Electrochemical discharge / magnetic field collaborative auxiliary grinding and polishing device for high-purity semiconductor material

Abstract

The invention provides an electrochemical discharge / magnetic field collaborative auxiliary grinding and polishing device for a high-purity semiconductor material. The electrochemical discharge / magnetic field collaborative auxiliary grinding and polishing device is characterized by comprising a grinding wheel spindle, a spindle sleeve, a grinding wheel, a magnetic field generating device, a workpiece, a suction cup, a rotary table, a pulse direct-current power source, an auxiliary electrode, a liquid inlet pipe, a liquid supply pump, grinding liquid, a cooling tank, a liquid outlet pipe, a machining tank and an alternating-current power source. The grinding wheel is composed of a grinding wheel disc and a grinding block, the grinding block serves as a cathode, the auxiliary electrode serves as an anode, and the grinding fluid is composed of iron powder, free diamond abrasive particles, starch, a chemical additive, NaOH and deionized water; the magnetic field generating device generates a magnetic field with adjustable size and direction around the grinding block, and the magnetic sensitive abrasive particles in the grinding fluid are directionally gathered to form a chain-shaped flexible polishing layer to polish a workpiece; the workpiece is made of hard and brittle semiconductors, and the surface of the workpiece needs to be ground and polished. According to the invention, surface defects of a workpiece can be effectively polished in the same process, so that high-efficiency, high-precision and low-damage grinding and polishing processing of a high-purity semiconductor material is realized.

Description

Technical Field

[0001] This invention relates to semiconductor polishing equipment, and in particular to an electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials. Technical Background

[0002] High-purity semiconductor materials, such as single-crystal silicon, single-crystal silicon carbide, and gallium nitride, have become key substrates for fabricating core micro-parts such as micro-sensors, micro-optical components, and semiconductor chips in cutting-edge fields such as aerospace, defense, microelectronics, and optoelectronics, due to their excellent properties of high hardness, high melting point, low loss, and poor electrical conductivity. These parts have stringent requirements for nanoscale roughness, submicron-level dimensional accuracy, and low-damage processing of the processed surface. However, the processing characteristics of hard and brittle high-purity semiconductor materials present a technical challenge that makes it difficult to balance efficiency, accuracy, and processing quality, posing a great challenge to processing technology.

[0003] To achieve high-precision, high-efficiency, and low-damage processing of hard and brittle semiconductor materials, our team applied for patents CN114434221A ("An Electrochemical Discharge-Assisted Micro-Grinding Device for Micro Parts of Hard and Brittle Materials") and CN114406375A ("An Electrochemical Discharge-Enabled Micro-Grinding Method for Micro Parts of Silicon-Based Materials"). This device and method achieve electrochemical discharge-assisted micro-grinding, rather than a simple superposition of electrochemical discharge machining and mechanical grinding. The electrochemical discharge process does not depend on the workpiece's conductivity. Through electrochemical discharge, the physical and chemical coupling modification of the workpiece's subsurface material is achieved, transforming the hard and brittle subsurface into a modified layer with significantly reduced mechanical properties. This subsurface modification effectively increases the critical depth of cut for the transition from brittle to ductile removal of hard and brittle materials. The modified layer is then removed using a micro-grinding tool, significantly weakening the mechanical grinding force between the tool and the workpiece and greatly improving material removal efficiency. This allows for stable ductile removal of the material, significantly reducing or even eliminating defects such as chipping, pitting, and cracking on the ground surface and subsurface. However, this technical solution still has the following problems: First, since the core of this technology is grinding, the subsurface material of the workpiece is ultimately removed by the micro-grinding tool. This inevitably results in surface defects such as micro-protrusions, micro-burrs, and grinding marks left by the mechanical grinding process. This prevents the achievement of high-precision, low-damage machining of hard and brittle semiconductor materials, thus limiting the improvement in part performance and requiring further improvement. Second, the micro-grinding tool is small, limiting the effective area of ​​the part processed in a single operation. After processing each workpiece, it is necessary to remove the processed workpiece and then fix the next workpiece to be processed, resulting in significant time waste and preventing uninterrupted processing of hard and brittle semiconductor materials. This also requires further improvement. Third, this device uses integrated grinding and polishing composite processing, completing the process simultaneously within the same step, rather than simply superimposing grinding and polishing processes. Given the above problems with existing equipment, it is urgent to develop a new processing device to overcome the bottleneck of high-efficiency, high-precision, and low-damage machining technology for micro-parts made of hard and brittle materials. Summary of the Invention

[0004] To overcome the shortcomings of existing processing devices for micro-parts made of hard and brittle semiconductor materials, this invention provides a high-purity semiconductor material electrochemical discharge / magnetic field synergistic assisted grinding and polishing device, characterized by: a grinding wheel spindle, a spindle sleeve, a grinding wheel, a magnetic field generator, a workpiece, a chuck, a turntable, a pulsed DC power supply, an auxiliary electrode, a liquid inlet pipe, a liquid supply pump, grinding fluid, a cooling tank, a liquid outlet pipe, a processing tank, and an AC power supply; the grinding wheel spindle drives the grinding wheel to rotate and feed; the spindle sleeve fixes the grinding wheel spindle; the grinding wheel consists of a grinding wheel disc and grinding blocks, with multiple grinding blocks evenly fixed on the end face of the grinding wheel disc; the grinding blocks are formed by bonding diamond abrasive grains with an adhesive, where the diamond abrasive grains are bonded diamond abrasive grains, and the adhesive material is metal; the workpiece is made of hard and brittle semiconductor material, requiring surface grinding and polishing, and the workpiece is adsorbed onto the chuck by negative pressure, the chuck being fixed above the turntable; the turntable is located in the processing tank, and its function is to drive the workpiece on the chuck to rotate.

[0005] The grinding block is connected to a wire, which in turn connects to a slip ring. The slip ring is engaged with a brush, which is connected to the negative terminal of a pulsed DC power supply, thus making the grinding block a cathode in the electrochemical discharge process. The auxiliary electrode is connected to the positive terminal of the pulsed DC power supply, thus forming the anode in the electrochemical discharge process. The grinding block and the auxiliary electrode are immersed in the grinding fluid, forming a closed circuit.

[0006] During the electrochemical discharge process, the temperature of the grinding fluid in the processing tank will rise significantly, which will seriously reduce the effect of subsequent magnetorheological polishing. Therefore, a cooling tank is needed to cool the grinding fluid. The high-temperature grinding fluid in the processing tank enters the cooling tank through the outlet pipe for cooling, and the supply pump injects the cooled grinding fluid into the processing tank through the inlet pipe.

[0007] The magnetic field generating device is embedded in the grinding wheel. After being powered on, a magnetic field is generated around the grinding block. The magnetic abrasive particles in the grinding fluid in the processing tank are oriented and aggregated under the action of the magnetic field to form a chain-like flexible polishing layer to polish the workpiece in the same process.

[0008] The working part of the grinding wheel is a segmented circular grinding block below the grinding wheel disc. The radial width of the grinding block is 0.5-2 mm, the tangential length is 1-3 mm, and the axial thickness is 1-5 mm. The grinding block is immersed in the grinding fluid to a depth of 0.5-2 mm. The working part of the grinding block consists of bonded diamond abrasive grains with a particle size of 1-20 μm. The grinding fluid also contains free diamond abrasive grains with a particle size of 0.5-10 μm, which are used to polish the workpiece in the same process.

[0009] The auxiliary electrode is made of inert conductive graphite and is connected to the positive terminal of the pulsed DC power supply. Together with the conductive grinding fluid, it forms an anode structure. The size of the auxiliary electrode is 10 to 100 times that of the grinding block.

[0010] The grinding fluid is composed of iron powder, free diamond abrasive grains, starch, chemical additives, NaOH and deionized water, and is conductive.

[0011] The cooling tank maintains the temperature of the grinding fluid in the processing tank within the range of 20–25 °C.

[0012] The AC power supply powers the magnetic field generator, enabling it to generate a magnetic field whose magnitude and direction are adjustable.

[0013] The following beneficial effects can be obtained by using the electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials described in this invention.

[0014] ① Achieve integrated grinding and polishing in the same process. Integrate electrochemical discharge and magnetic field synergistic polishing technology. Electrochemical discharge increases the critical depth of cut for the transition from brittle to ductile removal of hard and brittle materials. Solidified diamond abrasive grains quickly and efficiently remove the modified layer. Magnetic field controls free diamond abrasive grains to form a chain-like flexible polishing layer, completing high-precision polishing. Defect removal and polishing are achieved in the same process, rather than simply superimposing multiple processes, achieving high efficiency, high precision, and low damage.

[0015] ② Flexible polishing with high precision and low damage. The chain-like flexible polishing layer formed by the magnetic particles in the grinding fluid under the action of a magnetic field is a flexible contact process that removes surface defects such as micro-protrusions, micro-burrs, and grinding marks left by mechanical grinding. It effectively polishes the surface defects of the workpiece in the same process, thereby realizing efficient, high-precision, and low-damage grinding and polishing of high-purity semiconductor materials.

[0016] ③ Temperature control ensures the overall performance of the polishing medium. Equipped with a grinding fluid circulation cooling system, the temperature of the grinding fluid in the processing tank is precisely controlled at 20-25℃, solving the problem of attenuation of magnetic sensitivity and conductivity caused by the temperature rise of the grinding fluid during electrochemical discharge, and ensuring the stability of the grinding fluid performance.

[0017] ④ The magnetic field is highly adjustable and adaptable. The magnetic field generator is powered by AC power and can flexibly adjust the magnitude and direction of the magnetic field, thereby changing the shape and hardness of the chain-like flexible polishing layer. It is suitable for hard and brittle semiconductor materials with different hardness, such as silicon-based and silicon carbide-based materials, as well as grinding and polishing processes with different surface precision requirements, thus improving the versatility and process adaptability of the device.

[0018] ⑤ Rapid chip removal. The magnetic field generator is powered by AC power and the magnitude and direction of the magnetic field can be flexibly adjusted. The magnetic particles in the grinding fluid form a chain-like flexible polishing layer under the action of the magnetic field. The polishing layer and the equipped grinding fluid circulation cooling system work together to accelerate the removal of grinding chips. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to the present invention.

[0020] Figure 2 This is a three-dimensional assembly diagram of an electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to the present invention.

[0021] Figure 3 This is a structural diagram of the grinding wheel and turntable of an electrochemical discharge / magnetic field synergistic assisted grinding and polishing device for high-purity semiconductor materials according to the present invention.

[0022] Figure 4 for Figure 1 A magnified view of a portion of the grinding wheel.

[0023] Figure 5 This is a schematic diagram illustrating the processing principle of an electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials.

[0024] Figure reference numerals: 1. Grinding wheel spindle; 2. Spindle sleeve; 3. Grinding wheel; 3-1. Grinding wheel disc; 3-1-1. Brush; 3-1-2. Slip ring; 3-1-3. Wire; 3-2. Grinding block; 3-2-1. Adhesive; 3-2-2. Bonded diamond abrasive grains; 4. Magnetic field generating device; 5. Workpiece; 5-1. Workpiece substrate; 5-2. Surface material melting or even vaporization; 5-3. Ablation products; 5-4. Ablation pits; 5-5. Recast layer; 5-6 5-7. Heat-affected layer; 5-8. Chemical products; 5-9. Modified layer; 5-10. Grinding debris; 5-11. Surface defects; 6. Suction cup; 7. Turntable; 8. Pulsed DC power supply; 9. Auxiliary electrode; 10. Liquid inlet pipe; 11. Liquid supply pump; 12. Grinding fluid; 12-1. Iron powder; 12-2. Free diamond abrasive grains; 12-3. Starch; 12-4. Chain-like flexible polishing layer; 13. Cooling tank; 14. Liquid outlet pipe; 15. Machining tank; 16. AC power supply. Detailed Implementation

[0025] The apparatus of the present invention will be further described below with reference to the accompanying drawings and specific examples.

[0026] like Figure 1As shown, a high-purity semiconductor material electrochemical discharge / magnetic field synergistic assisted grinding and polishing device is characterized by: a grinding wheel spindle (1), a spindle sleeve (2), a grinding wheel (3), a magnetic field generating device (4), a workpiece (5), a suction cup (6), a turntable (7), a pulsed DC power supply (8), an auxiliary electrode (9), an inlet pipe (10), a liquid supply pump (11), a grinding fluid (12), a cooling tank (13), an outlet pipe (14), a processing tank (15), and an AC power supply (16); the grinding wheel spindle (1) is used to drive the grinding wheel (3) to perform rotation and feed motion; the spindle sleeve (2) is used to fix the grinding wheel spindle (1); the grinding wheel (3) is composed of a grinding wheel disc. It consists of (3-1) and grinding blocks (3-2). There are 60 grinding blocks (3-2), which are evenly fixed on the end face of the grinding wheel (3-1). The grinding blocks (3-2) are formed by bonding diamond abrasive grains with adhesive (3-2-1). The diamond abrasive grains here are bonded diamond abrasive grains (3-2-2). The material of adhesive (3-2-1) is nickel metal. The material of workpiece (5) is hard and brittle semiconductor, and its surface needs to be polished. Workpiece (5) is adsorbed on suction cup (6) by negative pressure. Suction cup (6) is fixed above turntable (7). Turntable (7) is located in processing tank (15). Its function is to drive workpiece (5) on suction cup (6) to rotate.

[0027] The grinding block (3-2) is connected to the wire (3-1-3), the wire (3-1-3) is connected to the slip ring (3-1-2), the slip ring (3-1-2) is in conjunction with the brush (3-1-1), and the brush (3-1-1) is connected to the negative terminal of the pulsed DC power supply (8), so that the grinding block (3-2) constitutes the cathode in the electrochemical discharge process; the auxiliary electrode (9) is connected to the positive terminal of the pulsed DC power supply (8), and constitutes the anode in the electrochemical discharge process; the grinding block (3-2) and the auxiliary electrode (9) are immersed in the grinding fluid (12) to form a closed circuit.

[0028] During the electrochemical discharge process, the temperature of the grinding fluid (12) in the processing tank (15) will increase significantly, which will seriously reduce the effect of subsequent magnetorheological polishing. Therefore, a cooling tank (13) is needed to cool the grinding fluid (12). The high-temperature grinding fluid (12) in the processing tank (15) enters the cooling tank (13) through the outlet pipe (14) for cooling. The liquid supply pump (11) injects the cooled grinding fluid (12) into the processing tank (15) through the inlet pipe (10).

[0029] The magnetic field generating device (4) is embedded in the grinding wheel (3-1). After being powered on, a magnetic field is generated around the grinding block (3-2). The magnetic abrasive particles in the grinding fluid (12) in the processing groove (15) are oriented and aggregated under the action of the magnetic field to form a chain-like flexible polishing layer (12-4) to polish the workpiece (5) in the same process.

[0030] The working part of the grinding wheel (3) is the segmented circular grinding block (3-2) below the grinding wheel disc (3-1). The radial width of the grinding block (3-2) is 1.5 mm, the tangential length is 2 mm, and the axial thickness is 3 mm. The grinding block (3-2) is immersed in the grinding fluid (12) to a depth of 2 mm. The working part of the grinding block (3-2) is a bonded diamond abrasive grain (3-2-2) with a grain size of 10 μm. The grinding fluid (12) also contains free diamond abrasive grains (12-2) with a grain size of 3 μm, which are used to polish the workpiece (5) in the same process.

[0031] The auxiliary electrode (9) is made of inert conductive graphite material and is connected to the positive terminal of the pulsed DC power supply (8). Together with the conductive grinding fluid (12), it forms an anode structure. The size of the auxiliary electrode (9) is 30 times that of the grinding block (3-2).

[0032] The grinding fluid (12) is composed of 3.5% iron powder (12-1), 8.5% free diamond abrasive grains (12-2), 29% starch (12-3), 1% chemical additives, 6.5% NaOH and 51.5% deionized water by mass, and has electrical conductivity.

[0033] The cooling tank (13) maintains the temperature range of the grinding fluid (12) in the processing tank (15) at 23 °C.

[0034] The AC power supply (16) supplies power to the magnetic field generator (4), enabling the magnetic field generator (4) to generate a magnetic field with adjustable magnitude and direction.

[0035] The specific descriptions of the above examples are only used to illustrate the present invention more clearly and are not intended to limit the scope of the present invention. Any equivalent substitutions, modifications, etc., made within the scope of the disclosure of the present invention are included within the protection scope of the present invention.

Claims

1. A high-purity semiconductor material electrochemical discharge / magnetic field synergistic assisted polishing device, characterized in that: The device includes: a grinding wheel spindle (1), a spindle sleeve (2), a grinding wheel (3), a magnetic field generator (4), a workpiece (5), a chuck (6), a turntable (7), a pulsed DC power supply (8), an auxiliary electrode (9), an inlet pipe (10), a supply pump (11), grinding fluid (12), a cooling tank (13), an outlet pipe (14), a machining tank (15), and an AC power supply (16). The grinding wheel spindle (1) is used to drive the grinding wheel (3) to rotate and feed. The spindle sleeve (2) is used to fix the grinding wheel spindle (1). The grinding wheel (3) is composed of a grinding wheel disc (3-1) and grinding blocks (3-2). There are multiple grinding blocks (3-2), which are evenly fixed on the end face of the grinding wheel (3-1). The grinding blocks (3-2) are formed by bonding diamond abrasive grains with adhesive (3-2-1). The diamond abrasive grains here are bonded diamond abrasive grains (3-2-2), and the adhesive (3-2-1) is made of metal. The workpiece (5) is made of hard and brittle semiconductor material, and its surface needs to be polished. The workpiece (5) is adsorbed on the suction cup (6) by negative pressure. The suction cup (6) is fixed above the turntable (7). The turntable (7) is located in the processing tank (15), and its function is to drive the workpiece (5) on the suction cup (6) to rotate.

2. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that... The grinding block (3-2) is connected to the wire (3-1-3), the wire (3-1-3) is connected to the slip ring (3-1-2), the slip ring (3-1-2) is in conjunction with the brush (3-1-1), and the brush (3-1-1) is connected to the negative terminal of the pulsed DC power supply (8), so that the grinding block (3-2) constitutes the cathode in the electrochemical discharge process; the auxiliary electrode (9) is connected to the positive terminal of the pulsed DC power supply (8), and constitutes the anode in the electrochemical discharge process; the grinding block (3-2) and the auxiliary electrode (9) are immersed in the grinding fluid (12) to form a closed circuit.

3. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that: During the electrochemical discharge process, the temperature of the grinding fluid (12) in the processing tank (15) will increase significantly, which will seriously reduce the effect of subsequent magnetorheological polishing. Therefore, a cooling tank (13) is needed to cool the grinding fluid (12). The high-temperature grinding fluid (12) in the processing tank (15) enters the cooling tank (13) through the outlet pipe (14) for cooling. The liquid supply pump (11) injects the cooled grinding fluid (12) into the processing tank (15) through the inlet pipe (10).

4. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that... The magnetic field generating device (4) is embedded in the grinding wheel (3-1). After being powered on, a magnetic field is generated around the grinding block (3-2). The magnetic abrasive particles in the grinding fluid (12) in the processing tank (15) are oriented and aggregated under the action of the magnetic field to form a chain-like flexible polishing layer (12-4) to polish the workpiece (5) in the same process.

5. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that... The working part of the grinding wheel (3) is a segmented circular grinding block (3-2) below the grinding wheel disc (3-1). The radial width of the grinding block (3-2) is 0.5-2 mm, the tangential length is 1-3 mm, and the axial thickness is 1-5 mm. The immersion depth of the grinding block (3-2) in the grinding fluid (12) is 0.5-2 mm. The working part of the grinding block (3-2) is a bonded diamond abrasive grain (3-2-2) with a grain size of 1-20 μm. The grinding fluid (12) also contains free diamond abrasive grains (12-2) with a grain size of 0.5-10 μm, which are used to polish the workpiece (5) in the same process.

6. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that: The auxiliary electrode (9) is made of inert conductive graphite material and is connected to the positive terminal of the pulsed DC power supply (8). Together with the conductive grinding fluid (12), it forms an anode structure. The size of the auxiliary electrode (9) is 10 to 100 times that of the grinding block (3-2).

7. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that: The grinding fluid (12) is composed of iron powder (12-1), free diamond abrasive grains (12-2), starch (12-3), chemical additives, NaOH and deionized water, and has electrical conductivity.

8. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that... The cooling tank (13) maintains the temperature of the grinding fluid (12) in the processing tank (15) within the range of 20 to 25 °C.

9. The electrochemical discharge / magnetic field synergistic assisted polishing device for high-purity semiconductor materials according to claim 1, characterized in that... The AC power supply (16) supplies power to the magnetic field generator (4), so that the magnetic field generator (4) generates a magnetic field with adjustable magnitude and direction.

Images