Polishing process method applied to silicon carbide substrate

Abstract

The invention provides a polishing process method applied to a silicon carbide substrate. The polishing process method comprises the steps that a wafer to be polished is transferred to a loading table; the polishing head adsorbs the wafer to the position above the polishing disc; the rotating speed of the polishing head is 100-145 rpm, the main polishing pressure is 5-9 psi, the rotating speed of the polishing disc is 110-150 rpm, the flow speed of the polishing solution is 50-100 mL / min, the flow speed of the cooling water is larger than 5 L / min, and the temperature of the cooling water is 5-15 DEG C; the polishing head transfers the polished wafer to a loading table; moving the wafer into a cleaning unit, and cleaning and drying the wafer by using a cleaning module; and the polishing pad is trimmed in an off-line mode, and a diamond trimmer is adopted for trimming for 10-60 s at the down pressure of 5-9 lbf. According to the polishing process method applied to the silicon carbide substrate, by defining a plurality of process parameters in the polishing process, a standardized operation process is formed, the process debugging time is shortened, the stability and repeatability of the process are effectively guaranteed, the research and development and production cost is reduced, and large-scale high-quality production of wafers is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of the processing of silicon carbide substrates, and particularly relates to a polishing process method applied to silicon carbide substrates. Background Art

[0002] Silicon carbide (SiC), as a material with excellent physical properties, is widely used in high-end fields such as new energy vehicles, 5G communications, smart grids, and aerospace due to its high thermal conductivity, high electron saturation drift velocity, and high breakdown electric field. The application prospects of SiC have continuously raised the processing requirements for SiC substrate wafers. However, its high hardness, high brittleness, and strong chemical inertness have brought great challenges to the processing process.

[0003] Currently, SiC is mainly processed by CMP (chemical mechanical polishing). CMP utilizes the synergistic effect of chemical action and mechanical action to effectively remove the SiC wafer, and can simultaneously obtain a high removal rate and a smooth and damage-free wafer surface. During the polishing process, the polishing head embedded with the SiC wafer presses on the polishing pad adhered to the polishing disc with a certain pressure and rotates with it. At the same time, the polishing liquid is sprayed onto the polishing disc, and a series of chemical reactions occur between the polishing liquid and the wafer surface, generating an oxide layer with lower hardness on the SiC surface. This oxide layer can be removed by mechanical grinding, thereby achieving global planarization.

[0004] However, in the prior art, the process limitations of CMP are relatively large. When polishing hard and brittle materials such as SiC, the optimization and adjustment of the process are more difficult, and it is difficult to obtain a high material removal rate and a high surface quality. If the pressure and rotation speed are too large, it is easy to cause deformation or even damage to the SiC wafer. In addition, due to the lack of a complete parameter optimization scheme in the existing CMP process for SiC, the trial-and-error cost and equipment loss are greatly increased, restricting the batch production efficiency of SiC wafers. Summary of the Invention

[0005] The embodiment of the present invention provides a polishing process method applied to silicon carbide substrates, which can form a standardized operation process, reduce the process debugging time, save the trial-and-error cost, and at the same time ensure the polishing quality of the SiC wafer, significantly improving the processing efficiency of the SiC wafer and being beneficial to meeting the requirements of large-scale and high-quality production of SiC wafers.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide a polishing process method applied to silicon carbide substrates, including the following steps: S1. Transfer the wafer to be polished to the load stage. S2. The polishing head on the rotating mechanism adsorbs the wafer to be polished on the load stage and transfers it above the corresponding polishing disc. S3. The polishing head rotates at a speed of 100 - 145 rpm and applies a main polishing pressure of 5 - 9 psi. The polishing pad rotates at a speed of 110 - 150 rpm. The polishing liquid is supplied to the polishing pad at a flow rate of 50 - 100 mL / min, and the cooling water is supplied to the polishing pad at a flow rate greater than 5 L / min. The temperature of the cooling water is 5 - 15 °C, and the wafer is polished. S4. The polishing head transfers the polished wafer to the loading stage. S5. The polished wafer on the loading stage is transferred to the cleaning unit, and the polished wafer is successively cleaned and dried by a plurality of cleaning modules. S6. The polishing pad on the polishing disc is trimmed through an offline mode, and the polishing pad is trimmed with a diamond dresser under a downward pressure of 5 - 9 lbf for a trimming duration of 10 - 60 s.

[0007] In a possible implementation manner, in step S3, the polishing liquid includes: Sodium permanganate with a concentration of 10 - 20 wt%; A pH regulator for adjusting the pH value of the polishing liquid to 2 - 3; and The balance of deionized water.

[0008] In some embodiments, the polishing liquid further includes an abrasive, the abrasive is cerium oxide with a concentration of 1 - 2 wt% and a median particle size of 60 - 130 nm.

[0009] In a possible implementation manner, the thickness of the polishing pad is 50 - 100 mil, and the Shore hardness is 60 - 68 HD; a plurality of annular grooves are provided on the polishing pad, the annular grooves are successively sleeved from the center to the outer periphery, and the distance between adjacent two annular grooves is 100 - 130 mil.

[0010] In some embodiments, a plurality of radial grooves arranged in a divergent shape are further provided on the polishing pad, the radial grooves extend along the radial direction of the polishing pad, and the radial grooves and the annular grooves communicate with each other.

[0011] In some embodiments, in step S6, the diamond density of the diamond dresser is 300 - 600 ea / cm², the diamond protrusion is 30 - 50 μm, and the cutting rate for the polishing pad is 130 - 200%.

[0012] In a possible implementation manner, before step S1, it further includes: S11. Using a first transfer mechanism to take out the wafer to be polished from the wafer cassette and transfer it to the transfer tray. S12. Use the second transfer mechanism to transfer the wafer to be polished on the transfer plate to the loading platform to be loaded; In step S1, use the transfer mechanism to transfer the wafer to be polished on the loading platform to be loaded to the loading platform.

[0013] In some embodiments, step S5 further includes: S51. Use the transfer mechanism to transfer the polished wafer on the loading platform to the unloading platform to be unloaded; S52. Use the second transfer mechanism to take out the polished wafer on the unloading platform to be unloaded, flip it, and transfer it to the cleaning unit.

[0014] In a possible implementation, the cleaning module is at least one of a drum - type cleaning module, a pencil - type cleaning module, and a single - wafer cleaning module.

[0015] In some embodiments, the process parameters of the polished wafer are: the material removal rate of the Si surface is 4 - 8 μm / h, the material removal rate of the C surface is 12 - 23 μm / h, the total thickness deviation < 5 μm, the local thickness deviation < 2 μm, the mechanical damage length < 50 μm, and the surface roughness Ra is 0.08 - 0.12 nm.

[0016] The beneficial effects of a polishing process method for a silicon carbide substrate provided by the present invention are as follows: Compared with the prior art, the polishing process method for a silicon carbide substrate of the present invention achieves dynamic balance by clearly optimizing the rotation speeds of the polishing head and the polishing plate, the main polishing pressure, and the flow rates of the polishing liquid and the cooling water. It not only ensures the polishing quality of the SiC wafer but also avoids wafer damage caused by excessive pressure and rotation speed; uses multiple cleaning modules to clean and dry the polished wafer in sequence to ensure high - quality cleaning of the SiC wafer surface; effectively improves the trimming accuracy and effect of the polishing pad by specifically defining the trimming mode and parameters of the polishing pad. The above - mentioned process method forms a standardized operation process by defining multiple process parameters in the polishing process, reduces the process debugging time, thereby effectively ensuring the stability and repeatability of the process, reducing the R & D and production costs, and being conducive to meeting the large - scale and high - quality production requirements of SiC wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a polishing device used for a polishing process method for a silicon carbide substrate provided by an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a polishing pad provided by an embodiment of the present invention; Figure 3 It is a schematic principle diagram of a drum - type cleaning module provided by an embodiment of the present invention; Figure 4 Schematic diagram of the principle of the pencil-shaped cleaning module provided by an embodiment of the present invention; Figure 5 Schematic diagram of the principle of the single-wafer cleaning module provided by an embodiment of the present invention.

[0018] In the figure: 1. Load stage; 2. Rotating mechanism; 21. Polishing head; 22. Polishing disc; 23. Polishing pad; 231. Annular groove; 232. Radial groove; 24. Polishing liquid guide arm; 25. Inter-disc flushing groove; 3. Cleaning unit; 31. Drum-shaped cleaning module; 32. Pencil-shaped cleaning module; 33. Single-wafer cleaning module; 4. Truing device; 5. First transfer mechanism; 6. Wafer cassette; 7. Transfer tray; 8. Second transfer mechanism; 9. Transfer mechanism; 91. Incoming load stage; 92. Outgoing load stage. Specific embodiments

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and 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.

[0020] It should be noted that when an element is referred to as "disposed on" another element, it can be directly on the other element or indirectly on the other element. It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or several of such features. In the description of the present invention, "a plurality of" and "several" mean two or more, unless otherwise specifically defined.

[0021] Please refer to Figure 1 , and now a polishing device used in a polishing process method applied to a silicon carbide substrate provided by the present invention will be described. The polishing device includes four parts: a front-end module A of the device, a transfer and transport module B, a polishing module C, and a cleaning unit 3.

[0022] The front-end module A of the device includes a first transfer mechanism 5 and four wafer cassettes 6. The transfer and transport module B includes a second transfer mechanism 8 and a transfer tray 7.

[0023] The polishing module C includes a transfer mechanism 9, a load stage 1, and a rotating mechanism 2. The transfer mechanism 9 is provided with a to-be-loaded stage 91 and a to-be-unloaded stage 92, which are used to temporarily store wafers between the transfer and transmission module B and the load stage 1. The rotating mechanism 2 is connected with four polishing heads 21. Three polishing pads 22 are arranged at intervals on the outer periphery of the rotating mechanism 2. A polishing pad 23 is provided on each polishing pad 22. A dresser 4 and a polishing liquid deflector arm 24 are respectively arranged corresponding to each polishing pad 22.

[0024] Each polishing head 21 can suck a wafer from the load stage 1 according to the equipment instruction and transfer it above the corresponding polishing pad 22. Then, the polishing head 21 drives the wafer to rotate and presses the wafer against the surface of the polishing pad 23 with a certain downward pressure. The polishing pad 23 rotates synchronously with the polishing pad 22 and generates relative movement with the wafer on the polishing head 21 to mechanically remove the surface material of the wafer. At the same time, the polishing liquid deflector arm 24 sprays polishing liquid onto the polishing pad 23 to promote chemical oxidation reaction on the surface of the wafer. Under the combined action of chemical oxidation and mechanical removal, high-efficiency polishing of the SiC wafer is achieved. The dresser 4 is used to dynamically sweep and adjust the polishing pad 23 to repair the surface of the polishing pad 23, remove debris and sundries, and keep the polishing pad 23 in the best performance.

[0025] The polishing module C further includes four inter-disk flushing tanks 25 arranged at intervals between the three polishing pads 22, which are used to spray cleaning liquid onto the polishing heads 21 in the non-polishing state to keep the polishing heads 21 clean and avoid contaminating the wafers.

[0026] A cooling pipeline is further arranged at the bottom of the polishing pad 22, and cooling water circulates in the cooling pipeline, which is used to cool down the polishing pad 22, help to extend the service life of the polishing pad 22, and at the same time can also avoid the problem of uneven polishing caused by thermal deformation of the polishing pad 22.

[0027] Three cleaning modules are arranged side by side in the cleaning unit 3. Different cleaning modules can process different pollutants and cleaning requirements to ensure that impurities and residual polishing liquid on the wafer surface are thoroughly removed. At the same time, the drying treatment prevents other defects from being generated due to water residue on the wafer surface.

[0028] The polishing equipment integrates the above four parts, correlates between each unit module, improves the cooperation degree, and improves the processing efficiency of the wafers.

[0029] Now, in combination with the structure of the above polishing equipment, a polishing process method applied to a silicon carbide substrate provided by the present invention will be described. The polishing process method applied to a silicon carbide substrate includes the following steps: S1. Transfer the wafer to be polished to the load stage 1; S2. The polishing head 21 on the rotating mechanism 2 adsorbs the wafer to be polished on the load stage 1 and transfers it above the corresponding polishing pad 22; S3. The polishing head 21 rotates at a speed of 100 - 145 rpm and applies a main polishing pressure of 5 - 9 psi. The polishing pad 22 rotates at a speed of 110 - 150 rpm. The polishing liquid is supplied to the polishing pad 22 at a flow rate of 50 - 100 mL / min, and the cooling water is supplied to the polishing pad 22 at a flow rate greater than 5 L / min. The temperature of the cooling water is 5 - 15 °C, and the wafer is polished; S4. The polishing head 21 transfers the polished wafer to the load stage 1; S5. The polished wafer on the load stage 1 is transferred to the cleaning unit 3, and the polished wafer is successively cleaned and dried by a plurality of cleaning modules; S6. The polishing pad 23 on the polishing pad 22 is trimmed through an offline mode, and the diamond trimmer 4 is used to trim the polishing pad 23 with a downward pressure of 5 - 9 lbf, and the trimming duration is 10 - 60 s.

[0030] A polishing process method applied to a silicon carbide substrate provided in this embodiment, compared with the prior art, through explicit optimization of the rotation speeds of the polishing head 21 and the polishing pad 22, the main polishing pressure, and the flow rates of the polishing liquid and the cooling water, realizes dynamic balance, which not only ensures the polishing quality of the SiC wafer but also can avoid wafer damage caused by too high pressure and rotation speed; using a plurality of cleaning modules to successively clean and dry the polished wafer ensures high-quality cleaning of the surface of the SiC wafer; by specifically defining the trimming mode and parameters of the polishing pad 23, the trimming accuracy and effect of the polishing pad 23 are effectively improved. The above process method forms a standardized operation process by defining multiple process parameters in the polishing process, reduces the process debugging time, thereby effectively ensuring the stability and repeatability of the process, reducing the R & D and production costs, and is conducive to meeting the large-scale high-quality production requirements of SiC wafers.

[0031] Specifically, the rotation speed of the polishing head 21 and the rotation speed of the polishing pad 22 cooperate with each other, jointly determining the relative movement trajectory and friction force between the wafer and the polishing pad 23. The reasonable matching of their rotation speeds can make the abrasive grains on the polishing pad 23 act on the wafer surface evenly, ensuring the stability and consistency of the polishing process. If the rotation speed is too low, the contact frequency and action intensity between the abrasive grains and the wafer surface are insufficient, resulting in low polishing efficiency and inability to meet production requirements; while if the rotation speed is too high, excessive frictional heat will be generated on the wafer surface, causing thermal deformation, and at the same time, it is also easy to cause abnormal wear and shedding of the abrasive grains, affecting the polishing quality.

[0032] The main polishing pressure is the vertical force applied to the wafer, which affects the ability of the abrasive grains on the polishing pad 23 to remove the surface material of the wafer. The optimal pressure value enables the abrasive grains to effectively embed into the wafer surface, achieving stable material removal. If the pressure is too small, the contact force between the abrasive grains and the wafer surface is insufficient, and the material removal rate slows down; if the pressure is too large, it may cause defects such as scratches and cracks on the wafer surface, and will accelerate the wear of the polishing pad 23, shortening its service life.

[0033] The polishing liquid plays a dual role of chemical corrosion and lubrication during the polishing process. A reasonable flow rate can ensure that the polishing liquid continuously and evenly covers the surface of the polishing pad 23, providing sufficient reactants for the chemical reaction, and at the same time can timely remove the debris and heat generated during the polishing process.

[0034] The optimal cooling water flow rate and temperature can timely and effectively remove the heat generated during the polishing process, which helps to maintain the balance between chemical and mechanical effects during the polishing process, keeps the polishing process parameters (such as the chemical reaction rate of the polishing liquid, the cutting ability of the abrasive grains, etc.) stable, improves the repeatability and stability of the process, and thus ensures the polishing quality.

[0035] The dressing effect on the polishing pad 23 is also one of the key factors related to the quality and efficiency of the entire polishing process. In this embodiment, the polishing pad 23 is dressed in an offline (Ex-situ) mode, which can deeply repair the damage of the polishing pad 23. The high hardness of the diamond dresser 4 can effectively remove the clogging and wear layer on the surface of the polishing pad 23. The magnitude of the downward pressure determines the intensity of the action of the dresser 4 on the surface of the polishing pad 23. Under the above conditions, a dressing operation with a duration of 10 - 60 s is carried out to ensure that the polishing pad 23 can be restored to the best working state and prepare for the next polishing.

[0036] In this embodiment, by clearly and optimally defining the parameters in the entire process method, the repeatability and stability of the process are guaranteed, the rework caused by unqualified polishing is reduced, thus reducing the trial-and-error cost, which is beneficial to maintaining the consistency of product quality in large-scale production.

[0037] In addition, using the above polishing equipment, the four polishing heads 21 sequentially suck the wafers onto the corresponding polishing plates 22, realizing parallel polishing of multiple wafers or multi-step processing of a single wafer, significantly improving the WPH (wafer per hour) of the SiC wafers.

[0038] In some possible embodiments, in step S3, the polishing liquid includes sodium permanganate (NaMnO4), a pH regulator, and the balance deionized water. The concentration of sodium permanganate is 10 - 20 wt%, and the pH regulator is used to adjust the pH value of the polishing liquid to 2 - 3.

[0039] Due to the high hardness of SiC, a strong oxidant is required to oxidize the surface of the SiC wafer, such as potassium permanganate or sodium permanganate. In this embodiment, sodium permanganate is specified as the oxidant because the solubility of sodium permanganate in water is better than that of potassium permanganate, which can contact the surface of the SiC wafer more evenly, and its reaction activity is higher, which can oxidize the surface of the SiC wafer more effectively to generate soft silicon dioxide, thereby forming a self-grinding effect. Therefore, when sodium permanganate is specified as the oxidant, the technical effect of not adding abrasives to the polishing liquid can be achieved, which can not only ensure the oxidation rate, but also simplify the process of the polishing liquid and reduce the use cost.

[0040] To ensure the oxidation efficiency of sodium permanganate when no abrasives are added, the concentration of sodium permanganate and the pH value of the polishing liquid are specifically limited in this embodiment. The concentration of sodium permanganate is limited to 10-20 wt%, ensuring that it provides sufficient active oxygen without causing waste of raw materials; the pH value of the polishing liquid is limited to 2-3, which can create an acidic environment for sodium permanganate and enable sodium permanganate to maintain high oxidation ability. By limiting the above parameters, the use performance of the polishing liquid is guaranteed.

[0041] Specifically, the pH regulator is selected from strong bases or strong acids, such as HCl, HNO3, KOH or NaOH, etc. The balance is deionized water, ensuring the stability of the components of the polishing liquid.

[0042] In some embodiments, the polishing liquid further includes an abrasive, and the abrasive is cerium oxide (CeO2) with a concentration of 1-2 wt% and a median particle size of 60-130 nm.

[0043] When abrasives need to be added to the polishing liquid, this embodiment provides cerium oxide as the abrasive in the polishing liquid. Cerium oxide has good hardness and chemical properties, and can quickly react with the oxidation product silicon dioxide of SiC, thereby accelerating the material removal of the SiC wafer.

[0044] This embodiment also makes specific limitations on the concentration and particle size of cerium oxide. If the concentration of cerium oxide is too high, it may cause the mechanical grinding to be too fast, exceeding the softening rate of the oxidation reaction and causing surface damage; if the particle size of cerium oxide is too large, even if the oxidation reaction is sufficient, the large particles may still damage the softened material layer. Therefore, by limiting the concentration and particle size of cerium oxide as the abrasive, it can better match with sodium permanganate to achieve efficient synergy, and then make the polishing liquid reach the best balance between chemical softening and mechanical grinding, realizing a polishing effect with high material removal rate, low surface damage and high uniformity. The specific setting of these parameters is the comprehensive result of process optimization and cost control, which is crucial for the high-quality processing of wafers in the polishing process.

[0045] In some embodiments, the polishing pad 23 adopts the structure as shown in Figure 2 See Figure 2, the thickness of the polishing pad 23 is 50 - 100 mil, and the Shore hardness is 60 - 68 HD; several annular grooves 231 are provided on the polishing pad 23, and the annular grooves 231 are sleeved in sequence from the center to the outer periphery, and the distance between adjacent two annular grooves 231 is 100 - 130 mil.

[0046] Specifically defining the thickness and hardness of the polishing pad 23 can enable the polishing pad 23 to maintain a certain mechanical force and extend the service life of the polishing pad 23 at the same time. Defining a relatively large distance between adjacent two annular grooves 231 helps the polishing liquid to flow fully in the annular grooves 231, so that the polishing liquid can fully contact and react with the wafer. On the other hand, it helps to timely discharge the debris generated during the polishing process, reduce the risk of blockage of the annular grooves 231, and further reduce the probability of scratching on the wafer surface.

[0047] The synergistic effect of the thickness, hardness of the polishing pad 23 and the structure of its annular grooves 231 ensures that the polishing pad 23 maintains stable performance during long-term use, reduces the fluctuation of the polishing rate caused by wear, and improves the processing efficiency.

[0048] Exemplarily, several radially arranged radial grooves 232 are also provided on the polishing pad 23, the radial grooves 232 extend along the radial direction of the polishing pad 23, and the radial grooves 232 and the annular grooves 231 communicate with each other. The above setting enables the polishing liquid to flow radially, further realizing the effect of global uniform coverage of the polishing liquid. At the same time, the radial grooves 232 can quickly guide the debris in the central area to the edge of the polishing pad 23, improving the self-cleaning ability of the polishing pad 23.

[0049] Specifically, the number of the radial grooves 232 can be set to 8 - 16.

[0050] In some embodiments, in step S6, the diamond density of the diamond dresser 4 is 300 - 600 ea / cm², the diamond protrusion is 30 - 50 μm, and the cutting rate for the polishing pad 23 is 130 - 200%.

[0051] High-density diamond particles (300 - 600 ea / cm²) can form dense cutting points on the surface of the polishing pad 23 to ensure uniform distribution of the trimmed grooves and textures. The protrusion height of the diamond matches the groove depth on the polishing pad 23, which can accurately repair the profiles of the annular grooves 231 and the radial grooves 232 and maintain their functions of guiding the flow of the polishing liquid and discharging chips. A cutting rate higher than the conventional rate (130 - 200%) can shorten the single trimming time and reduce the equipment downtime.

[0052] By specifically setting various parameters of the diamond dresser 4, a fine and regular microstructure can be formed on the surface of the polishing pad 23, which promotes the uniform distribution of the polishing liquid and the discharge of debris, and ultimately improves the global flatness of the SiC wafer.

[0053] In some possible embodiments, before step S1, it further includes: S11. Use the first transfer mechanism 5 to take out the wafer to be polished from the wafer cassette 6 and transfer it to the transfer tray 7; S12. Use the second transfer mechanism 8 to transfer the wafer to be polished on the transfer tray 7 to the to-be-loaded stage 91; When performing step S1, use the transfer mechanism 9 to transfer the wafer to be polished on the to-be-loaded stage 91 to the loading stage 1.

[0054] Specifically, both the first transfer mechanism 5 and the second transfer mechanism 8 have a linear movement module and a robotic arm for clamping the wafer. The transfer mechanism 9 is a robotic hand, which improves the transfer efficiency of the wafer. The settings of the transfer tray 7 and the to-be-loaded stage 91 play a role of temporary storage and transition in the transfer of the wafer from the wafer cassette 6 to the loading stage 1, increasing the safety during the wafer transfer process.

[0055] In some embodiments, in step S5, it further includes: S51. Use the transfer mechanism 9 to transfer the polished wafer on the loading stage 1 to the to-be-unloaded stage 92; S52. Use the second transfer mechanism 8 to take out the polished wafer on the to-be-unloaded stage 92, flip it, and transfer it to the cleaning unit 3.

[0056] Specifically, after the polishing head 21 transfers the polished wafer above the loading stage 1 and unloads it, the transfer mechanism 9 transfers the polished wafer to the to-be-unloaded stage 92. Then, the second transfer mechanism 8 transfers the wafer to the first cleaning module of the cleaning unit 3. After completing the cleaning process of the first cleaning module, the second transfer mechanism 8 takes it out and places it on the second cleaning module until the wafer is cleaned and dried. Then, the second transfer mechanism 8 transfers it to the transfer tray 7, which is convenient for the first transfer mechanism 5 to take out the dried wafer and store it.

[0057] In the above embodiments, the transfer mechanism 9 is arranged corresponding to the loading stage 1, the to-be-loaded stage 91, and the to-be-unloaded stage 92, and is specifically used to transfer the wafer to be polished from the to-be-loaded stage 91 into the loading stage 1 and transfer the polished wafer from the loading stage 1 out to the to-be-unloaded stage 92, so that the processes of wafer loading and unloading can be carried out stably and orderly, avoiding collision interference and hysteresis during transfer.

[0058] The robotic arm in the second transfer mechanism 8 also has the function of flipping the wafer, facilitating adaptation to different requirements for wafer placement methods in different cleaning modules. By establishing a connection between the transfer tray 7, the transfer mechanism 9, and the cleaning unit 3 through the second transfer mechanism 8, multiple processes are connected in series, forming a high degree of coherence and a high degree of cooperation, improving the transfer efficiency of the wafer.

[0059] In some possible embodiments, the cleaning module is at least one of a drum-type cleaning module 31, a pencil-type cleaning module 32, and a single-wafer cleaning module 33.

[0060] Specifically, referring to Figure 3 , the drum-type cleaning module 31 mainly includes a roller, a nozzle, and two cleaning brushes. The material of the cleaning brushes is polyvinyl alcohol to avoid damaging the polished wafer. The roller is used to drive the wafer to rotate at a certain speed, the nozzle is used to spray the cleaning liquid onto the wafer surface, and the two cleaning brushes are respectively close to the upper and lower surfaces of the wafer and clamp it. At the same time, the two cleaning brushes rotate synchronously to brush the wafer surface.

[0061] The drum-type cleaning module 31 can clean multiple wafers simultaneously, with a fast cleaning speed but limited cleaning ability.

[0062] Referring to Figure 4 , the pencil-type cleaning module 32 mainly includes a roller, a nozzle, and a pencil-type cleaning brush. The material of the pencil-type cleaning brush is also polyvinyl alcohol. The roller drives the wafer to rotate, the nozzle sprays the cleaning liquid to make it evenly distributed on the wafer surface, and the pencil-type cleaning brush is close to the wafer surface and rotates at a certain speed. While rotating, it reciprocates along the radial direction of the wafer to achieve full coverage cleaning of the wafer surface.

[0063] The pencil-type cleaning module 32 can make up for the deficiencies of the drum-type cleaning module 31 and achieve high-precision cleaning of local areas of the wafer, further improving the cleaning effect.

[0064] Referring to Figure 5 , the single-wafer cleaning module 33 sprays different cleaning liquids onto the wafer surface through multiple nozzles (①, ②, ③, ④). At the same time, the wafer rotates at a certain speed to ensure that the cleaning liquid can evenly cover the entire wafer surface, improving the cleaning effect. After cleaning, deionized water is used to rinse the wafer to remove the residual cleaning liquid and contaminants on the wafer surface. After rinsing, nitrogen is injected into the module to dry the rotating wafer to ensure that the wafer surface is clean and residue-free.

[0065] The single-wafer cleaning module 33 can only clean and dry one wafer at a time, but it can effectively remove particles, chemical residues, etc. on the wafer surface, and the cleaning effect is more thorough.

[0066] In practical applications, the combination of the required cleaning modules can be adjusted according to actual process requirements. For example, "drum - type cleaning module 31 + pencil - type cleaning module 32 + single - wafer cleaning module 33" or "drum - type cleaning module 31 + single - wafer cleaning module 33".

[0067] Illustratively, the process parameters of the polished wafer are as follows: the material removal rate of the Si surface is 4 - 8 μm / h, the material removal rate of the C surface is 12 - 23 μm / h, the total thickness deviation is <5 μm, the local thickness deviation is <2 μm, the length of mechanical damage is <50 μm, and the surface roughness Ra is 0.08 - 0.12 nm. The above parameters jointly define the characteristics of "high precision, low damage, and high consistency" of the polishing process, laying a solid foundation for the high performance and high reliability of advanced semiconductor devices.

[0068] The above - mentioned are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A polishing process method applied to a silicon carbide substrate, characterized in that, It includes the following steps: S1. Transfer the wafer to be polished onto the load stage (1); S2. The polishing head (21) on the rotating mechanism (2) adsorbs the wafer to be polished on the load stage (1) and transfers it above the corresponding polishing disc (22); S3. The polishing head (21) rotates at a speed of 100 - 145 rpm and applies a main polishing pressure of 5 - 9 psi. The polishing disc (22) rotates at a speed of 110 - 150 rpm. The polishing liquid is supplied to the polishing disc (22) at a flow rate of 50 - 100 mL / min, and the cooling water is supplied to the polishing disc (22) at a flow rate greater than 5 L / min. The temperature of the cooling water is 5 - 15 °C, and the wafer is polished; S4. The polishing head (21) transfers the polished wafer onto the load stage (1); S5. Transfer the polished wafer on the load stage (1) into the cleaning unit (3), and use multiple cleaning modules to clean and dry the polished wafer in sequence; S6. Trim the polishing pad (23) on the polishing disc (22) in an offline mode, and use a diamond dresser (4) to trim the polishing pad (23) with a downward pressure of 5 - 9 lbf, and the trimming duration is 10 - 60 s.

2. The polishing process method applied to a silicon carbide substrate according to claim 1, characterized in that, In step S3, the polishing liquid includes: Sodium permanganate with a concentration of 10 - 20 wt%; A pH regulator for adjusting the pH value of the polishing liquid to 2 - 3; and The balance is deionized water.

3. The polishing process method applied to a silicon carbide substrate according to claim 2, characterized in that, The polishing liquid also includes an abrasive, and the abrasive is cerium oxide with a concentration of 1 - 2 wt% and a median particle size of 60 - 130 nm.

4. A polishing process method applied to a silicon carbide substrate according to claim 1, characterized in that, The thickness of the polishing pad (23) is 50 - 100 mil, and the Shore hardness is 60 - 68 HD; several annular grooves (231) are provided on the polishing pad (23), and the annular grooves (231) are sleeved in sequence from the center to the outer periphery, and the distance between adjacent two annular grooves (231) is 100 - 130 mil.

5. The polishing process method applied to a silicon carbide substrate according to claim 4, wherein, Several radial grooves (232) arranged in a divergent shape are also provided on the polishing pad (23), the radial grooves (232) extend along the radial direction of the polishing pad (23), and the radial grooves (232) and the annular grooves (231) communicate with each other.

6. The polishing process method applied to a silicon carbide substrate according to claim 3, wherein, In step S6, the diamond density of the diamond dresser (4) is 300 - 600 ea / cm², the diamond protrusion is 30 - 50 μm, and the cutting rate for the polishing pad (23) is 130 - 200%.

7. The polishing process method applied to a silicon carbide substrate according to claim 1, characterized in that, Before step S1, it also includes: S11. Use the first transfer mechanism (5) to take out the wafer to be polished from the wafer cassette (6) and transfer it onto the transfer tray (7); S12. Use the second transfer mechanism (8) to transfer the wafer to be polished on the transfer tray (7) onto the waiting load stage (91); When performing step S1, use the transfer mechanism (9) to transfer the wafer to be polished on the waiting load stage (91) onto the load stage (1).

8. The polishing process method applied to a silicon carbide substrate as claimed in claim 7, wherein, In step S5, it also includes: S51. Use the transfer mechanism (9) to transfer the polished wafer on the load stage (1) to the to-be-unloaded stage (92). S52. Use the second transfer mechanism (8) to take out the polished wafer on the to-be-unloaded stage (92), flip it, and transfer it to the cleaning unit (3).

9. A polishing process method applied to a silicon carbide substrate according to claim 1, characterized in that, The cleaning module is at least one of a drum-type cleaning module (31), a pencil-type cleaning module (32), and a single-wafer cleaning module (33).

10. A polishing process method applied to a silicon carbide substrate according to any one of claims 1-9, characterized in that, The process parameters of the polished wafer are as follows: the material removal rate of the Si surface is 4 - 8 μm / h, the material removal rate of the C surface is 12 - 23 μm / h, the total thickness deviation is <5 μm, the local thickness deviation is <2 μm, the mechanical damage length is <50 μm, and the surface roughness Ra is 0.08 - 0.12 nm.

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