Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fie...Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fields, such as high speed and high temperature areojet engines, precision machine tools and chemical engineer machines. Silicon nitride ceramics is a kind of brittle and hard material that is difficult to machining. In the traditional finishing process of silicon nitride balls, balls are lapped by expensive diamond abrasive. The machining is inefficiency and the cost is high, but also lots of pits, scratch subsurface micro crazes and dislocations will be caused on the surface of the balls, the performance of the ball bearings would be declined seriously. In these year, a kind of new technology known as chemical mechanical polishing is introduced in the ultraprecision machining process of ceramic balls. In this technology, abrasives such as ZrO 2, CeO 2 whose hardness is close to or lower than the work material (Si 3N 4) are used to polishing the balls. In special slurry, these abrasives can chemo-mechanically react with the work material and environment (air or water) to generate softer material (SiO 2). And the resultants will be removed easily at 0.1 nm level. So the surface defects can be minimized, very smooth surface (Ra=4 nm) and fine sphericity (0.15~0.25 μm ) can be obtained, and the machining efficiency is also improved. The action mechanism of the abrasives in the chemical mechanical polishing process in finishing of silicon nitride ball will be introduced in this paper.展开更多
Effects of abrasive concentration on material removal rate CMRR) and surtace quality m the chemical mecnamcal polishing (CMP) of light-emitting diode sapphire substrates are investigated. Experimental results show ...Effects of abrasive concentration on material removal rate CMRR) and surtace quality m the chemical mecnamcal polishing (CMP) of light-emitting diode sapphire substrates are investigated. Experimental results show that the MRR increases linearly with the abrasive concentration, while the rms roughness decreases with the increasing abrasive concentration. In addition, the in situ coefficient of friction (COF) is also conducted during the sapphire polishing process. The results present that COF increases sharply with the abrasive concentration up to 20 wt% and then shows a slight decrease from 20wt% to 40wt%. Temperature is a product of the friction force that is proportional to COF, which is an indicator for the mechanism of the sapphire CMP.展开更多
In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing (CMP) of rigid disk substrate in the two s...In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing (CMP) of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness (Ra) and the average waviness (Wa) of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy (AFM) analysis shows that the final polished surfaces are ultra-smooth without micro-defects.展开更多
The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silico...The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies.The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP)were also studied.It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum(1.306 μA/cm2)at pH 10.5 when the material removal rate(MRR)comes to the fastest value.The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration.There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5.The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.展开更多
The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a sp...The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a special root mean square(RMS)value is constructed by multivariate Weierstrass–Mandelbrot(W–M)function and the rubbing process during that the chemical mechanical polishing(CMP)process of diamond is mimicked utilizing the reactive force field molecular dynamics(ReaxFF MD)simulation.It is found that the contact area A/A0 is positively related with the load,and the friction force F depends on the number of interfacial bridge bonds.Increasing the surface roughness will increase the friction force and friction coefficient.The model with low roughness and high lubrication has less friction force,and the presence of polishing liquid molecules can decrease the friction force and friction coefficient.The RMS value and the degree of damage show a functional relationship with the applied load and lubrication,i.e.,the RMS value decreases more under larger load and higher lubrication,and the diamond substrate occurs severer damage under larger load and lower lubrication.This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.展开更多
The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishi...The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.展开更多
Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing...Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO_(2)abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—visible diffuse reflectance spectroscopy(UV-Vis DRS),and X-ray photoelectron spectroscopy(XPS).The CeO_(2)abrasives were obtained under different atmospheres(Air,Ar,and Ar/H_(2)).With the enhancement of the reducing atmosphere,the morphology of the abrasives transforms from spherical to octahedral,while more oxygen vacancies and Ce^(3+)are generated on the surface of CeO_(2)abrasives.The CMP experiments show that the MRRs of the CeO_(2)-Air,CeO_(2)-Ar,and CeO_(2)-Ar/H_(2)abrasives on SiO_(2)substrates are 337.60,578.74,and 691.28 nm/min,respectively.Moreover,as confirmed by atomic force microscopy(AFM),the substrate surfaces exhibit low roughness(20.5 nm)after being polished using all of the prepared samples.Especially,the MRR of CeO_(2)-Ar/H_(2)abrasives is increased by 104.76%compared with CeO_(2)-air abrasives.The improved CMP performance is attributed to the increased Ce^(3+)concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive-substrate interface.展开更多
Chemical mechanical polishing (CMP) was used to polish Lithium triborate (LiB3O5 or LBO) crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate (MRR) and surface ...Chemical mechanical polishing (CMP) was used to polish Lithium triborate (LiB3O5 or LBO) crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate (MRR) and surface roughness are considered as criteria for the optimization. The polishing pressure, the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal. Experiment results indicate that for MRR the polishing pressure is the most significant polishing parameter followed by table velocity; while for the surface roughness, the abrasive concentration is the most important one. For high MRR in CMP of LBO ctystal the optimal conditions are: pressure 620 g/cm^2, concentration 5.0 wt pct, and velocity 60 r/min, respectively. For the best surface roughness the optimal conditions are: pressure 416 g/cm^2, concentration 5.0 wt pct, and velocity 40 r/min, respectively. The contributions of individual parameters for MRR and surface roughness were obtained.展开更多
Chemical Mechanical Polishing(CMP)工艺过程中产生大量运行数据,存在数据量庞大、数据种类复杂多样等特点。而且现有数据分析方法单一,造成数据资源浪费,限制研究人员对运行情况的掌握和优化。针对这些情况提出一种数据可视化分析系统...Chemical Mechanical Polishing(CMP)工艺过程中产生大量运行数据,存在数据量庞大、数据种类复杂多样等特点。而且现有数据分析方法单一,造成数据资源浪费,限制研究人员对运行情况的掌握和优化。针对这些情况提出一种数据可视化分析系统,对运行数据进行实时存储,提出4种可视化视图,针对不同数据分析需求,通过对比分析、关联分析和用户交互,可有效帮助研究人员探索工艺过程中影响工艺效果的原因,优化工艺参数,提升生产效率。展开更多
As an important optical component in laser system,silicon mirror surface is required to have micron-level flatness and subnanometer-level roughness.The research concentrates on how to improve roughness as far as possi...As an important optical component in laser system,silicon mirror surface is required to have micron-level flatness and subnanometer-level roughness.The research concentrates on how to improve roughness as far as possible while maintaining flatness of silicon mirror surface during chemical mechanical polishing(CMP)process.A polishing edge effect model is established to explain the reason of flatness deterioration,and a roughness theoretical model is set up to get the limit of perfect surface roughness.Based on the models above,a polishing device is designed to maintain the surface flatness,and the optimized polishing process parameters are obtained by orthogonal tests to get a near-perfect surface roughness.Finally the maintenance of flatness and the improvement of roughness can be achieved at the same time in one step of CMP process.This work can be a guide for silicon mirror manufacture to improve optical reflection performance significantly.展开更多
文摘Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fields, such as high speed and high temperature areojet engines, precision machine tools and chemical engineer machines. Silicon nitride ceramics is a kind of brittle and hard material that is difficult to machining. In the traditional finishing process of silicon nitride balls, balls are lapped by expensive diamond abrasive. The machining is inefficiency and the cost is high, but also lots of pits, scratch subsurface micro crazes and dislocations will be caused on the surface of the balls, the performance of the ball bearings would be declined seriously. In these year, a kind of new technology known as chemical mechanical polishing is introduced in the ultraprecision machining process of ceramic balls. In this technology, abrasives such as ZrO 2, CeO 2 whose hardness is close to or lower than the work material (Si 3N 4) are used to polishing the balls. In special slurry, these abrasives can chemo-mechanically react with the work material and environment (air or water) to generate softer material (SiO 2). And the resultants will be removed easily at 0.1 nm level. So the surface defects can be minimized, very smooth surface (Ra=4 nm) and fine sphericity (0.15~0.25 μm ) can be obtained, and the machining efficiency is also improved. The action mechanism of the abrasives in the chemical mechanical polishing process in finishing of silicon nitride ball will be introduced in this paper.
基金Supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period under Grant No 2011ZX02704the National Natural Science Foundation of China under Grant No 51205387the Science and Technology Commission of Shanghai under Grant Nos llnm0500300 and 14XD1425300
文摘Effects of abrasive concentration on material removal rate CMRR) and surtace quality m the chemical mecnamcal polishing (CMP) of light-emitting diode sapphire substrates are investigated. Experimental results show that the MRR increases linearly with the abrasive concentration, while the rms roughness decreases with the increasing abrasive concentration. In addition, the in situ coefficient of friction (COF) is also conducted during the sapphire polishing process. The results present that COF increases sharply with the abrasive concentration up to 20 wt% and then shows a slight decrease from 20wt% to 40wt%. Temperature is a product of the friction force that is proportional to COF, which is an indicator for the mechanism of the sapphire CMP.
基金This project is supported by National Basic Research Program of China (973 Program, N0.2003CB716201)National Natural Science Foundation of China (No.50575131)Science Foundation of Shanghai Municipal Commission of Science and Technology, China(No.0452nm013).
文摘In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing (CMP) of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness (Ra) and the average waviness (Wa) of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy (AFM) analysis shows that the final polished surfaces are ultra-smooth without micro-defects.
基金Project(2005DFBA028)supported by the International Cooperation of Science and Technology Ministry of ChinaProject(LA07023)supported by the National Undergraduate Innovative Experiment Plan
文摘The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies.The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP)were also studied.It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum(1.306 μA/cm2)at pH 10.5 when the material removal rate(MRR)comes to the fastest value.The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration.There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5.The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.
基金the National Key R&D Program of China(2022YFB3404304)the National Natural Science Foundation of China(No.5217052183).
文摘The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a special root mean square(RMS)value is constructed by multivariate Weierstrass–Mandelbrot(W–M)function and the rubbing process during that the chemical mechanical polishing(CMP)process of diamond is mimicked utilizing the reactive force field molecular dynamics(ReaxFF MD)simulation.It is found that the contact area A/A0 is positively related with the load,and the friction force F depends on the number of interfacial bridge bonds.Increasing the surface roughness will increase the friction force and friction coefficient.The model with low roughness and high lubrication has less friction force,and the presence of polishing liquid molecules can decrease the friction force and friction coefficient.The RMS value and the degree of damage show a functional relationship with the applied load and lubrication,i.e.,the RMS value decreases more under larger load and higher lubrication,and the diamond substrate occurs severer damage under larger load and lower lubrication.This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.
基金supported by the National Natural Science Foundation of China(No.51975343)Science and Technology Major Project of Inner Mongolia Autonomous Region in China(No.2021ZD0028)+1 种基金Shanghai Technical Service Center for Advanced Ceramics Structure Design and Precision Manufacturing(No.20DZ2294000)the China Scholarship Council.
文摘The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.
基金the National Natural Science Foundation of China(51905324)the Scientific Research Program Funded by Shaanxi Provincial Education Department(20JK0545)the Doctoral Scientific Research Startup Foundation of Shaanxi University of Science and Technology(2018BJ-14)。
文摘Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO_(2)abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—visible diffuse reflectance spectroscopy(UV-Vis DRS),and X-ray photoelectron spectroscopy(XPS).The CeO_(2)abrasives were obtained under different atmospheres(Air,Ar,and Ar/H_(2)).With the enhancement of the reducing atmosphere,the morphology of the abrasives transforms from spherical to octahedral,while more oxygen vacancies and Ce^(3+)are generated on the surface of CeO_(2)abrasives.The CMP experiments show that the MRRs of the CeO_(2)-Air,CeO_(2)-Ar,and CeO_(2)-Ar/H_(2)abrasives on SiO_(2)substrates are 337.60,578.74,and 691.28 nm/min,respectively.Moreover,as confirmed by atomic force microscopy(AFM),the substrate surfaces exhibit low roughness(20.5 nm)after being polished using all of the prepared samples.Especially,the MRR of CeO_(2)-Ar/H_(2)abrasives is increased by 104.76%compared with CeO_(2)-air abrasives.The improved CMP performance is attributed to the increased Ce^(3+)concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive-substrate interface.
基金supported by the National Natural Science Foundation of China(No.50675104 and 50905086)Six High Talent Fund of Jiangsu Province(No.06-D-024)Talent Fund of NUAA(No.S0782-052)
文摘Chemical mechanical polishing (CMP) was used to polish Lithium triborate (LiB3O5 or LBO) crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate (MRR) and surface roughness are considered as criteria for the optimization. The polishing pressure, the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal. Experiment results indicate that for MRR the polishing pressure is the most significant polishing parameter followed by table velocity; while for the surface roughness, the abrasive concentration is the most important one. For high MRR in CMP of LBO ctystal the optimal conditions are: pressure 620 g/cm^2, concentration 5.0 wt pct, and velocity 60 r/min, respectively. For the best surface roughness the optimal conditions are: pressure 416 g/cm^2, concentration 5.0 wt pct, and velocity 40 r/min, respectively. The contributions of individual parameters for MRR and surface roughness were obtained.
基金supported by the National Basic Research Program of China(Grant No.2015CB057203)the National Natural Science Foundation of China(Grant No.91323302)
文摘As an important optical component in laser system,silicon mirror surface is required to have micron-level flatness and subnanometer-level roughness.The research concentrates on how to improve roughness as far as possible while maintaining flatness of silicon mirror surface during chemical mechanical polishing(CMP)process.A polishing edge effect model is established to explain the reason of flatness deterioration,and a roughness theoretical model is set up to get the limit of perfect surface roughness.Based on the models above,a polishing device is designed to maintain the surface flatness,and the optimized polishing process parameters are obtained by orthogonal tests to get a near-perfect surface roughness.Finally the maintenance of flatness and the improvement of roughness can be achieved at the same time in one step of CMP process.This work can be a guide for silicon mirror manufacture to improve optical reflection performance significantly.