Machining device for plasma double-sided polishing of diamond and polishing machining method

Abstract

The invention provides a machining device for plasma double-sided polishing of diamond and a polishing machining method. The machining device comprises a plasma generator, a sealing cover and two polishing discs which can rotate mutually. The polishing disc is used as a polishing tool and also serves as a dielectric barrier layer of the plasma generator, the plasma generator is arranged in a closed cover, plasma containing active free radicals is generated between the upper polishing disc and the lower polishing disc, and the plasma containing the active free radicals can modify the diamond substrate, the upper polishing disc and the lower polishing disc. And finally, the diamond substrate is polished by the upper polishing disc and the lower polishing disc through rotation. The plasma auxiliary processing mode is effectively improved, and a vacuum chamber is not needed. According to the method, a surface damage layer left by grinding and rough polishing can be effectively eliminated, the polishing efficiency of the substrate can be effectively guaranteed, and meanwhile it can be guaranteed that the surface of the whole substrate reaches high surface quality.

Description

Technical Field

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

[0002] As the fourth generation of ultra-wide bandgap semiconductor materials, 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 huge development potential in the fields of high-power electronic power devices. In recent years, with the rapid development of chemical vapor deposition technology, the size of artificial diamonds has continued to expand, and the wafer-level heterogeneous 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, thermal and semiconductors.

[0003] The preparation of ideal diamond power semiconductor devices requires the use of atomically smooth and undamaged diamond surfaces. However, as a typical difficult-to-process material, diamond has extremely high mechanical hardness and chemical inertness. It is difficult to remove and easily damaged during the planarization process, which brings huge challenges to the planarization of diamond. This has become one of the key issues restricting the industrial application of wafer-level single-crystal diamond.

[0004] At present, mechanical polishing is still the most widely used method in diamond polishing, but this method has low processing efficiency and is very easy to produce processing damage, and the surface roughness is difficult to reach the sub-nanometer level. The technology based on plasma polishing diamond developed in recent years has shown relatively outstanding performance. For example, a relatively large material removal rate and the characteristics of no surface and sub-surface damage after processing. This shows that ultra-smooth and damage-free processing of diamond can be achieved through plasma polishing technology. However, most of the existing diamond plasma polishing technologies use atmospheric pressure inductively coupled plasma torches as ion sources, which require reciprocating scanning to process the surface; making it difficult to process large-area wafer surfaces at the same time; and it is impossible to perform batch polishing of multiple substrates at the same time.

[0005] In addition, the excitation mode of inductively coupled plasma needs to generate an alternating magnetic field in a coil to induce the generation of plasma, and the structure is relatively complex and costly, which makes it difficult to mass produce. Capacitive dielectric barrier plasma can produce 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 at the same time, and obtain a smooth and flat surface. Therefore, this method is an ideal processing method and development trend of sheet devices such as semiconductor substrates and optical elements. Such as the wafer grinding process and semiconductor wafer based on double-sided grinding equipment of CN113231957A and CN114290230B, but processing accuracy and processing efficiency need to be improved.

[0006] In view of this, the applicant filed this application after studying the existing technology. Summary of the invention

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

[0008] In order to solve the above technical problems, the present invention provides a plasma double-sided diamond polishing processing device, comprising a closed cover and a plasma generator rotatably connected to the closed cover, the plasma generator having an upper electrode plate and a lower electrode plate, the upper electrode plate and the lower electrode plate are placed in the closed cover, and further comprising: Two polishing discs are provided, respectively connected to the upper electrode plate and the lower electrode plate, and the polishing discs are made of dielectric barrier discharge material; A clamping mechanism, disposed between the two polishing discs, for clamping a workpiece, wherein the clamping mechanism is provided with a plurality of through holes; A gas supply mechanism, connected to the closed cover through an air inlet pipe, for inputting a mixed gas so that plasma can be generated between the two polishing discs; A driving mechanism is connected to the plasma generator, and the driving mechanism can drive the plasma generator to rotate, thereby driving the two polishing discs to rotate to perform polishing processing on the workpiece.

[0009] 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.

[0010] As a further optimization, a pressure sensor is also included, which is connected to the upper electrode plate and is used to apply a polishing load.

[0011] As a further optimization, the spacing between the two polishing discs is 2mm-10mm.

[0012] As a further optimization, the clamping mechanism includes a sun gear, an inner gear ring and several planetary gears, the sun gear is fixedly mounted on the polishing disc below, the inner gear ring is fixedly engaged on the inner wall of the closed cover, and the several planetary gears are meshed between the inner gear ring and the sun gear, so that when the polishing disc rotates, the sun gear can drive the planetary gear to realize self-rotation and revolution, the multiple through holes are arranged on the planetary gears, and each of the planetary gears is provided with a rectangular hole and a circular hole for clamping the workpiece.

[0013] As a further optimization, the sun gear and the planetary gear are made of a rigid material, which is at least one of quartz glass, polytetrafluoroethylene, an alumina plate, and an acrylic plate.

[0014] As a further optimization, the dielectric barrier discharge material is at least one of quartz glass, alumina, and silicon plate.

[0015] As a further optimization, the air inlet pipe passes through the lower electrode plate, the lower polishing plate and the axis of the sun gear from bottom to top in sequence, and an air outlet is provided on one side of the closed cover.

[0016] As a further optimization, the mixed gas is at least two of helium, argon, water vapor, oxygen, and hydrogen peroxide evaporated gas.

[0017] The present application further provides a diamond polishing method, using any of the above-mentioned plasma double-sided diamond polishing processing devices to polish the diamond through the following steps: S1: mounting the diamond substrate to be processed on the clamping mechanism and closing the sealed cover; S2: supplying mixed gas through the gas supply mechanism, starting the plasma generator, so that the mixed gas generates a large amount of plasma containing highly active free radicals between the upper and lower polishing discs under the strong electric field of the upper and lower electrode plates, and the plasma containing highly active free radicals adheres to the surface of the diamond substrate and the upper and lower polishing discs to be modified; S3: Start the driving mechanism to rotate the upper and lower polishing discs to perform double-sided polishing on the diamond substrate.

[0018] By adopting the above technical solution, the present invention can achieve the following technical effects: The present application discloses a plasma double-sided diamond polishing processing device, wherein the upper and lower polishing plates can be used as dielectric barriers of a plasma generator at the same time, and a mixed gas is supplied between the upper and lower polishing plates, and the plasma generator generates a large-area uniform plasma containing active free radicals between the upper and lower polishing plates, and 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 plates, and the double-sided polishing processing of the diamond substrate is realized by the rotation of the modified upper and lower polishing plates, thereby realizing polishing and material removal. Moreover, the plasma generator can be used as a polisher to process the diamond substrate while generating plasma, so that the plasma generation and polishing process can be better combined into one, and not only small-sized diamond substrates but also large-sized diamond substrates can be processed, with the advantages of faster processing efficiency, lower surface roughness and high finish. Secondly, the polishing process does not require the addition of any abrasives or polishing fluid, which is more environmentally friendly. Thirdly, the polishing disc is made of a material with a lower hardness than diamond, and the surface and sub-surface of the optical device can be undamaged during the polishing process, which can meet the needs of efficient processing of diamond substrates and has great application prospects in the field of micro-nano high-end technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a structural schematic diagram of a plasma double-sided polishing diamond processing device of the present invention; Figure 2 A schematic diagram of the polishing disc and the planet structure in an embodiment of the present invention; Figure 3 is the surface roughness after diamond polishing in the embodiment of the present invention, wherein a is a plane diagram and b is a contour diagram; Figure 4 is a sub-surface without crack damage obtained after diamond polishing in an embodiment of the present invention; Figure 5 A schematic diagram of a process of plasma-assisted double-sided diamond polishing according to an embodiment of the present invention; Markings in the figure: 1-plasma generator; 11-upper electrode plate; 13-ceramic bolt; 14-diamond substrate; 15-planetary wheel; 16-exhaust port; 17-through hole; 18-lower electrode plate; 2-upper polishing plate; 20-rectangular hole; 21-circular hole; 3-sealed cover; 4-inner gear ring; 5-air supply mechanism; 6-lower polishing plate; 7-sun gear; 8-intake pipe; 91-first motor; 92-second motor; 10-pressure sensor. DETAILED DESCRIPTION

[0021] In order 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 drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection 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 invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] Example Depend on Figure 1 , Figure 2 As shown, the present invention provides a plasma double-sided diamond polishing processing device, including a closed cover 3 and a plasma generator 1 rotatably connected to the closed 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 in the closed cover 3, and also includes two polishing discs, a clamping mechanism, a gas supply mechanism 5 and a driving mechanism. The two polishing discs are respectively connected to the upper electrode plate 11 and the lower electrode plate 18, and the two polishing discs are made of dielectric barrier discharge material, so that the upper and lower polishing discs can simultaneously serve as the dielectric barrier layer of the plasma generator 1. For the convenience of explanation, the two polishing discs are distinguished as an upper polishing disc 2 and a lower polishing disc 6 below.

[0023] 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 a first direction, thereby driving the upper polishing plate 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 a second direction, thereby driving the lower polishing plate 6 to rotate synchronously.

[0024] The clamping mechanism is arranged between the two polishing plates, and includes a sun gear 7, an inner gear ring 4 and a plurality of planetary gears 15. The sun gear 7 is fixed on the lower polishing plate 6, and the inner gear ring 4 is fixed on the inner wall of the closed cover 3. The plurality of planetary gears 15 are arranged between the sun gear 7 and the inner gear ring 4, and mesh with the sun gear 7 and the inner gear ring 4, so that when the lower polishing plate 6 rotates, the planetary gears 15 can be driven by the sun gear 7 and the inner gear ring 4 to rotate and revolve simultaneously. Each planetary gear 15 is provided with a rectangular hole 20 and a circular hole 21, so as to clamp the diamond substrate 14 to be processed of different shapes and sizes, and the surface of each planetary gear 15 is covered with tiny through holes 17, so that the plasma of active free radicals can pass through the through holes 17 to irradiate the diamond substrate 14, the upper polishing plate 2 and the surface of the lower polishing plate 6.

[0025] The gas supply mechanism 5 is connected to the closed cover 3 through the air inlet pipe 8 for inputting the mixed gas, and an exhaust port 16 for exhausting gas is provided on one side of the closed cover 3. The air inlet pipe 8 passes through the lower electrode plate 18, the lower polishing disc 6 and the axis of the sun gear 7 from bottom to top in sequence, so that the mixed gas can be supplied between the two polishing discs, and a large amount of plasma containing highly active free radicals is generated under the strong electric field of the upper and lower electrode plates of the plasma generator 1.

[0026] Furthermore, a pressure sensor 10 is included, and the pressure sensor 10 is connected to the upper electrode plate 11 for applying a polishing load.

[0027] In this embodiment, a polishing load is applied by a pressure sensor 10, and the load range is less than 10 kg. The first motor 91 and the second motor 92 respectively drive the upper polishing disc 2 and the lower polishing disc 6 to rotate relative to each other to achieve polishing of the diamond substrate 14. At the same time, the upper and lower polishing discs also serve as a dielectric barrier layer of the plasma generator 1, so that the plasma generator can process the diamond substrate as a polishing machine while generating plasma, thereby better combining plasma generation and polishing processing. The polishing process does not require the addition of any abrasive or polishing liquid, is more green and environmentally friendly, and does not require a complex and expensive vacuum chamber.

[0028] Furthermore, the upper polishing disc 2 and the lower polishing disc 6 are respectively fixed on the upper electrode plate 11 and the lower electrode plate 18 of the dielectric barrier through ceramic bolts 13, and the spacing between the upper polishing disc 2 and the lower polishing disc 6 is 2mm-10mm. The two polishing discs are made of low-hardness insulating material, and the low-hardness insulating material is at least one of quartz glass, alumina, and silicon plate. Diamonds are not easily damaged when processed with materials with lower hardness, and these materials can also undergo tribochemical reactions with diamonds during processing, thereby removing the surface material of the diamond substrate in a mechanical + chemical manner. Since the raised parts on the surface of the diamond substrate 14 are more likely to contact active free radicals and first contact the polishing disc during the polishing process, it has a greater material removal rate, and its surface flatness will eventually approach that of the polishing disc, thereby achieving overall polishing of the diamond substrate, and the surface roughness Ra<1nm.

[0029] Further, the mixed gas is at least two of helium, argon, water vapor, oxygen, and hydrogen peroxide vapor. During processing, the mixed gas generates a large amount of plasma containing highly active free radicals between the upper and lower polishing discs under the strong electric field of the plasma generator, and 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, the 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 difficulty of processing the diamond substrate. The modification also reacts chemically with the active free radicals contained in the plasma, such as hydroxyl, oxygen free radicals, etc., and the diamond substrate and the polishing disc, such as C*-OH+M-OH→CO / CO2+H2O or / and C*+O+M→C*-OM (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*-OM is a new bond formed on the interface.

[0030] Furthermore, the sun gear 4 and the planetary 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 sealing cover 3 is made of acrylic plate or K9 glass material.

[0031] like Figures 3 to 5 As shown, the present application further provides a diamond polishing method, using the plasma double-sided diamond polishing processing device described above, the diamond is polished by the following steps: S1: Mounting the diamond substrate 14 to be processed on the clamping mechanism and closing the sealing cover 3; S2: supplying mixed gas through the gas supply mechanism 5, starting the plasma generator, so that the mixed gas generates a large amount of plasma containing highly active free radicals between the upper and lower polishing discs under the strong electric field of the upper and lower electrode plates, and the plasma containing highly active free radicals adheres to the diamond substrate and the upper and lower polishing discs to be modified; S3: Apply a polishing load through the pressure sensor 10, the load range is less than 10kg, start the driving mechanism, rotate the upper and lower polishing discs, and perform double-sided polishing on the diamond substrate.

[0032] In this embodiment, the supplied mixed gas generates a large amount of plasma containing highly active free radicals between the upper and lower polishing discs under the action of the strong electric field of the plasma generator 1, and 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 undergoes large-area modification. The driving mechanism drives the upper and lower polishing discs to rotate, and 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 inner gear ring 4, so as to perform double-sided polishing of the diamond substrate.

[0033] The double-sided polishing method of the present application is an efficient precision machining technology, which can not only effectively eliminate the surface damage layer left by the grinding and rough polishing process, but also effectively ensure that the substrate surface reaches the nanometer surface roughness. Plasma processing technology is indispensable in the fields of optics and semiconductors. It is not only commonly used for cleaning, activating and modifying the surface of semiconductors, but also can achieve non-damage, efficient and atomic-level surface polishing of substrate sheets. In the present invention, while the plasma generator generates plasma, its own structure can also be used as a polishing machine to process diamond substrates. The plasma generator and the double-sided polishing device are effectively combined together to improve the processing efficiency and reduce the production cost. A method for plasma-assisted double-sided polishing of diamond, a dielectric barrier plasma generates a large amount of plasma containing highly active free radicals, which can uniformly modify the diamond substrate and the polishing disk over a large area. The modified polishing disk and the diamond substrate are prone to chemical reaction during friction. The polishing treatment of the diamond surface is achieved through plasma modification and friction chemical reaction, and atomic-level non-damage polishing is achieved to achieve 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.

[0034] After the above polishing process, the surface of the diamond substrate is fully trimmed and improved. This method can not only remove impurities on the diamond surface, but also reduce defects and thus improve the overall quality of the diamond substrate. Therefore, in the manufacturing process of diamond-related parts, this polishing method has important application value.

[0035] The above description is only a preferred embodiment of the present invention and is 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 in the protection scope of the present invention.

Claims

1. A plasma double-sided polishing diamond processing device, comprising a closed cover and a plasma generator rotatably connected to the closed cover, wherein the plasma generator has an upper electrode plate and a lower electrode plate, and the upper electrode plate and the lower electrode plate are placed in the closed cover, characterized in that: Also includes: Two polishing discs are provided, respectively connected to the upper electrode plate and the lower electrode plate, and the polishing discs are made of dielectric barrier discharge material; A clamping mechanism, disposed between the two polishing discs, for clamping a workpiece, wherein the clamping mechanism is provided with a plurality of through holes; A gas supply mechanism, connected to the closed cover through an air inlet pipe, for inputting a mixed gas so that plasma can be generated between the two polishing discs; A driving mechanism is connected to the plasma generator, and the driving mechanism can drive the plasma generator to rotate, thereby driving the two polishing discs to rotate to perform polishing processing on the workpiece.

2. A plasma double-sided diamond polishing processing device 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 to drive 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 to drive the lower electrode plate to rotate around the axis in a second direction.

3. A plasma double-sided diamond polishing processing device according to claim 1, characterized in that , also includes a pressure sensor, which is connected to the upper electrode plate and is used to apply a polishing load.

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

5. A plasma double-sided polishing diamond processing device according to claim 1, characterized in that The clamping mechanism includes a sun gear, an inner gear ring and a plurality of planetary gears. The sun gear is fixedly mounted on the polishing disk below. The inner gear ring is fixedly engaged with the inner wall of the closed cover. The plurality of planetary gears are meshed between the inner gear ring and the sun gear, so that when the polishing disk rotates, the planetary gears can be driven by the sun gear to realize self-rotation and revolution. The plurality of through holes are arranged on the planetary gears, and each of the planetary gears is provided with a rectangular hole and a circular hole for clamping the workpiece.

6. A plasma double-sided diamond polishing device according to claim 5, characterized in that The sun gear and the planetary gear are made of a rigid material, which is at least one of quartz glass, polytetrafluoroethylene, alumina plate, and acrylic plate.

7. A plasma double-sided diamond polishing device according to claim 1, characterized in that , the dielectric barrier discharge material is at least one of quartz glass, alumina, and silicon plate.

8. A plasma double-sided diamond polishing device according to claim 5, characterized in that The air inlet pipe passes through the lower electrode plate, the lower polishing plate and the axis of the sun gear from bottom to top in sequence, and an air outlet is provided on one side of the closed cover.

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

10. A diamond polishing method, characterized in that Using the plasma double-sided diamond polishing processing device described in any one of claims 1 to 9, the diamond is polished by the following steps: S1: mounting the diamond substrate to be processed on the clamping mechanism and closing the sealed cover; S2: supplying mixed gas through the gas supply mechanism, starting the plasma generator, so that the mixed gas generates a large amount of plasma containing highly active free radicals between the upper and lower polishing discs under the strong electric field of the upper and lower electrode plates, and the plasma containing highly active free radicals adheres to the surface of the diamond substrate and the upper and lower polishing discs to be modified; S3: Start the driving mechanism to rotate the upper and lower polishing discs to perform double-sided polishing on the diamond substrate.

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