Non-contact polishing apparatus and polishing method based on structured surface polishing tool

Abstract

The application discloses a non-contact polishing device based on a structured surface polishing tool, which comprises a work platform; a workpiece clamping driving assembly and a polishing liquid pressure increasing assembly are correspondingly arranged on the work platform; the polishing liquid pressure increasing assembly comprises a structured surface polishing tool arranged below the workpiece clamp; the structured surface polishing tool is of a groove type structure, the bottom of the structured surface polishing tool is in the shape of a conical surface with an outer high and an inner low, and a plurality of radial distribution stirring rods are arranged on the conical surface; during work, the polishing liquid in the structured surface polishing tool can be dispersed to the edge of the polishing tool driving device under the cooperation of centrifugal force and the stirring rods, and the pressure of the polishing liquid acting on the surface of the workpiece to be processed is improved. During the machining process, the polishing liquid forms a continuous flow field on the surface of the workpiece, and then the shear stress of the flow variable polishing liquid on the surface of the workpiece to be processed is generated, so that the surface material of the workpiece is uniformly removed; the pressure of the flow variable polishing liquid acting on the surface of the workpiece is improved by the structured surface polishing tool, and the polishing efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ball precision machining, in particular to a non-contact polishing device and method based on a structured surface polishing tool, which is suitable for efficient, high-quality and low-damage machining of hard and brittle materials. BACKGROUND

[0002] With the continuous development of electronic technology, aerospace technology, optical technology and other cutting-edge technologies, power semiconductor devices, which play a key role in these technologies, are also required to be more powerful, higher frequency, more efficient and more integrated.

[0003] Monocrystalline SiC is widely considered to be a typical third-generation semiconductor material for manufacturing power devices that work under high voltage, high frequency and high temperature conditions due to its many excellent electrical and chemical properties, such as high thermal conductivity, high critical breakdown field, high saturated electron drift rate, high bond energy and wide band gap. It is the preferred material for high-frequency, high-temperature, high-power, radiation-resistant electronic devices and sensor devices, and is also an ideal substrate material for manufacturing large-size, super-high-brightness white light, blue light diodes and laser diodes, and has important applications in the fields of aviation, space exploration, nuclear energy development, radar and communication.

[0004] Silicon carbide substrates for epitaxial growth of semiconductor devices need to go through crystal growth, crystal orientation, end face grinding, chamfering, slicing, thinning, grinding, polishing and final cleaning, and the polishing step accounts for 80% of the total processing cost. Silicon carbide itself is extremely inert and hard, making it a typical difficult-to-machine material. Although the chemical mechanical polishing technology widely used in industrial production has a high surface quality, the material removal rate is extremely low, which restricts the development of silicon carbide materials in the fields of communication equipment, new energy equipment, aerospace equipment manufacturing, etc. In order to solve the problem of SiC polishing and ensure the surface quality of SiC wafer after polishing and improve the material processing efficiency, it is very important to develop a high-efficiency, high-quality and non-damage polishing technology suitable for silicon carbide wafer surface processing. SUMMARY

[0005] The present invention provides a non-contact polishing device based on a structured surface polishing tool and a polishing method implemented on the polishing device. The technical solution of the present invention is used for polishing processing. During the processing, the polishing tool rotates to drive the polishing liquid to move, so that the polishing liquid forms a continuous flow field on the workpiece surface. Then, the mechanorheological polishing liquid generates shear stress on the surface of the workpiece to be processed, so that the surface material of the workpiece is evenly removed, and a high-precision processed surface is obtained. In addition, the structured surface polishing tool with a specific structure increases the pressure of the mechanorheological polishing liquid acting on the workpiece surface, thereby improving the polishing efficiency. It can achieve efficient removal of surface defects and sub-surface damage layers of SiC wafers, and realize efficient, high-quality, and damage-free polishing.

[0006] For the polishing device, the technical solution of the present invention is as follows:

[0007] A non-contact polishing device based on a structured surface polishing tool includes a work platform; a workpiece clamping drive assembly and a polishing liquid boosting assembly are correspondingly provided on the work platform; the workpiece clamping drive assembly includes a workpiece fixture and a workpiece drive device; the workpiece fixture is used to clamp the workpiece to be processed, and the workpiece drive device can drive the workpiece fixture to move the workpiece to a set position and can drive the workpiece fixture to rotate the workpiece; the polishing liquid boosting assembly includes a structured surface polishing tool correspondingly provided below the workpiece fixture; a polishing tool drive device is provided below the structured surface polishing tool, and the polishing tool drive device can drive the structured surface polishing tool to rotate; the structured surface polishing tool is a groove-shaped structure, the bottom of which is a conical surface with a high outer side and a low inner side, and radially distributed shifting rods are arranged in groups on the conical surface; when working, there is a gap between the workpiece to be processed and the bottom surface of the structured surface polishing tool and is close to the edge of the structured surface polishing tool. The polishing liquid in the structured surface polishing tool can be dispersed toward the edge of the polishing tool drive device under the coordinated action of centrifugal force and the shifting rod, thereby increasing the pressure of the polishing liquid acting on the surface of the workpiece to be processed.

[0008] Compared with the prior art, the non-contact polishing device based on the structured surface polishing tool of the present invention is used to perform force rheological polishing on the surface of the workpiece. Since it adopts a special structured surface polishing tool, during polishing, it can not only enable the force rheological polishing fluid to form a continuous flow field on the surface of the workpiece, produce a shear thickening effect, form a flexible abrasive tool that fits the surface of the workpiece, and uniformly remove material from the surface of the workpiece, but also the polishing fluid in the structured surface polishing tool can be dispersed to the edge of the polishing tool drive device under the synergistic action of centrifugal force and the lever, thereby increasing the pressure of the polishing fluid on the surface of the workpiece to be processed, thereby improving the material removal efficiency, and can perform efficient, high-quality, and damage-free polishing on the surface of the SiC wafer.

[0009] As an optimization solution, in order to obtain a better pressurization effect, in the aforementioned non-contact polishing device based on the structured surface polishing tool, the bottom taper of the structured surface polishing tool is 15°-30°.

[0010] As an optimization solution, in the aforementioned non-contact polishing device based on a structured surface polishing tool, the levers are curved, and the levers are arranged in groups to form an impeller shape. As a result, when the structured surface polishing tool rotates, the mechano-rheological polishing fluid can flow outward along the edges of the curved levers, dispersing the fluid toward the edge of the polishing tool more quickly and preventing the polishing fluid from accumulating at the bottom of the structured surface polishing tool.

[0011] As an optimization solution, in the aforementioned non-contact polishing device based on the structured surface polishing tool, the top of the lever is a horizontal planar structure. As a result, during machining, when the gap between the structured surface polishing tool and the workpiece remains the same, the workpiece can receive a higher polishing pressure.

[0012] As an optimization solution, in the aforementioned non-contact polishing device based on a structured surface polishing tool, a polishing liquid anti-accumulation component is provided on the work platform for stirring the polishing liquid accumulated on the wall surface of the structured surface polishing tool. Furthermore, the polishing liquid anti-accumulation component includes a cantilevered stirring head fixing bracket and a stirring head detachably connected to the cantilever of the cantilevered stirring head fixing bracket. Furthermore, the cantilevered stirring head fixing bracket is in the shape of a scraper. During operation, the polishing liquid anti-accumulation component stirs the polishing liquid accumulated on the wall surface of the structured surface polishing tool to prevent the polishing liquid from becoming ineffective.

[0013] For the polishing method, the technical solution of the present invention is as follows:

[0014] A non-contact polishing method based on a structured surface polishing tool, the method being implemented on the aforementioned non-contact polishing device of the present invention;

[0015] The method comprises the following steps:

[0016] S1. Clamp the workpiece to be processed on the workpiece fixture;

[0017] S2, placing the prepared mechanorheological polishing fluid into a structured surface polishing tool;

[0018] S3. Adjust the distance between the workpiece to be processed and the liquid level of the mechanorheological polishing fluid to 3-5 mm through the workpiece clamping drive assembly; and adjust the gap between the workpiece to be processed and the wall surface of the structured surface polishing tool to 2-3 mm;

[0019] S4. Start processing: Control the rotation speed of the workpiece to be processed to 30-50 r / min, the rotation speed of the structured surface polishing tool to 80-120 r / min, and the rotation directions of the workpiece to be processed and the structured surface polishing tool are opposite;

[0020] S5. After the processing reaches the set time, the polishing process is completed.

[0021] Compared with the prior art, the non-contact polishing method based on the structured surface polishing tool of the present invention can obtain a high-quality surface while having the advantage of high polishing efficiency, which is conducive to industrial promotion.

[0022] Preferably, in the aforementioned non-contact polishing method based on a structured surface polishing tool, the workpiece to be processed is a SiC wafer. Further, for ease of implementation, in step S1, the SiC wafer is adhered to the loading surface of the polishing fixture using paraffin wax. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic structural diagram of a non-contact polishing device based on a structured surface polishing tool according to the present invention;

[0024] Figure 2 Schematic diagram of the structure of the structured bottom element of the structured polishing tool of the present invention;

[0025] Figure 3 Schematic diagram of the structured surface polishing tool and the workpiece to be processed;

[0026] Figure 4 This is a nephogram of shear stress on the workpiece surface when the structured surface polishing tool with a taper of 15 degrees is polishing the workpiece;

[0027] Figure 5 This is a nephogram of shear stress on the workpiece surface when the structured surface polishing tool with a taper of 20 degrees is polishing the workpiece;

[0028] Figure 6 This is a nephogram of shear stress on the workpiece surface when the structured surface polishing tool with a taper of 25 degrees is polishing the workpiece;

[0029] Figure 7 This is a nephogram of shear stress on the workpiece surface when the structured surface polishing tool with a taper of 30 degrees is polishing the workpiece;

[0030] Figure 8 This is a shear stress cloud diagram of the workpiece surface when the workpiece is polished without using a structured surface polishing tool;

[0031] Figure 9 This is a white light interferometer inspection image of the workpiece before polishing with a structured surface polishing tool;

[0032] Figure 10This is a white light interferometer inspection image of a workpiece after polishing using a structured surface polishing tool;

[0033] Figure 11 This is a white light interferometer inspection image of the workpiece before polishing without using a structured surface polishing tool;

[0034] Figure 12 This is a white light interferometer inspection image of the workpiece after polishing without using a structured surface polishing tool.

[0035] The figures are marked as follows: 1-structured surface polishing tool, 101-shift rod; 2-workpiece clamp; 3-polishing tool driving device; 4-workpiece driving device; 5-stirring head fixing bracket; 6-stirring head; 7-workpiece to be processed. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments, but they are not intended to serve as the basis of the present invention.

[0037] Example (see Figure 1-12 ):

[0038] A non-contact polishing device based on a structured surface polishing tool includes a working platform; a workpiece clamping drive component and a polishing liquid boosting component are correspondingly provided on the working platform; the workpiece clamping drive component includes a workpiece fixture 2 and a workpiece drive device 4; the workpiece fixture 2 is used to clamp the workpiece 7 to be processed, and the workpiece drive device 4 can drive the workpiece fixture 2 to move the workpiece to a set position, and can drive the workpiece fixture 2 to rotate the workpiece (the workpiece clamping drive component belongs to the prior art and will not be described here); the polishing liquid boosting component includes a structured surface polishing tool 1 correspondingly provided below the workpiece fixture 2; a polishing tool drive device 3 is provided below the structured surface polishing tool 1, and the polishing liquid boosting component is provided below the structured surface polishing tool 1. The optical tool driving device 3 can drive the structured surface polishing tool 1 to perform rotational motion; the structured surface polishing tool 1 is a groove-type structure (in the embodiment, the structured surface polishing tool 1 is composed of a polishing groove body and a structured bottom element fixed to its bottom), and its bottom is a conical surface with a high outside and a low inside, and radially distributed shift rods 101 are arranged in groups on the conical surface; when working, there is a gap between the workpiece 7 to be processed and the bottom surface of the structured surface polishing tool 1 and is close to the edge of the structured surface polishing tool 1. The polishing liquid in the structured surface polishing tool 1 can be dispersed to the edge of the polishing tool driving device 3 under the synergistic action of centrifugal force and the shift rod 101, thereby increasing the pressure of the polishing liquid on the surface of the workpiece 7 to be processed.

[0039] In the embodiment, according to the simulation results, the bottom taper of the structured surface polishing tool 1 is set to 25 degrees. The lever 101 is arc-shaped, and the levers 101 arranged in groups form an impeller shape. The top of the lever 101 is a horizontal plane structure.

[0040] The simulation process is as follows: SolidWorks software was used to construct the relevant physical model, and Fluent software was used to numerically simulate the flow field of the non-Newtonian mechanorheological polishing fluid. The pressure field distribution on the workpiece surface during mechanorheological polishing of silicon carbide was simulated. Simulations were conducted using four structured surface polishing tools with different tapers and a polishing tank without a polishing tool. The workpiece was separated from the polishing plate by 2 mm. The rotational speed of workpiece 7 was set to 30 rpm, and the rotational speed of structured surface polishing tool 1 was set to 100 rpm, in the opposite direction of workpiece 7.

[0041] Figure 5-Figure 9 The following are shear stress cloud diagrams of the workpiece surface when the structured surface polishing tool 1 is tilted at 15 degrees, 20 degrees, 25 degrees, and 30 degrees, as well as when the polishing groove has no structured surface (i.e., a conventional polishing groove). As can be seen from the figure, in these simulation cases, when the structured surface polishing tool 1 is used to polish the workpiece, the stress on the workpiece surface is greater than when polishing with the unstructured surface polishing groove. Therefore, in order to reduce the roughness of the workpiece surface and improve polishing efficiency, it is more advantageous to use a structured surface polishing tool for polishing.

[0042] In this embodiment, the work platform is equipped with a polishing liquid anti-accumulation assembly for agitating polishing liquid that accumulates on the surface of the structured surface polishing tool 1. The polishing liquid anti-accumulation assembly includes a cantilevered stirring head fixed bracket 5 and a stirring head 6 detachably connected to the cantilever of the cantilevered stirring head fixed bracket 5. The cantilevered stirring head fixed bracket 5 is scraper-shaped. The polishing liquid anti-accumulation assembly agitates the polishing liquid during polishing to prevent the polishing liquid from accumulating and becoming ineffective.

[0043] In an embodiment, a non-contact polishing method based on a structured surface polishing tool comprises the following steps:

[0044] S1. Clamp the workpiece 7 (silicon carbide wafer, diameter Φ50 mm, thickness 350 μm) to be processed on the workpiece fixture 2 (using paraffin wax to stick on the loading surface of the polishing fixture 2);

[0045] S2. Place the prepared mechanorheological polishing fluid in the structured surface polishing tool 1. The mechanorheological polishing fluid is prepared by using a polyhydroxy aldehyde polymer (accounting for 45% by mass of the polishing fluid) as the dispersed phase and pure water (accounting for 40% by mass of the polishing fluid) as the solvent to prepare a non-Newtonian fluid with a shear thickening effect. Subsequently, diamond abrasive particles with a particle size of 1.0 μm (accounting for 15% by mass of the polishing fluid) are added to the non-Newtonian fluid and stirred uniformly.

[0046] S3. Adjust the distance between the workpiece 7 to be processed and the liquid level of the mechanorheological polishing fluid to 5 mm through the workpiece clamping drive assembly; and adjust the gap between the workpiece 7 to be processed and the wall surface of the structured surface polishing tool 1 to 2 mm;

[0047] S4, start processing: control the rotation speed of the workpiece 7 to be processed to 30 r / min, the rotation speed of the structured surface polishing tool 1 to 100 r / min, and the rotation directions of the workpiece 7 to be processed and the structured surface polishing tool 1 are opposite;

[0048] S5. After the processing reaches the set time (20 minutes), the polishing process is completed.

[0049] The surface roughness and material removal rate of silicon carbide wafers were tested using a white light interferometer and a precision balance. The results showed that the surface roughness after processing was 0.276nm and the material removal rate was 2.498um / h.

[0050] A comparative experiment was conducted using a polishing disk of an unstructured surface polishing tool. The workpiece and polishing liquid were the same as in the above embodiment. The workpiece speed was set to 30 r / min, and the polishing disk speed was set to 100 r / min. After polishing for 20 minutes, the surface roughness and material removal rate of the silicon carbide wafer were tested using a white light interferometer and a precision balance. The results showed that the surface roughness after processing was 0.464 nm and the material removal rate was 0.784 μm / h.

[0051] Experimental results show that the non-contact polishing device based on the structured surface polishing tool of the present invention can obviously achieve higher polishing quality and material removal efficiency.

[0052] It should be noted that the technical solution of the present invention is developed to meet the requirements of efficient, high-quality, and damage-free polishing of silicon carbide wafers, but is not limited to the polishing of silicon carbide wafers and can also be used for polishing of other materials.

[0053] The above general description of the invention and the description of its specific embodiments involved in this application should not be understood as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art may, without violating the constituent elements of the invention involved, add, subtract, or combine the disclosed technical features in the above general description and / or specific embodiments (including examples) to form other technical solutions within the scope of protection of this application.

Claims

1. A non-contact polishing device based on a structured surface polishing tool, characterized in that: It includes a working platform; the working platform is provided with a workpiece clamping drive component and a polishing liquid boosting component; The workpiece clamping drive assembly comprises a workpiece clamp (2) and a workpiece drive device (4); the workpiece clamp (2) is used to clamp a workpiece (7) to be processed, and the workpiece drive device (4) can drive the workpiece clamp (2) to move the workpiece to a set position, and can also drive the workpiece clamp (2) to rotate the workpiece; The polishing liquid boosting assembly comprises a structured surface polishing tool (1) correspondingly arranged below the workpiece fixture (2); a polishing tool driving device (3) is provided below the structured surface polishing tool (1), and the polishing tool driving device (3) can drive the structured surface polishing tool (1) to perform rotational motion; the structured surface polishing tool (1) is a groove-shaped structure, the bottom of which is a conical surface with a high outer surface and a low inner surface, and radially distributed shifting rods (101) are provided in groups on the conical surface; when working, there is a gap between the workpiece (7) to be processed and the bottom surface of the structured surface polishing tool (1) and the polishing liquid is close to the edge of the structured surface polishing tool (1), and the polishing liquid in the structured surface polishing tool (1) can be directed to the polishing tool driving device (3) under the coordinated action of centrifugal force and the shifting rod (101). The edge is dispersed to increase the pressure of the polishing liquid on the surface of the workpiece (7) to be processed; the bottom taper of the structured surface polishing tool (1) is 15°-30°; the work platform is provided with a polishing liquid anti-accumulation component for stirring the polishing liquid accumulated on the wall surface of the structured surface polishing tool (1); the polishing liquid anti-accumulation component includes a cantilever stirring head fixing bracket (5) and a stirring head (6) detachably connected to the cantilever of the cantilever stirring head fixing bracket (5).

2. The non-contact polishing device based on the structured surface polishing tool according to claim 1, characterized in that: The shifting rods (101) are arc-shaped, and the shifting rods (101) arranged in groups form an impeller shape.

3. The non-contact polishing device based on the structured surface polishing tool according to claim 2, characterized in that: The top of the shifting rod (101) is a horizontal plane structure.

4. The non-contact polishing device based on the structured surface polishing tool according to claim 1, characterized in that: The cantilevered stirring head fixing bracket (5) is in the shape of a scraper.

5. A non-contact polishing method based on a structured surface polishing tool, characterized in that: The method is implemented on the non-contact polishing device of claim 1; The method comprises the following steps: S1, clamping the workpiece to be processed (7) on the workpiece fixture (2); S2, placing the prepared mechanorheological polishing liquid into the structured surface polishing tool (1); S3, adjusting the distance between the workpiece to be processed (7) and the liquid surface of the mechanorheological polishing liquid to 3-5 mm through the workpiece clamping drive assembly; and adjusting the gap between the workpiece to be processed (7) and the wall surface of the structured surface polishing tool (1) to 2-3 mm; S4, start processing: control the rotation speed of the workpiece to be processed (7) to 30-50 r / min, the rotation speed of the structured surface polishing tool (1) to 80-120 r / min, and the rotation directions of the workpiece to be processed (7) and the structured surface polishing tool (1) are opposite; S5. After the processing reaches the set time, the polishing process is completed.

6. The non-contact polishing method based on a structured surface polishing tool according to claim 5, characterized in that: The workpiece (7) to be processed is a SiC wafer.

7. The non-contact polishing method based on a structured surface polishing tool according to claim 6, characterized in that: In step S1, the SiC wafer is adhered to the loading surface of the polishing fixture (2) through paraffin wax.

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