SiC crystal with small base plane bending and small optical path difference and SiC substrate

Abstract

The invention discloses a SiC crystal with small base plane bending and small optical path difference and a SiC substrate, and belongs to the technical field of SiC material preparation. The curvature of the C surface and the curvature of the Si surface of any SiC substrate prepared from the SiC crystal are both smaller than 1.5 * 10 <-6 > mm <-1 >. The optical path difference of any SiC substrate prepared from the SiC crystal is lt; the wavelength is 5.5 nm. The SiC crystal and the SiC substrate are low in in-plane bending warping degree and small in optical path difference, and meet the urgent demand of the market for high-performance SiC materials.

Description

Technical Field

[0001] The present application relates to a SiC crystal and a SiC substrate with small base plane curvature and small optical path difference, belonging to the technical field of SiC material preparation. Background Art

[0002] Polarized birefringence is used to test the stress of SiC substrate. Since the light source penetrates the entire SiC wafer, the optical path difference caused by the lattice distortion in the SiC wafer plane can be measured, so the optical path difference can be used to characterize its stress. XRD is used to test the upper and lower surfaces of the SiC substrate. The center point (0,0) of the substrate is used as the reference point. The curvature and curvature radius of the substrate are calculated by calculating the peak position difference between the test point and the reference point. The smaller the curvature, the larger the curvature radius, which means the flatness of the substrate is better.

[0003] In the preparation of SiC crystals, on the one hand, residual thermal stress or defects cause stress concentration, resulting in the generation of in-plane optical path difference. This reason not only increases the optical path difference of SiC crystals, but also makes the crystals more prone to in-plane bending during processing, making it difficult to obtain crystals with small curvature. On the other hand, the temperature gradient difference between the center and edge of the crystal growth and the surface damage caused by processing will lead to differences in the surface shapes of the C and Si surfaces, resulting in changes in the crystal plane spacing, which in turn produces an optical path difference.

[0004] Based on the above two reasons, there is an urgent need for a SiC crystal and a SiC substrate that can achieve dual reduction and uniform distribution of curvature and optical path difference. Summary of the invention

[0005] In order to solve the above problems, a SiC crystal and a SiC substrate with small base plane curvature and small optical path difference are provided. The SiC crystal and the SiC substrate have low in-plane curvature and small optical path difference, meeting the market's urgent demand for high-performance SiC materials.

[0006] According to one aspect of the present application, a SiC crystal with small base plane curvature and small optical path difference is provided, wherein the curvature of the C surface and the Si surface of any SiC substrate prepared from the SiC crystal is less than 1.5×

[0007] 10 -6 mm -1 ;

[0008] The optical path difference of any SiC substrate prepared by the SiC crystal is less than 5.5 nm.

[0009] The in-plane optical path difference of the present application refers to the optical path difference generated due to different paths when light propagates inside a medium. During the stress test on SiC products, different test results will be caused by the change of wavelength, and this shortcoming makes it impossible to effectively reflect the actual situation of the products. The present application uses the optical path difference to characterize SiC crystals and SiC substrates. This parameter is not affected by the test wavelength and can better characterize the actual parameters of the products, thereby optimizing production to obtain SiC products with significantly improved quality.

[0010] Optionally, for any SiC substrate prepared from the SiC crystal, |K1 - K2| < 1×10 -6 mm -1 , where K1 represents the curvature of the C plane of the SiC substrate, and K2 represents the curvature of the Si plane of the SiC substrate.

[0011] The smaller the value of |K1 - K2|, the smaller the difference in flatness between the C plane and the Si plane of the SiC substrate, indicating that the surface stress introduced by processing is small, the change in crystal plane spacing is small, and combined with the optical path difference, it can improve the application prospect of the SiC substrate.

[0012] Optionally, 0.6 < K3 / K4 < 1.2, where K3 represents the curvature of any SiC substrate prepared from the SiC crystal in the <1 - 100> crystal orientation family, and K4 represents the average value of the curvatures of all SiC substrates prepared from the SiC crystal in the <1 - 100> crystal orientation family.

[0013] Optionally, 0.4 < K5 / K6 < 1.4, where K5 represents the curvature of any SiC substrate obtained from the SiC crystal in the <11 - 20> crystal orientation family, and K6 represents the average value of the curvatures of all SiC substrates prepared from the SiC crystal in the <11 - 20> crystal orientation family.

[0014] The <11 - 20> crystal orientation family includes 6 crystal orientations, namely [11 - 20], [-11 - 20], [1 - 1 - 20],

[0015] [-1 - 1 - 20], [1 - 1 - 10], [-1 - 1 - 10]; the <1 - 100> crystal orientation family includes 6 crystal orientations, namely [1 - 100], [-1100], [01 - 10], [0 - 110], [10 - 10], [-1010].

[0016] Preferably, the <11 - 20> crystal orientation family is selected from the [11 - 20] crystal orientation, and the <1 - 100> crystal orientation family is selected from the [1 - 100] crystal orientation.

[0017] The difference between any SiC substrate in the crystal and the mean value of all SiC substrates is represented by the ratio of K3 / K4 and the ratio of K5 / K6. The closer the above two parameters are to 1, the more uniform the curvature distribution of the SiC crystal in the axial direction is.

[0018] Optionally, |OPD1 - OPD2| < 3 nm, where OPD1 represents the optical path difference of the SiC substrate containing the first end face prepared from the SiC crystal, and OPD2 represents the optical path difference of the SiC substrate containing the second end face prepared from the SiC crystal.

[0019] Preferably, |OPD1 - OPD2| < 1.5 nm.

[0020] After the head and tail of the SiC crystal are ground flat, several SiC substrates are prepared. In this application, the SiC substrate containing the first end face and the SiC substrate containing the second end face belong to the first substrates obtained after processing the two ends of the ground flat SiC crystal respectively.

[0021] The smaller the value of the above |OPD1 - OPD2|, the better the axial uniformity of the SiC crystal, and the better the performance consistency of several SiC substrates prepared from a single SiC crystal, which is more conducive to mass-producing devices with more stable performance.

[0022] Optionally, for any SiC substrate prepared from the SiC crystal, 0.4 < OPD3 / OPD4 < 0.85, where OPD3 represents the optical path difference in the 3 / 4 radius region of the SiC substrate, and OPD4 represents the optical path difference outside the 3 / 4 radius region of the SiC substrate.

[0023] OPD3 / OPD4 is used to represent the radial distribution uniformity of the optical path difference of the SiC substrate. Generally speaking, the closer this ratio is to 1, the closer the radial optical path difference of the SiC substrate is to the ideal uniformity. However, limited by the current process operation, in this application, OPD3 / OPD4 can only be as close to 1 as possible.

[0024] According to another aspect of the present application, there is provided an SiC substrate with a small basal plane curvature and a small optical path difference. The curvatures of the C plane and the Si plane of the SiC substrate are both less than 1.5×10 -6 mm -1 ;

[0025] And the optical path difference of the SiC substrate < 5.5 nm.

[0026] Optionally, |K1 - K2| < 1×10 -6 mm -1 , where K1 represents the curvature of the C plane of the SiC substrate, and K2 represents the curvature of the Si plane of the SiC substrate.

[0027] Optionally, the ratio of the curvature of the C plane of the SiC substrate in the <1-100> crystal orientation family to the curvature in the <11-20> crystal orientation family is 0.8 to 1.2.

[0028] Optionally, the ratio of the curvature of the Si plane of the SiC substrate in the <1-100> crystal orientation family to the curvature in the <11-20> crystal orientation family is 0.3 to 1.5.

[0029] The <1-100> direction and the <11-20> direction are two characteristic crystal orientation families of SiC. The closer the ratio of the C-plane curvature to the Si curvature in these two crystal orientation families is to 1, the more uniform the in-plane of the SiC substrate is, the larger the available area of the entire SiC substrate is, and the stability of the devices fabricated on this SiC substrate is consistent, which is beneficial to improving the commercial application prospects of the SiC substrate.

[0030] Optionally, for the SiC substrate, 0.4 < OPD3 / OPD4 < 0.85, where OPD3 represents the optical path difference within the 3 / 4 radius region of the SiC substrate, and OPD4 represents the optical path difference outside the 3 / 4 radius region of the SiC substrate.

[0031] Optionally, on any horizontal line of the SiC substrate, the standard deviation coefficient of the optical path difference ≤ 1.5, and the standard deviation coefficient of the optical path difference refers to the ratio of the standard deviation of the optical path difference calculated on this line to the mean value of the optical path difference.

[0032] Optionally, both the SiC crystal and the SiC substrate are single crystals.

[0033] Optionally, the crystal form of the SiC crystal and the SiC substrate is selected from one of 4H, 6H, and 3C, preferably 4H.

[0034] Optionally, the size of the SiC crystal and the SiC substrate is selected from one of 4 inches, 6 inches, 8 inches, and 12 inches, preferably 8 inches or 12 inches.

[0035] Optionally, the SiC crystal and the SiC substrate are semi-insulating or conductive.

[0036] Optionally, the thickness of the SiC substrate < 1 mm.

[0037] The beneficial effects of this application include but are not limited to:

[0038] 1. The SiC crystal and SiC substrate with small basal plane bending and small optical path difference according to this application can, while reducing the material curvature and optical path difference, achieve uniform distribution of curvature and optical path difference in the axial and radial directions, thereby obtaining high-quality SiC materials.

[0039] 2. According to the SiC crystal and SiC substrate with small base plane curvature and small optical path difference of the present application, the performance is consistent in the axial and radial directions, so it is possible to increase the area of ​​the crystal and substrate that can be used for chip manufacturing, greatly improve the output of qualified chips, significantly reduce unit costs, and provide possibilities for larger-scale application of SiC materials.

[0040] 3. According to the SiC crystal and SiC substrate with small base plane curvature and small optical path difference of the present application, the stress inside and on the surface of the material, lattice distortion, and defects such as microtubes, holes, and polycrystals caused by lattice distortion are all low, which is a SiC material with high and uniform crystal quality.

[0041] 4. According to the SiC crystal and SiC substrate with small base plane curvature and small optical path difference of the present application, the consistency of in-plane stress is high, which is conducive to improving the use stability of devices prepared from the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0043] Figure 1 This is a schematic diagram of the structure of the induction furnace with precise positioning and installation involved in Example 1 of the present application;

[0044] Figure 2 This is a schematic structural diagram of a planetary rotary cutting device for cutting silicon carbide according to Example 2 of the present application;

[0045] Figure 3 It is a front view of the sheave guide plate, the first sheave, the second sheave and the fixing plate involved in Example 2 of the present application;

[0046] Figure 4 A side view of a fixed plate and a rotating fixed table involved in Example 2 of the present application;

[0047] Figure 5 This is a statistical diagram of the basal plane bending diffraction peak positions of the C-plane and Si-plane of one of the SiC substrates prepared from SiC crystal 1# involved in Example 3 of the present application.

[0048] List of parts and reference numerals:

[0049] 1. Furnace chamber; 2. Upper flange; 3. Lower flange; 4. Crucible body; 5. Transition crucible cover; 6. Crucible holder; 7. External insulation; 8. Lower insulation; 9. Movable support rod; 10. Movable laser locator; 11. Horizontal slide rail; 12. Horizontal rail; 13. Graphitized carbon fiber cloth; 14. Horizontal moving part; 15. Longitudinal moving part; 16. Lifting assembly; 17. Rotating assembly; 18. Temperature measuring hole; 19. Induction coil; 20. Fixed plate; 21. Telescopic rod; 31. Adhesive plate; 32. Rotating axis; 33. Fixed axis; 40. Groove wheel guide plate; 41. First arc guide rail; 42. Second arc guide rail; 43. Reserved hole; 50. First groove wheel; 52. Second groove wheel; 53. Stopper; 60. Cutting chamber; 61. Liquid inlet, 62. Liquid outlet. DETAILED DESCRIPTION

[0050] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0051] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0052] Unless otherwise specified, the methods used in the embodiments of the present application are conventional methods in the prior art.

[0053] Example 1

[0054] like Figure 1 As shown, this embodiment provides an induction crystal growth furnace, including a furnace chamber 1 and an upper flange 2 on the top of the furnace chamber 1, and a lower flange 3 on the bottom of the furnace chamber 1. A crucible, an external insulation 7 and a lower insulation 8 are arranged in the furnace chamber 1. The external insulation 7 and the lower insulation 8 form an insulation layer. The crucible is arranged inside the insulation layer. A movable support rod 9 is fixed to the bottom of the lower insulation 8. A moving mechanism is arranged on the top of the lower flange 3. The moving mechanism includes a planar moving component. The planar moving component can drive the movable support rod 9 to drive the insulation layer to move. A closeable slide rail is arranged on the top of the furnace chamber 1, and a movable laser locator 10 is arranged on the closeable slide rail.

[0055] The movable laser locator 10 can move along the enclosed slide rail. The laser locator can determine the outer edge of the crucible and the inner edge of the outer insulation 7 by measuring the round-trip time and combining the distance relationship and then comparing the changing trend of the round-trip time, wherein the outer insulation 7 is the insulation felt, thereby determining the cavity width between the outer insulation 7 and the crucible, and then controlling the planar moving component in the motion mechanism according to the determined cavity width. The planar moving component can control the movable support rod 9 to drive the insulation layer to move, thereby driving the outer insulation 7 to move, and then the width of the cavity between the inner edge of the outer insulation 7 and the outer edge of the crucible can be adjusted to be similar, thereby ensuring the uniformity of the temperature field, reducing the influence of the temperature field disturbance on the growth of SiC, and thus ensuring the quality of SiC products.

[0056] The present application does not limit the implementation method of the plane moving assembly, as long as it can drive the movable support rod 9 to move and adjust within the plane. For example, as an implementation method, the plane moving assembly includes a transverse moving part 14 and a longitudinal moving part 15; the longitudinal moving part 15 is used to control the longitudinal movement of the movable support rod 9; the transverse moving part 14 is used to control the transverse movement of the movable support rod 9.

[0057] It should be noted that the closable slide rail in the present application is a closable type and can be used to protect the movable laser locator 10 and the slide rail. It is opened before crystal growth to allow the movable laser locator 10 to work, and is closed during the crystal growth process, thereby protecting the movable laser locator 10 and the slide rail and preventing them from being affected by the Si atmosphere or SiC atmosphere during the crystal growth process and affecting their subsequent normal operation.

[0058] As a specific implementation, the lower flange 3 is provided with a longitudinal track, and the longitudinal moving part 15 can move longitudinally along the longitudinal track provided on the lower flange 3 under the action of the driving mechanism. Further, the longitudinal moving part 15 is provided with a transverse track 12, and the transverse moving part 14 can move transversely along the transverse track 12 provided on the longitudinal moving part 15 under the action of the driving mechanism, and then drive the movable support rod 9 to move. Through the cooperation of the transverse moving part 14 and the longitudinal moving part 15, the movable support rod 9 can be moved in a plane, thereby driving the movement of the outer insulation 7 to adjust the relative position with the crucible. In addition, the skilled and technical personnel can understand that the order of setting the longitudinal moving part 15 and the transverse moving part 14 can be exchanged. It is only necessary to set the transverse track 12 corresponding to the lower flange 3, and the transverse moving part 14 moves on this transverse track 12, and then set the longitudinal track on the transverse moving part 14, and the longitudinal moving part 15 moves on this longitudinal track, so as to achieve the same function.

[0059] As an implementation mode, the motion mechanism further includes a rotating assembly 17 and a lifting assembly 16; the rotating assembly 17 is used to control the rotation of the movable support rod 9; and the lifting assembly 16 is used to control the movable support rod 9 to rise or fall.

[0060] By setting the rotating component 17, the movable support rod 9 can be rotated, thereby driving the rotation of the external insulation 7. Since the external insulation 7 is easily corroded by the Si atmosphere, its inner edge may change, thereby affecting the cavity distance between the inner edge of the external insulation 7 and the outer edge of the crucible. After the external insulation 7 is set to be rotatable, the movable laser positioner 10 can measure and adjust more radial directions of the external insulation 7, thereby ensuring that the uniformity of the cavity distance between the inner edge of the external insulation 7 and the outer edge of the crucible is more accurate, thereby further improving the uniformity of the temperature field.

[0061] By providing the lifting assembly 16 , the rise or fall of the thermal insulation layer can be controlled, thereby meeting different requirements for the thermal insulation layer during the SiC crystal growth process.

[0062] The present application does not impose any specific limitation on the implementation method of the rotating assembly 17 and the lifting assembly 16, which can be conventionally selected by those skilled in the art. There is no specific limitation on the connection method between the rotating assembly 17, the lifting assembly 16 and the planar moving assembly. For example, the planar moving assembly is arranged at the bottom, the lifting assembly 16 is arranged in the middle, and the rotating assembly 17 is arranged at the top, or the structural order of the three is swapped as long as the effect required by the present application can be normally met. Those skilled in the art can perform conventional implementation or make adjustments and solutions based on some problems that arise.

[0063] As an implementation mode, the closable slide rail includes a transverse slide rail 11 and a longitudinal slide rail, and a movable laser locator 10 is disposed on both the transverse slide rail 11 and the longitudinal slide rail.

[0064] By setting two slide rails, the number of movable laser locators 10 thereon can be increased, thereby improving the efficiency of determining the outer edge of the crucible and the inner edge of the outer insulation 7. At the same time, several movable laser locators 10 work at the same time, which can significantly improve the efficiency of adjusting the cavity distance between the outer edge of the crucible and the inner edge of the outer insulation 7.

[0065] As an implementation mode, a crucible holder 6 is fixed to the bottom of the upper flange 2, and the crucible includes a transitional crucible cover 5 and a crucible body 4;

[0066] The transitional crucible cover 5 is located between the crucible holder 6 and the crucible body 4 , and is respectively connected to the crucible holder 6 and the crucible body 4 through threads.

[0067] As a specific implementation manner, the bottom of the crucible holder 6 is provided with an internal thread, the top of the transitional crucible cover 5 is provided with an external thread that cooperates with the internal thread at the bottom of the crucible holder 6, the bottom of the transitional crucible cover 5 is provided with an internal thread, and the top of the crucible body 4 is provided with an external thread that cooperates with the internal thread at the bottom of the transitional crucible cover 5.

[0068] As another specific embodiment, the bottom of the crucible holder 6 is provided with an external thread, the top of the transition crucible cover 5 is provided with an internal thread that cooperates with the external thread at the bottom of the crucible holder 6, the bottom of the transition crucible cover 5 is provided with an external thread, and the top of the crucible body 4 is provided with an internal thread that cooperates with the external thread at the bottom of the transition crucible cover 5.

[0069] The skilled person and technicians know that since the intermediate transition crucible cover 5 is respectively connected to the upper and lower crucible holders 6 and the crucible body 4 by threads, there are other different implementation methods, and the skilled person and technicians can design them according to needs.

[0070] It should be noted that the skilled and technical personnel can adjust the shapes of the transition crucible cover 5, the crucible holder 6 and the crucible body 4 according to the situation to meet the technical effect to be achieved by the present application. For example, since the movable laser locator 10 needs to meet the positioning of the outer edge of the crucible body 4, the outer edges of the transition crucible cover 5 and the crucible holder 6 cannot block the positioning of the outer edge of the crucible body 4 by the movable laser locator 10, so the corresponding threaded connection structure can be designed according to the needs. For example, in the case where the bottom of the transition crucible cover 5 is provided with an internal thread, and the top of the crucible body 4 is provided with an external thread that matches the internal thread at the bottom of the transition crucible cover 5, in order to meet the positioning needs of the above-mentioned movable laser locator 10, a narrowed transition structure can be provided on the top of the crucible body 4, and then the outer edge of the transition crucible cover 5 can be set so that it cannot block the outer edge of the crucible body 4.

[0071] The crucible holder 6 is fixed on the bottom of the upper flange 2, and the crucible body 4 and the crucible holder 6 are respectively connected through the transition crucible cover 5. After the reaction materials are filled into the crucible body 4, the crucible body 4 can be fixed at a fixed position of the upper flange 2, and then the relative position of the external insulation 7 can be adjusted.

[0072] As an embodiment, a graphitized carbon fiber cloth 13 is also arranged between the outer insulation 7 and the crucible. The graphitized carbon fiber cloth 13 includes a matrix and carbon fiber bundles in the matrix. The matrix is ​​tar pitch, and the carbon fiber bundles are graphitized carbon fiber bundles. The graphitized carbon fiber bundles are arranged in parallel in the tar pitch matrix.

[0073] Tar pitch is the binder, and graphitized carbon fiber bundles are the support. Since Si atmosphere is more easily captured by the tar pitch binder, it can effectively reduce the erosion of Si atmosphere on the insulation felt during the preparation of SiC crystals by the PVT method, thereby ensuring the insulation effect of the insulation felt, ensuring the uniformity and stability of the temperature field during the crystal growth process, and reducing the generation of polymorphism. The support is a graphitized carbon fiber bundle, which can significantly improve the tensile strength and high temperature resistance of the carbon fiber cloth, and can meet the use environment of more than 2000°C during the SiC growth process.

[0074] It should be noted that the tar pitch and graphitized carbon fiber bundles used in the present application are commonly used materials, and those skilled in the art can select them according to their needs. In addition, the present application does not limit the preparation process of the graphitized carbon fiber cloth 13, and the commonly used preparation process in the field can be adopted, and the prepreg method can also be adjusted according to needs.

[0075] It should be noted that the present application scheme mainly describes the main invention points. Other structures in the induction furnace can be implemented by referring to the scheme of the induction furnace in the field. This is something that can be routinely determined by those skilled in the art and does not require additional elaboration. For example, those skilled in the art can set the deployment mode of the induction coil 19 as needed, and can also set the temperature measuring hole 18 structure on the upper flange 2 as needed. In addition, those skilled in the art can also adjust and set the position of the closable slide rail and the crucible holder 6 on the upper flange 2 as needed, and adjust the shape of the transition crucible cover 5 as needed, so that the movable laser positioner 10 on the closable slide rail can have sufficient movement space and can detect the outer edge of the crucible body 4 and the inner edge of the outer insulation 7. This is a routine skill of those skilled in the art and does not require additional explanation.

[0076] As an embodiment, the graphitized carbon fiber cloth 13 includes a matrix and carbon fiber bundles in the matrix, wherein the matrix is ​​tar pitch, and the carbon fiber bundles are graphitized carbon fiber bundles, and the graphitized carbon fiber bundles are arranged in parallel in the tar pitch matrix.

[0077] Example 2

[0078] refer to Figure 2-4 The present embodiment discloses a planetary rotary cutting device for silicon carbide, comprising: a cutting chamber 10, wherein the cutting chamber 10 is provided with a liquid inlet 11 and a liquid outlet 12, wherein the interior of the cutting chamber 10 is hollow and contains cutting liquid; a fixed plate 20, wherein the fixed plate 20 is fixed in the cutting chamber 10; a rotating fixed table, wherein the rotating fixed table is connected to the fixed plate 20 through a lifting assembly, wherein the rotating fixed table can rise or fall relative to the fixed plate 20, wherein the rotating fixed table is used to fix silicon carbide 34 and can drive the silicon carbide 34 to rotate; a groove wheel guide plate 40, wherein the groove wheel guide plate 40 is arranged on the cutting chamber 10; The bin 10 is provided with a first arc-shaped guide rail 41 on the groove wheel guide plate 40, the curvature of the first arc-shaped guide rail 41 does not exceed 90°, and two first groove wheels 50 are provided on the first arc-shaped guide rail 41, and the first groove wheels 50 can move along the first arc-shaped guide rail 41, and the first groove wheels 50 are located below the rotating fixed table; at least two second groove wheels 52, the second groove wheels 52 are arranged on the second arc-shaped guide rail 42 and are located above the rotating fixed table, the second arc-shaped guide rail 42 is cocentrically arranged with the first arc-shaped guide rail 41, and the second groove wheels 52 cooperate with the first groove wheels 50 for winding the cutting line.

[0079] In the device, the first sheave 50 and the second sheave 52 cooperate to realize the winding of the cutting line, so that a plurality of parallel cutting lines are arranged below the first sheave 50. During the cutting process, the silicon carbide 34 is fixed on the rotating fixed table, the rotating fixed table drives the silicon carbide 34 to rotate, and the lifting assembly drives the rotating fixed table to descend, so that the silicon carbide 34 moves toward the plurality of parallel cutting lines between the two first sheaves 50 to cut the silicon carbide 34. At the same time, the two first sheaves 50 reciprocate along the first arc-shaped guide rail 41, and the second sheave 52 reciprocates along the second arc-shaped guide rail 42, and the movement speeds of the first sheave 50 and the second sheave 52 are consistent.

[0080] In the cutting chamber 10, the cutting liquid is circulated through the cutting liquid inlet and the cutting liquid outlet, so that the contact friction between the cutting line and the crystal is not too large during the cutting process, and the cutting line is cooled at the same time.

[0081] During the cutting process, the movement of the first groove wheel 50 and the second groove wheel 52 can ensure that multiple parallel cutting lines are driven to move in an arc shape, and cooperate with the rotating silicon carbide 34 to achieve circular cutting and circular cutting. This setting can improve the force uniformity of the silicon carbide 34 during the cutting process, avoid excessive local force, thereby improving the surface quality of the silicon carbide 34, especially reducing the curvature of the silicon carbide 34, and improving the uniformity of the distribution of the curvature on the cutting surface. In addition, during the cutting process of the above-mentioned cutting equipment, the movement direction of the cutting line driven by the rotation of the silicon carbide 34 and the first groove wheel 50 can be consistent or inconsistent. When the movement directions are consistent, the cutting force can be buffered, but the cutting efficiency will be reduced. When the movement directions are inconsistent, the cutting efficiency can be improved.

[0082] Specifically, the silicon carbide 34 can be fixed on the rotating fixed table in various ways, as long as the silicon carbide 34 is fixed during the cutting process, and the silicon carbide 34 is ensured not to be offset during the cutting process and not to have a negative impact on the silicon carbide 34, for example, it can be a hot melt adhesive bonding method or a vacuum adsorption method. In addition, the rotation direction of the silicon carbide 34 can be clockwise or counterclockwise, and the rotation speed can be adjusted according to the cutting process.

[0083] Specifically, the rotating fixed platform can be connected to the fixed plate 20 through the lifting assembly in a manner known in the prior art and does not constitute a limitation to the present application. Figure 4The lifting component can be a telescopic rod 21, and the rotating fixed platform (fixed axis 33, rotating axis 32 and bonding plate 31) is fixed on the free end of the telescopic rod 21. The fixed end of the telescopic rod 21 is fixed above the fixed plate 20. The telescopic rod 21 is extended and retracted to drive the rotating fixed platform to rise and fall. The telescopic end of the telescopic rod 21 is connected to the fixed axis 33, and the fixed axis 33 is connected to the rotating axis 32. The bonding plate 31 is driven to rotate through the rotating axis 32, and the bonding plate 31 is bonded to the SiC crystal by hot melt adhesive.

[0084] The above method only needs to ensure that the crystal is in contact with the cutting line during the descending process, so as to achieve the cutting of the entire crystal and will not hinder the movement of the first groove wheel 50 .

[0085] Specifically, the telescopic rod 21 and the rotating shaft 32 may be driven by electric drive, hydraulic drive or other driving methods in the prior art.

[0086] Specifically, the second groove wheel 52 and the second arc guide rail 42 can be located inside the cutting chamber 10 or outside the cutting chamber 10. When they are located outside the cutting chamber 10, a passage needs to be opened at the top of the cutting chamber 10 to facilitate the passage of the cutting line.

[0087] As an implementation manner, a reserved hole 43 is provided at the center of the groove wheel guide plate 40 , and the rotating fixing platform passes through the reserved hole 43 .

[0088] If a sheave guide plate 40 without a reserved hole 43 is used, in order to achieve the non-interference between the cutting of silicon carbide 34 and the movement of the first sheave 50 on the first arc guide rail 41, the sheave guide plate 40 needs to be set below the rotating fixed table, and the area should not be too large. In addition, other components need to be set additionally for setting the second arc guide rail 42. Therefore, the reserved hole 43 set on the sheave guide plate 40 can set part of the sheave guide plate 40 above the rotating fixed table. This setting can increase the area of ​​the sheave guide plate 40, thereby improving the stability of the sheave guide plate 40 and achieving stable operation of the first sheave 50 on the first arc guide rail 41; secondly, the second arc guide rail 42 can also be set on the sheave guide plate 40, thereby improving the compactness of the structure of the cutting equipment and reducing the floor space.

[0089] As an embodiment, the second arc guide rail 42 is arranged on the groove wheel guide rail plate 40. Under this arrangement, the second arc guide rail 42 and the second groove wheel 52 are arranged in the cutting chamber 10, which can not only improve the compactness of the structure, but also prevent the cutting line from leaking out of the cutting chamber 10, avoid introducing impurities into the cutting chamber 10, improve the cleanliness of the cutting process, and further improve the cutting quality of the silicon carbide 34.

[0090] As an embodiment, the first sheave 50 moves along the first arc-shaped guide rail 41 at an angle of 10° to 80°, preferably 10° to 30°. The second arc-shaped guide rail 42 is connected to the first arc-shaped guide rail 41 to form a circular guide rail.

[0091] The angle of movement of the first groove wheel 50 along the first arc-shaped guide rail 41 is set within this range, firstly, to avoid the first groove wheel 50 from moving too far, thereby avoiding winding of the cutting line or excessive tension changes, and secondly, to increase the movement time of the first groove wheel 50 along the first arc-shaped guide rail 41 in the same direction as much as possible, thereby improving the stability of the cutting line and thus improving the cutting quality. The second arc-shaped guide rail 42 and the first arc-shaped guide rail 41 are connected to form a circular guide rail, which can improve the convenience of the processing equipment. Even without the action of the limiter 53, the first groove wheel 50 can smoothly enter the second arc-shaped guide rail 42 when rotating excessively, thereby increasing the operating reliability of the cutting equipment.

[0092] As an implementation manner, both the first arc-shaped guide rail 41 and the second arc-shaped guide rail 42 are provided with limiters 53 .

[0093] This setting can play the role of instructing the first groove wheel 50 and the second groove wheel 52 to turn. In actual cutting, when the first groove wheel 50 moves on the first arc guide rail 41 and contacts the limiter 53, the limiter 53 can send a signal to the control system. After receiving the signal, the control system can send an instruction to the first groove wheel 50 to make the first groove wheel 50 move in the opposite direction. At this time, the second groove wheel 52 also receives the command and moves in the opposite direction at the same time. Therefore, the setting of the limiter 53 also improves the automatic operation capability of the cutting equipment.

[0094] Specifically, the operation of the limiter 53, the first groove wheel 50, the second groove wheel 52, the rotating fixed platform, and the lifting assembly are all controlled by the control system, and the specific control method is the existing technology, which will not be described in detail.

[0095] Specifically, the first sheave 50 can move along the first arc-shaped guide rail 41 in an existing manner in the prior art, such as electromagnetic drive, or a rack can be provided on the upper surface of the first arc-shaped guide rail 41, and a gear meshing with the rack can be provided at the bottom of the first sheave 50, and the gear rotates to realize the movement of the first sheave 50 along the first arc-shaped guide rail 41. Similarly, the second sheave 52 can move along the second arc-shaped guide rail 42 in the same manner as the first sheave 50.

[0096] Example 3

[0097] The SiC crystal prepared in this embodiment is grown using the induction crystal growth furnace of Example 1. The specific crystal growth method is as follows:

[0098] (1) Place the raw materials in a crystal growth furnace, first raise the temperature to 1000-1500°C and maintain for 10-20 hours at a pressure of 50-60 mbar, during which time 300-330 sccm of Ar gas and 40-60 sccm of N2 gas are introduced;

[0099] (2) Then, the temperature is raised to 1800-1900°C within 10-15 hours, the pressure is changed to 30-35 mabr, maintained for 10-20 hours, and 280-300 sccm of Ar gas and 28-30 sccm of N2 gas are introduced;

[0100] (3) Finally, the temperature is raised to 2200-2300°C within 40-45 hours, the pressure is 15-20 mbar, and maintained for 130-150 hours. During this period, 90-100 sccm of Ar gas and 10-20 sccm of N2 gas are introduced. After the crystal growth is completed, the temperature is lowered to room temperature at a cooling rate of 80-150°C / min, and the furnace is opened to obtain crystals.

[0101] SiC crystals 1# to 3# are prepared according to the above-mentioned crystal growth method. The specific crystal growth method is as follows:

[0102] SiC crystal 1#

[0103] (1) Place the raw materials in a crystal growth furnace, first raise the temperature to 1000°C and maintain for 20 hours at a pressure of 60 mbar, during which time 330 sccm of Ar gas and 60 sccm of N2 gas are introduced;

[0104] (2) Then, the temperature was raised to 1800°C within 10 h, the pressure was changed to 35 mabr, maintained for 20 h, and 300 sccm of Ar gas and 30 sccm of N2 gas were introduced;

[0105] (3) Finally, the temperature was raised to 2200°C after 40 hours, the pressure was 15 mbar, and maintained for 150 hours. During this period, 100 sccm of Ar gas and 10 sccm of N2 gas were introduced. After the crystal growth was completed, the temperature was lowered to room temperature at a rate of 80°C / min, and the furnace was opened to obtain the crystal.

[0106] SiC crystal 2#

[0107] (1) Place the raw materials in a crystal growth furnace, first raise the temperature to 1500°C and maintain for 10 hours at a pressure of 50 mbar, during which time 330 sccm of Ar gas and 40 sccm of N2 gas are introduced;

[0108] (2) Then, the temperature was raised to 1900°C within 15 hours, the pressure was changed to 30 mabr, maintained for 10 hours, and 280 sccm of Ar gas and 28 sccm of N2 gas were introduced;

[0109] (3) Finally, the temperature was raised to 2300°C after 45 hours, the pressure was 20 mbar, and maintained for 130 hours. During this period, 90 sccm of Ar gas and 20 sccm of N2 gas were introduced. After the crystal growth was completed, the temperature was lowered to room temperature at a rate of 150°C / min, and the furnace was opened to obtain the crystal.

[0110] SiC crystal 3#

[0111] (1) Place the raw materials in a crystal growth furnace, first raise the temperature to 1350°C and maintain for 15 hours at a pressure of 55 mbar, during which time 300 sccm of Ar gas and 50 sccm of N2 gas are introduced;

[0112] (2) Then, the temperature was raised to 1850°C within 12 hours, the pressure was changed to 32 mabr, and maintained for 17 hours, and 290 sccm of Ar gas and 30 sccm of N2 gas were introduced;

[0113] (3) Finally, the temperature was raised to 2250°C after 40 hours, the pressure was 17 mbar, and maintained for 140 hours. During this period, 100 sccm of Ar gas and 15 sccm of N2 gas were introduced. After the crystal growth was completed, the temperature was lowered to room temperature at a rate of 110°C / min, and the furnace was opened to obtain the crystal.

[0114] The SiC substrates prepared above were cut, ground and polished to obtain a surface roughness Ra of no more than 10 nm and a thickness of 500 micrometers.

[0115] The cutting is performed using the cutting equipment of Example 2, and the specific cutting process is as follows:

[0116] (1) Fix the SiC crystal on a rotating fixed table;

[0117] (2) The rotating fixed table drives the SiC crystal to rotate, and the rotation speed of the SiC crystal is 0.05-0.1 rad / s. At the same time, the lifting assembly drives the SiC crystal to descend, and the speed of the SiC crystal descending downward is 0.002-0.005 mm / min; the two first groove wheels reciprocate along the first arc-shaped guide rail at a speed of 0.025-0.05 rad / s, and the second groove wheel reciprocates along the second arc-shaped guide rail, and the movement speed of the first groove wheel and the second groove wheel is consistent;

[0118] (3) The lifting assembly drives the rotating fixed table to descend so that the SiC crystal moves toward the cutting line between the two first groove wheels to cut the SiC crystal. The cutting line feed speed is 10 to 14 mm / s and the cutting line tension is 20 to 45 N until the cutting is completed.

[0119] The cutting process of SiC crystal 1# and 2# is as follows:

[0120] (1) Fix the SiC crystal on a rotating fixed table;

[0121] (2) The rotating fixed table drives the SiC crystal to rotate, and the rotation speed of the SiC crystal is 0.05 rad / s. At the same time, the lifting assembly drives the SiC crystal to descend, and the speed of the SiC crystal descending is 0.002 mm / min; the two first groove wheels reciprocate along the first arc-shaped guide rail at a speed of 0.05 rad / s, and the second groove wheel reciprocates along the second arc-shaped guide rail, and the movement speed of the first groove wheel and the second groove wheel is consistent;

[0122] (3) The lifting assembly drives the rotating fixed table to descend so that the SiC crystal moves toward the cutting line between the two first groove wheels to cut the SiC crystal. The cutting line feed speed is 14 mm / s and the cutting line tension is 45 N until the cutting is completed.

[0123] The cutting process of SiC crystal 3# is:

[0124] (1) Fix the SiC crystal on a rotating fixed table;

[0125] (2) The rotating fixed table drives the SiC crystal to rotate, and the rotation speed of the SiC crystal is 0.1 rad / s. At the same time, the lifting assembly drives the SiC crystal to descend, and the speed of the SiC crystal descending is 0.005 mm / min; the two first groove wheels reciprocate along the first arc-shaped guide rail at a speed of 0.025 rad / s, and the second groove wheel reciprocates along the second arc-shaped guide rail, and the movement speed of the first groove wheel and the second groove wheel is consistent;

[0126] (3) The lifting assembly drives the rotating fixed table to descend so that the SiC crystal moves toward the cutting line between the two first groove wheels to cut the SiC crystal. The cutting line feed speed is 10 mm / s and the cutting line tension is 20 N until the cutting is completed.

[0127] The parameters obtained by performing polarized light testing on each SiC substrate obtained from each SiC crystal are as follows:

[0128] 1. Convert the light source into polarized light through a polarizer,

[0129] 2. Polarized light is transmitted through a polished and transparent single-crystal SiC substrate through a preset optical path. When there is residual stress in the SiC substrate, the substrate lattice will be distorted, including crystal defects such as dislocations and microtubes, as well as processing damage such as edge collapse and scratches. Lattice distortion causes polarized light to deflect, and the deflection angle causes polarized light to undergo polarization birefringence, presenting polarized light in two directions.

[0130] 3. Then, the polarization camera is used to analyze the interference fringes of the two polarized lights in the optical path, and the polarization stress map can be qualitatively obtained. When the stress in the sample surface reaches equilibrium, the polarized lights in the two directions completely cancel each other out, resulting in black interference fringes; when residual stress exists, the polarized lights in the two directions do not completely cancel each other out, presenting bright colors, thereby achieving the residual stress characterization and analysis of the SiC single crystal substrate;

[0131]

[0132] in,

[0133] Δ: optical path difference between ordinary light (o light) and extraordinary light (e light);

[0134] d: sample thickness;

[0135] Δn: The difference in refractive index between ordinary light (o light) and extraordinary light (e light);

[0136] λ: wavelength.

[0137] The curvature test of each SiC substrate obtained from each SiC crystal is performed as follows:

[0138] Using HRXRD, the surface basal plane bending of the C and Si sides of SiC was tested respectively. Points were taken for the <1-100> crystal direction family and the <11-20> crystal direction family. The center point (0,0) of a wafer of any size was used as the reference point. The curvature and curvature radius in the measured direction were calculated by calculating the peak position difference between the reference point and the two sides of the reference point.

[0139] Several SiC substrates obtained from a SiC crystal, each SiC substrate obtains an optical path difference value. The values ​​represented in Table 1 with "maximum value" refer to the maximum value obtained by testing among several SiC substrates obtained from the SiC crystal, so the several SiC substrates obtained from the entire SiC crystal are less than or equal to the values ​​in Table 1; similarly, the values ​​with "minimum value" refer to the minimum value obtained by testing among several SiC substrates obtained from the SiC crystal. The above-mentioned SiC crystals 1#~3# are all 8 inches.

[0140] Table 1

[0141]

[0142]

[0143] In the above Table 1, K3 / K4 and K5 / K6 are obtained by comparing the 6 crystal directions of the <1-100> crystal direction family and the 6 crystal directions of the <11-20> crystal direction family, respectively, to obtain the minimum and maximum ratios, so the ratios of any two crystal directions in the <1-100> crystal direction family and the <11-20> crystal direction family are within the minimum and maximum ranges disclosed in Table 1. In addition, Table 1 only uses the ratios of the C plane and the Si plane in the two crystal directions [1-100] and [11-20] for characterization. The ratios of the two crystal directions are representative for the <1-100> crystal direction family and the <11-20> crystal direction family. When the <1-100> crystal direction family selects [1-100], [-1100], [01-10], [0-110], [10-10],

[0144] When the <11-20> crystal direction group selects 6 crystal directions: [11-20], [-11-20], [1-1-20], [-1-1-20], [1-1-10], and [-1-1-10], the above-mentioned SiC crystals 1# to 3# all satisfy that the ratio of the curvature of the C surface in the <1-100> crystal direction group and the <11-20> crystal direction group is 0.8 to 1.2, and the ratio of the curvature of the Si surface in the <1-100> crystal direction group and the <11-20> crystal direction group is 0.3 to 1.5.

[0145] Figure 5 This is a statistical diagram of the basal plane bending diffraction peaks of the C-plane and Si-plane of one of the SiC substrates prepared from SiC crystal 1#. From the figure, it can be seen that the basal plane results of the C-plane and Si-plane are roughly consistent in the two crystal directions [1-100] and [11-20], indicating that the surface quality of the SiC substrate is more uniform.

[0146] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A SiC crystal with small basal plane curvature and small optical path difference, characterized in that: The curvature of the C surface and Si surface of any SiC substrate prepared by the SiC crystal is less than 1.5×10 -6 mm -1 ; The optical path difference of any SiC substrate prepared from the SiC crystal is < 5.5 nm.

2. The SiC crystal with small basal plane curvature and small optical path difference according to claim 1, characterized in that: Any SiC substrate obtained by the SiC crystal, |K1-K2|<1×10 -6 mm -1 , K1 represents the curvature of the C surface of the SiC substrate, and K2 represents the curvature of the Si surface of the SiC substrate.

3. The SiC crystal with small basal plane curvature and small optical path difference according to claim 2, characterized in that: 0.6 < K3 / K4 < 1.2, where K3 represents the curvature of any SiC substrate prepared from the SiC crystal in the <1-100> crystal orientation family, and K4 represents the average value of the curvatures of all SiC substrates prepared from the SiC crystal in the <1-100> crystal orientation family.

4. The SiC crystal with small basal plane curvature and small optical path difference according to claim 1, characterized in that: |OPD1 - OPD2| < 3 nm, where OPD1 represents the optical path difference of the SiC substrate containing the first end face prepared from the SiC crystal, and OPD2 represents the optical path difference of the SiC substrate containing the second end face prepared from the SiC crystal.

5. The SiC crystal with small basal plane curvature and small optical path difference according to claim 1, characterized in that: For any SiC substrate prepared from the SiC crystal, 0.4 < OPD3 / OPD4 < 0.85, where OPD3 represents the optical path difference in the 3 / 4 radius region of the SiC substrate, and OPD4 represents the optical path difference outside the 3 / 4 radius region of the SiC substrate.

6. A SiC substrate with small base plane curvature and small optical path difference, characterized in that: The curvatures of the C surface and the Si surface of the SiC substrate are both less than 1.5×10 -6 mm -1 ; And the optical path difference of the SiC substrate is < 5.5 nm.

7. The SiC substrate with small base plane curvature and small optical path difference according to claim 6, characterized in that: |K1-K2|<1×10 -6 mm -1 , K1 represents the curvature of the C surface of the SiC substrate, and K2 represents the curvature of the Si surface of the SiC substrate.

8. The SiC substrate with small base plane curvature and small optical path difference according to claim 6, characterized in that: The ratio of the curvatures of the C plane of the SiC substrate in the <1-100> crystal orientation family and the <11-20> crystal orientation family is 0.8 - 1.

2.

9. The SiC substrate with small base plane curvature and small optical path difference according to claim 6, characterized in that: The ratio of the curvatures of the Si plane of the SiC substrate in the <1-100> crystal orientation family and the <11-20> crystal orientation family is 0.3 - 1.

5.

10. The SiC substrate with small base plane curvature and small optical path difference according to claim 6, characterized in that: On any horizontal line of the SiC substrate, the coefficient of variation of the optical path difference ≤ 1.5, and the coefficient of variation of the optical path difference refers to the ratio of the standard deviation of the optical path difference calculated on this line to the average value of the optical path difference.

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