A method and system for super low roughness composite polishing of diamond

Abstract

The application provides a super-low roughness composite polishing method and system for diamond, and the method comprises the following steps: modifying the surface of the diamond by a gas cluster ion beam, preliminarily processing defects on the surface layer of the diamond, and forming an amorphous layer on the surface of the diamond; and removing the amorphous layer on the surface of the diamond by a plasma-assisted polishing technology, and creating an atomic-level diamond surface. The atomic-level diamond surface is created based on the synergistic effect of the gas cluster ion beam and the plasma, which can effectively eliminate fine scratches on the surface of the sample, obtain an unprecedented low roughness, reduce damage to the subsurface of the sample, and multiply the roughness and processing efficiency of the surface of the sample; and the entire polishing process is green and environmentally friendly, and waste liquid and harmful waste are not needed to be treated.

Description

Technical Field

[0001] This application relates to the field of diamond polishing, and more specifically, to a composite polishing method and system for diamond with ultra-low roughness. Background Technology

[0002] Diamond's excellent physicochemical properties, along with its extremely high hardness and chemical stability, make it irreplaceable in many high-tech fields such as power devices, quantum sensing, and infrared optics. However, these properties also make diamond extremely difficult to process. Traditional processing techniques face a paradox between manufacturing precision and efficiency, and breakthroughs in diamond polishing precision are becoming increasingly difficult. For example, while mechanical polishing can achieve micron-level removal, it introduces a crack layer >100nm into the subsurface layer, and the grain boundaries of polycrystalline diamond are prone to chipping, making it difficult to achieve a surface roughness (Ra) below 1nm. Plasma etching (such as RIE) can avoid mechanical damage, but anisotropic etching creates "crystal steps" with depth differences >50nm on polycrystalline surfaces, failing to meet the atomic-level flatness requirements (Ra <0.5nm) of optical devices. The most popular chemical mechanical polishing (CMP) can achieve atomic-level surfaces locally, but its polishing efficiency is usually low (50–500nm / h), surface scratches still exist when polishing large-sized samples, and polishing waste liquid needs to be treated. Therefore, the industry urgently needs a disruptive processing solution that combines high removal rate (>500nm / h) with atomically smooth surface (Ra<0.2nm).

[0003] Current state-of-the-art plasma-assisted polishing (PAP) and gas cluster ion beam (GCIB) polishing still have inherent limitations. For example, PAP technology relies on hydroxyl oxide diamond surfaces, and although it can achieve localized smoothness with Ra 0.2–0.3 nm, its reaction rate is limited by the diamond spline surface area. 3 The energy barrier for bond breaking results in a removal rate of only 200-400 nm / h for polycrystalline diamond, and "ripple defects" with Ra>0.5 nm are formed at the grain boundaries due to uneven plasma irradiation. GCIB technology achieves nanoscale planarization of the diamond surface through gas cluster ion bombardment, but when used alone, it leaves nanoscale pits (Ra≈0.3 nm) on the diamond surface, with an overall roughness of over 1 nm. Furthermore, it leaves varying degrees of amorphous layers during the damage repair process, affecting its optical and thermal conductivity properties.

[0004] Therefore, a diamond polishing solution that balances processing efficiency and processing accuracy is needed. Summary of the Invention

[0005] This application provides a method and system for ultra-low roughness composite polishing of diamond to solve at least one of the above-mentioned problems. The specific solution is as follows:

[0006] A composite polishing method for diamond with ultra-low roughness includes:

[0007] The diamond surface is modified by gas cluster ion beam to preliminarily treat diamond surface defects and form an amorphous layer on the diamond surface.

[0008] The amorphous layer on the surface of diamond is removed by plasma-assisted polishing technology, creating an atomic-level diamond surface.

[0009] In some specific embodiments, the diamond surface is modified by a gas cluster ion beam, specifically including:

[0010] Fix the diamond to the worktable and evacuate to the preset vacuum level;

[0011] A gas cluster ion beam is generated and used to reciprocate scan the sample surface;

[0012] First, small clusters are used to disrupt the existing morphological features of the diamond surface, causing the diamond surface to become amorphous and generate an amorphous layer; then, large clusters are used to repair the diamond surface that has been disrupted by the small clusters, making the thickness of the amorphous layer of the diamond more uniform.

[0013] In some specific embodiments, the removal of the amorphous layer on the diamond surface using plasma-assisted polishing technology specifically includes:

[0014] The amorphous layer of diamond is brought into contact with the polishing pad. Using argon and water vapor as gas sources, and in conjunction with the polishing pad, the amorphous carbon atoms formed on the diamond surface by the gas cluster ion beam are removed layer by layer through hydroxylation, dehydration condensation and shearing in the polishing area.

[0015] In some specific embodiments, argon and water vapor are used as gas sources, and plasma is used to continuously irradiate the polishing pad to achieve hydroxylation of the polishing pad surface under the action of plasma.

[0016] In some specific embodiments, under the action of friction, the hydroxylated silicon on the surface of the polishing pad dehydrates and condenses with the diamond surface to form Si-OC bonds, while releasing a water molecule to achieve interfacial bonding; under the action of shearing, the CC bonds break, so that the amorphous carbon atoms on the diamond surface are removed.

[0017] In some specific embodiments, argon is used as the gas source to generate gas cluster ion beams.

[0018] In some specific embodiments, the accelerating voltage of the cluster ion beam on diamond is not less than 15kV.

[0019] In some specific embodiments, the thickness of the amorphous layer on the diamond surface is 5-10 nm.

[0020] In some specific embodiments, the small cluster size is concentrated below 1000 atoms / cluster, and the large cluster size is concentrated between 1000 and 2000 atoms / cluster.

[0021] In some specific embodiments, the irradiation dose of the gas cluster ion beam is adjusted according to the original surface morphology of the diamond until the surface morphology is homogenized.

[0022] An ultra-low roughness composite polishing system for diamond, comprising:

[0023] The first polishing unit is used to modify the diamond surface with a gas cluster ion beam, preliminarily treat diamond surface defects, and form an amorphous layer on the diamond surface.

[0024] The second polishing unit is used to remove the amorphous layer on the diamond surface using plasma-assisted polishing technology, creating an atomic-level diamond surface.

[0025] Beneficial effects: This application proposes an ultra-low roughness composite polishing method and system for diamond, which achieves atomic-level diamond surface creation based on the synergistic effect of gas cluster ion beam and plasma. It can not only effectively eliminate fine scratches on the sample surface and obtain unprecedented low roughness, but also reduce subsurface damage to the sample, resulting in a multiple improvement in both sample surface roughness and processing efficiency. Furthermore, the entire polishing process is green and environmentally friendly, requiring no waste liquid or hazardous waste treatment.

[0026] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the ultra-low roughness composite polishing method of this application;

[0029] Figure 2a This is a diagram illustrating the principle of gas cluster ion beams.

[0030] Figure 2b This is a schematic diagram of small clusters interacting with material surfaces;

[0031] Figure 2c This is a schematic diagram of large clusters and material surface operations;

[0032] Figure 3 This is a schematic diagram of the processing path of diamond using a gas cluster ion beam;

[0033] Figure 4a This is a schematic diagram of parameter control for small cluster ion beam processing of diamond;

[0034] Figure 4b This is a schematic diagram of parameter control for large cluster ion beam processing of diamond;

[0035] Figure 5 This is a schematic diagram illustrating the working principle of plasma-assisted polishing;

[0036] Figure 6 This is a schematic diagram illustrating the process of plasma beam-assisted polishing on a diamond surface.

[0037] Figure 7a This is a schematic diagram of the state of a diamond sample after chemical mechanical polishing.

[0038] Figure 7b This is a schematic diagram showing the state of a diamond surface after plasma-assisted polishing;

[0039] Figure 7c This is a schematic diagram showing the state of a diamond surface after treatment with a gas cluster ion beam.

[0040] Figure 7d This is a schematic diagram showing the state of the diamond surface after treatment by the method of this application;

[0041] Figure 8 This is a schematic diagram of the ultra-low roughness composite polishing system module of this application.

[0042] Reference numerals: 11-Nozzle; 12-Flange; 13-Ionizer; 14-Accelerator; 15-Electron Lens; 16-Analytical Magnet; 17-Neutralizer; 18-Aperture; 19-Stage; 20-Faraday Ring; 21-Microwave Plasma Exciter; 22-Plasma; 23-First Servo Motor; 24-Second Servo Motor; 25-Sample Holder; 26-Polycrystalline Diamond; 27-Polishing Disc; A1-First Polishing Unit; A2-Second Polishing Unit. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0044] This application proposes a composite polishing method for ultra-low roughness diamond, utilizing a combination of gas cluster ion beam (GCIB) and plasma-assisted polishing (PAP) to improve processing efficiency while addressing the challenge of achieving higher processing precision. A flowchart of the method is attached. Figure 1 As shown, the specific solution is as follows:

[0045] A composite polishing method for diamond with ultra-low roughness includes:

[0046] 101. Modify the diamond surface by gas cluster ion beam to preliminarily treat diamond surface defects and form an amorphous layer on the diamond surface;

[0047] 102. The amorphous layer on the surface of diamond is removed by plasma-assisted polishing technology to create an atomic-level diamond surface.

[0048] It should be noted that the process concept of this application involves first bombarding the surface with a gas cluster ion beam to form a uniform amorphous layer, and then using plasma-assisted polishing technology to remove atomic layers. The process involves first bombarding with gas clusters and then plasma-assisted polishing; reversing the order will not achieve the desired polishing effect.

[0049] The efficiency-precision dilemma of plasma-assisted polishing (PAP): To obtain atomically smooth surfaces (Ra < 0.2 nm), the removal rate needs to be significantly reduced (only 200-400 nm / h for polycrystalline diamond), because it relies on the high energy barrier of the plasma. 3 Direct bond oxidation (activation energy > 7 eV); plasma reaction lag at grain boundaries in polycrystalline materials leads to local roughness deterioration to Ra > 0.5 nm. Insufficient surface modification depth with gas cluster ion beam (GCIB): conventional irradiation dose (< 1 E17 ions / cm²) 2 It can only form an amorphous layer of <5nm, which cannot provide a continuous reaction interface for subsequent processing; after use alone, it leaves behind nanoscale pits (Ra>0.3nm), requiring secondary mechanical polishing, which reintroduces subsurface damage.

[0050] The polishing scheme in this application is based on the synergistic effect of gas cluster ion beam and plasma to create atomic-level diamond surfaces, and constructs a 10-30 nm thick uniform amorphous layer (carbon bond sp) through GCIB. 3 →sp 2 The conversion process reduces the activation energy of PAP oxidation reaction to <3eV, simultaneously achieving a removal rate of >800nm / h and a surface roughness of Ra≤0.1nm. By utilizing the isotropic characteristics of amorphous layers, the plasma achieves a uniform oxidation reaction at the polycrystalline grain boundaries (grain boundary / intracrystalline roughness difference <0.05nm), solving the common problem of ultra-smooth polishing of polycrystalline diamond.

[0051] Step 101 involves treating the diamond surface with a gas cluster ion beam to initially repair and eliminate surface defects, and to form a shallow, homogenized morphology on the diamond surface that differs from the subsurface texture.

[0052] The working principle of gas cluster ion beam technology processing is as follows: Figure 2a As shown, gas is ejected at high speed from a specially designed nozzle, undergoing adiabatic expansion to form gas clusters. These clusters are then accelerated by high-voltage ionization and an electron accelerator to form a high-speed gas cluster ion beam. Smaller cluster ions or single electrons in the gas cluster ion beam are deflected and blocked by the aperture when passing through the analytical electromagnet, while larger clusters pass directly through the analytical electromagnet. Their charges are then neutralized by a neutralizer before they bombard the target material perpendicularly. This differs from single-atom ion beams (such as...). Figure 2b As shown), a single cluster of a gas cluster ion beam contains tens to tens of thousands of atoms bound together by van der Waals forces (such as...). Figure 2c As shown (in the diagram), although individual clusters possess high energy as a whole, the energy averaged per atom is low. Therefore, when a gas cluster ion beam bombards a target, the "lateral sputtering effect" characteristic of cluster fragmentation only affects the very shallow surface region of the material. The sputtered target material atoms are removed in a direction almost parallel to the target material, with minimal impact on the subsurface material. This results in excellent cleaning and polishing of the target material surface. Figure 2a In this process, the gas cluster ion beam is achieved by means of a specific system, which includes a nozzle 11, a flaring nozzle 12, an ionizer 13, an accelerator 14, an electron lens 15, an analytical magnet 16, a neutralizer 17, an aperture 18, a worktable 19, and a Faraday ring 20.

[0053] In some specific embodiments, modifying the diamond surface using a gas cluster ion beam specifically includes: fixing the diamond on a worktable and evacuating it to a preset vacuum level; generating a gas cluster ion beam and using it to perform reciprocating scanning of the sample; first using small clusters to destroy the existing morphological features of the diamond surface, causing the diamond surface layer to become amorphous and generate an amorphous layer; then using large clusters to repair the diamond surface damaged by the small clusters, making the amorphous layer of the diamond more uniform.

[0054] Secure the diamond to the center of the GCIB equipment stage, close the sample chamber door, and evacuate to 1×10⁻⁶. -3 Below the Pa, the gas cluster ion beam generation device is activated. A vacuum environment prevents air molecules from colliding with the gas cluster ion beam, ensuring stable energy transfer to the diamond surface and reducing energy loss and interference. Simultaneously, it prevents impurities such as oxygen and water vapor in the air from undergoing side reactions (e.g., oxidation) with the diamond surface during bombardment, ensuring the purity of the amorphous layer. The gas cluster ion beam scans the sample via a reciprocating scan path at a speed of approximately 10 mm / s and a scan interval of 0.5 mm. Figure 3 As shown. The reciprocating scanning path ensures that the ion beam uniformly covers the diamond surface, avoiding insufficient processing of edge areas or excessive bombardment of the central area caused by scanning in one direction; the matching of scanning speed (10mm / s) and interval (0.5mm) can balance processing efficiency and surface uniformity - too fast a speed can easily lead to local missed scans, while too slow a speed will reduce efficiency; too wide an interval will produce uncovered areas, while too narrow an interval will increase redundant bombardment.

[0055] Small clusters have higher average energy per atom (because the total energy of the cluster is distributed among fewer atoms), resulting in strong penetrating power during bombardment and the ability to break through the original spline energy on the surface of diamond. 3 The crystal lattice structure transforms carbon atoms from an ordered crystal to sp. 2 Hybridized amorphous carbon (aC) is used to remove surface protrusions, scratches and other original defects through physical sputtering. The average energy of a single atom in the large cluster is low (total energy is distributed to more atoms) and the penetration depth is shallow (it only acts on the shallow layer of the amorphous layer formed by the small clusters). The collision force promotes the migration of atoms in the amorphous layer, filling the nano-pits or local density uneven areas that may remain after the small cluster treatment, and repairs the slight subsurface lattice disturbance introduced by the small clusters. Finally, the thickness of the amorphous layer is refined from 10-30 nm to 5-10 nm and the uniformity is improved. (3) The gas cluster ion beam first bombards the sample surface through the small clusters and then bombards it with the large clusters. The reason is that the single atom energy of the small clusters is higher, which can obtain a larger penetration depth and quickly homogenize the sample surface. The energy per atom of the large clusters is weaker and the penetration depth is shallower. While bombarding the sample, it promotes the repair of subsurface damage. Through the two-step treatment of small clusters and large clusters, the processing time of the sample surface can be greatly shortened.

[0056] Regarding GCIB processing parameters, the main focus is on how to adjust the cluster size. In some specific embodiments, small cluster sizes are concentrated below 1000 atoms / cluster, while large cluster sizes are concentrated between 1000 and 2000 atoms / cluster.

[0057] GCIB parameter settings to reduce cluster size were adopted: the GCIB acceleration energy was set to 20 kV, the gas source type was selected as argon, the gas source pressure was set to 0.36 MPa, the ionization voltage was set to 400 V, and the filament current was set to 45 A. The analytical magnet was not used. At this point, the beam current intensity was 88 ± 5% μA. The neutralizer was turned on and its voltage and current were adjusted (500 V / 26 A, which can be adjusted according to specific conditions) to gradually reduce the beam current intensity to 0 μA. The irradiation dose was set to 1 × 10⁻⁶. 17 ions / cm 2(This can be adjusted appropriately based on the sample surface morphology). The gas clusters are incident on the sample surface perpendicularly. Measurements using a Time-of-Flight (ToF) device show that the cluster size is mainly concentrated below 1000 atoms / cluster, with a half-width at half-maximum (FWHM) of the ion beam intensity distribution of approximately 8 mm. Clusters of this size distribution have strong penetrating power and can rapidly destroy the existing morphology of the diamond surface, causing the diamond surface to become amorphous and homogenized (to a depth of approximately 10-30 nm). Figure 4a As shown. In some embodiments, the cluster size is increased by reducing the gas source pressure, increasing the ionization current, increasing the ionization voltage, or removing the analytical magnet.

[0058] GCIB parameter settings to increase cluster size: Set the GCIB acceleration energy to 20kV, the gas source type to argon, the gas source pressure to 0.4MPa, the ionization voltage to 200V, and the filament current to 43A. Use an analytical magnet. At this point, the beam current intensity is 40±5%μA, and the half-width at half-maximum (FWHM) of the ion beam intensity distribution is approximately 6mm. Turn on the neutralizer and adjust its voltage and current (reference 500V / 24A, adjust according to specific conditions) to gradually reduce the beam current intensity to 0μA. Set the irradiation dose to 1×10⁻⁶. 17 ions / cm 2 (This can be adjusted appropriately based on the sample surface morphology). The gas clusters are incident on the sample surface perpendicularly. Time-of-flight (ToF) measurements show that the cluster size is mainly concentrated between 1000-2000 atoms / cluster. Within this size distribution, the average energy of each atom is relatively low, resulting in weak penetration. High-speed collisions with the shallow surface of the diamond can induce displacement, rearrangement, and release of interatomic forces, thereby repairing the diamond surface damaged by the previous small clusters and making the surface amorphization of the diamond more uniform. Figure 4b As shown. In some embodiments, the cluster size is increased by increasing the gas source pressure, decreasing the ionization current, decreasing the ionization voltage, or using an analytical magnet.

[0059] Step 102 involves further processing the surface treated with the gas cluster ion beam using plasma atomic layer polishing technology. This process removes amorphous carbon atoms from the diamond surface layer by layer at the atomic scale, creating an atomic-level diamond surface.

[0060] Plasma-assisted polishing (PAP) technology devices such as Figure 5As shown, the system includes a microwave plasma exciter 21, a plasma source 22, a first servo motor 23, a second servo motor 24, a sample holder 25, a polycrystalline diamond sample 26, and a polishing disc 27. The rotation of the diamond sample held on the workpiece axis and the polishing disc is controlled by two servo motors. The force applied to the sample can be adjusted by adjusting the load on the servo motor 1. The entire polishing operation is carried out in an atmospheric environment. The plasma jet and the diamond sample are vertically aligned on the same polishing disc (driven by a servo motor), and the two are arranged in a centrally symmetrical manner to ensure that the diamond surface is in contact with the modified polishing disc area. When the amorphous layer on the diamond surface comes into contact with the rotating polishing disc modified by the plasma jet, the material is sheared off.

[0061] In some specific embodiments, the removal of the amorphous layer on the diamond surface using plasma-assisted polishing technology specifically includes: contacting one side of the amorphous layer of diamond with a polishing pad; using argon and water vapor as gas sources, and in conjunction with the polishing pad, removing the amorphous carbon atoms formed on the diamond surface by the gas cluster ion beam layer by layer through hydroxylation, dehydration condensation, and shearing. Further, argon is used as the plasma gas source, and water vapor is mixed in the feed gas; the polishing pad is continuously irradiated by plasma, achieving hydroxylation of the polishing pad surface under the action of plasma. In some specific embodiments, under friction, the hydroxylated silicon on the polishing pad surface undergoes dehydration condensation with the diamond surface to form Si-OC bonds, while releasing a water molecule, achieving interfacial bonding; under shearing, the CC bonds break, thus removing the amorphous carbon atoms on the diamond surface. The process of plasma-assisted polishing on the diamond surface is shown in the attached figure. Figure 6 As shown. Plasma-assisted polishing uses argon gas excitation, and the participation of water vapor in the plasma is necessary to obtain good results. Polishing discs made of silicon dioxide or silicon can achieve good polishing effects. During the polishing process, no abrasive is involved; the polishing mainly relies on the dehydration condensation of hydroxyl groups to form new chemical bonds, and the shearing removal of carbon atoms under the dragging effect of the newly formed chemical bonds during the relative motion between the sample and the polishing disc.

[0062] The first stage is surface hydroxylation: Argon (Ar) gas is used as the plasma source, and water vapor (H2O) is mixed in the feed gas. The plasma continuously irradiates the polishing disk (silicon dioxide or silicon disk). Under the influence of plasma, the OH bonds in water molecules homolytically cleave to generate hydroxyl radicals ·OH (H2O→·OH+·H). ·OH attacks the silicon surface and forms silanol groups (Si-OH) on its surface. On the other hand, water molecules can also directly participate in the hydrolysis of the silicon surface Si-O-Si+H2O→2Si-OH, thereby introducing hydroxyl (-OH) functional groups on the surface of the polishing disk. Subsequently, under frictional induction, some Si-OH bonds gain energy and homolytically cleave to release ·OH, which bonds with active sites (dangling bonds or defects) on the diamond surface, realizing the hydroxylation (C-OH) of the workpiece surface.

[0063] The second stage is dehydration condensation: under the action of friction, hydroxylated silicon (Si-OH) and diamond (C-OH) undergo dehydration condensation to form Si-OC bonds, while releasing a water molecule to achieve interfacial bonding.

[0064] The third stage is shear removal: Since the strength of the newly formed Si-OC bond is greater than that of the CC bond in the amorphous diamond layer, the CC bond breaks under shearing, and the diamond surface atoms are removed.

[0065] The specific process involves irradiating a polishing disk (silicon dioxide or silicon disk) with a plasma containing water vapor, causing the surface of the disk to have hydroxyl groups (-OH). These hydroxyl groups then undergo dehydration condensation at the polishing interface, forming new chemical bonds. As the polishing disk rotates, protruding features on the sample surface are sheared away. Specifically, argon (Ar) gas is used as the plasma source, while H2O water vapor is mixed in the feed gas to generate a large number of -OH groups, which adhere to the polishing disk. Once the amorphous carbon atom layer on the diamond surface comes into contact with the polishing disk surface, these -OH groups are transferred to the diamond surface. Furthermore, the plasma rapidly raises the temperature of the polishing interface, providing sufficient activation energy for chemical bond recombination. When the diamond and polishing disk surfaces come into contact at a sufficiently high temperature, the -OH groups undergo dehydration condensation at the polishing interface, forming new chemical bonds such as CO, Si-O, and CO-Si. Among these, the C-C bond has the lowest binding energy. Protrusions on the diamond surface are more likely than the substrate to capture ·OH groups and preferentially undergo the above reactions. Simultaneously, the carbon atom bonds on the protrusions become weaker and are easily removed, either chemically or mechanically. In plasma-assisted polishing (PAP), the rotation speed and pressure are low, and no abrasives are used. Instead, material is removed from the diamond surface through a chemical reaction between a modified polishing disc and the diamond surface. This avoids surface scratches caused by the abrasive action of abrasives and contaminants generated during the chemical reaction that could contaminate the polished diamond surface. This is the process by which the PAP method achieves atomic-level smooth polishing of diamond surfaces.

[0066] For example, the actual operation steps include: (1) fixing the diamond (a polycrystalline diamond with a sample size of 10×10mm; due to the presence of polycrystalline faces, polishing polycrystalline diamond is more difficult than polishing single-crystal diamond) under the polishing head (sample holder), and making the amorphous diamond layer directly contact the polishing disk, and applying a load in the downward direction of the servo motor 1 to make the diamond tightly adhere to the silica polishing disk (the silicon polishing disk is also effective). (2) Plasma parameter settings. The plasma power is set to 225W, the argon flow rate is 8000sccm, and the water vapor flow rate is 140sccm. (3) The polishing disk rotation speed is 180-220 rpm, the sample rotation speed is 50-60 rpm, and to ensure that the sample surface is in full contact with the polishing disk, the downward load pressure of the servo motor 1 is set to 8-12N, and the polishing time is 2h. (4) After polishing, atomic force microscopy test showed that the average roughness of the diamond sample surface in the 10×10μm area after composite polishing was 0.07nm, which was better than the 0.22nm of PAP independent polishing result; the removal efficiency of diamond surface material was calculated to be about 800nm / h by weighing, which was better than the 200-400nm / h of PAP independent polishing result.

[0067] In some specific embodiments, argon gas is used as the gas source to generate a gas cluster ion beam. As an inert gas, argon does not chemically react with the diamond surface during cluster ion beam bombardment; surface atom sputtering and amorphization are achieved solely through physical collisions, avoiding the introduction of impurities and ensuring the purity of the amorphous layer. Argon clusters exhibit high stability and readily form size-controllable clusters through processes such as adiabatic expansion and ionization. Furthermore, the moderate mass of argon atoms results in high energy transfer efficiency during bombardment, effectively destroying the sputtered surface layer of diamond. 3 Crystal lattice, promoting sp 2 Amorphous carbon is formed.

[0068] In some specific embodiments, the accelerating voltage of the cluster ion beam on diamond is not less than 15kV. An accelerating voltage of 15kV or higher allows the argon clusters to acquire sufficient energy to penetrate the diamond surface during bombardment, breaking the spline structure. 3 The crystal lattice structure forms an amorphous layer 5-30 nm thick. If the voltage is below 15 kV, the cluster energy is insufficient, and the thickness of the amorphous layer will be less than 5 nm, which cannot provide a continuous reaction interface for subsequent plasma-assisted polishing (PAP), resulting in a sharp drop in polishing efficiency.

[0069] In some specific embodiments, the thickness of the amorphous layer on the diamond surface is 5-10 nm. This thickness range satisfies two core requirements simultaneously: firstly, it provides a sufficient reaction layer for PAP to avoid premature exposure of the diamond matrix and subsequent crystal damage; secondly, it avoids excessively thick amorphous layers that would increase polishing time, ensuring optimal polishing efficiency. An amorphous layer that is too thin (<5 nm) will cause PAP to penetrate rapidly into the matrix, introducing crystal plane steps; an amorphous layer that is too thick (>10 nm) will require prolonged polishing time and reduce efficiency. 5-10 nm is the experimentally verified optimal thickness range. The main target of plasma-assisted polishing is the 5-10 nm thick amorphous diamond layer formed after bombardment by gas cluster ion beams. The amount of diamond removed from the matrix is ​​very small, so appropriate over-polishing will not cause significant damage to the sample surface.

[0070] In some specific embodiments, the irradiation dose of the gas cluster ion beam is adjusted according to the original surface morphology of the diamond until the surface morphology is homogenized. Since the original surface morphology of diamond varies, the irradiation dose needs to be adjusted accordingly: when the original roughness is high, the dose needs to be increased to fully sputter protrusions and fill depressions; when the original surface is relatively smooth, the dose can be reduced to avoid over-processing. This dose adjustment ensures that regardless of the original morphology, GCIB treatment can form a "shallow, homogenized morphology different from the subsurface texture," laying the foundation for uniform removal of PAP and avoiding unstable final polishing results due to differences in the original morphology.

[0071] Figure 7a -d shows a comparison of the polishing effects of different processing methods. Among them, Figure 7a This is the initial state of the sample, representing the best result achievable with current chemical mechanical polishing. Figure 7b This represents a better result that plasma-assisted polishing can achieve; Figure 7c This is the state of the diamond surface after amorphization treatment by a gas cluster ion beam. Figure 7d The result is after gas cluster ion beam amorphization treatment followed by plasma-assisted polishing.

[0072] This application also proposes an ultra-low roughness composite polishing system for diamond, and a schematic diagram of the system modules is attached. Figure 8 As shown, it includes:

[0073] The first polishing unit A1 is used to modify the diamond surface with a gas cluster ion beam, preliminarily treat diamond surface defects, and form an amorphous layer on the diamond surface.

[0074] The second polishing unit A2 is used to remove the amorphous layer on the diamond surface using plasma-assisted polishing technology, creating an atomic-level diamond surface.

[0075] This application proposes an ultra-low roughness composite polishing method and system for diamond, which achieves atomic-level diamond surface creation based on the synergistic effect of gas cluster ion beam and plasma. It can not only effectively eliminate fine scratches on the sample surface and obtain unprecedented low roughness, but also reduce subsurface damage to the sample, resulting in a multiple improvement in both sample surface roughness and processing efficiency. The entire polishing process is green and environmentally friendly, requiring no waste liquid or hazardous waste treatment.

[0076] Those skilled in the art will understand that the modules described above can be implemented using general-purpose computing systems. They can be centralized on a single computing system or distributed across a network of multiple computing systems. Optionally, they can be implemented using computer-executable program code, allowing them to be stored in a storage system for execution by the computing system. Alternatively, they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0077] Note that the above description is merely a preferred embodiment and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of this application, and the scope of this application is determined by the scope of the appended claims.

[0078] The above-disclosed embodiments are merely a few specific examples of this application. However, this application is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A composite polishing method for diamond with ultra-low roughness, characterized in that, include: The diamond surface is modified by gas cluster ion beam to preliminarily treat diamond surface defects and form an amorphous layer on the diamond surface. The amorphous layer on the surface of the diamond is removed by plasma-assisted polishing technology to create an atomic-level diamond surface. The modification of diamond surface by gas cluster ion beam includes: fixing diamond on a work stage and evacuating to a preset vacuum level; generating gas cluster ion beam and using it to scan the sample surface repeatedly; first using small clusters to destroy the existing morphological features of diamond surface, causing the diamond surface layer to become amorphous and generate an amorphous layer; then using large clusters to repair the diamond surface damaged by small clusters, making the thickness of the amorphous layer of diamond more uniform.

2. The ultra-low roughness composite polishing method according to claim 1, characterized in that, The removal of the amorphous layer on the surface of diamond using plasma-assisted polishing technology specifically includes: The amorphous layer of diamond is brought into contact with the polishing pad; using argon and water vapor as gas sources, and in conjunction with the polishing pad, the amorphous carbon atoms formed on the diamond surface by the gas cluster ion beam are removed layer by layer through hydroxylation, dehydration condensation and shearing in the polishing area.

3. The ultra-low roughness composite polishing method according to claim 2, characterized in that, Using argon and water vapor as gas sources, the polishing pad is continuously irradiated with plasma to achieve hydroxylation of the polishing pad surface under the action of plasma.

4. The ultra-low roughness composite polishing method according to claim 2, characterized in that, Under friction, the hydroxylated silicon on the surface of the polishing pad dehydrates and condenses with the diamond surface to form Si-OC bonds, while releasing a water molecule to achieve interfacial bonding; under shearing, the CC bonds break, and the amorphous carbon atoms on the diamond surface are removed.

5. The ultra-low roughness composite polishing method according to claim 1, characterized in that, Argon gas is used as the gas source to generate gas cluster ion beams.

6. The ultra-low roughness composite polishing method according to claim 1, characterized in that, The accelerating voltage of the cluster ion beam on diamond is not less than 15kV.

7. The ultra-low roughness composite polishing method according to claim 1, characterized in that, The thickness of the amorphous layer on the diamond surface is 5-10 nm.

8. The ultra-low roughness composite polishing method according to claim 1, characterized in that, in, Small clusters are concentrated below 1000 atoms / cluster, while large clusters are concentrated between 1000 and 2000 atoms / cluster.

9. The ultra-low roughness composite polishing method according to claim 1, characterized in that, The irradiation dose of the gas cluster ion beam is adjusted according to the original surface morphology of the diamond until the surface morphology is homogenized.

10. A composite polishing system for diamond with ultra-low roughness, characterized in that, include: The first polishing unit is used to modify the diamond surface with a gas cluster ion beam, preliminarily treat diamond surface defects, and form an amorphous layer on the diamond surface. Modifying the diamond surface using a gas cluster ion beam involves: fixing the diamond on a worktable and evacuating it to a preset vacuum level; generating a gas cluster ion beam and using it to scan the sample surface repeatedly; first, using small clusters to destroy the existing morphological features of the diamond surface, causing the diamond surface to become amorphous and generate an amorphous layer; then, using large clusters to repair the diamond surface damaged by the small clusters, making the thickness of the amorphous layer of the diamond more uniform. The second polishing unit is used to remove the amorphous layer on the diamond surface using plasma-assisted polishing technology, creating an atomic-level diamond surface.

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