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

Abstract

The invention discloses a non-contact polishing device based on a structured surface polishing tool. The non-contact polishing device comprises a working platform, a workpiece clamping driving assembly and a polishing solution pressurizing assembly are correspondingly arranged on the working platform; the polishing solution pressurizing assembly comprises a structured surface polishing tool correspondingly arranged below the workpiece clamp. The structured surface polishing tool is of a groove-shaped structure, the bottom of the structured surface polishing tool is in a conical surface shape with the outer portion higher than the inner portion, and shifting rods distributed in a radial shape are arranged on the conical surface in groups. During working, polishing liquid in the structured surface polishing tool can be dispersed towards the edge of the polishing tool driving device under the synergistic effect of centrifugal force and the shifting rod, and the pressure of the polishing liquid acting on the surface of a workpiece to be machined is increased. In the machining process, the polishing solution forms a continuous flow field on the surface of the workpiece, then the force rheological polishing solution generates shear stress on the surface of the workpiece to be machined, the material on the surface of the workpiece is evenly removed, the pressure, acting on the surface of the workpiece, of the force rheological polishing solution is improved through the structured surface polishing tool, and the polishing efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sphere precision machining, and in particular to a non-contact polishing device and a polishing method based on a structured surface polishing tool, which are suitable for high-efficiency, high-quality and low-damage machining of hard and brittle materials. Background Art

[0002] With the continuous development of cutting-edge technologies such as electronic technology, aerospace technology, and optical technology, higher and higher requirements are placed on power semiconductor devices that play a key role in them, making them develop in the direction of greater power, higher frequency, higher efficiency, and greater integration.

[0003] Single crystal SiC is widely considered to be a typical third-generation semiconductor material for manufacturing power devices operating 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 electric field, high saturated electron drift rate, high bonding energy and wide bandgap. It is the preferred material for high-frequency, high-temperature, high-power, radiation-resistant electronic devices and sensor devices. It is also an ideal substrate material for manufacturing large-size, ultra-high brightness white light, blue light diodes and laser diodes. It has important applications in aviation, aerospace exploration, nuclear energy development, radar and communications.

[0004] As the epitaxial growth of semiconductor devices, silicon carbide substrate wafers need to go through multiple processing processes such as crystal growth, crystal orientation, end grinding, chamfering, slicing, thinning, grinding, polishing, and final cleaning, and the processing cost of the polishing step accounts for 80% of the total processing cost. The extremely high chemical inertness and hardness of silicon carbide itself make it a typical difficult-to-process material. Under the chemical mechanical polishing technology currently widely used in industrial production, although the surface quality is high, the material removal rate is extremely low, which restricts the development of silicon carbide materials in the fields of communication equipment, new energy equipment, and aerospace equipment manufacturing. In order to solve the problems in SiC polishing processing, ensure the surface quality of SiC wafers after polishing, and improve the material processing efficiency, it is very important to study an efficient, high-quality, and damage-free polishing technology suitable for silicon carbide wafer surface processing. Summary of the invention

[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 is rotated to drive the polishing liquid to move, so that the polishing liquid forms a continuous flow field on the surface of the workpiece, and 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 processing 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 surface of the workpiece, thereby improving the polishing efficiency, and can achieve efficient removal of surface defects and sub-surface damage layers of SiC wafers, thereby achieving 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 comprises a working platform; a workpiece clamping drive assembly and a polishing liquid boosting assembly are correspondingly arranged on the working platform; the workpiece clamping drive assembly comprises a workpiece fixture and a workpiece driving device; the workpiece fixture is used to clamp a workpiece to be processed, and the workpiece driving device can drive the workpiece fixture to move the workpiece to a set position, and can drive the workpiece fixture to make the workpiece perform a rotational motion; the polishing liquid boosting assembly comprises a structured surface polishing tool correspondingly arranged below the workpiece fixture; a polishing tool driving device is arranged below the structured surface polishing tool, and the polishing tool driving device can drive the structured surface polishing tool to perform a rotational motion; the structured surface polishing tool is a groove-shaped structure, and its bottom is in the shape of a conical surface with a high outer surface and a low inner surface, 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, and the polishing liquid in the structured surface polishing tool can be dispersed to the edge of the polishing tool driving device under the synergistic effect 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 mechanorheological polishing on the surface of the workpiece. Since it adopts a special structured surface polishing tool, during polishing, not only can the mechanorheological polishing fluid form a continuous flow field on the surface of the workpiece, producing a shear thickening effect, forming a flexible abrasive tool that fits the surface of the workpiece, and uniformly removing material from the surface of the workpiece, but the polishing fluid in the structured surface polishing tool can be dispersed to the edge of the polishing tool driving 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 being able to 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 the structured surface polishing tool, the lever is in an arc shape, and the levers arranged in groups form an impeller shape. Therefore, when the structured surface polishing tool rotates, the mechanorheological polishing liquid can flow outward along the edge of the arc-shaped lever, and the mechanorheological polishing liquid disperses faster toward the edge of the polishing tool, and the polishing liquid is not easy to accumulate 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 plane structure. Therefore, during processing, when the gap between the structured surface polishing tool and the workpiece is the same, the workpiece can obtain a higher polishing pressure.

[0012] As an optimization solution, in the aforementioned non-contact polishing device based on the structured surface polishing tool, a polishing liquid anti-deposition component is provided on the work platform, which is used to stir the polishing liquid deposited on the wall surface of the structured surface polishing tool. Furthermore, the polishing liquid anti-deposition component includes a cantilever stirring head fixing bracket, and a stirring head detachably connected to the cantilever of the cantilever stirring head fixing bracket. Furthermore, the cantilever stirring head fixing bracket is in the shape of a scraper. When working, the polishing liquid anti-deposition component stirs the polishing liquid deposited on the wall surface of the structured surface polishing tool to prevent the polishing liquid from failing.

[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 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 liquid in a structured surface polishing tool;

[0018] S3, adjusting the distance between the workpiece to be processed 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 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 30-50r / min, the rotation speed of the structured surface polishing tool to 80-120r / 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 structured surface polishing tool, the workpiece to be processed is a SiC wafer. Further, for the convenience of implementation, in step S1, the SiC wafer is adhered to the loading surface of the polishing fixture by paraffin wax. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 2 is a schematic structural diagram of a structured bottom element of a structured polishing tool in the present invention;

[0025] Figure 3 It is a schematic diagram of the processing state of the structured surface polishing tool and the workpiece to be processed;

[0026] Figure 4 This is a shear stress cloud diagram of 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 shear stress cloud diagram of 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 shear stress cloud diagram of 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 shear stress cloud diagram of 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] Fig. 9 This is a white light interferometer inspection image of the workpiece before polishing with a structured surface polishing tool;

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

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

[0034] Fig.12 This is the white light interferometer detection 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 fixture; 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 is further described below in conjunction with 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 comprises a working platform; a workpiece clamping drive component and a polishing liquid boosting component are correspondingly arranged on the working platform; the workpiece clamping drive component comprises a workpiece fixture 2 and a workpiece driving device 4; the workpiece fixture 2 is used to clamp a workpiece 7 to be processed, and the workpiece driving 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 comprises a structured surface polishing tool 1 correspondingly arranged below the workpiece fixture 2; a polishing tool driving device 3 is arranged below the structured surface polishing tool 1, and the polishing liquid boosting device 4 is arranged 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 at its bottom), and its bottom is a conical surface with a high outside and a low inside, and radially distributed levers 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 lever 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: The relevant physical model is modeled by solidworks software, and the flow field of the non-Newtonian fluid rheological polishing fluid is numerically simulated and analyzed by Fluent software. The distribution of the pressure field on the workpiece surface during the rheological polishing of silicon carbide is simulated and simulated. Four structured surface polishing tools with different tapers are used for simulation and comparison with the polishing groove without polishing tools. The interval between the workpiece and the wall of the polishing disk is 2mm, the speed of the workpiece 7 to be processed is set to 30rpm, and the speed of the structured surface polishing tool 1 is set to 100rpm and the rotation direction is opposite to that of the workpiece 7 to be processed.

[0041] Figure 5-Figure 9 The shear stress cloud diagrams of the workpiece surface when the structured surface polishing tool 1 is inclined at 15 degrees, 20 degrees, 25 degrees, and 30 degrees, and when the polishing groove has no structured surface (i.e., conventional polishing groove). It can be seen from the figure that in these simulation cases, when the workpiece is polished using the structured surface polishing tool 1, 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 working surface and improve the polishing efficiency, it is more advantageous to use a structured surface polishing tool for polishing.

[0042] In the embodiment, the work platform is provided with a polishing liquid anti-deposition component, which is used to stir the polishing liquid deposited on the wall surface of the structured surface polishing tool 1. The polishing liquid anti-deposition 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. The cantilever stirring head fixing bracket 5 is in the shape of a scraper. The polishing liquid anti-deposition component stirs the polishing liquid during polishing to prevent the polishing liquid from accumulating and failing.

[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 to be processed (silicon carbide wafer, diameter Φ50mm, thickness 350um) on the workpiece fixture 2 (paste it on the loading surface of the polishing fixture 2 with paraffin wax);

[0045] S2. Place the prepared mechanorheological polishing liquid in the structured surface polishing tool 1; the preparation process of the mechanorheological polishing liquid: a non-Newtonian fluid with a shear thickening effect is prepared using polyhydroxy aldehyde polymer (accounting for 45% of the mass fraction of the polishing liquid) as the dispersed phase and pure water (accounting for 40% of the mass fraction of the polishing liquid) as the solvent, and then diamond abrasive particles with a particle size of 1.0 um (accounting for 15% of the mass fraction of the polishing liquid) are added to the non-Newtonian fluid and stirred evenly;

[0046] S3, adjusting the distance between the workpiece 7 to be processed and the liquid surface of the mechanorheological polishing liquid to 5 mm through the workpiece clamping drive assembly; and adjusting 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 carried out 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 um / h.

[0051] The 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 pointed out 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 involved in this application and the description of its specific implementation methods should not be understood as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art can add, reduce or combine the disclosed technical features in the above general description and / or specific implementation methods (including examples) without violating the constituent elements of the invention involved, 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 comprises a working platform; the working platform is provided with a workpiece clamping drive component and a polishing liquid pressurizing 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 drive the workpiece clamp (2) to make the workpiece rotate; The polishing liquid booster assembly comprises a structured surface polishing tool (1) correspondingly arranged below the workpiece fixture (2); a polishing tool driving device (3) is arranged 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 levers (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), and 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 effect of centrifugal force and the lever (101), thereby increasing the pressure of the polishing liquid acting on the surface of the workpiece (7) to be processed.

2. The non-contact polishing device based on the structured surface polishing tool according to claim 1, characterized in that: The bottom taper of the structured surface polishing tool (1) is 15°-30°.

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

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

5. The non-contact polishing device based on the structured surface polishing tool according to claim 1, characterized in that: The working platform is provided with a polishing liquid anti-deposit component, which is used to stir the polishing liquid deposited on the wall surface of the structured surface polishing tool (1).

6. The non-contact polishing device based on the structured surface polishing tool according to claim 5, characterized in that: The polishing liquid anti-deposition component comprises 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).

7. The non-contact polishing device based on the structured surface polishing tool according to claim 6, characterized in that: The cantilever stirring head fixing bracket (5) is in the shape of a scraper.

8. 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 in 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.

9. The non-contact polishing method based on a structured surface polishing tool according to claim 8, characterized in that: The workpiece (7) to be processed is a SiC wafer.

10. The non-contact polishing method based on a structured surface polishing tool according to claim 9, characterized in that: In step S1, the SiC wafer is adhered to the loading surface of the polishing fixture (2) by means of paraffin wax.

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