Diamond Polishing Method and Device Based on Multi-Wavelength Composite Irradiation

Abstract

The present invention provides a diamond polishing method and device based on multi-wavelength composite irradiation, including: polishing the diamond sheet by means of the mechanical shearing action between the diamond sheet and the cast iron disc; during the polishing process, irradiating the diamond polishing working area with ultraviolet light and infrared light; the irradiation of the ultraviolet light breaks and recombines the C-C bonds of the carbon atoms on the surface of the diamond sheet, and at the same time, the irradiation of the ultraviolet light excites the iron oxide of the cast iron disc to generate electron-hole pairs and oxidizes the surface of the diamond sheet to achieve the polishing of the diamond; the irradiation of the infrared light locally heats the surface of the diamond sheet, accelerates the chemical removal rate, softens the surface of the diamond sheet, and at the same time can enhance the lattice vibration of the diamond sheet and promote the breaking and recombination of the C-C bonds of the carbon atoms on the surface of the diamond sheet; the wavelength of the ultraviolet light is 300nm-500nm; the wavelength of the infrared light is 915nm. The present invention has the advantages of controllable regional range, high processing efficiency, low cost and good polishing quality.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond ultra-precision polishing, and in particular to a diamond polishing method and device based on multi-wavelength composite irradiation. Background Art

[0002] Since the birth of synthetic diamond, diamond has been hailed as the "ultimate semiconductor" material by the industry due to its excellent semiconductor properties; it has an ultra-wide bandgap (5.45 eV), high electron mobility (4500 cm 2 ·V -1 ·s -1 ), high electron saturation velocity (2.7×10 7 cm·s -1 ), high breakdown field strength (10 7 V·cm -1 ), high thermal conductivity (2000 W·m -1 ·K -1 ), and low dielectric constant (5.5). However, in order to fully utilize the semiconductor properties of diamond, certain requirements are often imposed on its surface quality. When the diamond film is used as a window material for different wavelength bands, in order to meet the requirements of imaging or energy transmission, it is required that its two surfaces are very smooth and have low damage, and the defects on the diamond film surface should be minimized as much as possible to avoid imaging distortion and component breakdown caused by the rough surface; when used as a microwave power device, if the surface quality is too poor, the excellent properties of the material itself, such as high frequency, high power, and high temperature resistance, will be difficult to reflect, and even the information such as the distance from the predicted target to the electromagnetic wave emission point, radial velocity, and azimuth will be inaccurate. Unfortunately, due to the extremely stable physical and chemical properties of diamond, how to perform ultra-precision machining on it to obtain diamond with high surface quality and meeting industrial requirements has always been the key and an urgent technical problem in the application of diamond semiconductors.

[0003] So far, to reduce the surface roughness of single-crystal diamond, researchers have developed many polishing techniques, including: Mechanical Polishing (MP), Chemical Mechanical Polishing (CMP), Thermochemical Polishing (TCP), Dynamic Friction Polishing (DFP), Laser Polishing (LP), Ion Beam Polishing (IBP), Hydroxyl Radicals Enhanced Chemical Polishing, and so on. Due to different removal mechanisms, these methods show differences in the final diamond surface quality and polishing efficiency. However, upon careful analysis, it is not difficult to find that they all have a common feature: creating an extreme environment (high temperature, high pressure, strong oxidation, etc.) to achieve the phase change or qualitative change of diamond, thereby realizing its efficient removal. For example, the earliest MP method uses an ultra-high rotation speed to rapidly increase the temperature in the processing area, and the DFP method generates a considerable amount of heat by applying a very high mechanical load on the rotating polishing disc, thereby activating the thermochemical reaction of diamond to achieve the phase change of diamond, and thus realizing the effective removal of the diamond surface material. However, the above methods usually have high requirements for equipment and the environment, and have problems such as high energy consumption, poor safety, and environmental protection.

[0004] Ultraviolet light irradiation-assisted diamond ultra-precision polishing is a new non-contact polishing technique developed in recent years. By utilizing the high-energy characteristics of ultraviolet light, it initiates photochemical reactions or photophysical effects on the diamond surface, thereby achieving ultra-precision removal of materials. This technique combines the advantages of traditional mechanical polishing and photochemical treatment, and can achieve extremely high surface accuracy and finish at the nanometer or even sub-nanometer scale, especially suitable for the processing of hard and brittle materials (such as diamond, silicon carbide, etc.). However, precisely because of its higher surface accuracy, it usually means that it requires a longer ultraviolet light irradiation time, thus prolonging the processing cycle. Especially when facing large-sized workpieces or mass production, its processing efficiency is low, and at present, it is only applicable to specific fields with high added value and high precision requirements (such as optical components, semiconductor devices, etc.). Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the present invention provides a diamond polishing method and device based on multi-wavelength composite irradiation.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a diamond polishing method based on multi-wavelength composite irradiation, including:

[0008] Polishing the diamond sheet by means of the mechanical shearing action between the diamond sheet and the cast iron disc;

[0009] During the polishing process, irradiate the diamond polishing working area with ultraviolet light and infrared light; the irradiation of the ultraviolet light breaks and reorganizes the C-C bonds of the carbon atoms on the surface of the diamond sheet. At the same time, the irradiation of the ultraviolet light excites the iron oxide of the cast iron disc to generate electron-hole pairs, and oxidizes the surface of the diamond sheet, promoting chemical removal and realizing the polishing of the diamond; the irradiation of the infrared light locally heats the surface of the diamond sheet, accelerating the chemical removal rate and softening the surface of the diamond sheet. At the same time, the irradiation of the infrared light can enhance the lattice vibration of the diamond sheet and promote the breaking and reorganization of the C-C bonds of the carbon atoms on the surface of the diamond sheet;

[0010] The wavelength of the ultraviolet light is 300nm - 500nm; the wavelength of the infrared light is 915nm.

[0011] Further, during the polishing process, the temperature of the polishing working area is maintained at 200°C - 400°C.

[0012] On the other hand, the present invention also provides a diamond polishing device based on multi-wavelength composite irradiation for implementing the above method, including an ultraviolet light source, an infrared light source, a multi-wavelength composite optical fiber, a load, a cast iron disc, a sample spinning device, and a main drive motor;

[0013] The sample spinning device is used to fix and rotate the diamond;

[0014] The load is placed on the sample spinning device. The load and the middle of the sample spinning device are hollow. The multi-wavelength composite optical fiber sequentially passes through the hollow of the load and the sample spinning device; one end of the multi-wavelength composite optical fiber is connected to the ultraviolet light source and the infrared light source, and the other end is placed above the diamond for irradiating the diamond surface with ultraviolet light and infrared light;

[0015] A cast iron disc for frictionally contacting the diamond is arranged below the sample spinning device, and a main drive motor is arranged below the cast iron disc.

[0016] Further, the sample spinning device includes a sample drive motor, a quartz glass sheet, and a metal fixture. A clamping groove is provided at the center of the metal fixture. The sample drive motor is connected to the metal fixture. The quartz glass sheet is fixed inside the metal fixture, with one side connected to the sample drive motor and the other side connected to the diamond.

[0017] Further, the size of the clamping groove of the metal fixture is 5mm × 5mm × 0.3mm.

[0018] Further, it also includes an oxygen enrichment device for providing a locally oxygen-enriched environment at the diamond.

[0019] Further, the ultraviolet light source outputs ultraviolet light with a wavelength of 300 nm - 500 nm and an output power of 250 W - 350 W.

[0020] Further, the infrared light source outputs infrared light with a wavelength of 915 nm and an output power of 0 W - 300 W.

[0021] Further, the rotational speed of the cast iron disk is 150 rpm.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0023] The diamond polishing method and device based on multi-wavelength composite irradiation provided by the present invention irradiate ultraviolet light and infrared light in the diamond polishing working area during the mechanical polishing process of the diamond wafer and the cast iron disk, so as to achieve high-efficiency and high-precision polishing of the diamond wafer.

[0024] Under the irradiation of ultraviolet light, carbon atoms on the surface of the diamond wafer absorb photon energy, directly causing the C-C bonds to break and recombine. At the same time, since the ultraviolet light irradiates the cast iron disk, the iron oxide in the cast iron disk is excited, causing electrons to jump from the valence band to the conduction band, generating electron-hole pairs (electron e - and hole h + ), which combine with oxygen and water molecules in the air to undergo a bonding reaction, generating a large number of superoxide radicals (-O2) and hydroxyl radicals (-OH). On the one hand, the two generated radicals oxidize the carbon atoms on the surface of the diamond wafer to form CO or CO2 and discharge them; on the other hand, the hydroxyl radicals are adsorbed by the iron oxide to form unstable intermediate products, such as iron carbides or hydroxyl compounds. These active products further react with the surface of the diamond wafer to promote the chemical removal of the material and achieve high-efficiency and high-quality polishing of the diamond.

[0025] Under the irradiation of infrared light, on the one hand, the surface of the diamond wafer absorbs infrared light, resulting in local surface heating, accelerating the photochemical reaction rate initiated by ultraviolet light, and at the same time softening the surface of the diamond wafer, enhancing the effect of mechanical shear removal of the surface material; on the other hand, the photon energy of infrared light is low, which can interact with the vibration mode of the diamond wafer lattice, enhance the lattice vibration, promote the breaking and recombination of C-C bonds caused by ultraviolet light, and at the same time relieve the residual stress on the surface of the diamond wafer during the polishing process, thereby reducing microcracks or defects generated during polishing.

[0026] The diamond polishing method and device based on multi-wavelength composite irradiation provided by the present invention have the advantages of controllable area range, high processing efficiency, low cost and good polishing quality, and can solve the problem that it is difficult to balance the processing efficiency and quality in the current technology. At the same time, the present invention is energy-saving, intensive and efficient, meeting the needs of industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0028] Figure 1 Schematic diagram of a diamond polishing device based on multi-wavelength composite irradiation provided for one embodiment;

[0029] Figure 2 Schematic diagram of a sample spinning device provided for one embodiment;

[0030] Figure 3 Schematic diagram of the mechanism of a diamond polishing method based on multi-wavelength composite irradiation provided for one embodiment.

[0031] Reference numerals in the drawings:

[0032] 1. Multi-wavelength composite optical fiber; 2. Load; 3. Diamond wafer; 4. Cast iron disk; 5. Sample spinning device; 6. Main drive motor; 7. Sample drive motor; 8. Quartz glass sheet; 9. Metal fixture. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] One embodiment provides a diamond polishing method based on multi-wavelength composite irradiation, including:

[0035] Polishing the diamond wafer by using the mechanical shearing action between the diamond wafer 3 and the cast iron disk 4;

[0036] During the polishing process, ultraviolet light and infrared light irradiate the diamond polishing working area; the irradiation of ultraviolet light breaks and reorganizes the C-C bonds of carbon atoms on the surface of the diamond wafer, and at the same time, the irradiation of ultraviolet light excites the iron oxide of the cast iron disk to generate electron-hole pairs, and oxidizes the surface of the diamond wafer, promoting chemical removal and achieving the polishing of the diamond; the irradiation of infrared light locally heats up the surface of the diamond wafer 3, accelerates the chemical removal rate, and softens the surface of the diamond wafer 3. At the same time, the irradiation of infrared light can enhance the lattice vibration of the diamond wafer 3 and promote the breaking and reorganization of the C-C bonds of carbon atoms on the surface of the diamond wafer 3.

[0037] The wavelength of the ultraviolet light is 300nm - 500nm; the wavelength of the infrared light is 915nm.

[0038] Refer to Figure 3 , under the irradiation of ultraviolet light, the carbon atoms on the surface of the diamond wafer 3 absorb photon energy, directly causing the C-C bonds to break and reorganize. At the same time, because the ultraviolet light irradiates the cast iron disk 4, the iron oxide in the cast iron disk 4 is excited, causing electrons to jump from the valence band to the conduction band, generating electron-hole pairs (electrons e - and holes h + ), and combining with oxygen and water molecules in the air to undergo a bonding reaction, generating a large number of superoxide radicals (-O2) and hydroxyl radicals (-OH). On the one hand, the two generated radicals oxidize the carbon atoms on the surface of the diamond wafer 3 to form CO or CO2 and discharge them; on the other hand, the hydroxyl radicals are adsorbed by the iron oxide to form unstable intermediate products, such as iron carbides or hydroxyl compounds. These active products further react with the surface of the diamond wafer 3 to promote the chemical removal of the material and achieve high-efficiency and high-quality polishing of the diamond.

[0039] In one embodiment, during the polishing process, the temperature of the polishing working area is maintained at 200°C - 400°C. During the polishing process, infrared light irradiates the surfaces of the cast iron disk 4 and the diamond wafer 3. By adjusting the power and irradiation time of the infrared light, the temperature conditions can be locally changed, reducing the time required for the transformation of diamond carbon into a non-diamond phase, thereby improving the diamond polishing efficiency; by adjusting and controlling the power and irradiation time of the infrared light and only irradiating the diamond polishing working area, efficient utilization of energy can be achieved.

[0040] Specifically, by maintaining the temperature of the polishing working area at 200°C - 400°C, polishing can be carried out smoothly and efficiently within this temperature range. This is because at high temperatures of 200°C - 400°C, the diamond wafer 3 is more likely to react with oxygen (O2) or hydroxyl radicals (-OH) to generate CO or CO2, which volatilizes and is discharged; at the same time, within this temperature range, the process of diamond graphitization caused by ultraviolet light can be accelerated, improving the polishing efficiency. When the temperature exceeds 400°C, it may lead to overreaction, causing damage to the surface of the diamond wafer 3 and affecting the final polishing quality; moreover, too high a temperature may also lead to excessive graphitization and cause microstructural damage due to thermal stress.

[0041] In a preferred embodiment, the temperature of the polishing working area during the polishing process is maintained at 300°C. At this temperature, the oxidation rate of the surface of the diamond wafer 3 is significantly increased, and the degree of graphitization is within a controllable range.

[0042] Refer to Figure 1 , an embodiment provides a diamond polishing device based on multi-wavelength composite irradiation for implementing the above diamond polishing method, including an ultraviolet light source, an infrared light source, a multi-wavelength composite optical fiber 1, a load 2, a cast iron disk 4, a sample spinning device 5, and a main drive motor 6;

[0043] The sample spinning device 5 is used to fix and rotate the diamond;

[0044] The load 2 is placed on the sample spinning device 5. The load 2 and the middle of the sample spinning device 5 are hollow. The multi-wavelength composite optical fiber 1 passes through the hollow cores of the load 2 and the sample spinning device 5 in sequence; one end of the multi-wavelength composite optical fiber 1 is connected to the ultraviolet light source and the infrared light source, and the other end is placed above the diamond for irradiating the diamond surface with ultraviolet light and infrared light;

[0045] A cast iron disk 4 for frictionally contacting the diamond is provided below the sample spinning device 5, and a main drive motor 6 is provided below the cast iron disk.

[0046] The multi-wavelength composite optical fiber 1 allows light in the infrared band and the ultraviolet band to pass through together.

[0047] In an embodiment, the ultraviolet light source outputs ultraviolet light with a wavelength of 300 nm - 500 nm and an output power of 250 W - 350 W; the infrared light source outputs infrared light with a wavelength of 915 nm and an output power of 0 W - 300 W. Within this wavelength and output power range, it is beneficial to improve the polishing quality and polishing efficiency.

[0048] Refer to Figure 2, In one embodiment, the sample spinning device 5 includes a sample driving motor 7, a quartz glass sheet 8, and a metal fixture 9. A clamping groove is provided at the center of the metal fixture 9. The sample driving motor 7 is connected to the metal fixture 9. The quartz glass sheet 8 is fixed inside the metal fixture, with one side connected to the sample driving motor 7 and the other side connected to the diamond sheet 3. The diamond sheet is fixed by the metal fixture 9, thus preventing lateral movement. Ultraviolet light and infrared light are irradiated on the surface of the diamond sheet 3 through the multi-wavelength composite optical fiber 1 and the quartz glass sheet 8. Through such a setting, while fixing the diamond sheet 3, the area to be processed is exposed, which is conducive to the smooth progress of the polishing process.

[0049] The size of the clamping groove of the metal fixture is determined according to the size of the diamond.

[0050] Embodiment:

[0051] In one embodiment, the diamond sheet 3 is a single-crystal diamond sheet (100 crystal orientation), with dimensions of 5 mm × 5 mm × 1 mm. The single-crystal diamond sheet is a single-crystal diamond sheet that has undergone primary grinding treatment when leaving the factory. The initial surface roughness Ra is 2.51 nm (test area 0.14 mm × 0.16 mm). After further grinding after purchase, the surface roughness Ra is 0.80 nm. Taking this surface roughness as the surface roughness before polishing, the single-crystal diamond sheet is processed using the diamond polishing method and device based on multi-wavelength composite irradiation described in the present invention.

[0052] In this embodiment, the size of the clamping groove of the metal fixture 9 is 5 mm × 5 mm × 0.3 mm.

[0053] During the polishing process, the sample driving motor 7 and the main driving motor 6 drive the single-crystal diamond sheet and the cast iron disk 4 to rotate in opposite directions respectively, and the rotation speeds are kept the same. The rotation speed of the cast iron disk 4 is 150 rpm. The pressure of the load 2 is kept at 0.4 Mpa. The ultraviolet light source outputs ultraviolet light with a wavelength of 300 nm - 500 nm and an output power of 278 W, and the ultraviolet light intensity is 200 mW / cm 2 ; The infrared light source outputs infrared light with a wavelength of 915 nm and an output power of 300 W, and the infrared light intensity is 200 mW / cm 2 ; The polishing time is 8 h, the ultraviolet light irradiation time is 8 h, and the infrared light irradiation time is 1 h.

[0054] Comparative example:

[0055] While maintaining the same settings as above, the infrared light irradiation is removed, and the ultraviolet light irradiation time is controlled to be 8 h and 10 h, and the single-crystal diamond sheet is polished.

[0056] Under the above processing conditions, the surface roughness of the single-crystal diamond wafers in the comparative examples decreased to 0.48 nm (8 h) and 0.37 nm (10 h), respectively; the surface roughness of the single-crystal diamond wafers in the examples decreased to 0.175 nm, and the surface of the single-crystal diamond wafers in the examples was uniformly smooth, without obvious scratches and defects, meeting the surface quality requirements of high precision and low damage for the composite diamond devices. It can be seen from the above comparison that compared with single ultraviolet light irradiation-assisted polishing, the polishing method provided by the present invention has faster polishing efficiency and better polishing quality.

[0057] Matters not covered by the present invention are well-known technologies.

[0058] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0059] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

[0060] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. 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 diamond polishing device based on multi-wavelength composite irradiation, characterized in that: It includes ultraviolet light source, infrared light source, multi-wavelength composite optical fiber, load, cast iron plate, sample spinning device, and main drive motor; The sample spinning device is used to fix and spin the diamond; The load is placed on the sample spinning device, the load and the sample spinning device are hollow in the middle, and the multi-wavelength composite optical fiber passes through the hollow cores of the load and the sample spinning device in sequence; one end of the multi-wavelength composite optical fiber is connected to the ultraviolet light source and the infrared light source, and the other end is placed above the diamond to irradiate the ultraviolet light and the infrared light on the surface of the diamond; A cast iron disk for rubbing diamond is arranged below the sample spinning device, and a main driving motor is arranged below the cast iron disk.

2. The diamond polishing device based on multi-wavelength composite irradiation according to claim 1, characterized in that: The sample spinning device comprises a sample driving motor, a quartz glass sheet and a metal clamp. A slot is provided at the center of the metal clamp. The sample driving motor is connected to the metal clamp. The quartz glass sheet is fixed inside the metal clamp, with one side connected to the sample driving motor and the other side connected to the diamond.

3. The diamond polishing device based on multi-wavelength composite irradiation as claimed in claim 2, characterized in that: The size of the card slot of the metal clamp is 5mm×5mm×0.3mm.

4. The diamond polishing device based on multi-wavelength composite irradiation according to claim 1, characterized in that: Also included is an oxygen enrichment device for providing a local oxygen-enriched environment at the diamond.

5. The diamond polishing device based on multi-wavelength composite irradiation according to claim 1, characterized in that: The ultraviolet light source outputs ultraviolet light with a wavelength of 300nm-500nm and an output power of 250W-350W.

6. The diamond polishing device based on multi-wavelength composite irradiation according to claim 1, characterized in that: The infrared light source outputs infrared light with a wavelength of 915nm and an output power of 0W-300W.

7. The diamond polishing device based on multi-wavelength composite irradiation according to claim 1, characterized in that: The cast iron disc was rotated at 150 rpm.

8. A diamond polishing method based on multi-wavelength composite irradiation, implemented based on the device of claim 1, characterized in that: include: The diamond sheet is polished by utilizing the mechanical shearing action between the diamond sheet and the cast iron disc; During the polishing process, ultraviolet light and infrared light are irradiated to the diamond polishing working area; the ultraviolet light irradiation causes the carbon atom CC bond on the surface of the diamond sheet to break and recombine, and at the same time, the ultraviolet light irradiation excites the iron oxide of the cast iron disk to produce electron-hole pairs, and oxidizes the surface of the diamond sheet, promotes chemical removal, and realizes the polishing of the diamond; the infrared light irradiation causes the surface of the diamond sheet to heat up locally, accelerates the chemical removal rate, and softens the surface of the diamond sheet. At the same time, the infrared light irradiation can enhance the lattice vibration of the diamond sheet and promote the breakage and recombination of the carbon atom CC bond on the surface of the diamond sheet; The wavelength of the ultraviolet light is 300nm-500nm; the wavelength of the infrared light is 915nm.

9. The diamond polishing method based on multi-wavelength composite irradiation according to claim 8, characterized in that: During the polishing process, the temperature of the polishing working area is maintained at 200° C.-400° C.

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