High-temperature silicon carbide polishing device and process

Abstract

The invention belongs to the technical field of silicon carbide wafer polishing, and particularly discloses a high-temperature silicon carbide polishing device and process, the device comprises a polishing machine body, a supporting base is arranged at the bottom end in the polishing machine body, and an automatic lifting platform is arranged at the top of the supporting base; a constant-temperature heating table is arranged at the top of the automatic lifting platform, the top of the constant-temperature heating table is connected with an objective table, and the constant-temperature heating table provides a constant-temperature heating environment for the objective table; the silicon carbide wafer is arranged on the top of the objective table, the polishing pads are arranged on the top of the silicon carbide wafer and the bevel gear and fixedly connected into the polishing machine body through the bearing supporting column, and the speed regulating motor drives the polishing pads through the bevel gear and the bearing supporting column so that the polishing pads and the silicon carbide wafer can form process interaction. According to the high-temperature silicon carbide polishing device and the high-temperature silicon carbide polishing process, a method of grinding a silicon carbide wafer at a high temperature is adopted, and the high-temperature silicon carbide polishing process has the advantages of stable heating, high efficiency and low cost.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide wafer polishing technology, specifically relating to a high-temperature silicon carbide polishing device and process. Background Technology

[0002] Silicon carbide, as a representative of third-generation semiconductor materials with a wide bandgap, has always been at the forefront of scientific and technological research due to its excellent mechanical properties, wide bandgap, good carrier mobility and thermal properties. However, it is difficult to polish due to the physicochemical inertness of silicon carbide wafer substrates.

[0003] Currently, the polishing of silicon carbide wafers is carried out using polishing slurries prepared with oxidants and abrasives in specific ratios, along with different polishing pads. Industry professionals have achieved high removal rates by polishing silicon carbide and pure iron, but have found that the temperature is difficult to control during the process. Since temperature is a variable that cannot be controlled, this method does not provide an accurate understanding of the mechanism of silicon carbide polishing.

[0004] Traditional polishing processes lack designs that guarantee high-temperature stability during polishing, and pure iron polishing struggles to prevent surface damage to the wafer. To address this, Chinese invention patent CN202311612547 provides a novel silicon carbide polishing device and process, establishing a current loop between the positive and negative electrodes of a power source to catalyze the generation of hydroxyl radicals; however, it cannot maintain sustained high-temperature stability. Chinese invention patent CN202410385154 discloses a silicon carbide polishing slurry containing transition metal or its oxide abrasive grains, offering advantages such as high cutting rate and stable surface quality; however, waste liquid treatment is difficult, and it does not involve polishing pure ferrous metals with silicon carbide, making it difficult to achieve the required polishing planarization. Chinese invention patent CN202211427667 discloses a temperature monitoring device and method for the silicon carbide polishing process, capable of real-time detection of the polishing interface temperature without affecting the silicon carbide wafer polishing process; however, it cannot guarantee temperature stability.

[0005] Therefore, there is a need in the field to develop a high-temperature silicon carbide polishing device and process that can effectively solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature silicon carbide polishing device and process. This process uses a high-temperature grinding method for silicon carbide wafers, which has the advantages of stable heating, high efficiency, and low cost.

[0007] To achieve the above objectives, the present invention provides a high-temperature silicon carbide polishing apparatus, comprising a polishing machine body, a support base at the bottom of the polishing machine body, and an automatic lifting platform at the top of the support base; the support base supports the automatic lifting platform, providing stable bottom support for the entire polishing apparatus; a constant-temperature heating stage is provided at the top of the automatic lifting platform, and a carrying platform is connected to the top of the constant-temperature heating stage, providing a constant-temperature heating environment for the carrying platform; a silicon carbide wafer is placed on the top of the carrying platform, and polishing pads are respectively disposed on the top of the silicon carbide wafer and on the bevel gear, and are connected and fixed inside the polishing machine body through bearing support columns; a speed-regulating motor drives the polishing pads through the bevel gears and bearing support columns, so that the polishing pads and silicon carbide wafers form a process interaction.

[0008] Preferably, the polishing pad is a pure metal disc, including a pure iron disc.

[0009] Preferably, the bevel gear includes a large bevel gear and a small bevel gear, a polishing pad is disposed on the small bevel gear, and the large bevel gear is connected to the speed regulating motor and perpendicularly connected to the small bevel gear.

[0010] This invention also provides a high-temperature silicon carbide polishing process, comprising the following steps: Step S1: Start the high-temperature silicon carbide polishing device. The automatic lifting platform controls the pressure by lifting distance. The pressure is adjusted by pressure measuring paper and corresponds to the moving distance of the automatic lifting platform. Step S2: Control the temperature of the stage by using a constant temperature heating table, and adjust the speed of the speed-regulating motor. Step S3: Use liquid-free polishing to polish the silicon carbide wafer and the polishing pad together; The polishing is dry polishing, which does not involve polishing fluid. The main consideration is to efficiently remove silicon carbide by friction catalysis of ferrous metals. During the polishing process, the contact surface between silicon carbide and pure iron will generate strong friction, which will reduce the activation energy of the chemical reaction and increase the chemical reaction rate between silicon carbide and pure iron.

[0011] Friction induces a chemical reaction between silicon carbide and pure iron. As the surfaces of silicon carbide and pure iron come into contact, the atomic activity on the surfaces of silicon carbide and pure iron increases under the action of pressure and rotation speed. The chemical bonds of silicon carbide break into carbon atoms and silicon atoms, which combine with iron atoms in an oxygen environment to form iron silicide and iron carbide, forming a softening layer.

[0012] Step S4: After polishing, allow the silicon carbide wafer to cool naturally to room temperature, remove it from the stage, and place it in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes. Then, take it out and place it in deionized water for ultrasonic cleaning for 15 minutes. After cleaning, use clean, dry air to dry the silicon carbide wafer, thus completing the high-temperature silicon carbide polishing process. The anhydrous ethanol solution was 99.7% analytical grade.

[0013] Preferably, in step S3, the polishing process values ​​are as follows: polishing pressure is 1-4 psi, polishing linear speed is 3.2 m / s, and polishing temperature is 120℃.

[0014] Preferably, step S3 further includes combining polishing pressure, polishing linear speed, polishing temperature with the traditional Arrhenius equation to obtain a modified Arrhenius equation, establishing a relationship model between process parameters and material removal rate, and achieving precise optimization of process parameters to perform counter-polishing of silicon carbide wafers and polishing pads.

[0015] Preferably, a relationship model between process parameters and material removal rate is established to achieve precise optimization of process parameters. Specifically, A. Combine polishing pressure, polishing linear velocity, and polishing temperature with the traditional Arrhenius equation, and introduce the calculation of friction power density and steady-state temperature; B. The modified Arrhenius equation is obtained; C. Substitute the polishing pressure, polishing linear velocity, and polishing temperature into the modified Arrhenius equation, draw the PV, PT, and VT phase diagrams, and determine the critical operating window. D. Adjust the model parameters based on the actual polishing results to achieve precise optimization of process parameters.

[0016] As temperature increases, the activity of the contact surface between silicon carbide and pure iron increases, and the reaction becomes more intense. However, the temperature generated by self-friction at room temperature is insufficient to reach the critical reaction point between iron and silicon carbide. By fitting polishing pressure, polishing linear speed, and polishing temperature to the traditional Arrhenius equation, a modified Arrhenius equation is obtained. By controlling different polishing variables, the required process values ​​at the reaction critical point can be calculated. Analysis of the polishing results reveals different polishing outcomes under different processes. Considering factors such as material waste, environmental pollution, and cost calculations in the actual process, polishing processes under different conditions can be selected.

[0017] Preferably, the frictional power density is specifically, ; In the formula, q For frictional power density, μ The coefficient of friction, P For pressure, v Linear velocity; The steady-state temperature calculation is as follows: ; In the formula, T Thermodynamic temperature T 0 For ambient temperature, μ The coefficient of friction, P For pressure,v For linear velocity, h is the heat transfer coefficient.

[0018] The preferred, traditional Arrhenius equation is: ; In the formula, K The reaction rate constant is... A Pre-exponential factor, E a The activation energy of the reaction. R Let be the ideal gas constant. T Thermodynamic temperature; The modified Arrhenius equation is: ; In the formula, k For the reaction rate, A Pre-exponential factor, E a The activation energy of the reaction. P For pressure, To activate the volume, R Let be the ideal gas constant. T It is the thermodynamic temperature.

[0019] Preferably, when the effective activation energy decreases to a critical value, the reaction rate k increases sharply; ; In the formula, E a ' To effectively activate energy, E a For activation energy, P For pressure, For activation volume; When the reaction rate exceeds a critical value due to a sudden change in reaction, the corresponding condition is: ; In the formula, E a For activation energy, P For pressure, To activate the volume, R Let be the ideal gas constant. T Thermodynamic temperature A Pre-exponential factor, k crit The critical reaction rate is given.

[0020] The present invention employs the above-mentioned high-temperature silicon carbide polishing device and process, and has the following beneficial effects: (1) The high-temperature silicon carbide polishing technology in this invention uses friction catalysis between silicon carbide wafers and iron disks to avoid the problems of polishing waste liquid corroding equipment, harming human health, and polluting the environment generated in traditional polishing processes. Silicon carbide has a large surface energy. Mechanical action causes the surface chemical bonds to break as the driving force, which softens the silicon carbide surface. Then, the softened layer on the silicon carbide surface is removed by mechanical shearing force.

[0021] (2) The high-temperature silicon carbide polishing device provided by this invention can be heated at a constant temperature, reducing uncontrollable variables in the polishing experiment and avoiding difficulties in the study of the polishing mechanism. Temperature, as another form of energy input in the polishing process, plays an important role in this type of research.

[0022] (3) The high-temperature silicon carbide polishing process provided in this invention can achieve high flatness and high efficiency polishing results when the polishing pressure is 4psi, the linear speed is 3.2m / s, the temperature is 120℃, and the pure iron disk is the polishing pad. The surface roughness Sa is 2nm and the material removal rate is 300nm / min.

[0023] (4) The present invention establishes a parameter relationship model by modifying the Arrhenius equation, optimizes the polishing process, and can flexibly adjust the process parameters according to actual needs (material waste, production efficiency, environmental pollution, etc.).

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of a high-temperature silicon carbide polishing device and its process embodiment according to the present invention. Figure 2 This is an atomic force microscope image of a silicon carbide wafer in Example 1 of the high-temperature silicon carbide polishing device and process of the present invention.

[0026] Figure Labels 1. Support base; 2. Automatic lifting platform; 3. Constant temperature heating table; 4. Loading stage; 5. Silicon carbide wafer; 6. Polishing pad; 7. Large bevel gear; 8. Small bevel gear; 9. Bearing support column; 10. Speed ​​regulating motor. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] like Figure 1As shown, a high-temperature silicon carbide polishing apparatus includes a polishing machine body. A support base 1 is located at the bottom of the polishing machine body, and an automatic lifting platform 2 is located on top of the support base 1. A constant-temperature heating stage 3 is located on top of the automatic lifting platform 2, and a carrying platform 4 is connected to the top of the constant-temperature heating stage 3, providing a constant-temperature heating environment for the carrying platform 4. A silicon carbide wafer 5 is placed on top of the carrying platform 4. Polishing pads 6 are respectively placed on the top of the silicon carbide wafer 5 and on bevel gears, and are connected and fixed inside the polishing machine body via bearing support columns 9. The polishing pad 6 is a pure metal disk, including a pure iron disk. The bevel gears include a large bevel gear 7 and a small bevel gear 8. The polishing pad 6 is placed on the small bevel gear 8. The large bevel gear 7 is connected to a speed-regulating motor 10 and perpendicularly connected to the small bevel gear 8. The speed-regulating motor 10 drives the polishing pad 6 through the bevel gears and bearing support columns 9, enabling the polishing pad 6 to interact with the silicon carbide wafer 5.

[0030] A high-temperature silicon carbide polishing process based on a high-temperature silicon carbide polishing device includes the following steps: Step S1: Start the high-temperature silicon carbide polishing device. The automatic lifting platform 2 controls the pressure by lifting distance. The pressure is adjusted by pressure measuring paper and corresponds to the moving distance of the automatic lifting platform 2. Step S2: Control the temperature of the stage 4 by using the constant temperature heating stage 3, and adjust the speed of the speed regulating motor 10 to control the rotation speed; Step S3: Use liquid-free polishing to polish the silicon carbide wafer 5 and the polishing pad 6 together; The specific values ​​for the polishing process are as follows: polishing pressure of 1-4 psi, polishing linear speed of 3.2 m / s, and polishing temperature of 120℃.

[0031] By combining polishing pressure, polishing line speed, polishing temperature with the traditional Arrhenius equation, a modified Arrhenius equation is obtained. A relationship model between process parameters and material removal rate is established, and the silicon carbide wafer 5 and polishing pad 6 are polished together after the process parameters are accurately optimized.

[0032] A. Combine polishing pressure, polishing linear velocity, polishing temperature with the Arrhenius equation, and introduce the calculation of friction power density and steady-state temperature; The frictional power density is specifically, ; In the formula, q For frictional power density, μ The coefficient of friction, P For pressure, v Linear velocity; The steady-state temperature calculation is as follows: ; In the formula, T Thermodynamic temperature T0 For ambient temperature, μ The coefficient of friction, P For pressure, v For linear velocity, h is the heat transfer coefficient.

[0033] The Arrhenius equation is, ; In the formula, K The reaction rate constant is... A Pre-exponential factor, E a The activation energy of the reaction. R Let be the ideal gas constant. T Thermodynamic temperature; B. The modified Arrhenius equation is obtained; The modified Arrhenius equation is: ; In the formula, k For the reaction rate, A Pre-exponential factor, E a The activation energy of the reaction. P For pressure, To activate the volume, R Let be the ideal gas constant. T It is the thermodynamic temperature.

[0034] C. Substitute the polishing pressure, polishing linear velocity, and polishing temperature into the modified Arrhenius equation, draw the PV, PT, and VT phase diagrams, and determine the critical operating window.

[0035] When the effective activation energy decreases to the critical value, the reaction rate k increases sharply; ; In the formula, E a ' To effectively activate energy, E a For activation energy, P For pressure, For activation volume; When the reaction rate exceeds a critical value due to a sudden change in reaction, the corresponding condition is: ; In the formula, E a For activation energy, P For pressure, To activate the volume, R Let be the ideal gas constant. TThermodynamic temperature A Pre-exponential factor, k crit The critical reaction rate is given.

[0036] D. Adjust the model parameters based on the actual polishing results to achieve precise optimization of process parameters.

[0037] Step S4: After polishing, allow the silicon carbide wafer 5 to cool naturally to room temperature, remove it from the stage 4, and place the silicon carbide wafer 5 in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes. Then, take it out and place it in deionized water for ultrasonic cleaning for 15 minutes. After cleaning, use clean, dry air to dry the silicon carbide wafer 5, thus completing the high-temperature silicon carbide polishing process.

[0038] Example 1 Polishing experiments were conducted at a fixed polishing pressure of 3 psi and a polishing linear speed of 3.2 m / s, and at polishing temperatures of 20℃, 40℃, 60℃, 80℃, 100℃, and 120℃.

[0039] As the temperature increases, the material removal rate also increases, with an increase of about 40% at 20-60℃ and about 80% at 80-120℃; compared to room temperature, the rate is about 240% higher at 120℃.

[0040] After polishing, the silicon carbide wafer 5 was ultrasonically cleaned in anhydrous ethanol solution for 15 minutes, then removed and ultrasonically cleaned in deionized water for 15 minutes. After cleaning, the silicon carbide wafer 5 was dried with clean, dry air. The surface roughness of the silicon carbide wafer 5 was then measured. As the temperature increased, the surface of the silicon carbide wafer 5 became increasingly smooth. Figure 2 As shown, the surface roughness Sa is 2 nm at 120℃, and the surface quality is improved by 40%.

[0041] Example 2 Polishing experiments were conducted at a fixed polishing pressure of 3 psi and a polishing temperature of 120℃, with polishing linear speeds of 0.8 m / s, 1.6 m / s, 2.4 m / s, and 3.2 m / s, respectively.

[0042] As the linear velocity increases, the material removal rate also increases, with an increase of approximately 30% in the 0.8-1.6 m / s range and approximately 40% in the 2.4-3.2 m / s range. Compared to the 0.8-1.6 m / s range, the overall maximum increase is approximately 180%.

[0043] After polishing, the silicon carbide wafer 5 was placed in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes, then removed and placed in deionized water for ultrasonic cleaning for 15 minutes. After cleaning, the silicon carbide wafer 5 was dried with clean, dry air. After cleaning the silicon carbide wafer 5, the surface roughness was measured. As the linear speed increased, the surface of the silicon carbide wafer 5 became smoother. At 3.2 m / s, the surface quality was improved by 25% compared to 0.8 m / s.

[0044] Example 3 Polishing experiments were conducted at a fixed polishing linear speed of 3.2 m / s and a polishing temperature of 120°C, with polishing pressures of 1 psi, 2 psi, 3 psi, and 4 psi respectively.

[0045] As the pressure increases, the material removal rate also increases, with an increase of about 16% at 1-2 psi, about 130% at 3-4 psi, and a maximum increase of about 180% at 4 psi compared to 1 psi.

[0046] After polishing, the silicon carbide wafer 5 was placed in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes, and then removed and placed in deionized water for ultrasonic cleaning for 15 minutes. After cleaning, the silicon carbide wafer 5 was dried with clean, dry air. After cleaning the silicon carbide wafer 5, the surface roughness was measured. As the linear speed increased, the surface of the silicon carbide wafer 5 became smoother and smoother. At 4 psi, the surface quality was improved by 40% compared with 1 psi.

[0047] Example 4 In this embodiment, to more intuitively illustrate the energy threshold of the Fe-SiC reaction, experimental parameters were optimized. Polishing pressure, polishing linear velocity, and polishing temperature were substituted into the modified Arrhenius equation, and a VT diagram was plotted with constant pressure to determine the basic reaction conditions required for efficient removal. When the pressure was set at 1 psi, the reactions at temperatures of 20°C, 40°C, and 60°C, and velocities of 0.8 m / s and 1.6 m / s did not reach the required energy, resulting in slightly lower material removal rates. Above 80°C and above 1.6 m / s, Fe and SiC reached the reaction threshold, and the material removal rate increased rapidly. Compared to experimental parameters below the reaction threshold, the experimental parameters above the reaction threshold showed a maximum improvement of approximately 240%.

[0048] Therefore, the present invention adopts the above-mentioned high-temperature silicon carbide polishing device and process, which uses a high-temperature grinding method for silicon carbide wafers and has the advantages of stable heating, high efficiency and low cost.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-temperature silicon carbide polishing apparatus, characterized in that, The polishing machine includes a polishing machine body, with a support base at the bottom inside the polishing machine body. An automatic lifting platform is located on top of the support base. A constant temperature heating stage is located on top of the automatic lifting platform, and a carrying platform is connected to the top of the constant temperature heating stage. A silicon carbide wafer is placed on top of the carrying platform. Polishing pads are respectively placed on the top of the silicon carbide wafer and on the bevel gear, and are connected and fixed inside the polishing machine body through bearing support columns. A speed-regulating motor drives the polishing pads through the bevel gears and bearing support columns, so that the polishing pads and silicon carbide wafers can form a process interaction.

2. The high-temperature silicon carbide polishing apparatus according to claim 1, characterized in that: The polishing pad is a pure metal disc, including a pure iron disc.

3. The high-temperature silicon carbide polishing apparatus according to claim 1, characterized in that: The bevel gear includes a large bevel gear and a small bevel gear. A polishing pad is placed on the small bevel gear. The large bevel gear is connected to the speed-regulating motor and perpendicularly connected to the small bevel gear.

4. A high-temperature silicon carbide polishing process based on the high-temperature silicon carbide polishing apparatus according to any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Start the high-temperature silicon carbide polishing device. The automatic lifting platform controls the pressure by lifting distance. The pressure is adjusted by pressure measuring paper and corresponds to the moving distance of the automatic lifting platform. Step S2: Control the temperature of the stage by using a constant temperature heating table, and adjust the speed of the speed-regulating motor. Step S3: Use liquid-free polishing to polish the silicon carbide wafer and the polishing pad together; Step S4: After polishing, allow the silicon carbide wafer to cool naturally to room temperature, remove it from the stage, and place it in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes. Then, take it out and place it in deionized water for ultrasonic cleaning for 15 minutes. After cleaning, use clean, dry air to dry the silicon carbide wafer, thus completing the high-temperature silicon carbide polishing process. The anhydrous ethanol solution was 99.7% analytical grade.

5. The high-temperature silicon carbide polishing process according to claim 4, characterized in that: In step S3, the specific values ​​for the polishing process are as follows: polishing pressure is 1-4 psi, polishing linear speed is 3.2 m / s, and polishing temperature is 120℃.

6. The high-temperature silicon carbide polishing process according to claim 5, characterized in that: Step S3 also includes combining polishing pressure, polishing line speed, polishing temperature with the traditional Arrhenius equation to obtain a modified Arrhenius equation, establishing a relationship model between process parameters and material removal rate, and achieving precise optimization of process parameters to perform counter-polishing of silicon carbide wafers and polishing pads.

7. The high-temperature silicon carbide polishing process according to claim 6, characterized in that: Establish a model relating process parameters to material removal rate to achieve precise optimization of process parameters. A. Combine polishing pressure, polishing linear velocity, polishing temperature with the Arrhenius equation, and introduce the calculation of friction power density and steady-state temperature; B. The modified Arrhenius equation is obtained; C. Substitute the polishing pressure, polishing linear velocity, and polishing temperature into the modified Arrhenius equation, draw the PV, PT, and VT phase diagrams, and determine the critical operating window. D. Adjust the model parameters based on the actual polishing results to achieve precise optimization of process parameters.

8. The high-temperature silicon carbide polishing process according to claim 7, characterized in that: The frictional power density is specifically, ； In the formula, q For frictional power density, μ The coefficient of friction, P For pressure, v Linear velocity; The steady-state temperature calculation is as follows: ； In the formula, T Thermodynamic temperature T 0 For ambient temperature, μ The coefficient of friction, P For pressure, v For linear velocity, h is the heat transfer coefficient.

9. The high-temperature silicon carbide polishing process according to claim 7, characterized in that: The Arrhenius equation is: ； In the formula, K The reaction rate constant is... A Pre-exponential factor, E a The activation energy of the reaction. R Let be the ideal gas constant. T Thermodynamic temperature; The modified Arrhenius equation is: ； In the formula, k For the reaction rate, A Pre-exponential factor, E a The activation energy of the reaction. P For pressure, To activate the volume, R Let be the ideal gas constant. T It is the thermodynamic temperature.

10. The high-temperature silicon carbide polishing process according to claim 7, characterized in that: When the effective activation energy decreases to a critical value, the reaction rate increases sharply; ； In the formula, E a ' To effectively activate energy, E a For activation energy, P For pressure, For activation volume; When the reaction rate exceeds a critical value due to a sudden change in reaction, the corresponding condition is: ； In the formula, E a For activation energy, P For pressure, To activate the volume, R Let be the ideal gas constant. T Thermodynamic temperature A Pre-exponential factor, k crit The critical reaction rate is given.

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