A method for preparing substrates using the head and tail wafers of SiC crystal rods

Abstract

This invention provides a method for fabricating a substrate using the head and tail portions of a silicon carbide (SiC) crystal rod, comprising: acquiring the thickness and a first appearance image of the wafer; if the thickness is greater than or equal to a first preset thickness value and there are no defects in the appearance, marking the uncut side of the wafer; grinding this side until the thickness of the wafer is within a second preset range; grinding the wafer on both sides until the thickness is within a third preset range; acquiring the surface quality parameters and a second appearance image of the wafer; if the surface quality parameters meet the target parameters and there are no defects in the appearance, performing circumferential chamfering according to preset process parameters; polishing the wafer on both sides until the thickness of the wafer is within a fourth preset range; and selecting qualified wafers according to preset requirements. This method can reprocess the head and tail portions of the SiC crystal rod to fabricate SiC substrates with thinner or smaller thickness specifications, thereby reducing material waste.

Description

Technical Field

[0001] This invention relates to the field of SiC crystal rod processing technology, and in particular to a method for preparing a substrate using the head and tail sheets of a SiC crystal rod. Background Technology

[0002] Silicon carbide (SiC) is currently the most mature third-generation semiconductor material, possessing advantages such as a high critical breakdown electric field, a large bandgap, and high electron mobility. The most widely used SiC crystal forms are 4H-SiC and 6H-SiC. 6H-SiC is suitable for optoelectronic applications such as LEDs, while 4H-SiC has higher electron mobility than 6H-SiC, making it particularly suitable for fabricating high-frequency, high-temperature, high-power microelectronic devices, especially in applications involving SiC substrates. A SiC substrate is a thin-film silicon carbide wafer manufactured from high-purity polycrystalline SiC powder through processes such as sublimation, crystal growth, cutting, grinding, cleaning, vacuum annealing, and polishing. Epitaxy refers to the growth of a single-crystal material on the upper surface of a substrate. If the substrate and the epitaxial layer are the same material, this epitaxial layer is called homoepitaxial growth; if the substrate and the epitaxial layer are different materials, it is called heteroepitaxial growth. During the forming and processing of SiC substrates, defects are inevitably introduced onto or near the surface, affecting the bulk material quality and surface quality of the SiC substrate. Devices fabricated directly from this substrate will exhibit poor performance. Epitaxial growth, however, can eliminate many defects, resulting in a more orderly lattice arrangement and a significantly improved surface morphology compared to the substrate. Such epitaxial wafers, when used to manufacture semiconductor devices, can greatly improve the parameter stability and yield of these devices. For example, heterogeneous growth of gallium nitride epitaxial layers on silicon carbide substrates can be used to manufacture low-to-medium voltage high-frequency power devices, high-power microwave RF devices, and optoelectronic devices; homogeneous growth of silicon carbide epitaxial layers on silicon carbide substrates can be used to manufacture power devices.

[0003] Because crystal structures exhibit periodicity and symmetry, crystal planes and directions are generally used to describe the relative positions of atoms within the crystal. For hexagonal crystal systems, the plane and direction indices are typically defined using Miller-Brafel indices (hkil). For example, 4H-SiC has a hexagonal lattice structure, and its plane indices are represented by (UVTW), while its direction indices are represented by [uvtw]. In SiC homoepitaxialization, to ensure the epitaxial material effectively inherits the substrate's stacking sequence and maintains crystal quality, SiC substrates with an off-axis angle of 4° or 8° are often used. The significance of this off-axis substrate cutting lies in introducing atomic-level steps on the substrate surface. During epitaxy, adsorbed atoms tend to nucleate and grow at these steps, ensuring that the epitaxial process follows a step-flow growth pattern. For example, when homogeneously growing a 4H-SiC single-crystal epitaxial layer on a conductive 4H-SiC substrate, the required crystal orientation angles are generally 4° towards the off-axis (<11-20°> ± 0.5° for 4H-N), and generally... <0001> ±0.5° for 4H-Si.

[0004] Currently, diamond wire cutting machines are generally used to cut SiC crystal rods. Due to the anisotropic nature of SiC crystals, the SiC crystal rods are oriented and bonded before cutting to ensure that the crystal orientation angles of the cut SiC substrate meet technical requirements. The multi-wire cutting machine then slowly moves the SiC crystal rod downwards at a set downward feed rate. Two high-speed rotating wire rollers in the same direction machine grooves with a specific spacing. Diamond wire is wound around these grooves to form a cutting wire mesh. As the SiC crystal rod is pressed downwards, the diamond wire, driven by the rotation of the wire rollers, generates a sawing cutting force, thus cutting the SiC crystal rod. The distance between the diamond wire meshes is the thickness of the SiC wafer. After the SiC crystal rod is cut by the diamond wire mesh, a wafer is produced at each end of the SiC crystal rod. One side of this wafer is completely cut by the diamond wire, while the other side is not completely cut. Because the physical cylindrical centerline of the SiC crystal rod and the actual crystal orientation line have a certain angle between them after the rod is bonded, the cylindrical centerline of the crystal rod cannot be guaranteed to be completely perpendicular to the silicon and carbon surfaces at both ends. The cut surface has a certain tilt. At this time, some SiC crystal rod head and tail pieces will not be used because they do not meet the standard thickness, which increases the waste of materials and affects production efficiency. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a method for preparing a substrate using the head and tail wafers of a SiC crystal rod, which can reprocess the wafers at the head and tail of a portion of the SiC crystal rod to produce a SiC substrate with a thinner or smaller thickness specification, thereby reducing material waste.

[0006] This invention provides a method for preparing a substrate using the head and tail pieces of a SiC crystal rod, specifically including the following steps:

[0007] S100: Obtain the thickness and first appearance image of the wafer;

[0008] S200: Determine whether the thickness is less than a first preset thickness value, and at the same time determine whether there are defects in the appearance of the wafer based on the first appearance image;

[0009] S300, If not, mark the uncut side of the wafer;

[0010] S400: Grind the marked side of the wafer until the thickness of the wafer is within a second preset range;

[0011] S500: Grind both sides of the wafer until the thickness of the wafer is within a third preset range;

[0012] S600: Obtain the surface quality parameters and second appearance image of the wafer;

[0013] S700: Determine whether the surface quality parameters do not meet the target parameters, and at the same time determine whether there are defects in the appearance of the wafer based on the second appearance image;

[0014] S800, if not, then perform circumferential chamfering according to the preset process parameters;

[0015] S900. The wafer after circumferential chamfering is polished on both sides until the thickness of the wafer is within the fourth preset range.

[0016] S1000: Select qualified wafers according to preset requirements.

[0017] By using the aforementioned method of preparing substrates from the head and tail pieces of SiC crystal rods, the head and tail pieces of SiC crystal rods that would otherwise be scrapped are first selected. Then, through single-sided grinding, the uncut side of the wafer is made parallel to the cut side, resulting in a wafer with both sides meeting the crystal orientation requirements. Next, through double-sided grinding, polishing, and circumferential chamfering, thinner or smaller-thickness finished wafers can be obtained, thereby improving the utilization rate of SiC crystal rods, reducing secondary consumption caused by remelting the head and tail pieces, and saving manufacturing costs. Furthermore, based on the number of head and tail pieces that meet the thickness requirements after wire cutting, the finished product yield can reach over 65%, improving enterprise efficiency.

[0018] In addition, the method for preparing a substrate using the head and tail sheets of a SiC crystal rod according to the present invention may also have the following additional technical features:

[0019] Furthermore, step S400 specifically includes:

[0020] S410. Divide the thickness of the wafer into different thickness ranges with a predetermined step size;

[0021] S420. Divide the wafers belonging to the same thickness range into several groups containing the same number of wafers, and use a waxing machine to attach the unmarked side of the wafers in the same group to the front of one of the ceramic disks.

[0022] S430. Place several ceramic discs face down on the planetary wheel fixture;

[0023] S440. Turn on the double-sided grinding machine to perform multiple segmented accelerated grinding on the surface until the thickness of the wafer is within the second preset range.

[0024] S450, The heated and ground wafer is removed from the ceramic disk.

[0025] Furthermore, step S440 specifically includes:

[0026] S441. Each grinding session is divided into multiple grinding segments. The double-sided grinding machine performs the first grinding of the wafer by circulating the grinding slurry according to the preset processing time. The rotation speed of the double-sided grinding machine is greater than that of the previous segment in each grinding segment, and each segment has its own corresponding processing time.

[0027] S442. The double-sided grinding machine uses a grinding slurry circulation method to grind the wafer N times until the thickness of the wafer measured after grinding is within a second preset range. The grinding time of the Nth grinding is determined by the grinding rate of the (N-1)th grinding, and the grinding rate of the (N-1)th grinding is obtained by the thickness difference of the wafer before and after the (N-1)th grinding and the sum of the grinding times of each grinding segment. N is a positive integer ≥2.

[0028] The grinding slurry used includes boron carbide powder with a particle size of 240#, pure water, and a suspending agent, with a mass ratio of 1-1.5: 1.8-2.5: 0.1-0.15.

[0029] Furthermore, step S500 specifically includes:

[0030] S510. Evenly attach multiple wafers into the planetary gear hole;

[0031] S520. Press the upper grinding disc of the double-sided grinding machine flat onto the side of the wafer facing upwards;

[0032] S530. Start the double-sided grinding machine to perform multiple segmented accelerated pressure grinding on both sides of the wafer until the wafer thickness is within the third preset range.

[0033] Furthermore, step S530 specifically includes:

[0034] S531. Each grinding session is divided into multiple grinding segments. The double-sided grinding machine uses a direct discharge method for grinding slurry to perform the first grinding of the wafer with a preset processing time. The rotation speed of the double-sided grinding machine in each grinding segment is greater than that in the previous segment, and each grinding segment has a corresponding processing time.

[0035] S532. The double-sided grinding machine uses a direct discharge method to grind the wafer a second time so that the thickness of the wafer measured after grinding reaches the range of the third preset thickness value. The grinding time of the second grinding is determined by the grinding rate of the first grinding. The grinding rate of the first grinding is obtained by the thickness difference of the wafer before and after the first grinding and the sum of the grinding time of each grinding segment.

[0036] The grinding slurry used includes boron carbide powder with a particle size of W14, pure water, and a suspending agent, with a mass ratio of 1-1.5: 1.8-2.5: 0.1-0.15.

[0037] Furthermore, before step S100, the head and tail of the silicon carbide crystal rod are sequentially cleaned and dried to obtain a clean wafer.

[0038] Furthermore, the head and tail ends of the silicon carbide crystal rod are sequentially cleaned and dried to obtain clean wafers, specifically including:

[0039] The wafer is placed in the first tank of the three-tank cleaning machine, which contains the cleaning solution, and is then ultrasonically agitated and cleaned. At the same time, the filter element in the first tank circulates and filters the cleaning solution. The cleaning solution includes alkaline solution and pure water in a mass ratio of 1:10-15. The cleaning solution temperature is 60-65℃, the ultrasonic frequency is 28-40KHz, the agitation method is up and down agitation, the agitation distance is 150-300mm, the agitation frequency is 10-20 times / minute, and the cleaning time is 8-12 minutes.

[0040] The wafer is placed in the second tank of the three-tank cleaning machine for ultrasonic pure water rinsing, where the pure water temperature is 60-65℃, the ultrasonic frequency is 28-40KHz, and the cleaning time is 8-12 minutes.

[0041] The wafer is placed in the third tank of the three-tank cleaning machine for two quick rinses, with each rinse lasting 2 to 5 minutes, each quick injection lasting no more than 20 seconds, and each quick discharge lasting no more than 10 seconds.

[0042] Furthermore, after step S500 and before step S600, the process further includes: sequentially cleaning and drying the polished wafer.

[0043] Further, the ground wafer is sequentially cleaned and dried, specifically including: S

[0044] Pour the prepared cleaning solution into the first and second tanks of the four-tank cleaning machine. The cleaning solution includes oxalic acid, alkaline dewaxing agent, and pure water, with a mass ratio of 2:1:15 to 25.

[0045] The wafer is placed in the first tank for the first ultrasonic polishing and cleaning, wherein the cleaning fluid temperature is 85±5℃, the ultrasonic frequency is 28~40KHz, the cleaning time is 180~360 seconds, the polishing time is 90~180 seconds, the ultrasonic cleaning time is 90~180 seconds, and the circulation overflow time is 15~25 seconds.

[0046] The wafer is placed in the second tank for a second ultrasonic polishing and cleaning, wherein the cleaning fluid temperature is 75±5℃, the ultrasonic frequency is 28~40KHz, the cleaning time is 180~360 seconds, the polishing time is 90~180 seconds, the ultrasonic cleaning time is 90~180 seconds, and the circulation overflow time is 25~40 seconds.

[0047] The wafer is placed in the third tank for pure water rinsing, where the water temperature is 60±5℃, the rinsing time is 180~360s, and the circulation overflow is always open.

[0048] The wafer is placed in the fourth tank for two quick flushing processes, with each flushing time being 30-48 seconds and each quick flushing time being 10-15 seconds.

[0049] The cleaned wafers are then spun dry, with rinsing for 20–40 seconds at 420–600 rpm, blowing for 20–30 seconds at 1200–1800 rpm, and drying for 180–210 seconds at 1200–1800 rpm.

[0050] Furthermore, step S800 specifically includes:

[0051] The edges of the wafers are chamfered using a 500-mesh silicon carbide grinding wheel, with a diameter processing speed of 2–3 mm / s and a flat edge processing speed of 0.8–1.5 mm / s. Attached Figure Description

[0052] Figure 1 This is a flowchart of an embodiment of the present invention;

[0053] Figure 2 This is a schematic diagram of the lower grinding disc from a first-view perspective in an embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram of the lower grinding disk from a second perspective in an embodiment of the present invention;

[0055] Explanation of key component symbols:

[0056] 100 ceramic discs, 200 planetary gear fixtures, 300 lower grinding discs, 400 counterweights, and 500 central gears.

[0057] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0058] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0059] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0061] To facilitate understanding of the present invention, several embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0062] The head and tail wafers of a silicon carbide crystal rod refer to the first wafer after the head and tail of the silicon carbide crystal rod are wire-cut. This application takes the fabrication of a 6-inch silicon carbide wafer as an example, with the following specific parameters: wafer diameter 150±0.2mm, wafer flat edge length 47.5±2.5mm. The various embodiments of this invention are clearly and completely described below.

[0063] Please see Figure 1This invention provides a method for preparing a substrate using the head and tail wafers of a SiC crystal rod, comprising the following steps:

[0064] S100: Obtain the thickness and first appearance image of the wafer;

[0065] S200: Determine whether the thickness is less than the first preset thickness value, and at the same time determine whether there are defects in the appearance of the wafer based on the first appearance image;

[0066] S300: If the thickness is less than the first preset thickness value and / or the wafer has defects in appearance, then no further processing is performed; if the thickness is greater than or equal to the first preset thickness value and the wafer has no defects in appearance, then the uncut side of the wafer is marked.

[0067] Specifically, firstly, a thickness gauge is used to measure the actual thickness of each beginning and end wafer. Silicon carbide wafers with an actual thickness exceeding 415μm are selected. Then, the selected wafers are visually inspected, mainly checking for large damage and chipping on the circumferential surface. Simultaneously, based on the wire cutting marks on the wafer surface, the side of the selected wafer that was not completely cut by the wire mesh is marked with an oil-based pen. It is important to understand that the surface of the completely cut side is flat and serves as the reference plane for crystal orientation angles, while the surface of the side that was not completely cut by the wire mesh is uneven or skewed.

[0068] S400: Grind the marked side of the wafer until the thickness of the wafer is within the second preset range.

[0069] Specifically, a grinding machine is used to grind the side of the selected wafer that was not completely cut by the wire mesh until the thickness of the wafer after grinding is within the range of 385μm±5μm, at which point grinding stops. Since the side that was completely cut by the wire mesh is flat and serves as the reference plane for crystal orientation angles, this side is used as the reference plane when grinding the side that was not completely cut by the wire mesh. After grinding the entire side, a single-sided ground surface parallel to the side that was completely cut by the wire mesh can be obtained. At this point, both sides of the wafer meet the crystal orientation requirements.

[0070] S500: Grind both sides of the wafer until the thickness of the wafer is within the third preset range.

[0071] Specifically, a double-sided polishing machine is used to polish the wafers after single-sided polishing, so that the thickness of the wafers is within the range of 355μm±3μm. Because the wafers have undergone wire cutting and single-sided polishing, there will be cutting marks and unpolished areas on the surface of the wafers. Double-sided polishing can remove these defects and provide good flatness for further polishing.

[0072] S600: Obtain the surface quality parameters and second appearance image of the wafer;

[0073] S700: Determine whether the surface quality parameters meet the target parameters, and at the same time, determine whether there are defects in the appearance of the wafer based on the second appearance image.

[0074] S800. If the surface quality parameters do not meet the target parameters and / or the wafer has defects in appearance, then no further processing will be performed; if the surface quality parameters meet the target parameters and the wafer has no defects in appearance, then circumferential chamfering will be performed according to the preset process parameters.

[0075] Specifically, before chamfering, a crystal orientation analyzer is used to measure both sides of each wafer, selecting wafers that meet the crystal orientation angles of 4°±0.5° in the Off axis direction and 0°±0.5° in the ON axis direction. Simultaneously, a visual inspection is conducted to ensure that the surface of each wafer is completely ground, without wire cutting marks or unground areas, and without any chipping or breakage exceeding 0.2mm in size. The wafer surface must also be free of visible scratches. Furthermore, an AOI (Automated Optical Inspection) instrument is used to inspect the ground surface, requiring the wafers to meet the following parameters: WARP (warpage) ≤ 85μm, TTV (total thickness deviation) ≤ 30μm, THK (thickness) 355μm±3μm, and BOW (bending) ≤ 65μm. After selecting wafers that meet the aforementioned requirements, the chamfering operation can be performed according to the preset process parameters.

[0076] Specifically, the edges of the wafer are chamfered using a 500-mesh silicon carbide grinding wheel. Preferably, the diameter processing speed is 2 mm / s and the flat edge processing speed is 1 mm / s.

[0077] In this embodiment, since the edges of the wire-cut wafers are generally sharp right angles, and silicon carbide material has hard and brittle properties, its right angles are prone to breakage. This can easily lead to thermal stress, cracking, edge chipping, and other quality defects in subsequent processes. Besides affecting the wafer's strength, the presence of right angles can also become a source of contaminating particles throughout the process. Therefore, a chamfering process, also known as circumferential chamfering, is required for the edges of the silicon carbide wafers. Through circumferential chamfering, the silicon carbide wafers have smooth edges and lower central stress, which can effectively improve and enhance the overall mechanical strength and machinability of the silicon wafer.

[0078] S900: Polish both sides of the wafer after chamfering until the thickness of the wafer is within the fourth preset range.

[0079] Because a damaged layer is formed on the surface of the wafer after double-sided grinding, double-sided polishing of the wafer is required to lay the foundation for manufacturing complete and defect-free wafer materials.

[0080] Optionally, chemical mechanical polishing (CMP) can be used to flatten both sides of the wafer to a nanometer-level smoothness, meeting the warpage and flatness requirements of silicon carbide wafers, and controlling the thickness of the wafer within the range of 340μm±3μm after polishing. For example, using a double-sided polishing machine, the wafer is placed between the upper and lower plates of the polishing machine, and polishing pads are attached to the wafer-facing side of the upper and lower plates. During polishing, the wafer is clamped between the two polishing pads, and the polishing slurry flows continuously between the wafer and the polishing pads. The high-speed counter-rotation of the upper and lower plates causes the reaction products on the wafer surface to be continuously peeled off. New polishing slurry is added, and the reaction products are carried away with the polishing slurry. A chemical reaction occurs on the newly exposed wafer surface, and the products are peeled off again in a cycle. Under the combined action of the substrate, abrasive particles, and chemical reactants, an ultra-fine surface is formed.

[0081] It should be understood that a single-sided polishing machine can also be used to polish one side of the wafer, then dewax the wafer, remove it, and reattach it to polish the other side.

[0082] S1000: Select qualified wafers according to preset requirements.

[0083] Specifically, instruments and equipment such as surface flatness testers and surface defect comprehensive testers are used to detect parameters such as warpage, curvature, thickness variation, and surface scratches of silicon carbide wafers, and wafers that meet these parameters are selected.

[0084] In this embodiment, by processing the head and tail of SiC crystal rods through a series of processes, thinner or smaller finished wafers can be obtained. These finished wafers can be used to manufacture certain types of semiconductor devices, thereby improving the utilization rate of SiC crystal rods, reducing the secondary consumption caused by remelting the head and tail of SiC crystal rods, and saving manufacturing costs.

[0085] In some embodiments of the present invention, step S400: grinding the marked side of the wafer until the thickness of the wafer is within a second preset range is specifically implemented as follows:

[0086] S410, Divide the thickness of the wafer into different thickness ranges with a predetermined step size;

[0087] S420. Divide wafers belonging to the same thickness range into several groups containing the same number of wafers, and use liquid wax to attach the unmarked side of the wafers in the same group to the front of one of the ceramic disks 100.

[0088] S430. Place several ceramic discs 100 face down on the planetary wheel fixture 200;

[0089] S440. Turn on the double-sided grinding machine to perform multiple segmented accelerated grinding on the surface until the thickness of the wafer is within the second preset range.

[0090] S450, the heated and ground wafer is removed from the ceramic disk 100.

[0091] Specifically, refer to Figure 2 and Figure 3 First, the selected wafers are sorted by thickness, and then divided into thickness increments of 5μm. Specifically, this division can start with the smallest thickness value and divide into increments of 5μm, or it can start with the largest thickness value and divide into increments of 5μm.

[0092] Next, based on the size of the front side of the ceramic disk 100, the number of wafers that can be bonded is determined, and wafers belonging to the same thickness range are grouped together according to this number. Specifically, in this embodiment, since each ceramic disk 100 can bond 6 wafers on its front side, 6 wafers belonging to the same thickness range need to be selected to form a group, and this group of 6 wafers is bonded to the front side of the same ceramic disk 100 using a waxing machine. During bonding, the positioning edge of the wafer is facing inward, and a dial indicator is used to measure the height of the wafer on the surface of the ceramic disk 100, and the thickness value is recorded, which is the thickness value A of the wafer before grinding.

[0093] Optionally, one of the waxing processes using a waxing machine is described in detail below:

[0094] 1. Clean and spin-dry the wafer to remove dust particles from its surface. Then, use a mechanical vacuum arm to adsorb the wafer onto a wax-spinning vacuum stage. Drop an appropriate amount of liquid wax onto the center of the wafer and rotate the wafer at high speed to evenly spread the liquid wax from the center of the wafer to its circumference, thereby forming a wax layer of 0.001mm-0.002mm on the wafer surface.

[0095] 2. Prepare several cleaned and dried empty ceramic discs 100. Use a mechanical vacuum arm to transfer the ceramic discs 100 to the preheating station's circular platform, preheating them to 80-90℃. Then, use the mechanical vacuum arm to transfer the ceramic discs 100 to the waxing station's circular platform. Apply the wax-coated side of the wafer to the predetermined waxing position on the ceramic disc 100 one by one, maintaining the ceramic disc 100 temperature between 85-95℃ during this process. Generally, one ring is applied to both the inner and outer rings to improve the utilization rate of the ceramic disc 100 surface, thereby increasing processing efficiency.

[0096] 3. Finally, place the ceramic disk 100 covered with wafers onto the rotary table of the lamination station, press the wafers firmly onto the surface of the ceramic disk 100, ensuring that there are no gaps between the wafers and the ceramic disk 100. The rotary table is equipped with water cooling pipes. During lamination, the temperature of the ceramic disk 100 is reduced to 20-25℃. Then, remove the ceramic disk 100 with the wafers attached. At this point, the wax application process is complete.

[0097] Next, the three ceramic disks 100 are inverted so that the marked side of the wafer is attached to the planetary gear fixture 200. It should be noted that, under normal circumstances, the wafers on the three ceramic disks 100 belong to the same thickness range. However, when there are not enough wafers belonging to the same thickness range, it is only necessary to ensure that the wafers on a single ceramic disk 100 belong to the same thickness range.

[0098] It should be noted that in this embodiment, the eccentricity of the planetary gear fixture 200 is 35mm. The main purpose of the offset center is to increase the displacement frequency and distance of the ceramic disk 100 during single-sided grinding, thereby improving the grinding efficiency. The outer ring teeth of the planetary gear fixture 200 mesh with the ring teeth and center teeth of the double-sided grinding machine. The motor drives the center teeth to rotate, and the center teeth drive the planetary gear fixture 200 to revolve around and rotate on its own axis. At this time, the surface of the wafer moves relative to the surface of the lower grinding disk 300. That is, the wafer will revolve around the center of the lower grinding disk 300 and rotate on its own axis under the drive of the planetary gear fixture 200. This allows each point on the lower surface of the wafer to have the same or similar grinding stroke, thereby ensuring the uniformity of the movement of the wafer surface during the grinding process.

[0099] During the actual grinding process, the motor drives the center tooth to rotate forward or backward, so that the planetary gear fixture 200 drives the wafer to rotate and revolve in both directions, avoiding the periodic repetition of the motion trajectory, thereby ensuring that the lower surface of the wafer is uniformly worn, and thus improving the flatness of the wafer surface.

[0100] Next, a stainless steel circular counterweight 400 is glued to the center of the back of the ceramic disk 100 using AB glue. The counterweight 400 is 65mm high and 150mm in diameter. Then, the double-sided grinder is turned on to repeatedly perform segmented accelerated grinding on the marked side of the wafer.

[0101] It is important to understand that in order to provide corresponding grinding pressure to accommodate different wafer sizes, the unit grinding pressure needs to be calculated based on the size of the wafer being processed. Of course, the weight of the counterweight block 400 bonded to the large wafer should be increased accordingly.

[0102] It should be noted that if the wafer is ground at the high speed used in normal processing at the beginning of this step, the wafer is prone to breakage and damage because the force on the wafer changes greatly in a short period of time. Therefore, in the single-sided grinding operation, the double-sided grinding machine needs to gradually increase the speed so that the wafer and the planetary gear fixture 200 gradually cooperate.

[0103] In addition, after each grinding is completed, the counterweight 400 is removed first, and then the ceramic disk 100 is removed from the planetary gear fixture 200 so that the side of the wafer being ground is facing upward. At this time, a dial indicator is used to measure the height of the wafer on the surface of the ceramic disk 100. Grinding is stopped when the wafer thickness is reduced to 385μm±5μm.

[0104] After the final grinding, first remove the counterweight 400, then remove the ceramic disk 100 from the planetary gear fixture 200 so that the ground side of the wafer faces upwards. Simultaneously, place the ceramic disk 100 on a constant-temperature heating platform to melt the liquid wax, thereby separating the ceramic disk 100 from the wafer. Preferably, the temperature is set to 95°C and baked for 5 minutes. Afterwards, using a high-temperature resistant spatula, the wafer is removed from the ceramic disk 100 and inserted into an acid- and alkali-resistant wafer cassette.

[0105] In some embodiments of the present invention, the specific implementation process of step S440: turning on the double-sided grinding machine to perform multiple segmented accelerated grinding on the surface until the thickness of the wafer is within a second preset range is as follows:

[0106] First, each grinding process is divided into 5 grinding segments. In each grinding segment, the rotation speed of the double-sided grinding machine is greater than that of the previous segment, and each grinding segment has its own corresponding processing time.

[0107] It is understood that the number of grinding sections is only for the purpose of explaining this step and should not be construed as the only limitation on the number of grinding sections in this step.

[0108] In this embodiment, the double-sided polishing machine does not use an upper polishing disc. Instead, a counterweight 400 is pressed down on the back of the ceramic disc 100 to provide a certain polishing pressure, thereby ensuring that the wire-cut side of the wafer is tightly adhered to the surface of the polishing disc of the double-sided polishing machine. During operation, the double-sided polishing machine uses a circulating polishing slurry to polish the wafer; that is, the polishing slurry circulates onto the upper polishing disc until its polishing performance deteriorates to the point of being unusable.

[0109] The specific operating conditions are as follows: the flow rate of the grinding slurry is set to 200±5 ml / min for each grinding. Other grinding parameters for the first grinding are shown in Table 1.

[0110]

[0111] Table 1

[0112] As shown in Table 1, during the first single-sided grinding, the rotational speeds of the lower grinding disc (300 rpm), the ring gear, and the center gear (500 rpm) increase sequentially. The processing times for the first to fourth grinding stages are set to preset values. Due to the use of a grinding slurry circulation method, the removal capacity of the grinding slurry gradually decreases as the grinding process progresses. Therefore, the processing time for the fifth stage is generally set as an estimated value based on previous processing data, specifically 30 minutes in this implementation. After the first grinding is completed, the counterweight 400 is removed, and then the ceramic disc 100 is removed from the planetary gear fixture 200 so that the side of the wafer being ground faces upward. A dial indicator is used to measure the height of the wafer on the surface of the ceramic disc 100, and the thickness value at this time is recorded, which is the thickness value B of the wafer after grinding. The grinding rate of the first grinding is obtained by dividing the removed thickness value (BA) by (1+0.5+0.5+1.5+30) minutes. Then, based on the target thickness of 385 μm and the grinding rate of the first grinding, the processing time for the second grinding is set. The specific operating conditions are as follows: the flow rate of the grinding slurry is set to 200 ml / min for each grinding session, and the other grinding parameters for the second grinding session are shown in Table 2.

[0113]

[0114] Table 2

[0115] As shown in Table 2, during every two single-sided grinding cycles, the rotational speeds of the lower grinding disc (300 rpm), the ring gear, and the center gear (500 rpm) increase sequentially. The processing times for the first to fourth grinding stages are set to preset values.

[0116] The processing time for the fifth grinding stage is set based on the target thickness of 385 μm and the grinding rate of the first single-sided grinding. Due to the use of a circulating grinding slurry, the slurry removal capacity gradually decreases as grinding progresses. Therefore, the wafer thickness is generally not within the 385 μm ± 5 μm range after the second grinding. Thus, grinding needs to be repeated until the wafer thickness is within the 385 μm ± 5 μm range. The flow rate of the grinding slurry remains constant for each grinding stage, as do the processing times for the first to fourth grinding stages, and the rotational speeds of the lower grinding disc (300 rpm), ring gear, and center gear (500 rpm) for the first to fifth grinding stages. The processing time for the fifth stage is set based on the target thickness of 385 μm and the grinding rate of the previous grinding stage.

[0117] Specifically, in this embodiment, the grinding slurry used includes boron carbide powder with a particle size of 240#, pure water, and a suspension. These three components are prepared in a preferred ratio of 15 kg boron carbide powder: 30 L pure water: 1.5 kg suspending agent. The mixture is then stirred for at least 30 minutes and poured into a grinding slurry container. The suspending agent is a commonly used additive. It enables solid particles to be uniformly dispersed in a liquid, forming a suspension. Its main components typically include the following: 1. Thickener: Thickeners are one of the main components of suspending agents. They increase the viscosity of the liquid, suspending particles in the liquid and preventing sedimentation. Examples include sodium carboxymethyl cellulose and calcium carboxymethyl cellulose. 2. Dispersant: Dispersant is one of the key components of suspending agents. It disperses particles, preventing them from agglomerating and forming sediment. Examples include polyvinylpyrrolidone and hydroxypropyl methylcellulose. 3. Stabilizers: Stabilizers are important components of suspending agents. They prevent particle sedimentation and stratification. Stabilizers can also stabilize the suspension by changing the particle charge or forming a surface film. Examples include gelatin, calcium carbonate, and xanthan gum. 4. pH Adjusters: pH adjusters can change the acidity or alkalinity of the suspension to make it suitable for particle suspension. Examples include sodium hydroxide and phosphates. In addition to the above main components, suspending agents may also contain other auxiliary components, such as preservatives, antioxidants, and sweeteners. The addition of these auxiliary components can be adjusted according to specific needs. In summary, these components, through different mechanisms of action, enable solid particles to be uniformly dispersed in a liquid, forming a suspension and maintaining its stability.

[0118] In some embodiments of the present invention, step S500: grinding both sides of the wafer until the thickness of the wafer is within a third preset range is specifically implemented as follows:

[0119] S510. First, select 6 wafers from the single-sided polished wafers to form a group. Then, place this group of 6 wafers into the 6-inch planetary gear hole and record the current wafer thickness value C.

[0120] S520 Next, press the upper grinding disc of the double-sided grinding machine flat onto the side of the wafer facing upwards;

[0121] S530. Finally, the double-sided polishing machine is turned on to perform multiple segmented accelerated and pressurized polishing operations on both sides of the wafer until the wafer thickness is within the range of 355μm±3μm. It should be noted that in this step, if the wafer is polished at the high speed and high pressure used in normal processing from the beginning, the wafer is prone to breakage and damage due to the large changes in force experienced by the wafer in a short period of time. Therefore, during the double-sided polishing operation, the speed and pressure of the upper polishing disc of the double-sided polishing machine need to be gradually increased to gradually align the wafer with the planetary gear fixture 200. Furthermore, after each polishing operation, the upper polishing disc is removed first, and then the wafer thickness is measured using a dial indicator. Polishing is stopped when the wafer thickness is within the range of 355μm±3μm.

[0122] Specifically, step S530: The double-sided polishing machine is turned on to repeatedly perform segmented accelerated pressure polishing on both sides of the wafer to make the thickness of the wafer within the range of 355μm±3μm. The specific implementation process is as follows:

[0123] First, each grinding process is divided into 5 grinding segments. In each segment, the double-sided grinding machine rotates at a higher speed than in the previous segment, and each segment has its own corresponding processing time. It should be understood that the number of grinding segments is only for ease of explanation and should not be construed as the sole limitation on the number of grinding segments in this step.

[0124] In this embodiment, the double-sided polishing machine uses an upper polishing disc to provide a certain polishing pressure. During operation, the double-sided polishing machine uses a direct discharge method to polish both sides of the wafer; that is, the polishing slurry is discharged directly after each polishing pass, and then unused polishing slurry is applied again. Specifically, the flow rate of the polishing slurry is set to 55±5 ml / min for each polishing pass. Other polishing parameters for the first polishing pass are shown in Table 3.

[0125]

[0126] Table 3

[0127] As shown in Table 3, during the first double-sided grinding, the rotation speeds of the upper grinding disc, the lower grinding disc (300 rpm), the ring gear, and the center gear (500 rpm) increase sequentially. The processing time for the first to fourth grinding stages is set to a preset value, while the processing time for the fifth stage is generally set to an estimated value based on experience to prevent over-grinding that could result in an underly thin wafer. In this implementation, it is set to 10 minutes. After the first double-sided grinding is completed, the upper grinding disc is removed, and the thickness of the wafer is measured using a dial indicator. The thickness value at this point is recorded as the thickness D of the wafer after the first double-sided grinding. The grinding rate of the first double-sided grinding is obtained by dividing the removed thickness value (DC) by (1 + 0.5 + 0.5 + 0.5 + 10) minutes.

[0128] Next, based on the target thickness of 355µm and the grinding rate of the first double-sided grinding, the processing time for the second double-sided grinding was set. Specifically, the time taken for the double-sided grinding machine to increase its speed from the first to the second stage was determined as follows: the flow rate of the grinding slurry was set to 55±5 ml / min for each double-sided grinding operation. Other grinding parameters for the second double-sided grinding are shown in Table 4.

[0129]

[0130] Table 4

[0131] As shown in Table 4, during the second double-sided grinding, the rotation speeds of the upper grinding disc (300 rpm), the lower grinding disc (300 rpm), the ring gear (500 rpm), and the center gear (500 rpm) increased sequentially. The processing times for the first to fourth grinding stages were set to preset values, while the processing time for the fifth stage was set based on the target thickness of 355 μm and the grinding rate of the first double-sided grinding. Specifically, the processing times for the first to fourth grinding stages, the rotation speeds of the lower grinding disc (300 rpm), the ring gear, and the center gear (500 rpm) remained constant throughout the two double-sided grinding processes, as did the flow rate of the grinding slurry. The processing time for the fifth stage was set based on the target thickness of 355 μm and the grinding rate of the first double-sided grinding.

[0132] Finally, after double-sided grinding, the wafer is removed and inserted into an acid and alkali resistant wafer box for storage.

[0133] Specifically, in this embodiment, the grinding slurry used includes boron carbide powder with a particle size of W14, pure water, and a suspending agent. The three are prepared in a preferred ratio of 15 kg boron carbide powder: 30 L pure water: 1.5 kg suspending agent. After stirring for more than 30 minutes, the mixture is poured into a grinding slurry tank.

[0134] In this embodiment, the grinding slurry uses boron carbide with a smaller particle size to achieve graded grinding. That is, using grinding powder with a smaller particle size can make the damage layer on the wafer surface shallower, while further reducing the amount of material removed during grinding and improving the yield of silicon carbide wafers.

[0135] In some embodiments, before step S100, the head and tail of the silicon carbide crystal rod are sequentially cleaned and dried to obtain a clean wafer.

[0136] Specifically, the wafers produced from the head and tail of the silicon carbide crystal rod are first cleaned to remove impurities. Since water stains will be left on the wafers after cleaning, the wafers must be dried immediately after cleaning to prevent water stains from contaminating the wafers.

[0137] The specific implementation process is as follows:

[0138] The wafer is placed in the first tank of the three-tank cleaning machine, which contains the cleaning solution, and is then ultrasonically agitated and cleaned. At the same time, the filter element in the first tank circulates and filters the cleaning solution.

[0139] Preferably, in this example, the cleaning solution is prepared according to the ratio of 1L of alkaline solution to 12L of 16M pure water. During cleaning, the cleaning solution is heated to 65℃, the ultrasonic frequency is set to 40KHz, the agitation method is up and down agitation, the agitation distance is 150-300mm, the agitation frequency is 10-20 times / minute, and the cleaning time is 10 minutes.

[0140] Next, the wafer is placed in the second tank of the three-tank cleaning machine for ultrasonic pure water rinsing. Preferably, the pure water is heated to 65°C, the ultrasonic frequency is 40KHz, and the cleaning time is 10 minutes.

[0141] Finally, the wafers are placed in the third tank of the three-tank cleaning machine for two rapid rinsing processes. Preferably, each rinsing time is 2 minutes, the rapid injection time is no more than 20 seconds, and the rapid discharge time is no more than 10 seconds. The rapid rinsing and discharge process is illustrated as follows: water fills the tank → workpiece is placed in → rapid discharge valve opens → spraying → rapid discharge valve closes, while water is injected from the bottom to carry away the washed-down particles.

[0142] The process includes cleaning and drying the polished wafer sequentially after step S500 and before step S600.

[0143] After grinding, wafers often retain residues such as abrasive particles, organic matter, metallic contaminants, and other specific impurities. Therefore, wafers must be cleaned. Ineffective cleaning can lead to contamination of the wafer surface. If integrated circuits are manufactured on contaminated wafers, their quality and performance can be significantly reduced. After cleaning, the wafers must be dried to prevent water stains.

[0144] The specific implementation process includes:

[0145] Pour the prepared cleaning solution into the first and second tanks of the four-tank cleaning machine. Preferably, the cleaning solution is prepared in the following ratio: 2L oxalic acid: 1.5L alkaline dewaxing agent: 30L pure water.

[0146] The wafer is placed in the first tank for the first ultrasonic polishing and cleaning. Preferably, the cleaning solution is heated to 85±5℃, the ultrasonic frequency is set to 40KHz, the cleaning time is 300 seconds, the polishing time is 150 seconds, the ultrasonic cleaning time is 100 seconds, and the circulation overflow time is 20 seconds.

[0147] Next, the wafer is placed in the second tank for a second ultrasonic polishing and cleaning. Preferably, the cleaning solution is heated to 75±5℃, the ultrasonic frequency is set to 40KHz, the cleaning time is 300 seconds, the polishing time is 150 seconds, the ultrasonic cleaning time is 100 seconds, and the circulation overflow is 40 seconds.

[0148] Next, the wafer is placed in the third tank for pure water rinsing. Preferably, the pure water is heated to 60±5℃, the rinsing time is 300s, and the circulation overflow is always open.

[0149] Next, the wafer is placed in the fourth tank for two quick flushing processes. Preferably, the single flushing time is 48 seconds and the single quick flushing time is 12 seconds.

[0150] Finally, the cleaned wafers are spun dry. Specifically, a spin dryer is used to dry the wafers. Preferably, the rinsing time is set to 30 seconds and the speed is 500 rpm, the blowing time is set to 30 seconds and the speed is 1500 rpm, and the drying time is set to 210 seconds and the speed is 1500 rpm.

[0151] This embodiment uses a four-tank cleaning machine that can reuse overflow water. During wafer processing, contaminants and impurities exist on the wafers. These contaminants include organic and inorganic substances, some adhering in an atomic or ionic state, and others existing on the wafer surface in the form of thin films or particles. The presence of these impurities can easily lead to device failure in subsequent processes; therefore, rigorous cleaning is necessary to remove these contaminants from the wafers. Furthermore, the cleaning machine used in this embodiment features a circulation device between the multiple tanks to achieve a circulating overflow function, thereby conserving water during cleaning.

[0152] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0153] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a substrate using the head and tail portions of a silicon carbide crystal rod, characterized in that, The method includes: S100: Obtain the thickness and first appearance image of the wafer; S200: Determine whether the thickness is less than a first preset thickness value, and at the same time determine whether there are defects in the appearance of the wafer based on the first appearance image; S300, If not, mark the uncut side of the wafer; S400: Grind the marked side of the wafer until the thickness of the wafer is within a second preset range; S500: Grind both sides of the wafer until the thickness of the wafer is within a third preset range; S600: Obtain the surface quality parameters and second appearance image of the wafer; S700: Determine whether the surface quality parameters do not meet the target parameters, and at the same time determine whether there are defects in the appearance of the wafer based on the second appearance image; S800, if not, then perform circumferential chamfering according to the preset process parameters; S900. The wafer after circumferential chamfering is polished on both sides until the thickness of the wafer is within the fourth preset range. S1000: Select qualified wafers according to preset requirements; Step S400 includes: S410. Divide the thickness of the wafer into different thickness ranges with a predetermined step size; S420. Divide the wafers belonging to the same thickness range into several groups containing the same number of wafers, and use a waxing machine to attach the unmarked side of the wafers in the same group to the front of one of the ceramic disks. S430. Place several ceramic discs face down on the planetary wheel fixture; S440. Turn on the double-sided grinding machine to perform multiple segmented accelerated grinding on the surface until the thickness of the wafer is within the second preset range. S450, The heated and ground wafer is removed from the ceramic disk; Step S440 includes: S441. Each grinding session is divided into multiple grinding segments. The double-sided grinding machine performs the first grinding of the wafer by circulating the grinding slurry according to the preset processing time. The rotation speed of the double-sided grinding machine is greater than that of the previous segment in each grinding segment, and each grinding segment has its own corresponding processing time. S442. The double-sided polishing machine uses a polishing slurry circulation method to polish the wafer N times until the thickness of the wafer measured after polishing is within a second preset range. The polishing time of the Nth polishing is determined by the polishing rate of the (N-1)th polishing. The polishing rate of the (N-1)th polishing is obtained by the thickness difference of the wafer before and after the (N-1)th polishing and the sum of the polishing times of each polishing segment. N is a positive integer ≥2. The grinding slurry used includes boron carbide powder with a particle size of 240#, pure water, and a suspending agent, with a mass ratio of 1~1.5:1.8~2.5:0.1~0.

15.

2. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to claim 1, characterized in that, Step S500 includes: S510. The plurality of said wafers are uniformly attached to the planetary gear hole; S520. Press the upper grinding disc of the double-sided grinding machine flat onto the upward-facing side of the wafer. S530. Turn on the double-sided grinding machine to perform multiple segmented accelerated pressure grinding on both sides of the wafer until the thickness of the wafer is within a third preset range.

3. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to claim 2, characterized in that, Step S530 includes: S531. Each grinding session is divided into multiple grinding segments. The double-sided grinding machine uses a direct discharge method for grinding slurry to perform the first grinding of the wafer with a preset processing time. The rotation speed of the double-sided grinding machine is greater than that of the previous segment in each grinding segment, and each grinding segment has a corresponding processing time. S532. The double-sided grinding machine uses a grinding slurry direct discharge method to perform a second grinding on the wafer, so that the thickness of the wafer measured after grinding is within a third preset range. The second grinding time is determined by the grinding rate of the first grinding, and the grinding rate of the first grinding is obtained by the thickness difference of the wafer before and after the first grinding and the sum of the grinding time of each grinding segment. The grinding slurry used includes boron carbide powder with a particle size of W14, pure water, and a suspending agent, with a mass ratio of 1~1.5:1.8~2.5:0.1~0.

15.

4. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to any one of claims 1 to 3, characterized in that, The procedure before step S100 also includes: The head and tail of the silicon carbide crystal rod are cleaned and dried sequentially to obtain the clean wafer.

5. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to claim 4, characterized in that, The step of sequentially cleaning and drying the head and tail of the silicon carbide crystal rod to obtain the clean wafer specifically includes: The wafer is placed in the first tank of a three-tank cleaning machine containing cleaning solution for ultrasonic agitation cleaning. At the same time, the filter element in the first tank circulates and filters the cleaning solution. The cleaning solution includes alkaline solution and pure water in a mass ratio of 1:10~15. The cleaning solution temperature is 60~65℃, the ultrasonic frequency is 28~40KHz, the agitation method is up and down agitation, the agitation distance is 150~300mm, the agitation frequency is 10~20 times / minute, and the cleaning time is 8~12 minutes. The wafer is placed in the second tank of a three-tank cleaning machine for ultrasonic pure water rinsing, wherein the pure water temperature is 60~65℃, the ultrasonic frequency is 28~40KHz, and the cleaning time is 8~12 minutes. The wafer is placed in the third tank of a three-tank cleaning machine for two rapid rinsing processes, with each rinsing session lasting 2 to 5 minutes, each rapid injection session lasting no more than 20 seconds, and each rapid discharge session lasting no more than 10 seconds.

6. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to any one of claims 1 to 3, characterized in that, The steps following step S500 and before step S600 also include: The ground wafers are then sequentially cleaned and dried.

7. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to claim 6, characterized in that, The step of sequentially cleaning and drying the polished wafers specifically includes: Pour the prepared cleaning solution into the first and second tanks of the four-tank cleaning machine. The cleaning solution includes oxalic acid, alkaline dewaxing agent, and pure water, with a mass ratio of 2:1:15~25. The wafer is placed in the first tank for the first ultrasonic polishing cleaning, wherein the cleaning fluid temperature is 85±5℃, the ultrasonic frequency is 28~40KHz, the cleaning time is 180~360 seconds, the polishing time is 90~180 seconds, the ultrasonic cleaning time is 90~180 seconds, and the circulation overflow time is 15~25 seconds. The wafer is placed in the second tank for a second ultrasonic polishing and cleaning, wherein the cleaning fluid temperature is 75±5℃, the ultrasonic frequency is 28~40KHz, the cleaning time is 180~360 seconds, the polishing time is 90~180 seconds, the ultrasonic cleaning time is 90~180 seconds, and the circulation overflow time is 25~40 seconds. The wafer is placed in the third tank for pure water rinsing, where the water temperature is 60±5℃, the rinsing time is 180~360s, and the circulation overflow is always open. The wafer is placed in the fourth tank for two quick flushing processes, with each flushing time being 30-48 seconds and each quick flushing time being 10-15 seconds. The cleaned wafers are then spun dry, with rinsing for 20-40 seconds at 420-600 rpm, blowing for 20-30 seconds at 1200-1800 rpm, and drying for 180-210 seconds at 1200-1800 rpm.

8. The method for preparing a substrate using the head and tail wafers of a silicon carbide crystal rod according to any one of claims 1 to 3, characterized in that, Step S800 includes: The edges of the wafer are chamfered using a 500-mesh silicon carbide grinding wheel, with a diameter processing speed of 2-3 mm / s and a flat edge processing speed of 0.8-1.5 mm / s.

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