Preparation method of silicon carbide substrate

Abstract

The invention relates to the technical field of substrate preparation, in particular to a preparation method of a silicon carbide substrate, which comprises the following steps: detecting the surface of a prepared silicon carbide crystal bar to obtain the surface roughness of the silicon carbide crystal bar and the diameter of the crystal bar; determining an initial cutting mode of the silicon carbide crystal bar according to the surface roughness, wherein the initial cutting mode comprises a first cutting mode and a second cutting mode; cutting the silicon carbide crystal bar according to the initial cutting mode to obtain a silicon carbide wafer; grinding parameters are determined according to the cutting texture trend and the curvature of the surface of the silicon carbide wafer; the grinding parameters comprise grinding granularity and grinding pressure; and grinding the silicon carbide wafer according to the grinding parameters, and polishing the ground silicon carbide wafer to obtain the silicon carbide substrate. The production efficiency and the production quality of the silicon carbide substrate can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of substrate preparation, and in particular to a method for preparing a silicon carbide substrate. Background Art

[0002] Devices made of silicon carbide materials have the characteristics of high temperature resistance, high voltage resistance, high frequency, high power, and radiation resistance. They also have the advantages of fast switching speed and high efficiency, which can greatly reduce product power consumption, improve energy conversion efficiency and reduce product volume. At present, silicon carbide semiconductors are widely used in radio frequency fields represented by 5G communications, national defense and military industry, aerospace, and power electronics represented by new energy vehicles. Silicon carbide substrates prepared using silicon carbide materials have the characteristics of large bandgap width, high thermal conductivity, high critical breakdown field strength, and high electron saturation drift rate. These characteristics make their application performance under high temperature, high pressure, high frequency, high power and other conditions better than silicon substrates. They are widely used in the manufacture of radio frequency devices and power devices. The global silicon carbide substrate market size has shown a significant growth trend in recent years and is expected to achieve rapid growth in the next few years.

[0003] The preparation process of silicon carbide substrates includes raw material synthesis, crystal growth, ingot processing, crystal rod cutting, cutting wheel grinding, grinding wheel polishing, polishing wheel cleaning and other links. At present, in order to improve the performance of silicon carbide substrates, most of them are optimized in terms of raw material synthesis and crystal growth. However, crystal rod cutting and cutting wheel grinding have a great impact on the performance of silicon carbide substrates. If there is damage on the surface of the substrate after cutting and grinding, it will directly spread to the surface of the epitaxial wafer in the form of triangular defects, forming a large number of unqualified areas. In the subsequent chip manufacturing process, these unqualified areas will greatly reduce the chip yield, which is the primary factor affecting the chip yield.

[0004] Chinese patent publication number CN109545680B discloses a method for rapidly preparing a high-flatness, low-damage single-crystal silicon carbide substrate, comprising the following steps: performing fully consolidated abrasive processing on the single-crystal silicon carbide, and then performing chemical mechanical polishing to obtain the high-flatness, low-damage single-crystal silicon carbide substrate; wherein the consolidated abrasive processing includes wire cutting and grinding wheel grinding, consolidating abrasive particles on the cutting wire, and consolidating abrasive particles on the grinding wheel.

[0005] It can be seen that the above invention has the following problems: the preparation process is relatively complicated, and the influence of the surface roughness of the silicon carbide crystal rod on the cutting and grinding process is not considered, resulting in relatively low production efficiency and low quality of the silicon carbide substrate. Summary of the invention

[0006] To this end, the present invention provides a method for preparing a silicon carbide substrate, so as to overcome the problem that the preparation process in the prior art is relatively complicated, resulting in relatively low production efficiency, and does not consider the influence of the surface roughness of the silicon carbide crystal rod on the cutting and grinding process, resulting in low quality of the silicon carbide substrate.

[0007] To achieve the above object, the present invention provides a method for preparing a silicon carbide substrate, comprising:

[0008] Step S1, detecting the surface of the prepared silicon carbide crystal rod to obtain the surface roughness and the diameter of the silicon carbide crystal rod; wherein the surface roughness includes a first roughness corresponding to the first surface and a second roughness corresponding to the second surface;

[0009] Step S2, determining an initial cutting method of the silicon carbide crystal rod according to the surface roughness, including a first cutting method and a second cutting method;

[0010] Wherein, under the first condition, the first cutting method is used, and the first cutting parameters corresponding to the first cutting method are determined according to the crystal rod diameter, and the first cutting parameters include a first cutting point and a first cutting speed;

[0011] Under the second condition, the second cutting method is used, and second cutting parameters are determined according to the surface roughness and the diameter of the crystal rod, wherein the second cutting parameters include a second cutting point, a second cutting speed, an initial cutting depth, and a third cutting speed;

[0012] Step S3, cutting the silicon carbide crystal rod according to the initial cutting method to obtain silicon carbide wafers;

[0013] Step S4, determining grinding parameters according to the cutting texture direction and curvature of the surface of the silicon carbide wafer; the grinding parameters include grinding particle size and grinding pressure;

[0014] Step S5, grinding the silicon carbide wafer according to the grinding parameters, and polishing the ground silicon carbide wafer to obtain a silicon carbide substrate.

[0015] Furthermore, in the step S2, determining the initial cutting method of the silicon carbide crystal rod includes:

[0016] If the first roughness and the second roughness are both smaller than a preset roughness threshold, and the difference between the first roughness and the second roughness is smaller than a first preset difference, it is determined that the first condition is met, and the first cutting method is used;

[0017] If the first roughness and the second roughness are both smaller than a preset roughness threshold, and the difference between the first roughness and the second roughness is greater than or equal to a first preset difference, it is determined that the second condition is met and the second cutting method is used.

[0018] Further, in step S2, the first cutting method includes:

[0019] During the cutting process, the cutting device uses the first cutting point as the initial cutting point and performs cutting at a uniform speed at a first cutting speed to complete the cutting process of the silicon carbide crystal rod; wherein the obtained silicon carbide wafer has the second surface as the bottom surface.

[0020] Further, in the step S2, the second cutting method divides the silicon carbide crystal rod into a first cutting part and a second cutting part;

[0021] Wherein, during the cutting process of the first cutting part, the cutting device takes the second cutting point as the initial cutting point and the cutting depth as the initial cutting depth, and starts rotating cutting at a uniform speed at the second cutting speed to complete the cutting process of the first cutting part;

[0022] During the cutting process of the second cutting portion, the cutting device performs cutting at a uniform speed at a third cutting speed to complete the cutting process of the second cutting portion;

[0023] During the cutting process, the cutting device sequentially completes the cutting of the first cutting part and the second cutting part to complete the cutting process of the silicon carbide crystal rod.

[0024] Further, in step S2, the first cutting parameter is determined by the following steps:

[0025] Step S21, comparing the diameter of the crystal rod with a preset diameter threshold, and determining a first cutting coefficient according to the comparison result;

[0026] Step S22, determining a first cutting length according to the crystal rod diameter and the first cutting coefficient; wherein any point on the arc on the first surface whose distance from the edge of the second surface to the first cutting length is the first cutting point;

[0027] Step S23, comparing the first cutting length with a preset cutting length, and determining the first cutting speed according to the comparison result and a standard cutting speed.

[0028] Further, in step S2, the second cutting parameter is determined by the following steps:

[0029] Step S24, determining a second cutting coefficient according to the first roughness and the second roughness;

[0030] Step S25, determining a second cutting length according to the crystal rod diameter and the second cutting coefficient; wherein any point on the arc on the first surface whose distance from the edge of the second surface to the second surface is the second cutting length is the second cutting point;

[0031] Step S26, comparing the second cutting length with a preset cutting length, and determining the second cutting speed according to the comparison result and a standard cutting speed;

[0032] Step S27, determining a third cutting coefficient according to the ratio of the first roughness to the second roughness, and determining the initial cutting depth according to the second cutting length and the third cutting coefficient;

[0033] Step S28, comparing the initial cutting depth with the crystal rod diameter, and determining the third cutting speed according to the comparison result and the standard cutting speed.

[0034] Furthermore, in the step S4, the grinding parameters are determined according to the cutting texture orientation and curvature of the surface of the silicon carbide wafer, including:

[0035] Comparing the cutting texture direction with a preset cutting texture direction to determine whether the cutting texture direction conforms to the preset cutting texture direction;

[0036] Wherein, if the cutting texture direction conforms to the preset cutting texture direction, the grinding particle size is set to the standard grinding particle size, and the grinding pressure is set to the standard grinding pressure;

[0037] If the cutting texture orientation does not conform to the preset cutting texture orientation, the grinding parameters are determined according to the curvature.

[0038] Further, determining the grinding parameters according to the curvature includes:

[0039] The curvature is compared with a standard curvature to determine a first comparison value, and the grinding particle size is determined according to the first comparison value and a standard grinding particle size, and the grinding pressure is determined according to the first comparison value and a standard grinding pressure.

[0040] Further, in step S2, if the first roughness and the second roughness are both greater than or equal to a preset roughness threshold, it is determined that a third condition is met and a third cutting method is used.

[0041] Furthermore, the third cutting method includes:

[0042] During the cutting process, the cutting equipment uses the third cutting point as the initial cutting point and cuts at a uniform speed at a standard cutting speed to complete the cutting process of the silicon carbide crystal rod; wherein any point on the arc on the first surface with a preset cutting length from the edge of the second surface is the third cutting point.

[0043] Compared with the prior art, the beneficial effect of the present invention is that the present invention determines the initial cutting method of the silicon carbide crystal rod by the surface roughness of the silicon carbide crystal rod, which can reduce the influence of the surface roughness of the silicon carbide crystal rod on the cutting process, improve production efficiency and the quality of the silicon carbide substrate. Since the cutting texture direction of the wafer surface will affect the material removal rate and surface roughness during the grinding process, and the curvature of the wafer can affect the distribution of pressure during the grinding process, thereby affecting the flatness of the entire wafer, the grinding parameters are determined by the cutting texture direction and curvature of the silicon carbide wafer surface, which can further improve the quality of the silicon carbide substrate.

[0044] Furthermore, the first roughness and the second roughness corresponding to the first cutting method of the present invention are relatively small, and the difference between the two is also relatively small, indicating that the surface roughness distribution of the corresponding silicon carbide wafer is relatively uniform. By taking the first cutting point as the initial cutting point and cutting at a uniform speed at the first cutting speed, the production efficiency can be improved.

[0045] Furthermore, the first roughness corresponding to the second cutting method of the present invention is relatively small, but the difference between the two is relatively large, indicating that the surface roughness distribution of the corresponding silicon carbide wafer is not uniform enough. By dividing the silicon carbide crystal rod into a first cutting part and a second cutting part and cutting them separately, the cutting quality can be improved, thereby improving the quality of the silicon carbide substrate.

[0046] Furthermore, the first cutting parameter of the present invention is determined by the diameter of the crystal rod, and the second cutting parameter is determined by the surface roughness and the diameter of the silicon carbide crystal rod, which can improve the cutting quality and production efficiency of each silicon carbide crystal rod.

[0047] Furthermore, the first roughness and the second roughness of the present invention are both relatively large, which will increase the friction during the cutting process. By taking the third cutting point as the initial cutting point and cutting at a uniform speed at a standard cutting speed, the cutting quality of the silicon carbide crystal rod can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a flow chart of a method for preparing a silicon carbide substrate according to an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of a process for determining a first cutting parameter according to an embodiment of the present invention;

[0050] Figure 3A schematic diagram of a process for determining a second cutting parameter according to an embodiment of the present invention;

[0051] Figure 4 A logic decision diagram for determining an initial cutting method in an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the structure of the first cutting method according to an embodiment of the present invention;

[0053] Figure 6 It is a structural schematic diagram of the second cutting method according to an embodiment of the present invention;

[0054] In the figure: 1. Silicon carbide crystal rod; 2. First surface; 3. Second surface; 4. First cutting point; 5. Second cutting point. DETAILED DESCRIPTION

[0055] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0057] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0058] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] See also Figure 1 As shown, it is a flow chart of a method for preparing a silicon carbide substrate according to an embodiment of the present invention; an embodiment of the present invention provides a method for preparing a silicon carbide substrate, comprising:

[0060] Step S1, detecting the surface of the prepared silicon carbide crystal rod to obtain the surface roughness and the diameter of the silicon carbide crystal rod; wherein the surface roughness includes a first roughness corresponding to the first surface and a second roughness corresponding to the second surface;

[0061] In implementation, there is no limitation on the specific method or equipment for detecting the surface of the silicon carbide crystal rod. The surface roughness of the silicon carbide crystal rod can be directly measured by a roughness measuring instrument, and the crystal rod diameter of the silicon carbide crystal rod can be measured by a laser diameter measuring instrument. These are all existing technologies and will not be described in detail.

[0062] Step S2, determining an initial cutting method of the silicon carbide crystal rod according to the surface roughness, including a first cutting method and a second cutting method;

[0063] Wherein, under the first condition, the first cutting method is used, and the first cutting parameters corresponding to the first cutting method are determined according to the crystal rod diameter, and the first cutting parameters include a first cutting point and a first cutting speed;

[0064] Under the second condition, the second cutting method is used, and second cutting parameters are determined according to the surface roughness and the diameter of the crystal rod, wherein the second cutting parameters include a second cutting point, a second cutting speed, an initial cutting depth, and a third cutting speed;

[0065] It should be noted that those skilled in the art are aware that any method and device in the prior art capable of cutting a silicon carbide crystal rod, such as laser cutting, falls within the protection scope of the present invention and will not be described in detail herein.

[0066] See also Figure 4 As shown, it is a logical decision diagram for determining the initial cutting method in an embodiment of the present invention; specifically, in the step S2, determining the initial cutting method of the silicon carbide crystal rod includes:

[0067] If the first roughness and the second roughness are both smaller than a preset roughness threshold, and the difference between the first roughness and the second roughness is smaller than a first preset difference, it is determined that the first condition is met, and the first cutting method is used;

[0068] If the first roughness and the second roughness are both smaller than a preset roughness threshold, and the difference between the first roughness and the second roughness is greater than or equal to a first preset difference, it is determined that the second condition is met and the second cutting method is used.

[0069] In implementation, the actual implementers can set a preset roughness threshold value based on actual conditions or based on the average value of the surface roughness corresponding to the silicon carbide wafers that have passed the qualification test in historical data. Preferably, the preset roughness threshold value range is set to 7nm~15nm; the actual implementers can set the first preset difference value based on actual conditions or based on the average value of the difference between the first roughness and the second roughness corresponding to the silicon carbide wafers that have passed the qualification test in historical data. Preferably, the first preset difference value range is set to 2nm~5nm.

[0070] See also Figure 5 As shown, it is a structural schematic diagram of the first cutting method of an embodiment of the present invention; the figure includes a silicon carbide crystal rod 1, a first surface 2, a second surface 3 and a first cutting point 4.

[0071] Specifically, in step S2, the first cutting method includes:

[0072] During the cutting process, the cutting device uses the first cutting point as the initial cutting point and performs cutting at a uniform speed at a first cutting speed to complete the cutting process of the silicon carbide crystal rod; wherein the obtained silicon carbide wafer has the second surface as the bottom surface.

[0073] The first roughness and the second roughness corresponding to the first cutting method of the present invention are relatively small, and the difference between the two is also relatively small, indicating that the surface roughness distribution of the corresponding silicon carbide wafer is relatively uniform. By taking the first cutting point as the initial cutting point and cutting at a uniform speed at the first cutting speed, the production efficiency can be improved.

[0074] See also Figure 6 As shown, it is a structural schematic diagram of the second cutting method of an embodiment of the present invention; the figure includes: a silicon carbide crystal rod 1, a first surface 2, a second surface 3, and a second cutting point 5.

[0075] Specifically, in the step S2, the second cutting method divides the silicon carbide crystal rod into a first cutting part and a second cutting part;

[0076] Wherein, during the cutting process of the first cutting part, the cutting device takes the second cutting point as the initial cutting point and the cutting depth as the initial cutting depth, and starts rotating cutting at a uniform speed at the second cutting speed to complete the cutting process of the first cutting part;

[0077] During the cutting process of the second cutting portion, the cutting device performs cutting at a uniform speed at a third cutting speed to complete the cutting process of the second cutting portion;

[0078] During the cutting process, the cutting device sequentially completes the cutting of the first cutting part and the second cutting part to complete the cutting process of the silicon carbide crystal rod.

[0079] The first roughness corresponding to the second cutting method of the present invention is relatively small, but the difference between the two is relatively large, indicating that the surface roughness distribution of the corresponding silicon carbide wafer is not uniform enough. By dividing the silicon carbide crystal rod into a first cutting part and a second cutting part and cutting them separately, the cutting quality can be improved, thereby improving the quality of the silicon carbide substrate.

[0080] See also Figure 2 As shown, it is a schematic diagram of a process of determining the first cutting parameter according to an embodiment of the present invention; specifically, in step S2, the first cutting parameter is determined by the following steps:

[0081] Step S21, comparing the diameter of the crystal rod with a preset diameter threshold, and determining a first cutting coefficient according to the comparison result;

[0082] In implementation, the first cutting coefficient is determined according to the square of the ratio of the difference between the diameter of the crystal rod and the preset diameter threshold to the preset diameter threshold.

[0083] It should be noted that the actual implementers can set a preset diameter threshold based on the average of the crystal rod diameters corresponding to the silicon carbide wafers that have passed the qualification test in the historical data. Preferably, the preset diameter threshold is set to 101% to 110% of the standard diameter of the silicon carbide substrate in actual demand. For example, the standard diameter of the silicon carbide substrate actually required is 8 inches (200mm), then the preset diameter threshold can be set to 202mm to 220mm.

[0084] Step S22, determining a first cutting length according to the crystal rod diameter and the first cutting coefficient; wherein any point on the arc on the first surface whose distance from the edge of the second surface to the first cutting length is the first cutting point;

[0085] In an implementation, the first cutting length is determined according to the product of the crystal rod diameter and the first cutting coefficient.

[0086] Step S23, comparing the first cutting length with a preset cutting length, and determining the first cutting speed according to the comparison result and a standard cutting speed.

[0087] In implementation, the first intermediate value is determined according to the ratio of the first cutting length to the preset cutting length, and the first cutting speed is determined according to the product of the first intermediate value and the standard cutting speed.

[0088] It should be noted that the actual implementers can set the preset cutting length based on the actual situation or based on the average cutting speed corresponding to the silicon carbide wafers that have passed the qualification test in the historical data. Preferably, the preset cutting length value range is set to 101% to 105% of the standard thickness of the silicon carbide substrate in actual demand. For example, the standard diameter of the silicon carbide substrate actually required is 8 inches (200mm) and the corresponding standard thickness is 500μm, then the preset cutting length can be set to 505μm to 525μm.

[0089] Specifically, the actual implementer may determine the standard cutting speed based on the minimum value of the silicon carbide wafer cutting speed that has passed the qualification test in the historical data. Preferably, the standard cutting speed value range may be set to 100 mm / s to 150 mm / s.

[0090] See also Figure 3 As shown, it is a schematic diagram of a process of determining the second cutting parameter according to an embodiment of the present invention; specifically, in step S2, the second cutting parameter is determined by the following steps:

[0091] Step S24, determining a second cutting coefficient according to the first roughness and the second roughness;

[0092] In an implementation, the second cutting coefficient is determined according to the square of the ratio of the difference between the first roughness and the second roughness to the second roughness.

[0093] Step S25, determining a second cutting length according to the crystal rod diameter and the second cutting coefficient; wherein any point on the arc on the first surface whose distance from the edge of the second surface to the second surface is the second cutting length is the second cutting point;

[0094] In implementation, the second cutting length is determined according to the product of the crystal rod diameter and the second cutting coefficient.

[0095] Step S26, comparing the second cutting length with a preset cutting length, and determining the second cutting speed according to the comparison result and a standard cutting speed;

[0096] In implementation, the second intermediate value is determined according to the ratio of the second cutting length to the preset cutting length, and the second cutting speed is determined according to the product of the second intermediate value and the standard cutting speed.

[0097] Step S27, determining a third cutting coefficient according to the ratio of the first roughness to the second roughness, and determining the initial cutting depth according to the second cutting length and the third cutting coefficient;

[0098] In an implementation, the initial cutting depth is determined according to the product of the second cutting length and the third cutting coefficient.

[0099] Step S28, comparing the initial cutting depth with the crystal rod diameter, and determining the third cutting speed according to the comparison result and the standard cutting speed.

[0100] In implementation, the third intermediate value is determined according to the ratio of the initial cutting depth to 0.5 times the diameter of the crystal rod, and the third cutting speed is determined according to the ratio of the standard cutting speed to the third intermediate value.

[0101] The first cutting parameter of the present invention is determined by the crystal rod diameter, and the second cutting parameter is determined by the surface roughness and the crystal rod diameter of the silicon carbide crystal rod, which can improve the cutting quality and production efficiency of each silicon carbide crystal rod.

[0102] Please continue reading Figure 4 As shown, specifically, in the step S2, if the first roughness and the second roughness are both greater than or equal to a preset roughness threshold, it is determined that the third condition is met and the third cutting method is used.

[0103] Specifically, the third cutting method includes:

[0104] During the cutting process, the cutting equipment uses the third cutting point as the initial cutting point and cuts at a uniform speed at a standard cutting speed to complete the cutting process of the silicon carbide crystal rod; wherein any point on the arc on the first surface with a preset cutting length from the edge of the second surface is the third cutting point.

[0105] In the present invention, both the first roughness and the second roughness are relatively large, which will increase the friction during the cutting process. By taking the third cutting point as the initial cutting point and cutting at a uniform speed at a standard cutting speed, the cutting quality of the silicon carbide crystal rod can be improved.

[0106] Step S3, cutting the silicon carbide crystal rod according to the initial cutting method to obtain silicon carbide wafers;

[0107] Step S4, determining grinding parameters according to the cutting texture direction and curvature of the surface of the silicon carbide wafer; the grinding parameters include grinding particle size and grinding pressure;

[0108] Specifically, in step S4, the grinding parameters are determined according to the cutting texture orientation and curvature of the surface of the silicon carbide wafer, including:

[0109] Comparing the cutting texture direction with a preset cutting texture direction to determine whether the cutting texture direction conforms to the preset cutting texture direction;

[0110] Wherein, if the cutting texture direction conforms to the preset cutting texture direction, the grinding particle size is set to the standard grinding particle size, and the grinding pressure is set to the standard grinding pressure;

[0111] If the cutting texture orientation does not conform to the preset cutting texture orientation, the grinding parameters are determined according to the curvature.

[0112] It is understandable that those skilled in the art know that any method and device in the prior art that can detect the cutting texture direction of the cutting surface of a silicon carbide wafer, such as an optical profilometer, a texture analysis method based on computer vision, etc., falls within the scope of protection of the present invention and will not be described in detail here.

[0113] In implementation, the cutting texture orientation is set as the angle range corresponding to the maximum number of cutting scratch tracks on the cutting surface of the silicon carbide wafer within a unit angle range centered on the initial cutting point, and the preset cutting texture orientation is defined as the angle range corresponding to the preset number of cutting scratch tracks on the cutting surface of the silicon carbide wafer within a unit angle range centered on the initial cutting point. The cutting texture orientation conforms to the preset cutting texture orientation, which is defined as the maximum number of cutting scratch tracks on the cutting surface of the silicon carbide wafer within the unit angle range centered on the initial cutting point conforms to the preset number range, and the cutting texture orientation does not conform to the preset cutting texture orientation, which is defined as the maximum number of cutting scratch tracks on the cutting surface of the silicon carbide wafer within the unit angle range centered on the initial cutting point exceeds the preset number range.

[0114] Specifically, the actual implementers can determine the standard grinding particle size based on the average grinding particle size of the silicon carbide substrate that has passed the qualification test in the historical data. Preferably, the standard grinding particle size value range can be set to 0.5μm~150μm; the actual implementers can determine the standard grinding pressure based on the average grinding pressure of the silicon carbide substrate that has passed the qualification test in the historical data. Preferably, the standard grinding pressure value range can be set to 1psi~3psi.

[0115] Specifically, determining the grinding parameters according to the curvature includes:

[0116] The curvature is compared with a standard curvature to determine a first comparison value, and the grinding particle size is determined according to the first comparison value and a standard grinding particle size, and the grinding pressure is determined according to the first comparison value and a standard grinding pressure.

[0117] In implementation, the first comparison value is determined according to the ratio of the curvature to the standard curvature, the grinding particle size is determined according to the ratio of the standard grinding particle size to the first comparison value, and the grinding pressure is determined according to the ratio of the standard grinding pressure to the first comparison value.

[0118] Step S5, grinding the silicon carbide wafer according to the grinding parameters, and polishing the ground silicon carbide wafer to obtain a silicon carbide substrate.

[0119] In implementation, actual implementers may set a standard curvature based on the average curvature of silicon carbide wafers that have passed qualification inspection in historical data. Preferably, the standard curvature is set to 10 μm to 20 μm.

[0120] It should be noted that those skilled in the art are aware that any device and method in the prior art that can polish a silicon carbide wafer falls within the protection scope of the present invention and will not be described in detail herein.

[0121] The present invention determines the initial cutting method of the silicon carbide crystal rod by the surface roughness of the silicon carbide crystal rod, which can reduce the influence of the surface roughness of the silicon carbide crystal rod on the cutting process, improve production efficiency and the quality of the silicon carbide substrate. Since the cutting texture direction of the wafer surface will affect the material removal rate and surface roughness during the grinding process, and the curvature of the wafer can affect the distribution of pressure during the grinding process, thereby affecting the flatness of the entire wafer, the grinding parameters are determined by the cutting texture direction and curvature of the silicon carbide wafer surface, which can further improve the quality of the silicon carbide substrate.

[0122] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing a silicon carbide substrate, characterized in that: include: Step S1, detecting the surface of the prepared silicon carbide crystal rod to obtain the surface roughness and the diameter of the silicon carbide crystal rod; wherein the surface roughness includes a first roughness corresponding to the first surface and a second roughness corresponding to the second surface; Step S2, determining an initial cutting method of the silicon carbide crystal rod according to the surface roughness, including a first cutting method and a second cutting method; Wherein, under the first condition, the first cutting method is used, and the first cutting parameters corresponding to the first cutting method are determined according to the crystal rod diameter, and the first cutting parameters include a first cutting point and a first cutting speed; Under the second condition, the second cutting method is used, and second cutting parameters are determined according to the surface roughness and the diameter of the crystal rod, wherein the second cutting parameters include a second cutting point, a second cutting speed, an initial cutting depth, and a third cutting speed; Step S3, cutting the silicon carbide crystal rod according to the initial cutting method to obtain silicon carbide wafers; Step S4, determining grinding parameters according to the cutting texture direction and curvature of the surface of the silicon carbide wafer; the grinding parameters include grinding particle size and grinding pressure; Step S5, grinding the silicon carbide wafer according to the grinding parameters, and polishing the ground silicon carbide wafer to obtain a silicon carbide substrate.

2. The method for preparing a silicon carbide substrate according to claim 1, characterized in that: In the step S2, determining the initial cutting method of the silicon carbide crystal rod includes: If the first roughness and the second roughness are both smaller than a preset roughness threshold, and the difference between the first roughness and the second roughness is smaller than a first preset difference, it is determined that the first condition is met, and the first cutting method is used; If the first roughness and the second roughness are both smaller than a preset roughness threshold, and the difference between the first roughness and the second roughness is greater than or equal to a first preset difference, it is determined that the second condition is met and the second cutting method is used.

3. The method for preparing a silicon carbide substrate according to claim 2, characterized in that: In the step S2, the first cutting method includes: During the cutting process, the cutting device uses the first cutting point as the initial cutting point and performs cutting at a uniform speed at a first cutting speed to complete the cutting process of the silicon carbide crystal rod; wherein the obtained silicon carbide wafer has the second surface as the bottom surface.

4. The method for preparing a silicon carbide substrate according to claim 3, characterized in that: In the step S2, the second cutting method divides the silicon carbide crystal rod into a first cutting part and a second cutting part; Wherein, during the cutting process of the first cutting part, the cutting device takes the second cutting point as the initial cutting point and the cutting depth as the initial cutting depth, and starts rotating cutting at a uniform speed at the second cutting speed to complete the cutting process of the first cutting part; During the cutting process of the second cutting portion, the cutting device performs cutting at a uniform speed at a third cutting speed to complete the cutting process of the second cutting portion; During the cutting process, the cutting device sequentially completes the cutting of the first cutting part and the second cutting part to complete the cutting process of the silicon carbide crystal rod.

5. The method for preparing a silicon carbide substrate according to claim 4, characterized in that: In step S2, the first cutting parameter is determined by the following steps: Step S21, comparing the diameter of the crystal rod with a preset diameter threshold, and determining a first cutting coefficient according to the comparison result; Step S22, determining a first cutting length according to the crystal rod diameter and the first cutting coefficient; wherein any point on the arc on the first surface whose distance from the edge of the second surface to the first cutting length is the first cutting point; Step S23, comparing the first cutting length with a preset cutting length, and determining the first cutting speed according to the comparison result and a standard cutting speed.

6. The method for preparing a silicon carbide substrate according to claim 5, characterized in that: In step S2, the second cutting parameter is determined by the following steps: Step S24, determining a second cutting coefficient according to the first roughness and the second roughness; Step S25, determining a second cutting length according to the crystal rod diameter and the second cutting coefficient; wherein any point on the arc on the first surface whose distance from the edge of the second surface to the second surface is the second cutting length is the second cutting point; Step S26, comparing the second cutting length with a preset cutting length, and determining the second cutting speed according to the comparison result and a standard cutting speed; Step S27, determining a third cutting coefficient according to the ratio of the first roughness to the second roughness, and determining the initial cutting depth according to the second cutting length and the third cutting coefficient; Step S28, comparing the initial cutting depth with the crystal rod diameter, and determining the third cutting speed according to the comparison result and the standard cutting speed.

7. The method for preparing a silicon carbide substrate according to claim 6, characterized in that: In the step S4, the grinding parameters are determined according to the cutting texture orientation and curvature of the surface of the silicon carbide wafer, including: Comparing the cutting texture direction with a preset cutting texture direction to determine whether the cutting texture direction conforms to the preset cutting texture direction; Wherein, if the cutting texture direction conforms to the preset cutting texture direction, the grinding particle size is set to the standard grinding particle size, and the grinding pressure is set to the standard grinding pressure; If the cutting texture orientation does not conform to the preset cutting texture orientation, the grinding parameters are determined according to the curvature.

8. The method for preparing a silicon carbide substrate according to claim 7, characterized in that: Determining the grinding parameters according to the curvature includes: The curvature is compared with a standard curvature to determine a first comparison value, and the grinding particle size is determined according to the first comparison value and a standard grinding particle size, and the grinding pressure is determined according to the first comparison value and a standard grinding pressure.

9. The method for preparing a silicon carbide substrate according to claim 8, characterized in that: In the step S2, if the first roughness and the second roughness are both greater than or equal to a preset roughness threshold, it is determined that the third condition is met and the third cutting method is used.

10. The method for preparing a silicon carbide substrate according to claim 9, characterized in that: The third cutting method includes: During the cutting process, the cutting equipment uses the third cutting point as the initial cutting point and cuts at a uniform speed at a standard cutting speed to complete the cutting process of the silicon carbide crystal rod; wherein any point on the arc on the first surface with a preset cutting length from the edge of the second surface is the third cutting point.

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