A processing device and a polishing processing method for double-sided plasma polishing of diamond

Abstract

The present invention provides a processing device and a polishing processing method for plasma double-sided polishing of diamond. The processing device includes a plasma generator, an enclosure, and two polishing discs that can rotate relative to each other; the polishing discs are used as polishing tools and also act as dielectric barriers for the plasma generator. The plasma generator is placed in the enclosure to generate a plasma containing active radicals between the upper and lower polishing discs. The plasma containing active radicals can modify the diamond substrate, the upper polishing disc, and the lower polishing disc. Finally, polishing of the diamond substrate is achieved by the rotation of the upper and lower polishing discs. This effectively improves the plasma-assisted processing method and does not require a vacuum chamber. This method can effectively eliminate the surface damage layer left by grinding and rough polishing, ensuring both the polishing efficiency of the substrate and a high surface quality of the entire substrate surface.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma polishing devices, and in particular, to a processing device and a polishing processing method for plasma double-sided polishing of diamond. Background Art

[0002] As a fourth-generation ultra-wide bandgap semiconductor material, single-crystal diamond has excellent properties such as high thermal conductivity, excellent wear resistance, and low friction coefficient. These excellent properties give it significant advantages and great development potential in fields such as high-power electronic power devices. In recent years, with the rapid development of chemical vapor deposition technology, the size of artificial diamond has been continuously enlarged, and the wafer-level heteroepitaxial chemical vapor deposition single-crystal diamond substrate can reach 4 inches. This makes it possible for diamond to be widely used in high-tech fields such as optics, thermotics, and semiconductors.

[0003] To prepare an ideal diamond power semiconductor device, an atomically smooth and damage-free diamond surface is required. However, as a typical difficult-to-process material, diamond has extremely high mechanical hardness and chemical inertness, making it difficult to remove and extremely easy to damage during the planarization process, which poses a huge challenge to the planarization processing of diamond. It has become one of the key problems restricting the industrial application of wafer-level single-crystal diamond.

[0004] Currently, in the diamond polishing method, the mechanical polishing method is still the most widely used, but this method has low processing efficiency and is extremely easy to cause processing damage, and it is also very difficult to achieve a surface roughness of sub-nanometer level. In recent years, the technology based on plasma polishing of diamond has shown relatively excellent performance. For example, relatively large material removal rate and the characteristics of no surface and subsurface damage after processing. This indicates that ultra-smooth and damage-free processing of diamond can be achieved through plasma polishing technology. However, in most of the existing diamond plasma polishing technologies, an atmospheric pressure inductively coupled plasma torch is used as the ion source, which requires reciprocating scanning to process the surface; it is difficult to process a large-area wafer surface simultaneously; and it is impossible to perform batch polishing processing on multiple substrate wafers at the same time.

[0005] In addition, the excitation method of inductively coupled plasma needs to generate an alternating magnetic field in a coil to induce the generation of plasma, with a relatively complex structure and high cost, resulting in difficulty in mass production. The capacitive dielectric barrier plasma can generate uniform large-area plasma, which is suitable for large-area modification of semiconductor substrates. In addition, the double-sided polishing processing method can process multiple diamond substrates simultaneously and obtain a smooth and flat surface. Therefore, this method is an ideal processing method and development trend for sheet devices such as semiconductor substrates and optical components. For example, the wafer grinding process and semiconductor wafers based on double-sided grinding equipment in CN113231957A and CN114290230B, but the processing accuracy and processing efficiency need to be improved.

[0006] In view of this, the applicant has specifically filed this application after studying the existing technologies. Summary of the Invention

[0007] The present invention provides a processing device and a polishing processing method for double-sided polishing of diamond by plasma, aiming to improve at least one of the above technical problems.

[0008] To solve the above technical problems, the present invention provides a processing device for double-sided polishing of diamond by plasma, including an enclosure and a plasma generator rotatably engaged on the enclosure. The plasma generator has an upper electrode plate and a lower electrode plate, and the upper electrode plate and the lower electrode plate are disposed inside the enclosure. The device further includes:

[0009] Two polishing discs, respectively engaged on the upper electrode plate and the lower electrode plate, and the polishing discs are made of dielectric barrier discharge materials;

[0010] A clamping mechanism, disposed between the two polishing discs, for clamping a workpiece, and the clamping mechanism is provided with a plurality of through holes;

[0011] An air supply mechanism, communicated with the enclosure through an intake pipe, for inputting a mixed gas to enable plasma to be generated between the two polishing discs;

[0012] A driving mechanism, connected to the plasma generator, and the driving mechanism can drive the plasma generator to rotate, thereby driving the two polishing discs to rotate for polishing the workpiece.

[0013] As a further optimization, the driving mechanism includes a first motor and a second motor. The first motor is connected to the upper electrode plate and is used to drive the upper electrode plate to rotate around the axis in a first direction, and the second motor is connected to the lower electrode plate and is used to drive the lower electrode plate to rotate around the axis in a second direction.

[0014] As a further optimization, a pressure sensor is further included, and the pressure sensor is connected to the upper electrode plate for applying a polishing load.

[0015] As a further optimization, the distance between the two polishing discs is 2 mm - 10 mm.

[0016] As a further optimization, the clamping mechanism includes a sun gear, an internal gear ring, and a plurality of planet gears. The sun gear is fixedly installed on the polishing disc below, the internal gear ring is fixedly engaged with the inner wall of the closed cover, and the plurality of planet gears are meshed between the internal gear ring and the sun gear. When the polishing disc rotates, the planet gears can be driven by the sun gear to achieve self-rotation and revolution. The multiple through holes are provided on the planet gears, and each planet gear is provided with a rectangular hole and a circular hole for clamping the workpiece.

[0017] As a further optimization, the sun gear and the planet gears are made of a rigid material, which is at least one of quartz glass, polytetrafluoroethylene, alumina plate, and acrylic plate.

[0018] As a further optimization, the dielectric barrier discharge material is at least one of quartz glass, alumina, and silicon plate.

[0019] As a further optimization, the intake pipe sequentially penetrates through the lower electrode plate, the lower polishing disc, and the axis of the sun gear from bottom to top, and an air outlet is provided on one side of the closed cover.

[0020] As a further optimization, the mixed gas is at least two of helium, argon, water vapor, oxygen, and hydrogen peroxide evaporation gas.

[0021] The present application further provides a method for polishing and processing diamond. Using any one of the above-mentioned plasma double-sided polishing diamond processing devices, the diamond is polished and processed through the following steps:

[0022] S1: Install the diamond substrate to be processed on the clamping mechanism and close the closed cover;

[0023] S2: Supply the mixed gas through the gas supply mechanism, start the plasma generator, and make the mixed gas generate a large amount of highly active radical plasma between the upper and lower polishing discs under the strong electric field action of the upper and lower electrode plates. The plasma containing highly active radicals adheres to the surfaces of the diamond substrate and the upper and lower polishing discs for modification;

[0024] S3: Start the driving mechanism to rotate the upper and lower polishing discs to perform double-sided polishing on the diamond substrate.

[0025] By adopting the above technical solutions, the present invention can achieve the following technical effects:

[0026] A processing device for plasma double-sided polishing of diamond according to the present application. The upper and lower polishing disks can simultaneously be used as the dielectric barrier layer of the plasma generator. A mixed gas is supplied between the upper and lower polishing disks. The plasma generator generates a large-area uniform plasma containing active free radicals between the upper and lower polishing disks. The plasma containing active free radicals passes through the through holes on the clamping mechanism to modify the diamond substrate and the upper and lower polishing disks. By rotating the modified upper and lower polishing disks, double-sided polishing of the diamond substrate is achieved, thereby realizing polishing and material removal. Moreover, the plasma generator also acts as a polishing machine to process the diamond substrate while generating plasma, better combining plasma generation and polishing processing. It can not only process small-sized diamond substrates but also large-sized diamond substrates, having the advantages of faster processing efficiency, lower surface roughness, and high surface finish. Second, no abrasive or polishing liquid needs to be added during the polishing process, which is more environmentally friendly. Third, the polishing disk is made of a material with a hardness lower than that of diamond, and non-damaged surfaces on the surface and subsurface of the optical device can be achieved during the polishing process, meeting the high-efficiency processing requirements of diamond substrates and having great application prospects in the micro-nano high-tech field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 Structural schematic diagram of a processing device for plasma double-sided polishing of diamond according to the present invention;

[0029] Figure 2 Schematic diagram of the polishing disk and planetary structure in the embodiment of the present invention;

[0030] Figure 3 Surface roughness of the diamond after polishing in the embodiment of the present invention, where a is a plan view and b is a contour line view;

[0031] Figure 4 Subsurface without crack damage obtained after polishing the diamond in the embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the process of plasma-assisted double-sided polishing of diamond in the embodiment of the present invention;

[0033] Markings in the figure: 1 - Plasma generator; 11 - Upper electrode plate; 13 - Ceramic bolt; 14 - Diamond substrate; 15 - Planet gear; 16 - Exhaust port; 17 - Through hole; 18 - Lower electrode plate; 2 - Upper polishing disc; 20 - Rectangular hole; 21 - Circular hole; 3 - Sealing cover; 4 - Internal gear ring; 5 - Gas supply mechanism; 6 - Lower polishing disc; 7 - Sun gear; 8 - Inlet pipe; 91 - First motor; 92 - Second motor; 10 - Pressure sensor. Detailed implementation mode

[0034] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0035] Embodiment

[0036] As Figure 1 , Figure 2 shown, the present invention provides a processing device for double-sided plasma polishing of diamond, including a sealing cover 3 and a plasma generator 1 rotatably engaged on the sealing cover 3. The plasma generator 1 has an upper electrode plate 11 and a lower electrode plate 18. The upper electrode plate 11 and the lower electrode plate 18 are placed inside the sealing cover 3. It also includes two polishing discs, a clamping mechanism, a gas supply mechanism 5 and a driving mechanism. The two polishing discs are respectively engaged on the upper electrode plate 11 and the lower electrode plate 18. The two polishing discs are both made of dielectric barrier discharge materials, so that the upper and lower polishing discs can simultaneously serve as the dielectric barrier layers of the plasma generator 1. For the convenience of description, the two polishing discs are hereinafter distinguished as the upper polishing disc 2 and the lower polishing disc 6.

[0037] The driving mechanism includes a first motor 91 and a second motor 92. The first motor 91 is connected to the upper electrode plate 11 and is used to drive the upper electrode plate 11 to rotate around the axis in the first direction, thereby driving the upper polishing disc 2 to rotate synchronously; the second motor 92 is connected to the lower electrode plate 18 and is used to drive the lower electrode plate 18 to rotate around the axis in the second direction, and then drive the lower polishing disc 6 to rotate synchronously.

[0038] The clamping mechanism is arranged between the two polishing discs. It includes a sun gear 7, an internal gear ring 4 and a number of planet gears 15. The sun gear 7 is fixedly installed on the lower polishing disc 6, the internal gear ring 4 is fixed on the inner wall of the closed cover 3, and a number of planet gears 15 are arranged between the sun gear 7 and the internal gear ring 4 and mesh with the sun gear 7 and the internal gear ring 4. Thus, when the lower polishing disc 6 rotates, the planet gears 15 can be driven by the sun gear 7 and the internal gear ring 4 to rotate around their own axes and revolve around the sun gear 7 at the same time. Each planet gear 15 is provided with a rectangular hole 20 and a circular hole 21 to clamp diamond substrates 14 to be processed with different shapes and sizes. The surface of each planet gear 15 is covered with tiny through holes 17 so that the plasma of active free radicals can pass through the through holes 17 and irradiate the surfaces of the diamond substrate 14, the upper polishing disc 2 and the lower polishing disc 6.

[0039] The gas supply mechanism 5 is connected to the closed cover 3 through an inlet pipe 8 for inputting a mixed gas. An exhaust port 16 for exhausting gas is provided on one side of the closed cover 3. The inlet pipe 8 passes through the centers of the lower electrode plate 18, the lower polishing disc 6 and the sun gear 7 from bottom to top, so that the mixed gas can be supplied between the two polishing discs and a large amount of plasma containing highly active free radicals can be generated under the strong electric field of the upper and lower electrode plates of the plasma generator 1.

[0040] Furthermore, it further includes a pressure sensor 10 which is connected to the upper electrode plate 11 and used to apply a polishing load.

[0041] In this embodiment, the polishing load is applied through the pressure sensor 10, and the load range is < 10 kg. The first motor 91 and the second motor 92 drive the relative rotation of the upper polishing disc 2 and the lower polishing disc 6 respectively to polish the diamond substrate 14. At the same time, the upper and lower polishing discs also serve as the dielectric barrier layer of the plasma generator 1. Thus, the plasma generator can generate plasma and process the diamond substrate as a polishing machine at the same time, better combining plasma generation and polishing. No abrasive or polishing liquid is needed during the polishing process, which is more environmentally friendly and does not require a complex and expensive vacuum chamber.

[0042] Further, the upper polishing disc 2 and the lower polishing disc 6 are respectively fixedly mounted on the dielectric barrier upper electrode plate 11 and the lower electrode plate 18 through ceramic bolts 13, and the distance between the upper polishing disc 2 and the lower polishing disc 6 is 2 mm - 10 mm. The two polishing discs are made of a low-hardness insulating material, which is at least one of quartz glass, alumina, and silicon plate. Materials with lower hardness are not easily damaged when processing diamond, and these materials can also undergo tribochemical reactions with diamond during processing to remove the surface material of the diamond substrate in a mechanical + chemical manner. Since the convex parts on the surface of the diamond substrate 14 are more likely to contact active free radicals and come into contact with the polishing disc first during the polishing process, they have a greater material removal rate, and their surface flatness will ultimately approach that of the polishing disc, thereby achieving the overall polishing of the diamond substrate with a surface roughness Ra < 1 nm.

[0043] Further, the mixed gas is at least two of helium, argon, water vapor, oxygen, and hydrogen peroxide evaporation gas. During processing, under the strong electric field of the plasma generator, a large amount of plasma containing highly active free radicals is generated between the upper and lower polishing discs. The plasma containing highly active free radicals adheres to the diamond substrate 14, the upper polishing disc 2, and the lower polishing disc 6, and a modification effect occurs. For example, this modification can soften the surface layer of the diamond substrate or / and amorphize the surface atoms through ion implantation, bombardment, and etching. Surface softening and amorphization can greatly reduce the processing difficulty of the diamond substrate. Another example of this modification is that the active free radicals contained in the plasma, such as hydroxyl radicals and oxygen radicals, react chemically with the diamond substrate and the polishing disc, such as C*-OH + M-OH → CO / CO2 + H2O or / and C* + O + M → C*-O-M (C* refers to amorphous carbon or modified carbon atoms on the diamond surface, and M refers to Si or / and Al atoms on the surface of the polishing disc material), and C*-O-M is the new bond formed at the interface.

[0044] Further, the sun gear 4 and the planet gear 15 are made of a rigid material, which is at least one of quartz glass, 304 stainless steel, polytetrafluoroethylene, acrylic plate, and alumina plate. The material of the closed cover 3 is made of acrylic plate or K9 glass material.

[0045] As Figures 3 to 5 shown, the present application further provides a polishing processing method for diamond, using the above-mentioned plasma double-sided polishing diamond processing device, and polishing the diamond through the following steps:

[0046] S1: Mount the diamond substrate 14 to be processed on the clamping mechanism and close the closed cover 3;

[0047] S2: Feed in the mixed gas through the gas supply mechanism 5, start the plasma generator, so that under the strong electric field of the upper and lower electrode plates, a large amount of plasma containing highly active free radicals is generated between the upper and lower polishing discs. The plasma containing highly active free radicals adheres to the diamond substrate and the upper and lower polishing discs for modification.

[0048] S3: Apply a polishing load through the pressure sensor 10, with the load range < 10 kg. Start the driving mechanism to rotate the upper and lower polishing discs to perform double-sided polishing on the diamond substrate.

[0049] In this embodiment, under the strong electric field of the plasma generator 1, a large amount of plasma containing highly active free radicals is generated between the upper and lower polishing discs. The plasma containing highly active free radicals adheres to the diamond substrate 14, the upper polishing disc 2 and the lower polishing disc 6, and large-area modification occurs. The driving mechanism drives the upper and lower polishing discs to rotate. The diamond substrate 14 performs a planetary motion of both revolution and rotation under the action of the sun gear 7, the planetary gear 15 and the internal gear ring 4 to perform double-sided polishing of the diamond substrate.

[0050] The double-sided polishing method of this application is an efficient precision machining technology, which can not only effectively eliminate the surface damage layer left by the grinding and rough polishing processes, but also effectively ensure that the substrate surface reaches a nanoscale surface roughness. The plasma processing technology is essential in the fields of optics and semiconductors, etc. It is not only commonly used for the cleaning, activation and modification of the semiconductor surface, but also can achieve non-damaging, efficient and atomic-level surface polishing of the substrate wafer. In the present invention, while generating plasma, the structure of the plasma generator itself can also be used as a polishing machine to process the diamond substrate. Effectively combining the plasma generator and the double-sided polishing device improves the processing efficiency and reduces the production cost. A method for plasma-assisted double-sided polishing of diamond, the dielectric barrier plasma generates a large amount of plasma containing highly active free radicals, which can uniformly modify the diamond substrate and the polishing disc over a large area. It is easy to have a chemical reaction when the modified polishing disc and the diamond substrate rub against each other. The polishing treatment of the diamond surface is realized through plasma modification and friction chemical reaction, achieving atomic-level non-damaging polishing and reaching ultra-precision machining. Polishing by this method can reduce surface damage or achieve non-damage, greatly improve the surface quality of the workpiece, and improve the production efficiency of related industries.

[0051] After the above polishing process, the surface of the diamond substrate has been fully trimmed and improved. This method can not only remove the impurity materials on the diamond surface, but also reduce defects and thus improve the overall quality of the diamond substrate. Therefore, in the manufacturing process of related parts of diamond, this polishing method has important application value.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A processing device for plasma double-sided polishing of diamond, comprising an enclosure and a plasma generator rotatably engaged on the enclosure, the plasma generator having an upper electrode plate and a lower electrode plate, the upper electrode plate and the lower electrode plate being disposed within the enclosure, characterized in that, It further includes: Two polishing pads, which are respectively joined to the upper electrode plate and the lower electrode plate. The polishing pads are made of a dielectric barrier discharge material, and the dielectric barrier discharge material is quartz glass; A clamping mechanism, which is arranged between the two polishing pads and is used for clamping the workpiece. A plurality of through holes are provided on the clamping mechanism; An air supply mechanism, which is connected to the closed cover through an air inlet pipe and is used for inputting a mixed gas so that plasma can be generated between the two polishing pads; A driving mechanism, which is connected to the plasma generator. The driving mechanism can drive the plasma generator to rotate, thereby driving the two polishing pads to rotate to polish the workpiece; The clamping mechanism includes a sun gear, an internal gear ring and a plurality of planet gears. The sun gear is fixedly installed on the lower polishing pad, the internal gear ring is fixedly joined to the inner wall of the closed cover, and the plurality of planet gears are engaged between the internal gear ring and the sun gear. When the polishing pad rotates, the planet gears can be driven by the sun gear to achieve self-rotation and revolution. The plurality of through holes are provided on the planet gears, and each planet gear is provided with a rectangular hole and a circular hole for clamping the workpiece; The air inlet pipe sequentially penetrates through the axis of the lower electrode plate, the lower polishing pad and the sun gear from bottom to top. An air outlet is provided on one side of the closed cover.

2. The processing device for plasma double-sided polishing diamond according to claim 1, characterized in that , The driving mechanism includes a first motor and a second motor. The first motor is connected to the upper electrode plate and is used for driving the upper electrode plate to rotate around the axis in a first direction. The second motor is connected to the lower electrode plate and is used for driving the lower electrode plate to rotate around the axis in a second direction.

3. The processing device for plasma double-sided polishing diamond according to claim 1, wherein , It further includes a pressure sensor, which is connected to the upper electrode plate and is used for applying a polishing load.

4. The processing device for plasma double-sided polishing diamond according to claim 3, characterized in that , The distance between the two polishing pads is 2 mm - 10 mm.

5. The processing device for plasma double-sided polishing of diamonds according to claim 1, characterized in that , The sun gear and the planet gears are made of a rigid material, and the rigid material is at least one of quartz glass, polytetrafluoroethylene, alumina plate, and acrylic plate.

6. The processing device for plasma double-sided polishing diamond according to claim 1, characterized in that , The mixed gas is at least two of helium, argon, water vapor, oxygen, and hydrogen peroxide evaporation gas.

7. A method for polishing and processing diamond, characterized in that , Using the processing device for plasma double-sided polishing of diamond according to any one of claims 1 - 6, the diamond is polished through the following steps: S1: Install the diamond substrate to be processed on the clamping mechanism and close the closed cover; S2: Supply the mixed gas through the air supply mechanism, start the plasma generator, so that under the strong electric field action of the upper and lower electrode plates, a large amount of plasma containing highly active free radicals is generated between the upper and lower polishing pads. The plasma containing highly active free radicals adheres to the surfaces of the diamond substrate and the upper and lower polishing pads for modification; S3: Start the driving mechanism to rotate the upper and lower polishing pads to perform double-sided polishing on the diamond substrate.

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