefficient of thermal expansion of the filling material is less than that of silicon carbide. The coefficient of thermal expansion of silicon carbide is approximately 4.0 × 10⁻⁶. -6 / K, the filler material can be tungsten or molybdenum, with tungsten having a thermal expansion coefficient of approximately 4.3-4.5 × 10⁻⁶. -6 K, the coefficient of thermal expansion of molybdenum is approximately 4.8-5.0 × 10⁻⁶. -6 At high temperatures, the coefficient of thermal expansion of tungsten or molybdenum is still lower than that of silicon carbide. Therefore, tungsten or molybdenum shrinks faster during the cooling annealing stage, thereby generating reverse tensile stress in the groove of the microgroove structure 20 to compensate for the compressive stress generated by the silicon carbide substrate 10.

[0031] After filling, the process also includes chemical mechanical polishing of the back side of the silicon carbide substrate 10 to remove the filling material from the surface of the microgroove structure 20. Only the excess filling material on the outer surface of the groove is removed, while the filling material inside the groove of the microgroove structure 20 is retained, making the back side of the silicon carbide substrate 10 generally flat.

[0032] Low-energy nitrogen ions or nitrogen plasma are injected into the inner and bottom walls of the microgroove structure 20 to form a modified layer on the inner and bottom walls of the microgroove. For example, an extremely thin, nanoscale, nitrogen-rich SiCxNy or similar modified layer can be formed on the inner and bottom walls of the microgroove structure 20. This modified layer has higher hardness and modulus, as well as a slightly lower coefficient of thermal expansion, and can serve as a stress anchor point to effectively "pin" the groove wall, limit the deformation of the groove wall in the subsequent heat treatment stage, and enhance the stability of the stress-controlled structure.

[0033] Step S3: Place the silicon carbide substrate 10 in a high-purity argon or vacuum environment and perform multi-segment nonlinear gradient annealing; utilize the controlled heat treatment process, in conjunction with the effect of the microgroove structure 20, to deeply release harmful stress and actively induce the filling material or modified layer in the microgroove structure 20 to generate the required compensating stress.

[0034] For example, a highly uniform tube furnace or a dedicated annealing furnace is used to perform multi-segment nonlinear gradient annealing. The highly uniform tube furnace or dedicated annealing furnace has precise multi-segment programmable cooling capabilities. The specific steps and stages of performing multi-segment nonlinear gradient annealing include: Heating stage: The temperature is increased to the target temperature at a rate of 5-15℃ / min, which effectively promotes the release of stress introduced by cutting, grinding, polishing, etc.; the target temperature is between 1650-1750℃; preferably, the target high temperature is 1700±15℃, which balances the activation energy of silicon carbide lattice and the thermal stability of the material, and avoids excessive high temperature from causing the microgroove structure 20 to degrade.

[0035] High-temperature holding stage: Maintain at the target temperature for 60-90 minutes; ensure that the silicon carbide substrate 10 reaches thermal equilibrium as a whole, so that the stress distribution is uniform and initially relaxed, and the local stress gradient is reduced.

[0036] Gradient cooling stage: Step A, rapid relaxation stage, cooling from the target temperature to 1500℃ at a rate of 8-12℃ / min; rapidly passing through the high-temperature zone to avoid excessive creep caused by prolonged stay in the high-temperature zone, and to prevent excessive stress relaxation from damaging the control effect of the microgroove structure 20. Step B, main compensation induction stage, cooling from 1500℃ to 1200℃ at a rate of 1-2℃ / min; this temperature range is a critical area where the thermal expansion coefficients of the silicon carbide substrate 10 and the filling material differ significantly, and the material still has sufficient plasticity. Using an extremely slow cooling rate allows the filling material to produce a "hysteresis contraction" effect due to its lower thermal expansion coefficient, and allows the "hysteresis contraction" effect to fully play its role, inducing a continuous and uniform tensile stress compensation layer in the silicon carbide substrate 10; at the same time, under the synergistic effect of the microgroove structure 20, the tensile stress distribution is optimized and guided. Step C, the stress stabilization stage, involves cooling from 1200℃ to 1000℃ at a rate of 3-5℃ / min. In this step, a slightly faster cooling rate is used to pass through the lower temperature range to lock in the optimized stress state and prevent secondary stress from being introduced by the low-temperature phase transition. The gradient cooling stage reduces the temperature from the target temperature to 1000℃. During this cooling process, multiple nonlinear cooling stages are performed to release and compensate for stress, reducing the warpage of the silicon carbide substrate 10.

[0037] Low-temperature rapid cooling stage: Cool from 1000℃ to room temperature at a rate of natural cooling or greater than 20℃ / min. Rapidly pass through the brittle temperature range to ensure that the warpage of the silicon carbide substrate 10 is stably controlled below 50μm.

[0038] Step S4: Perform chemical mechanical polishing on the front side of the silicon carbide substrate 10 to remove the reserved processing allowance and obtain the target silicon carbide substrate 10. Afterwards, cleaning can be performed and the warpage and curvature of the silicon carbide substrate 10 can be measured using a non-contact laser interferometer or an automatic flatness measuring instrument to ensure that the warpage is less than 50 μm (the target is usually 20-40 μm).

[0039] Comparative Example 1: No processing.

[0040] Comparative Example 2: The microgroove structure 20 is only formed on the back side of the silicon carbide substrate 10, without any other treatment.

[0041] Comparative Example 3: A microgroove structure 20 is formed on the back side of the silicon carbide substrate 10, and then subjected to conventional annealing.

[0042] Test example: The above-described Examples 1 to 3 were tested.

[0043] Test results and analysis: Table 1 Test results of Example 1 and Comparative Examples 1-3

[0044] From the data in Table 1 and combined with Figures 4 to 8 It can be seen that the warpage of the silicon carbide substrate 10 in Embodiment 1 of the present invention is 28 μm, which is much less than 50 μm, while the warpage of the silicon carbide substrate 10 without corresponding treatment is 80 μm, which is much greater than 50 μm. The warpage of the silicon carbide substrate 10 with only the microgroove structure 20 is 60 μm, indicating that the microgroove structure of this application can effectively release the harmful stress of the silicon carbide substrate 10. The warpage of the microgroove structure 20 with conventional annealing is 55 μm, which is significantly different from the warpage of 28 μm in the embodiment of this application. This indicates that in the processing method of this application, the filling or formation of the modified layer of the microgroove structure 20 and the multi-segment nonlinear gradient annealing can effectively release and compensate the stress of the silicon carbide substrate 10. In the processing method of this application, a non-uniformly distributed microgroove structure 20 is formed on the back side of the silicon carbide substrate 10. A modified layer is formed by filling or injecting into the microgroove structure. A multi-segment nonlinear gradient annealing process is used to deeply release harmful stress and actively induce compensation stress in the microgroove to generate compensation stress opposite to the warping stress. The stress distribution is reshaped so that the warping of the silicon carbide substrate is stably controlled below 50μm, which meets the requirements of subsequent processes such as high-temperature epitaxy and photolithography.

[0045] Example 2: An exemplary embodiment of this application provides a silicon carbide substrate prepared using the silicon carbide substrate processing method based on backside microgrooves and gradient annealing as described in Example 1. The backside of the silicon carbide substrate 10 is provided with a microgroove structure 20; the microgroove structure 20 is filled with a filling material with a thermal expansion coefficient less than that of silicon carbide, or the inner wall and bottom wall of the microgroove structure 20 form a modified layer composed of low-energy nitrogen ions or nitrogen plasma.

[0046] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0047] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0048] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, the intent of this application also includes these modifications and variations.

Claims

1. A method for processing silicon carbide substrates based on backside microgrooving and gradient annealing, the method being used for silicon carbide substrate blanks that have been cut and have obtained a target thickness profile, characterized in that... The method includes the following steps: Step S1: A non-uniformly distributed microgroove structure (20) is fabricated on the back side of a silicon carbide substrate (10) using an ultraviolet nanosecond laser or a femtosecond laser; the depth dimension of the microgroove structure (20) is 8%-15% of the thickness of the silicon carbide substrate (10); the width dimension of the microgroove structure (20) is between 15μm and 40μm. Step S2: Fill the microgroove structure (20) or inject low-energy nitrogen ions or nitrogen plasma into the inner wall and bottom wall of the microgroove structure (20) to form a modified layer on the inner wall and bottom wall of the microgroove structure (20); Step S3: Place the silicon carbide substrate (10) in a high-purity argon or vacuum environment and perform multi-stage nonlinear gradient annealing; Step S4: Perform chemical mechanical polishing on the front side of the silicon carbide substrate (10) to obtain the target silicon carbide substrate (10).

2. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 1, characterized in that, In step S1, the microgroove structure (20) includes multiple concentric annular grooves with a spacing between 80μm and 300μm, and the spacing between the rings is gradually distributed from the center to the edge.

3. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 1, characterized in that, In step S1, the microgroove structure (20) is a spiral involute groove with its starting point at the center. Its pitch size is between 80μm and 300μm, and the pitch changes nonlinearly along the radial direction.

4. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 1, characterized in that, In step S2, the microgroove structure (20) is filled using physical vapor deposition; the coefficient of thermal expansion of the filling material is less than that of silicon carbide.

5. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 4, characterized in that, The filler material can be tungsten or molybdenum.

6. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 4, characterized in that, After filling is completed, the back side of the silicon carbide substrate (10) is chemically and mechanically polished to remove the filling material from the surface of the microgroove structure (20).

7. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 1, characterized in that, In step S3, multi-segment nonlinear gradient annealing is performed, including: Heating phase: Increase the temperature to the target temperature at a rate of 5-15℃ / min, where the target temperature is between 1650-1750℃; High-temperature insulation stage: Maintain at the target temperature for 60-90 minutes; Gradient cooling stage: Step A, reduce the temperature from the target temperature to 1500℃ at a rate of 8-12℃ / min; Step B, reduce the temperature from 1500℃ to 1200℃ at a rate of 1-2℃ / min; Step C, reduce the temperature from 1200℃ to 1000℃ at a rate of 3-5℃ / min. Low-temperature rapid cooling stage: Cool from 1000℃ to room temperature at a rate of natural cooling or greater than 20℃ / min.

8. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 7, characterized in that, Multi-stage nonlinear gradient annealing is performed using a highly uniform tubular furnace or a dedicated annealing furnace.

9. The silicon carbide substrate processing method based on backside microgrooves and gradient annealing according to claim 2, characterized in that, The microgroove structure (20) includes 3 to 10 concentric annular grooves, the spacing between the rings gradually decreasing from the center to the edge.

10. A silicon carbide substrate prepared using the silicon carbide substrate processing method based on backside microgrooving and gradient annealing as described in any one of claims 1 to 9, characterized in that, A microgroove structure (20) is provided on the back side of the silicon carbide substrate (10); the microgroove structure (20) is filled with a filling material with a thermal expansion coefficient less than that of silicon carbide, or the inner wall and bottom wall of the microgroove structure (20) form a modified layer composed of low-energy nitrogen ions or nitrogen plasma.

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