Diamond polishing method and diamond polishing system

Abstract

The application relates to a diamond polishing method and a diamond polishing system, wherein the diamond polishing method comprises the following steps: when a current region of a target diamond is in a laser processing process, the graphitization degree of a current processing point in the current region is detected in real time; when it is determined that the graphitization degree reaches a preset degree condition, laser processing of the current processing point is controlled to be ended, laser processing of a next processing point in the current region is controlled to be started, until laser processing of the current region is completed, mechanical polishing of the current region is controlled to be started; after the mechanical polishing of the current region is completed, the polishing quality of the current region is detected, and according to quantitative information of the polishing quality and a preset polishing quality condition, polishing parameters are adjusted, and laser processing and / or mechanical polishing of the current region are carried out based on the adjusted polishing parameters, until the polishing quality of the current region reaches the polishing quality condition. The consistency of the workpiece polishing quality is improved, and the polishing process is controllable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diamond processing, and in particular to a diamond polishing method and a diamond polishing system. BACKGROUND

[0002] As a superhard material (Vickers hardness or Vickers hardness > 40 GPa), diamond has high hardness, excellent thermal conductivity, wide band gap and chemical stability, and therefore has wide application in high-end cutting tools, optical windows, semiconductor heat dissipation and quantum devices. Due to the above-mentioned physical and chemical properties of diamond, especially its characteristics in hardness and chemical inertness, precise and efficient polishing of diamond has become a manufacturing bottleneck restricting the industrial application of high-performance devices.

[0003] At present, the traditional mechanical polishing method is the main technical means for processing diamond. This method mainly relies on mechanical friction and wear between the polishing disc (usually made of cast iron, tungsten carbide or diamond) and the surface of the diamond to achieve material removal. This method has low material removal efficiency, resulting in a long processing period and high production cost. Secondly, during the polishing process, the severe mechanical action can introduce micro-cracks, dislocations and other damage defects in the subsurface layer of the diamond, which can worsen the mechanical, optical and electrical properties of the final device.

[0004] To overcome the limitations of traditional mechanical polishing, laser polishing as a non-contact processing technology has received widespread attention. Among them, laser-assisted polishing (LAP) is considered an effective way to solve the processing problem of superhard materials. The basic principle of LAP is to use a laser beam to locally irradiate the surface of the diamond, causing phase transition (usually graphitization) at the irradiated site, generating a layer of soft graphite, which is then easily removed by mechanical means, thereby improving the polishing efficiency. Although this technology has made some progress, the quality and uniformity of the final graphitized layer are highly dependent on the accuracy of the laser focus position, the stability of the beam energy distribution, and the consistency of the material itself. In actual processing, any slight parameter fluctuation, such as fluctuations in laser pulse energy, focal point drift caused by thermal lens effect of focusing mirrors, and jitter in scanning speed, will result in uneven thickness or varying degrees of graphitization of the generated graphitized layer. This non-uniformity can cause fluctuations in material removal rate during subsequent mechanical polishing processes, which can cause excessive polishing in some areas and damage the underlying diamond substrate, while other areas may form "spot" defects due to residual graphite layer, which can severely deteriorate the surface flatness and surface integrity of the workpiece.

[0005] Therefore, the existing laser-assisted polishing technology still has the problems that the polishing quality consistency of different workpieces and different regions of the same workpiece is poor, and the polishing process is uncontrollable. SUMMARY

[0006] In the embodiments, a diamond polishing method and a diamond polishing system are provided to solve the problems in the related art that the polishing quality consistency of different workpieces and different regions of the same workpiece is poor, and the polishing process is uncontrollable.

[0007] In a first aspect, in the embodiments, a diamond polishing method is provided, including:

[0008] When a current region of the target diamond is in a laser processing process, detecting a graphitization degree of a current processing point in the current region in real time;

[0009] When it is determined that the graphitization degree reaches a preset degree condition, controlling to end laser processing on the current processing point, and controlling to start laser processing on a next processing point of the current region until laser processing on the current region is completed, and controlling to start mechanical polishing on the current region;

[0010] After the mechanical polishing on the current region is completed, detecting a polishing quality of the current region, and according to quantified information of the polishing quality and a preset polishing quality condition, adjusting a polishing parameter and performing laser processing and / or mechanical polishing on the current region based on the adjusted polishing parameter until the polishing quality of the current region reaches the polishing quality condition.

[0011] In some embodiments, the laser processing on the current region includes:

[0012] Controlling a picosecond laser to perform laser processing on the current region.

[0013] In some embodiments, when the current region of the target diamond is in the laser processing process, the graphitization degree of the current processing point in the current region is detected in real time, including:

[0014] When the current region of the target diamond is in the laser processing process, acquiring the real-time collected Raman spectrum information;

[0015] According to the Raman spectrum information, detecting the graphitization degree of the current processing point in the current region.

[0016] In some embodiments, according to the Raman spectrum information, detecting the graphitization degree of the current processing point in the current region includes:

[0017] extracting a corresponding graphite G peak intensity and a diamond D peak intensity from the Raman spectrum information of the current processing point in the current region;

[0018] determining a graphitization degree of the current processing point in the current region according to a ratio of the graphite G peak intensity and the diamond D peak intensity.

[0019] In some embodiments, after completing mechanical polishing of the current region, the polishing quality of the current region is detected, and according to quantitative information of the polishing quality and a preset polishing quality condition, the polishing parameters are adjusted and laser processing and / or mechanical polishing of the current region is performed based on the adjusted polishing parameters until the polishing quality of the current region reaches the polishing quality condition, including:

[0020] After completing mechanical polishing of the current region, the surface roughness and the removal depth of the current region are collected based on a white light interferometer;

[0021] According to the surface roughness, the removal depth and a preset polishing quality condition, the polishing parameters are adjusted.

[0022] In some embodiments, the polishing quality condition includes a preset roughness target value and a preset depth target value; according to the surface roughness, the removal depth and the preset polishing quality condition, the polishing parameters are adjusted, including:

[0023] In the case where the surface roughness is greater than the roughness target value, the mechanical polishing pressure is increased;

[0024] In the case where the removal depth is greater than the depth target value, the laser energy of laser processing is reduced.

[0025] In a second aspect, a diamond polishing system is provided in the embodiments, including a laser generation module, a mechanical polishing module, an online detection module and a central control unit; wherein: the laser generation module, the mechanical polishing module, the online detection module are in communication connection with the central control unit;

[0026] The laser generation module is used for laser processing of each region of a target diamond;

[0027] The mechanical polishing module is used for mechanical polishing of each region of the target diamond;

[0028] The online detection module is used for detecting the graphitization degree of a processing point of each region of the target diamond and the polishing quality of the each region;

[0029] The central control unit is used for executing the diamond polishing method of the first aspect.

[0030] In some embodiments, the online detection module comprises a Raman spectrometer and a white light interferometer; the Raman spectrometer is coaxially integrated with the laser generation module;

[0031] The Raman spectrometer is configured to detect the graphitization degree of the machining point of each region of the target diamond in real time;

[0032] The white light interferometer is configured to detect the polishing quality of each region of the target diamond.

[0033] In some embodiments, the diamond polishing system further comprises a motion platform;

[0034] The central control unit is configured to plan a motion path of the motion platform according to the three-dimensional model of the target diamond;

[0035] The motion platform is configured to carry the laser generation module, the mechanical polishing module and the online detection module to different regions of the target diamond based on the motion path.

[0036] In some embodiments, the laser generation module comprises an ultraviolet picosecond laser.

[0037] Compared with the related art, the diamond polishing method and the diamond polishing system are provided in the embodiments. The diamond polishing method detects the graphitization degree of a current machining point in a current region of a target diamond in real time when the current region is in a laser machining process; controls to end the laser machining of the current machining point and to start the laser machining of a next machining point of the current region when it is determined that the graphitization degree reaches a preset degree, until the laser machining of the current region is completed, and the mechanical polishing of the current region is started; detects the polishing quality of the current region after the mechanical polishing of the current region is completed, and adjusts the polishing parameters according to the quantitative information of the polishing quality and a preset polishing quality condition, and performs the laser machining and / or the mechanical polishing on the current region based on the adjusted polishing parameters until the polishing quality of the current region reaches the polishing quality condition. It can improve the consistency of the workpiece polishing quality and realize the controllability of the polishing process.

[0038] The details of one or more embodiments of the present application are presented in the following drawings and description to make other features, objects and advantages of the present application more apparent. BRIEF DESCRIPTION OF DRAWINGS

[0039] The drawings described herein are intended to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their description serve to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0040] Figure 1 is a hardware structure block diagram of a terminal of a diamond polishing method of an embodiment of the present application;

[0041] Figure 2 is a flow chart of a diamond polishing method of an embodiment of the present application;

[0042] Figure 3 is a structural schematic diagram of a diamond polishing system of an embodiment of the present application;

[0043] Figure 4 is a flow chart of a diamond polishing method of some embodiments of the present application. DETAILED DESCRIPTION

[0044] In order to more clearly understand the objects, technical solutions and advantages of the present application, the present application will be described and explained in detail below in conjunction with the accompanying drawings and embodiments.

[0045] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the general meaning understood by a person with ordinary skill in the art to which the present application belongs. In the present application, "one", "a", "an", "the", "these" and similar words do not represent a quantitative limitation, and they can be singular or plural. In the present application, the terms "include", "contain", "have" and any variants thereof have the purpose of covering non-exclusive inclusion; for example, a process, method and system, product or device containing a series of steps or modules (units) are not limited to the listed steps or modules (units), but can include steps or modules (units) not listed, or can include other steps or modules (units) inherent to the process, method, product or device. In the present application, the terms "connected", "connected", "coupled" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. In the present application, "multiple" means two or more. The association between the associated objects described by "and / or" can represent three relationships, for example, "A and / or B" can represent three cases: A exists alone, A and B exist together, and B exists alone. In general, the character " / " represents an "or" relationship between the objects associated before and after. In the present application, the terms "first", "second", "third" and the like are only used to distinguish similar objects, and do not represent a specific order of the objects.

[0046] The method embodiments provided in the present embodiment can be executed in a terminal, a computer or a similar computing device. For example, the method embodiments are executed on a terminal, Figure 1 is a hardware structure block diagram of a terminal of a diamond polishing method of an embodiment of the present application. As shown in Figure 1 , the terminal can include one or more (CPU) 1001, ROM 1002, and RAM 1003. The terminal can also include a host computer, a computer, or a similar computing device. Figure 1The terminal shown in FIG. 1 includes only one processor 102 and a memory 104 for storing data, wherein the processor 102 can include, but is not limited to, a processing device such as a microprocessor MCU or a programmable logic device FPGA. The terminal can also include a transmission device 106 for communication function and an input / output device 108. Those skilled in the art can understand that Figure 1 The structure shown in FIG. 1 is only schematic and does not limit the structure of the terminal. For example, the terminal can include more or fewer components than those shown in FIG. 1, or have a different configuration from that shown in FIG. 1. Figure 1 The terminal shown in FIG. 1 includes only one processor 102 and a memory 104 for storing data, wherein the processor 102 can include, but is not limited to, a processing device such as a microprocessor MCU or a programmable logic device FPGA. The terminal can also include a transmission device 106 for communication function and an input / output device 108. Those skilled in the art can understand that Figure 1 The structure shown in FIG. 1 is only schematic and does not limit the structure of the terminal. For example, the terminal can include more or fewer components than those shown in FIG. 1, or have a different configuration from that shown in FIG. 1.

[0047] The memory 104 can be used to store computer programs, such as software programs of application software and modules, such as the computer program corresponding to the diamond polishing method in the present embodiment. The processor 102 can execute various functional applications and data processing by running the computer programs stored in the memory 104, i.e., implement the method described above. The memory 104 can include a high-speed random access memory and can also include a non-volatile memory, such as one or more magnetic storage devices, flash memories, or other non-volatile solid-state memories. In some examples, the memory 104 can further include a memory remotely arranged with respect to the processor 102, and these remote memories can be connected to the terminal through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0048] The transmission device 106 is used to receive or send data via a network. The network includes a wireless network provided by a communication provider of the terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, NIC) which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (Radio Frequency, RF) module which is used to communicate with the Internet in a wireless manner.

[0049] In the present embodiment, a diamond polishing method is provided, Figure 2 A flowchart of the diamond polishing method of the present embodiment is shown in FIG. 2, which includes the following steps: Figure 2

[0050] In step S210, the degree of graphitization of a current processing point in a current region of a target diamond is detected in real time when the current region is in a laser processing process.

[0051] ​The surface of the target diamond to be polished can be divided into several regions in advance, for example, into a plurality of adjacent preset square millimeters (mm) regions (for example, the surface of a diamond wafer is divided into a plurality of adjacent 2 mm x 2 mm regions), and each pre-planned processing point in each region is sequentially subjected to laser processing. The order of polishing each region can be set according to the pre-planned path. When laser processing is performed on the current region, the laser can be driven to scan from the starting point of the current region, while the graphitization degree of the processing point on which the laser currently acts in the current region is detected in real time.

[0052] The laser used for laser processing of the target diamond can be any laser suitable for providing laser assistance for polishing of the diamond. In particular, in some embodiments, it can be a picosecond laser. The current processing point described above can be the point of action of the laser spot. The graphitization degree described above is used to represent the degree of formation of a graphite layer of the current processing point in the current region of the target diamond under laser processing, and can be quantified as the relative content of the graphite phase and the diamond phase of the current processing point. In some embodiments, the spectrum information of the current processing point can be collected by a Raman probe, and then the ratio (I G / I D ) of the graphite G peak (~1580 cm -1 ) intensity (I D ) and the diamond D peak (~1332 cm -1 ) intensity (I G ) of the current processing point can be calculated from the spectrum information as a quantitative indicator of the graphitization degree. In other embodiments, high-resolution spectra of electrons on the 1s orbital of carbon atoms can also be collected by X-ray photoelectron spectroscopy, and the progress of graphitization can be determined by the area ratio of sp3 carbon bonds and sp2 carbon bonds; or the graphitization degree can also be determined by calculating the broadening of the half-height width (FWHM) or the peak shift of the diamond D peak in Raman measurement; or the absolute intensity (I D ) of the Raman diamond D peak can be calculated to determine the graphitization degree.

[0053] Step S220, in the case where the graphitization degree reaches the preset degree condition, the laser processing of the current processing point is controlled to end, and the laser processing of the next processing point in the current region is controlled to start, until the laser processing of the current region is completed, and the mechanical polishing of the current region is controlled to start.

[0054] When the graphitization degree detected in real time continuously rises and reaches a preset quantitative threshold, it is determined that the graphitization degree reaches the preset degree condition. For example, if the graphitization degree is the ratio (I G / I D) represents, when this ratio starts rising from 0 to a preset ratio threshold, which can be 0.8 for example, the degree of graphitization reaches the preset degree condition. At this time, the laser is immediately instructed to stop laser processing at the current processing point and move to the next processing point. The next processing point is taken as the new current processing point, and laser processing is performed on the new current processing point while the corresponding degree of graphitization is detected in real time. When the degree of graphitization reaches the preset degree condition, the laser processing of the current processing point is ended, and the movement to the new next processing point is continued. In this way, the laser processing of all processing points in the current region is completed.

[0055] For example, the target diamond is divided into several regions, including region one, region two, etc. First, the laser is driven to scan from the starting point in region one, and at the same time, the degree of graphitization corresponding to the laser spot is detected in real time. During the laser scanning process, the degree of graphitization will continuously change and rise. When the degree of graphitization of the current processing point in region one reaches the preset degree condition, the laser is moved to the next processing point in region one for laser processing, and the laser processing of all processing points in region one is completed.

[0056] This step can construct a phase transition degree (graphitization degree) control feedback loop for the laser processing process of the diamond material, realize real-time perception and control of the degree of graphitization of the diamond, and ensure that each processing point in a region can reach a consistent degree of graphitization, thereby forming a uniform and consistent thickness (for example, 150 nanometers (nm)) graphitic layer.

[0057] Step S230, after completing the mechanical polishing of the current region, detecting the polishing quality of the current region, and adjusting the polishing parameters according to the quantitative information of the polishing quality and the preset polishing quality condition, and based on the adjusted polishing parameters, the current region is processed by laser and / or mechanical polishing until the polishing quality of the current region reaches the polishing quality condition.

[0058] The polishing quality condition can be whether the surface roughness of the current region meets a preset roughness target value or whether the removal depth meets a preset depth target value. The mechanical polishing process can specifically be: using a numerical control polishing tool, performing mechanical polishing on the current region under motor control according to a set polishing pressure, to remove the graphite layer. After the mechanical polishing of the current region is completed, the current region can be scanned to measure the polishing quality of the current region. The polishing quality can be quantified by the surface roughness (Ra) and the average removal depth (Δz). Wherein, after the mechanical polishing is completed, the white light interferometer probe can be controlled to automatically move to the center of the current region, to perform a rapid scan (for example, a 5-second scan) on the current region, to measure the surface roughness (Ra) and the average removal depth (Δz) of the current region. Then, if the surface roughness of the current region is still higher than the preset roughness target value (for example, the current region Ra=5nm, Δz is 108nm), the polishing pressure can be increased by a small amplitude (the laser parameters remain unchanged to improve the removal efficiency), and the mechanical polishing of the current region is continued, so that the surface roughness (Ra) of the current region is equal to the preset roughness target value, thereby realizing adaptive parameter adjustment of the polishing process. Correspondingly, if the removal depth of the current region is less than the preset depth target value, the laser energy can be increased by a small amplitude to continue laser processing and mechanical polishing of the current region until the removal depth is equal to the depth target value.

[0059] In this step, according to the rules of the adaptive algorithm, the polishing parameters are adjusted according to the detected polishing quality, and the current region is further polished until the polishing quality of the current region meets the polishing quality condition. The adjusted polishing parameters can be used for the polishing of the next region. For example, if the surface roughness and the removal depth of the current region meet the standards, the current latest laser parameters and mechanical polishing parameters can be maintained for polishing the subsequent regions until the entire workpiece is polished.

[0060] For example, after the laser processing of region one is completed, the mechanical polishing tool automatically moves above region one to perform mechanical polishing on region one to remove the graphite layer. After the polishing is completed, the probe of the white light interferometer automatically moves to the center of region one to scan region one to measure the surface roughness and the average removal depth of region one to determine the polishing quality of region one. According to the polishing quality detection result, the polishing parameters such as the polishing pressure and the laser energy are adjusted, and then the laser processing and / or mechanical polishing of region one is performed according to the adjusted polishing parameters until the polishing quality of region one meets the polishing quality condition. Then the laser is moved to region two, and the above steps S210 to S230 are repeatedly executed. In this way, the polishing of each region of the target diamond is completed.

[0061] In this step, a feedback loop is realized for controlling the entire machining process by detecting the polishing quality of the target diamond and adjusting the polishing parameters based on the feedback of the polishing quality, so that the polishing quality of the diamond surface can be timely fed back and controlled, and the polishing quality is controllable.

[0062] In the related art, the polishing process cannot perceive the difference of the material itself and the fluctuation of the laser energy, resulting in uneven thickness of the graphitized layer or different degrees of graphitization. Such unevenness can cause fluctuation of material removal rate in the subsequent mechanical polishing process, which can cause excessive polishing of some areas and damage the underlying diamond substrate, while some other areas form "spot" defects due to the residual graphite layer, and finally seriously deteriorate the surface flatness and surface integrity of the workpiece. In addition, the related art also lacks real-time feedback, and cannot dynamically adjust the polishing process, making it difficult to ensure the consistency of the surface quality of each workpiece and each area of the workpiece in batch production. Therefore, the related art has the problems of uncontrollable polishing process and poor surface quality consistency.

[0063] To this end, the embodiment constructs a double feedback loop through steps S210 to S230, including a feedback loop for controlling the laser machining process based on the phase change degree (graphitization degree) of the diamond material, and a feedback loop for controlling the entire machining process by adjusting the polishing parameters based on the feedback of the polishing quality. On the one hand, the judgment based on time / experience in the related art is changed to a judgment based on physical state, in order to solve the problem that the traditional open-loop machining cannot perceive the difference of the material itself (such as impurities, crystal direction) and the slight fluctuation of the laser energy. Specifically, for difficult-to-machine points (such as hard grains), more laser pulses may be needed to achieve the required degree of graphitization, so the laser can stay longer; for easy-to-machine points (such as defects), the threshold can be reached quickly, so the laser can be moved away faster to prevent overburning. In this way, each machining point on the diamond surface can be machined to a consistent graphitization state, providing a highly consistent pretreatment layer for subsequent mechanical polishing and ensuring laser machining consistency; on the other hand, the polishing parameters can be adjusted adaptively according to the polishing quality after polishing. Through the combination of the two feedback loops, a unique full-closed-loop intelligent machining control system based on perception-decision-execution is formed, thereby solving the problem of control loss in the diamond polishing process, realizing the controllability of the polishing quality, and improving the consistency of the polishing quality.

[0064] Therefore, through the above steps S210 to S230, when the current region of the target diamond is in the laser processing process, the graphitization degree of the current processing point in the current region is detected in real time; in the case where it is determined that the graphitization degree reaches the preset degree condition, the laser processing of the current processing point is controlled to end, and the laser processing of the next processing point of the current region is controlled to start, until the laser processing of the current region is completed, the mechanical polishing of the current region is controlled to start; after the mechanical polishing of the current region is completed, the polishing quality of the current region is detected, and the polishing parameters are adjusted according to the quantitative information of the polishing quality and the preset polishing quality condition, and the laser processing and / or mechanical polishing of the current region are performed based on the adjusted polishing parameters, until the polishing quality of the current region reaches the polishing quality condition. It can improve the consistency of the workpiece polishing quality and realize the controllability of the polishing process.

[0065] In one embodiment, the laser processing of the current region can include: controlling the picosecond laser to perform laser processing on the current region.

[0066] Specifically, in the present embodiment, a picosecond laser can be used to perform laser processing on the diamond. In particular, a picosecond laser with a high repetition frequency, for example, a repetition frequency range of 100 kilohertz (kHz) to 2 megahertz (MHz), and a high average power (>20 watts (W)) can be selected. In addition, the wavelength of the picosecond laser can be selected as ultraviolet (355 nm) or green light (532 nm).

[0067] Considering the femtosecond laser used in the related art, although the pulse width is shorter, the amplification system used is more complex and the average power is lower, resulting in higher polishing cost and lower efficiency, which is difficult to meet the needs of large-scale industrial applications and causes economic and efficiency problems. Specifically, the cost of the femtosecond laser used is relatively high. In addition, due to the low average power and material removal rate of the femtosecond laser, although the single-point processing efficiency is higher than that of the traditional mechanical polishing, for industrial scenarios that require polishing of a large area (such as CVD diamond free-standing sheet and large-area window), the overall throughput of the femtosecond laser is still insufficient, which is difficult to meet the needs of mass production.

[0068] Thus, from the perspective of laser processing efficiency, the embodiment uses a picosecond laser instead of a femtosecond laser. The high repetition frequency (100 kHz to 2 MHz) of the picosecond laser supports more pulses acting on the material per unit time, thereby increasing the speed of laser scanning. The high average power (>20 W) of the picosecond laser can ensure that there is still sufficient energy density to initiate diamond phase transition at a higher scanning speed. In this way, based on the combination of high repetition frequency and high average power, the material removal rate (MMR) can be improved by orders of magnitude. In addition, the picosecond laser can maintain the cold processing characteristics of a pulse width <15 picoseconds (ps), which is much lower than the electron-phonon coupling time ~10 ps.

[0069] Additionally, from the perspective of laser processing cost, the absorption rate of diamond for ultraviolet light will be much higher than that for infrared light. Thus, the 355 nm wavelength photon energy emitted by the picosecond laser is high (~3.5 eV), which is closer to the band gap of diamond (~5.5 eV), and can achieve efficient energy deposition mainly through nonlinear effects such as two-photon absorption, rather than relying on thermal accumulation. This means that the energy utilization rate of the picosecond laser used in the laser processing of the embodiment will be higher, and the same graphitization effect can be achieved with lower pulse energy, reducing the limit requirements on the performance of the laser, thereby making the picosecond laser more cost-effective than the expensive femtosecond laser, and reducing the processing cost.

[0070] In one embodiment, while the current region of the target diamond is in the laser processing process, the graphitization degree of the current processing point in the current region is detected in real time, which can specifically include:

[0071] While the current region of the target diamond is in the laser processing process, the real-time collected Raman spectrum information is obtained; and the graphitization degree of the current processing point in the current region is detected according to the Raman spectrum information.

[0072] The Raman spectrum information is a molecular vibration spectrum, and different chemical bonds and crystal structures will produce unique characteristic peaks. Among them, the diamond D peak corresponds to the vibration of sp 3 carbon bond, and the graphite G peak corresponds to the vibration of sp 2 carbon bond. Therefore, based on the Raman spectrum information, diamond and graphite can be distinguished. Optionally, a coaxial integrated design can be used for the laser head of the laser and the Raman probe, and a beam splitter is used to combine the laser processing light path (incident) and the Raman signal collection light path (exit) into one, so that the laser processing point and the Raman spectrum detection point are coincided.

[0073] While the laser head performs laser processing on the current processing point in the current area, the Raman probe acquires the Raman spectral information of the current processing point in real time, calculates the real-time graphitization degree of the current processing point based on the Raman spectrum, and terminates the laser processing on the current processing point when the graphitization degree reaches a preset condition. Therefore, this embodiment realizes real-time monitoring of the graphitization degree based on Raman spectroscopy, improves the accuracy of graphitization degree monitoring, and thus enables timely and accurate control of the laser processing progress.

[0074] Specifically, in some embodiments, detecting the degree of graphitization at the current processing point in the current region based on Raman spectral information may include:

[0075] From the Raman spectral information of the current processing point in the current region, extract the corresponding graphite G peak intensity and diamond D peak intensity; determine the degree of graphitization of the current processing point in the current region based on the ratio of the graphite G peak intensity to the diamond D peak intensity.

[0076] After acquiring the Raman spectrum, the graphite G peak (~1580 cm⁻¹) can be calculated from the Raman spectrum. -1 The intensity of (I) G ) and the diamond D peak (~1332cm) -1 The intensity of (I) D The ratio of (I) G / I D When the ratio exceeds a preset ratio threshold, such as 0.8, graphitization is confirmed to be complete.

[0077] Specifically, the diamond D peak (~1332cm) -1 ) and graphite G peak (~1580cm) -1 ) correspond to the characteristic vibrations of sp³ and sp² carbon bonds, respectively, and the intensity ratio (I G / I D This method can quantitatively characterize the relative content of graphite and diamond phases within a micro-region. The ratio (I0.05) is... G / I D An increase in the ratio indicates graphitization is underway, while reaching a stable value indicates the phase transition is complete. Optionally, for specific optical systems and laser parameters, a ratio threshold can be determined experimentally, for example, setting the optimal ratio threshold to 0.8. When (I G / I D When the intensity ratio exceeds this threshold, it is confirmed that a graphite layer of suitable thickness has been formed at the current processing point, and the laser operation needs to be terminated immediately to achieve precise laser processing control. This avoids both insufficient graphitization at the processing point and over-processing damage to the diamond substrate. Therefore, the intensity ratio (IG) of the graphite G peak to the diamond D peak is used to determine the optimal laser processing intensity. G / I DAs a core judgment index, the accuracy and convenience of the graphitization degree judgment can be improved.

[0078] The calculation of the above (I G / I D ) can be completed by a pre-set software algorithm. In the specific calculation of the above ratio (I G / I D ), first, the original collected Raman spectrum information is pre-processed to remove the fluorescence background and make the characteristic peaks stand out from the noise background. Then, a digital filter can be used to smooth the Raman spectrum information while preserving the original peak shape, removing high-frequency noise. Then, the pure characteristic peaks are subjected to peak area quantitative analysis. The integral ranges of the two characteristic peaks, graphite G peak and diamond D peak, are determined, for example, the integral range D of the diamond D peak is 1310cm -1 to 1350cm -1 , and the integral range G of the graphite G peak is 1560cm -1 to 1600cm -1 . Then, the area is obtained by software integration, and the calculated area represents the intensity of each characteristic peak. The ratio (I G / I D ) of the intensity is calculated, and then the ratio (I G / I D ) is compared with the pre-set ratio threshold to determine the graphitization degree.

[0079] Therefore, in the present embodiment, the graphitization degree of the diamond material is fed back by the Raman spectrometer to control the laser processing process. The specific control standard is that if the ratio (I G / I D ) of the current processing point is less than the pre-set ratio threshold, the laser processes the current processing point; otherwise, the laser processing of the current processing point is stopped. After completing the laser processing of all processing points in the current area, mechanical polishing processing is performed. The present embodiment can realize real-time feedback and control of the laser processing process, so that each processing point is processed to a consistent graphitization state, realizing controllability of the laser processing process, and providing a relatively consistent pretreatment layer for subsequent mechanical polishing.

[0080] In addition, in one embodiment, after completing the mechanical polishing of the current area, the polishing quality of the current area is detected, and based on the quantitative information of the polishing quality and the pre-set polishing quality condition, the polishing parameters are adjusted and the current area is processed by laser and / or mechanical polishing based on the adjusted polishing parameters until the polishing quality of the current area meets the polishing quality condition, which can specifically include:

[0081] After the mechanical polishing of the current region is completed, the surface roughness and the removal depth of the current region are collected based on the white light interferometer; and the polishing parameters are adjusted according to the surface roughness, the removal depth and the preset polishing quality condition.

[0082] Specifically, during the mechanical polishing, the entire machining process can be controlled based on the material surface topography. Specifically, the surface roughness (Ra) and the removal depth (Δz) of the current region of the diamond can be fed back by the white light interferometer to control the entire machining result.

[0083] Specifically, the current region after the mechanical polishing can be scanned by using the white light interferometer to obtain three-dimensional topography data. Then, the roughness component is extracted from the three-dimensional topography data by digital filtering. Finally, the arithmetic average deviation (Sa) of the roughness component is calculated to obtain the surface roughness. The removal depth is calculated by measuring the three-dimensional topography data of the same region before and after polishing by the white light interferometer, then accurately matching each point in the three-dimensional images before and after polishing by an algorithm, and finally performing subtraction operation to obtain the removal depth.

[0084] Since the purpose of polishing the diamond is to obtain an ultra-smooth surface and a high-quality diamond with a certain thickness. The surface roughness (Ra) is a recognized surface smoothness quantitative indicator in the industry, which directly determines the optical performance (such as transmittance, scattering), tribological performance, and contact thermal resistance as a semiconductor heat dissipation substrate, etc. of the diamond workpiece. Therefore, the surface roughness is the gold standard for measuring whether the machining quality meets the standard. The surface roughness is fed back to the mechanical polishing module to control the polishing pressure, and the polishing effect is improved by adjusting the pressure or polishing time. In addition, considering that the thickness of the diamond workpiece also has a significant impact on the application performance of the diamond, the machining precision and safety are reflected by the removal depth to prevent over-processing of the laser-assisted polishing from damaging the diamond body. Therefore, the removal depth can be fed back to the laser generation module to control the laser energy or scanning time to improve graphitization.

[0085] In one embodiment, the polishing quality condition includes a preset roughness target value and a preset depth target value; and the polishing parameters are adjusted according to the surface roughness, the removal depth and the preset polishing quality condition, which can specifically include:

[0086] In the case where the surface roughness is greater than the roughness target value, the mechanical polishing pressure is increased; and in the case where the removal depth is greater than the depth target value, the laser energy of the laser machining is reduced.

[0087] In this embodiment, the entire processing is controlled based on the polishing quality detection results of surface roughness and removal depth. The control criteria are as follows: if surface roughness (Ra) > target roughness value, the mechanical polishing pressure is increased; if removal depth > target depth value, the laser energy is reduced. This allows for adaptive adjustment of polishing parameters, improving polishing effect and efficiency.

[0088] In this embodiment, a diamond polishing system is also provided. Figure 3 This is a schematic diagram of the diamond polishing system 30 in this embodiment, as shown below. Figure 3 As shown, the diamond polishing system 30 may specifically include: a laser generating module 31, a mechanical polishing module 32, an online detection module 33, and a central control unit 34; wherein: the laser generating module 31, the mechanical polishing module 32, and the online detection module 33 are all communicatively connected to the central control unit 34; the laser generating module 31 is used to perform laser processing on various areas of the target diamond; the mechanical polishing module 32 is used to perform mechanical polishing on various areas of the target diamond; the online detection module 33 is used to detect the degree of graphitization of the processing points in various areas of the target diamond, as well as the polishing quality of each area; the central control unit 34 is used to execute the diamond polishing method provided in any of the above embodiments.

[0089] Specifically, in this embodiment, the laser generation module 31, the mechanical polishing module 32, and the online detection module 33 are all integrated on the same platform and uniformly scheduled and controlled by the central control unit 34. In this way, the central control unit 34 can ensure the precise timing matching of all control commands, thereby avoiding communication delays and coordination problems caused by discrete systems. This central control unit 34 can be an electronic device with data processing, computing, and communication capabilities. Furthermore, exemplarily, the laser generation module 31 can be an ultraviolet picosecond laser of model "Edge Wave PX100-355-GF," and the laser parameters can be set to wavelength 355nm, average power 30W, repetition frequency 500kHz (adjustable), and pulse width 10ps. The mechanical polishing module 32 can use a CNC polishing unit, where the polishing tool can be a 5mm diameter polyurethane polishing pad, and the polishing fluid can be a diamond suspension (particle size ~100nm). The polishing pressure of the mechanical polishing module 32 can be controlled by a servo motor. The polishing pressure range can be from 0 N / m² to 20 N / m², and the resolution can be 0.1 N / m².

[0090] The central control unit 34 can be deployed with a pre-written computer program, which can implement a signal processing algorithm and an adaptive control algorithm (i.e., the adaptive logic for adjusting the polishing parameters according to the polishing quality in the above embodiment), so as to implement the diamond polishing method provided in the above embodiment. The central control unit 34 can issue control instructions and communicate information to the laser generation module 31, the mechanical polishing module 32 and the online detection module 33 by executing the diamond polishing method, so as to complete the polishing process of the target diamond.

[0091] The degree condition and the polishing quality condition of the graphitization degree can be set according to the volume, the initial surface roughness and the polishing target of the target diamond. For example, for a polycrystalline CVD diamond wafer with a diameter of 4 inches (about 101.6 mm) and a thickness of 500 μm, the initial surface roughness Sa>500 nm; the polishing target of the target diamond is to polish the upper surface of the target diamond to a surface roughness Ra<1 nm, and the total thickness variation (TTV) <1 μm is required, and sub-surface damage needs to be avoided to ensure excellent thermal conductivity of the target diamond. Based on this, the polishing quality condition can be set as: the surface roughness Ra≤1 nm after polishing, and the single removal depth is 100 nm; the degree condition can be set as: the intensity ratio (I G / I D ) of the graphite G peak and the diamond D peak ≥0.8. In addition, the initial values of other process parameters can also be set: the laser parameters of the laser generation module 31 are set as: single pulse energy 60 microjoules (μJ), laser scanning speed 100 mm / s, and scanning line spacing 5 μm; the polishing parameters are set as: polishing pressure 4.0 N / m2, polishing disc rotation speed 150 revolutions per minute (rpm), and polishing liquid flow rate 10 ml / min.

[0092] The diamond polishing system 30 provided in the embodiment can realize the polishing processing loop of the intelligent control with double feedback, which can improve the consistency of the workpiece polishing quality, realize the controllability of the polishing process, and be suitable for the high-efficiency and high-precision polishing of the CVD diamond heat sink.

[0093] It should be noted that the above polishing targets and the settings of various polishing parameters are only examples, and other parameters can be selected according to the needs of actual application scenarios by those skilled in the art, and the above examples do not constitute a specific limitation on the diamond polishing method of the present embodiment.

[0094] In one of the embodiments, the online detection module 33 includes a Raman spectrometer and a white light interferometer; the Raman spectrometer is coaxially integrated with the laser generation module; the Raman spectrometer is used to detect the graphitization degree of the machining point of each region of the target diamond in real time; and the white light interferometer is used to detect the polishing quality of each region of the target diamond.

[0095] The Raman spectrometer can use a confocal Raman probe coaxially integrated with the laser head of the laser generation module 31. Exemplarily, the Raman spectral range can be 1000 cm -1 to 2000 cm -1 , the spectral acquisition time can be 10 ms, and the spot diameter can be about 1 μm. The white light interferometer can use a commercially available WLI probe arranged vertically, such as model "Keyence SI-F010", the measurement range can be 100 μm, and the longitudinal resolution can be 0.1 nm for point measurement. The Raman spectrometer detects the graphitization degree of the current machining point in the laser machining process in real time, and sends the detection result to the central control unit 34 to control the laser machining process; the white light interferometer is used to detect the polishing quality after mechanical polishing of each region, and sends the detection result to the central control unit 34 to adjust the polishing parameters and re-machining and / or mechanical polishing of the regions that do not meet the polishing target. Therefore, the present embodiment can realize the double controllability of the laser machining process and the mechanical polishing process, and improve the consistency of the polishing quality of different surfaces of the diamond and different diamond workpieces. In addition, the synchronization and coaxiality of laser machining and Raman monitoring can eliminate the error caused by measurement lag and realize real-time control.

[0096] In addition, in one of the embodiments, the diamond polishing system 30 further includes a motion platform 35; the central control unit 34 is used to plan a motion path of the motion platform 35 according to a three-dimensional model of the target diamond; and the motion platform 35 is used to carry the laser generation module 31, the mechanical polishing module 32 and the online detection module 33 to different regions of the target diamond based on the motion path.

[0097] The target diamond to be polished can be pre-constructed into a three-dimensional model, and then a motion path is pre-planned based on the three-dimensional model. The motion path is used to provide a machining path for surface machining of the diamond, and can adapt to polishing of a complex curved surface, thereby improving the adaptability of diamond machining. In particular, in some embodiments, the motion platform can be expanded to a five-axis system to realize normal machining. Thus, in some embodiments, the motion platform 35 can be a five-axis air floating motion platform, and the positioning accuracy can be better than ±1 μm. The motion platform 35 can carry the laser generating module 31 to perform laser machining on the target diamond, carry the mechanical polishing module 32 to perform mechanical polishing on the target diamond, and carry the online detection module 33 to detect the graphitization degree and polishing quality of the target diamond.

[0098] Therefore, the embodiment can improve the adaptability of polishing different curved surfaces of the diamond, and reduce the difficulty of diamond polishing.

[0099] In addition, in one embodiment, the laser generating module 31 includes an ultraviolet picosecond laser. The absorption rate of the diamond to ultraviolet light is much higher than that to infrared light, and the photon energy of 355 nm wavelength emitted by the picosecond laser is high (~3.5 eV), which is closer to the band gap of the diamond (~5.5 eV), and can realize efficient energy deposition mainly through nonlinear effects such as two-photon absorption, rather than relying on thermal accumulation. Therefore, using the ultraviolet picosecond laser for laser machining can improve the energy utilization rate, reduce the limit requirements on the performance of the laser, reduce the machining cost, and at the same time improve the laser machining efficiency.

[0100] Figure 4 is a flowchart of a diamond polishing method of some embodiments, as shown in Figure 4 The diamond polishing method includes the following steps:

[0101] In step S401, while the ultraviolet picosecond laser performs laser machining on a current region of the target diamond, a Raman spectrometer is used to detect the graphitization degree of a current machining point in the current region in real time; wherein the graphitization degree is the intensity ratio of the above-mentioned graphite G peak to the diamond D peak.

[0102] In step S402, when it is determined that the graphitization degree reaches a preset degree, the ultraviolet picosecond laser is controlled to end the laser machining on the current machining point, and to start the laser machining on a next machining point of the current region, until the laser machining on the current region is completed.

[0103] In step S403, the mechanical polishing module is controlled to perform mechanical polishing on the current region.

[0104] Step S404, after completing the mechanical polishing of the current region, the surface roughness and removal depth of the current region are detected by the white light interferometer, and when the surface roughness is greater than the roughness target value, the mechanical polishing pressure is increased, and the current region is mechanically polished again to make the surface roughness less than or equal to the roughness target value; and when the removal depth is greater than the depth target value, the laser energy of the laser processing is reduced.

[0105] Step S405, taking the next region as a new current region, repeating steps S401 to S404.

[0106] The above steps S401 to S405 use picosecond laser to scan the diamond surface to graphitize it; simultaneously, the degree of graphitization is monitored in real time by using confocal Raman spectroscopy, which can ensure the consistency of laser processing. After completing the laser processing, mechanical polishing is performed and the surface quality is measured online using a white light interferometer. Finally, the polishing parameters are adjusted adaptively according to the measurement results. The picosecond laser source with higher processing efficiency and lower cost is combined with online Raman and white light interferometric monitoring technology to form a unique closed-loop intelligent control system, effectively solving the problems of low efficiency, high cost and poor quality consistency in related technologies, and realizing the polishing of diamond with higher efficiency, higher precision and higher intelligence.

[0107] From the perspective of data quantization, the ultraviolet picosecond laser with an average power > 20W and a repetition frequency in the range of 100kHz to 2MHz is used in the embodiment, which can reduce the cost by 40% to 50% and increase the processing efficiency by 5 times compared with femtosecond laser; the online Raman spectroscopy real-time detection is introduced, which can improve the workpiece uniformity by 10 times compared with the open-loop feedback-free processing in related technologies; by detecting the polishing quality, a second feedback loop is formed, which can make the subsurface defect density less than 10² / cm² (the traditional polishing technology is usually around 10³ / cm²); by integrating multiple modules and controlling them by a central control unit, the system response time can be reduced to below 100ms; by using a five-axis air floating motion platform and combining with the intelligent closed-loop control mechanism, the polishing quality consistency of different regions can be guaranteed, so that the polishing of large-size diamond workpieces with a size of 4 inches or more can be realized.

[0108] The following table shows the effect data comparison of the diamond polishing method (processing workpiece size ≥ 4 inches) of the embodiment and the diamond polishing method (processing workpiece size is medium and small size, for example, 2 inches to 3 inches) in related technologies:

[0109] Table 1

[0110]

[0111] Among them, from the material removal rate after polishing, the surface accuracy, the surface roughness, the uniformity in the workpiece, the etching surface defect density and the like, the diamond polishing method of the embodiment can achieve better performance than the related art.

[0112] It should be noted that the specific examples in the embodiment can refer to the examples described in the above embodiments and optional implementation manners, which will not be described herein.

[0113] It should be understood that the specific embodiments described herein are intended to explain the application, but not to limit it. According to the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0114] It should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data authorized by the user or authorized by all parties.

[0115] Obviously, the drawings are only some examples or embodiments of the present application, and those of ordinary skill in the art can also apply the present application to other similar situations according to the drawings without creative labor. In addition, it can be understood that although the work done in the development process may be complex and long, some design, manufacture or production changes according to the technical content disclosed in the present application are only routine technical means for those of ordinary skill in the art, and should not be regarded as insufficient disclosure of the present application.

[0116] The term "embodiment" in the present application means that the specific features, structures or characteristics described in combination with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean independence or alternative to other embodiments. Those of ordinary skill in the art can clearly or implicitly understand that the embodiments described in the present application can be combined with other embodiments without conflict.

[0117] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of patent protection. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A diamond polishing method, characterized in that, include: While the target diamond is being processed by laser, real-time Raman spectral information is acquired. Based on the Raman spectral information, the degree of graphitization at the current processing point in the current region is detected; the degree of graphitization is used to characterize the extent to which a graphite layer is formed at the current processing point in the current region of the target diamond under laser processing; When the degree of graphitization reaches a preset level, control the laser processing of the current processing point to end, and control the laser processing of the next processing point in the current area to begin, until the laser processing of the current area is completed, and control the mechanical polishing of the current area to begin. After mechanical polishing of the current area is completed, the polishing quality of the current area is detected, and the polishing parameters are adjusted according to the quantitative information of the polishing quality and the preset polishing quality conditions. Based on the adjusted polishing parameters, the current area is subjected to laser processing and / or mechanical polishing until the polishing quality of the current area reaches the polishing quality conditions.

2. The diamond polishing method according to claim 1, characterized in that, Laser processing of the current area includes: Control the picosecond laser to perform laser processing on the current area.

3. The diamond polishing method according to claim 1, characterized in that, Based on the Raman spectral information, the degree of graphitization at the current processing point in the current region is detected, including: Extract the corresponding graphite G peak intensity and diamond D peak intensity from the Raman spectral information of the current processing point in the current region; The degree of graphitization at the current processing point in the current region is determined based on the ratio of the graphite G peak intensity to the diamond D peak intensity.

4. The diamond polishing method according to claim 1, characterized in that, After completing the mechanical polishing of the current area, the polishing quality of the current area is detected. Based on the quantitative information of the polishing quality and the preset polishing quality conditions, the polishing parameters are adjusted, and the current area is subjected to laser processing and / or mechanical polishing based on the adjusted polishing parameters until the polishing quality of the current area reaches the polishing quality conditions, including: After mechanical polishing of the current area is completed, the surface roughness and removal depth of the current area are collected using a white light interferometer. The polishing parameters are adjusted based on the surface roughness, the removal depth, and the preset polishing quality conditions.

5. The diamond polishing method according to claim 4, characterized in that, The polishing quality conditions include preset roughness target values ​​and preset depth target values; The polishing parameters are adjusted based on the surface roughness, the removal depth, and preset polishing quality conditions, including: If the surface roughness is greater than the target roughness value, increase the mechanical polishing pressure; If the removal depth is greater than the target depth value, the laser energy for laser processing is reduced.

6. A diamond polishing system, characterized in that, It includes a laser generating module, a mechanical polishing module, an online detection module, and a central control unit; wherein: the laser generating module, the mechanical polishing module, and the online detection module are all communicatively connected to the central control unit; The laser generating module is used to perform laser processing on various areas of the target diamond; The mechanical polishing module is used to mechanically polish various areas of the target diamond. The online detection module is used to detect the degree of graphitization of the processing points in each region of the target diamond, as well as the polishing quality of each region; The central control unit is used to perform the diamond polishing method according to any one of claims 1 to 5.

7. The diamond polishing system according to claim 6, characterized in that, The online detection module includes a Raman spectrometer and a white light interferometer; the Raman spectrometer is coaxially integrated with the laser generation module. The Raman spectrometer is used to detect the degree of graphitization at processing points in various regions of the target diamond in real time. The white light interferometer is used to detect the polishing quality of each area of ​​the target diamond.

8. The diamond polishing system according to claim 6, characterized in that, The diamond polishing system also includes a motion platform; The central control unit is used to plan the motion path of the motion platform based on the three-dimensional model of the target diamond. The motion platform is used to carry the laser generating module, the mechanical polishing module, and the online detection module to different areas of the target diamond based on the motion path.

9. The diamond polishing system according to claim 6, characterized in that, The laser generating module includes an ultraviolet picosecond laser.

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