集群磁流变变间隙动压平坦化加工试验研究

为了提高光电晶片集群磁流变平坦化加工效果,提出集群磁流变变间隙动压平坦化加工方法,探究各工艺参数对加工效果的影响规律。以蓝宝石晶片为研究对象开展了集群磁流变变间隙动压平坦化加工和集群磁流变抛光对比试验,通过检测加工表面粗糙度、材料去除率,观测加工表面形貌、集群磁流变抛光垫中磁链串受动态挤压前后形态变化,研究挤压幅值、工件盘转速、挤压频率以及最小加工间隙等工艺参数对加工效果的影响规律。试验结果表明：集群磁流变平坦化加工在施加工件轴向微幅低频振动后,集群磁流变抛光垫中形成的磁链串更粗壮,不但使其沿工件的径向流动实现磨粒动态更新、促使加工界面内有效磨粒数增多,而且在工件与抛光盘之间的加工间隙产生动态抛光压力、使磨粒与加工表面划擦过程柔和微量化,形成了提高材料去除效率、降低加工表面粗糙度的机制。对于2英寸蓝宝石晶电（1英寸=2.54 cm）集群磁流变变间隙动压平坦化加工与集群磁流变抛光加工效果相比,材料去除率提高19.5%,表面粗糙度降低了42.96%,在挤压振动频率1 Hz、最小加工间隙1 mm、挤压幅值0.5 mm、工件盘转速500 r/min的工艺参数下进行抛光可获得表面粗糙度为Ra0.45 nm的超光滑表面,材料去除率达到3.28 nm/min。证明了集群磁流变变间隙动压平坦化加工方法可行有效。     

磁流变平整加工中平动对平整度的影响

为改善平整度,提出在磁流变平整加工中加入平动。建立工件在磁流变硬化研抛工具上的运动轨迹方程,以该轨迹方程为基础建立了材料去除量的数学模型,对材料去除量分布作了仿真分析,探讨了轨迹规划、平动行程及平动速率等加工参数对平整度的影响;并进行了研抛试验。结果表明:工件沿磁轭的宽度方向单向平动,对平整度的改善最为显著,且平整度随平动行程增加而大幅降低,而平动速率对平整度的影响较弱。利用平动方式的磁流变平整加工方法研抛K9光学玻璃可获得微米级面形精度的超光滑平面。     

在线电解修整磨削与化学机械抛光相结合的蓝宝石基片组合加工技术

通过分析ELID磨削和CMP抛光两种加工技术的原理和特点,充分结合两种技术的优点,对蓝宝石基片进行超光滑纳米级精度的组合加工。从理论上分析和计算了蓝宝石的临界切削深度,以及在不同粒度砂轮下的脆性和延性磨削方式;采用不同粒度的砂轮对蓝宝石基片进行超精密ELID磨削实验,快速地获得高质量的加工表面,同时采用磁流变斑点法对加工面的亚表面损伤进行测量;利用CMP抛光技术对磨削加工后的表面进行光整,以减少磨削时产生的加工缺陷,使工件的表面质量得到进一步改善与提高,最终获得亚纳米级的表面粗糙度。     

单晶蓝宝石基片抛光工艺研究进展

对目前抛光单晶蓝宝石基片的工艺方法,如游离磨料磨削、金刚石砂轮磨削、在线电解修整磨削(ELID)、化学机械抛光(CMP)、固结软磨料抛光、磁流变抛光(MRF)、超声振动辅助磨削的加工原理、方法和特点进行综述。分析了各方法的优势和不足以及最新研究成果存在的关键问题。其中游离磨料磨削、在线电解修整磨削、金刚石砂轮磨削的材料去除速率较高,化学机械抛光是抛光大面积基片的唯一方法,磁流变抛光后的基片表面不存在亚表面损伤。根据单晶蓝宝石基片的应用需求和目前抛光方法的不足,对后续研究的方向进行了预测。     

单晶SiC基片的集群磁流变平面抛光加工

基于集群磁流变效应超光滑平面抛光理论及研制的试验装置,对单晶SiC基片进行了平面抛光试验研究。研究结果表明,金刚石磨料对单晶SiC基片具有较好的抛光效果;加工间隙在1.4mm以内抛光效果较好,30min抛光能使表面粗糙度值减小87%以上;随着加工时间的延长,表面粗糙度越来越小,加工30min时粗糙度减小率达到86.54%,继续延长加工时间,加工表面粗糙度趋向稳定。通过优化工艺参数对直径为50.8mm(2英寸)6H单晶SiC进行了集群磁流变平面抛光,并用原子力显微镜观察了试件加工前后的三维形貌和表面粗糙度,发现经过30min加工,表面粗糙度Ra从72.89nm减小至1.9nm,说明集群磁流变效应超光滑平面抛光用于抛光单晶SiC基片可行有效且效果显著。     

氮化硅陶瓷滚子磁流变、化学与超声复合抛光工艺试验

为实现氮化硅陶瓷滚子抛光的高效、高精度要求,提出磁流变、化学与超声复合的抛光工艺方法。分析复合抛光的加工机理;利用试验机,在不同工艺参数下进行了复合抛光工艺试验,分析各主要工艺参数对抛光材料去除率和滚子表面粗糙度的影响规律,确定出复合抛光的最佳工艺参数。结果表明:复合抛光后陶瓷滚子表面粗糙度Ra由0.3μm减小至0.03μm;在最佳工艺参数下,滚子能够在保持较高材料去除率的同时获得较好的表面质量;材料去除过程主要是磁流变抛光的剪切作用、超声波抛光的冲击作用以及抛光过程中一系列化学反应综合作用的结果。     

集群磁流变效应平面抛光力特性试验研究

集群磁流变平面抛光加工硬脆材料可以高效率获得纳米/亚纳米级表面粗糙度,其中集群磁流变效应抛光垫对加工表面的作用力(抛光力)是材料去除的关键因素,搭建了集群磁流变平面抛光三向测力平台,对模拟的集群磁流变抛光加工过程抛光力(切向力F_t和法向力F_n)进行了系统试验研究。结果表明,2'单晶硅片试验条件下集群磁流变平面抛光切向力Ft最大达到32.25 N、法向力Fn最大达到62.35 N、F_t/F_n值为0.46~0.77;对抛光力影响最大的工艺参数是磁场强度和加工间隙,其次是羰基铁粉与磨料质量分数、磁流变液流量、抛光盘转速,工件摆幅与速率影响最小。集群磁流变平面抛光力大小以及Ft/Fn值随着工件材料硬度的增大而增大,具有低正压力高剪切力特征,有利于提高硬脆材料的超光滑平坦化抛光加工效果。     

蓝宝石衬底基片表面平整加工工艺研究

重点探讨了蓝宝石衬底基片表面平整加工工艺方案,并开展了表面平整加工工艺的实验研究。采用形状测量激光显微系统、接触式测厚仪等,对平整加工工艺各阶段的表面形貌、表面粗糙度Ra、翘曲度、平整度及加工去除量等进行测量和对比分析。结果表明:随着本实验平整加工工艺方案的进行,蓝宝石衬底基片的表面质量不断提高,最终获得了超光滑无损伤镜面表面,化学机械抛光后的衬底表面粗糙度Ra达0.3nm,翘曲度为3.8μm,平整度为1.5μm,符合蓝宝石衬底基片超精密加工的表面质量要求。     

蓝宝石基片的单面研磨工艺研究

为了实现蓝宝石基片的快速平坦化,对蓝宝石基片进行系统的单因素单面研磨试验,研究了磨料种类、磨料粒径、研磨盘转速、研磨压力以及磨料质量分数等研磨工艺参数对蓝宝石基片材料去除率和表面粗糙度的影响规律。试验结果表明:金刚石磨料适合蓝宝石基片的单面研磨;随着磨料粒径的增大,材料去除率逐渐增大,表面越来越粗糙;随着研磨盘转速的增大,材料去除率先增大后减小,表面粗糙度值在20～60 r/min区间变化不大,稳定在Ra 0. 12～Ra 0. 13μm之间,而在60～100 r/min区间波动较大,当研磨盘转速为60 r/min时,材料去除率最大;随着研磨压力的增大,材料去除率逐渐增大,而表面粗糙度值越来越低;随着磨料质量分数的增大,材料去除率先增大后减小,表面粗糙度先增大然后趋于平缓,当磨料质量分数为3 wt%时,材料去除率最大,且表面粗糙度值相对较小;最后通过正交试验优化了工艺参数,在优化的工艺条件下依次选用粒径为W40、W14、W3的金刚石磨料对蓝宝石基片进行粗研、半精研及精研,取得了表面粗糙度为Ra 7. 9 nm的平坦表面。     

考虑磁场的磁流变效应Bingham建模

作为可控智能材料,磁流变体在车辆减振器、发动机悬置等减振领域应用日趋广泛。磁流变效应表现为在磁场作用下,磁流变体的剪切屈服应力将显著增长,从液态转变为半固态。通过考虑磁场条件下的磁流变效应 Bingham建模,研究了不同激励电流和剪切速率条件下磁流变体的轴对称环状间隙流动。同时,研究不同间隙宽度、不同粘度和不同剪切速率条件下,阻尼力随激励电流的变化关系。     

A study of material removal amount of sapphire wafer in application of chemical mechanical polishing with different polishing pads

The study mainly explores the fabrication mechanism for fabricating sapphire wafer substrate, by using chemical mechanical polishing (CMP) method. A slurry containing the abrasive particles of SiO₂ is used to contact with the sapphire substrate polish and to produce chemical reaction for removal of sapphire wafer substrate when CMP method is used. The study observes the changes of the removal amount of sapphire wafer substrate when the pattern-free polishing pad and hole-pattern polishing pad are used under different down forces, polishing velocities, abrasive particle sizes and slurry concentrations. Employing regression analysis theory, the study makes improvement of the equation of material removal rate (MRR) to be the material removal height per 30 minutes (MRRh), and develops a compensation parameter C_rv of the error caused by the volume concentration of slurry. The results of experimental analysis show that under a certain down force, if the polishing velocity is greater, the material removal amount will be greater. Generally speaking, the material removal amount of hole-pattern polishing pad is greater than that of pattern-free polishing pad. As to the relationship between abrasive particle size and slurry concentration, when particle size is smaller, the volume concentration of slurry will be higher, and the number of abrasives for polishing wafer will be greater. As a result, a better material removal depth can be acquired. Through the above analytical results, considerable help is offered to the polishing of sapphire wafer.     

Preparation of La-doped colloidal SiO2 composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of the key elements in CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel La-doped colloidal SiO₂ composite abrasives were prepared by seed-induced growth method. The CMP performance of the La-doped colloidal SiO₂ composite abrasives on sapphire substrate were investigated using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the La-doped colloidal SiO₂ composite abrasives achieve lower surface roughness, higher material removal rate than that of pure colloidal SiO₂ abrasive under the same testing conditions. Furthermore, the acting mechanism of the La-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between La-doped colloidal SiO₂ abrasive and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removal rate.     

磁流变变间隙动压平坦化加工力特性研究

磁流变变间隙动压平坦化加工利用工件的轴向低频振动使磁流变液产生挤压强化效应,可以有效提高加工效果并使光电晶片快速获得纳米级表面粗糙度。通过旋转式测力仪试验研究不同变间隙参数对磁流变变间隙动压平坦化加工过程中抛光正压力的影响规律,结果表明,在工件轴向低频振动作用下,抛光正压力形成脉冲正值和负值周期性的动态变化过程;将工件轴向低频振动过程分解为下压过程与拉升过程,下压速度和拉升速度对动态抛光力有不同的响应特性;随着最小加工间隙的减小抛光正压力会急剧增大;设置最小加工间隙停留时间观察抛光正压力变化,可以发现在工件最小加工间隙停留期间抛光力从峰值逐渐衰减并趋于平稳;挤压振动幅值对抛光正压力影响较小。建立了磁流变变间隙动压平坦化加工材料去除模型,弄清了在动态压力作用下,磨料更新及其附加运动机制,研究了磁流变变间隙动压平坦化加工过程中磨料颗粒对工件表面柔性划擦和微量去除的作用机理,为磁流变变间隙动压平坦化加工的工艺优化提供了理论依据。     

LED蓝宝石衬底抛光表面原子台阶形貌及其周期性研究

LED蓝宝石衬底的表面质量会极大影响到后续外延质量,进而影响到LED器件性能。蓝宝石研磨片经Al2O3磨粒粗抛液、SiO2磨粒精抛液下进行化学机械抛光(CMP),最终表面经原子力显微镜(AFM)所测表面粗糙度达到0.101nm,获得亚纳米级粗糙度超光滑表面,并呈现出原子台阶形貌。同时,通过使用Zygo表面形貌仪、AFM观察蓝宝石从研磨片经Al2O3粗抛液、SiO2精抛液抛光后的表面变化,阐述蓝宝石表面原子台阶形貌的形成原因,提出蓝宝石原子级超光滑表面形成的CMP去除机理。通过控制蓝宝石抛光中的工艺条件,获得a-a型、a-b型两种不同周期规律性的台阶形貌表面,并探讨不同周期规律性台阶形貌的形成机理。     

Effect of Rheological Properties of a Magnetosensitive Tool on the Friction and Wear of Polished Surface

The results of an experimental investigation on determining the characteristics of a magnetorheological polishing composition prevailing in the course of the abrasive removal of the material of a treated surface have been presented. The similar character of relative rate of material removal in the course magnetorheological polishing and the friction force increment in the course of the model experiment depending on the strength of the external magnetic field has been revealed. It has been shown that, in the course of magnetorheological polishing, a determining role in the abrasive material removal is played by viscoplastic properties of the magnetorheological matrix formed in the magnetic field.     

Effect of processing parameters of laser on microstructure and properties of cladding 42CrMo steel

Hard-inert materials such as diamond, silicon carbide, gallium nitride, and sapphire are difficult to obtain from the smooth and damage-free surfaces efficiently required by semiconductor field. Therefore, this study proposed a chemical kinetics model to evaluate the material removal rate of diamond in chemical mechanical polishing process and to investigate the material removal mechanism by examining the surface information with optical microscopy, surface profilometry, and atomic force microscopy as well as X-ray photoelectron spectroscopy. The theoretical and experimental results show that chemical and mechanical synergic effect may promote the diamond oxidation reaction in chemical kinetics. The material removal rate is acceptable when the mechanical activation coefficient is smaller than 0.48. The 2.5 μm B₄C abrasives, the polishing temperature of 50 °C, and the polishing pressure of 266.7 MPa are optimal parameters for diamond polishing with potassium ferrate slurry. It provides the highest material removal rate of 0.055 mg/h, the best surface finish (about Ra 0.5 nm) and surface quality (no surface scratches or pits). It then discusses how mechanical stress may promote the chemical oxidation of oxidant and diamond by forming “C-O,” “C=O,” and “O=C-OH” on diamond surface. The study concludes that chemical kinetics mechanism is effective for the investigation of the synergic effect in chemical mechanical polishing hard-inert materials.     

CMP behavior of alumina/metatitanic acid core–shell abrasives on sapphire substrates

The abrasive is one of the important influencing factors during the chemical mechanical polishing (CMP) process. Although α-alumina is one of the most commonly used sapphire polishing abrasives due to its high hardness, it often results in surface damage. To receive lower surface roughness and high material removal rate, a common approach is to modify the surface of alumina. In this work, a series of alumina/metatitanic acid composite abrasives with core–shell structure were synthesized. The CMP performances of the pure alumina and alumina/metatitanic acid core–shell abrasives on sapphire substrates were investigated after polishing under the same conditions. Experimental results indicate that the alumina/metatitanic acid core–shell abrasives can not only improve the surface quality, but also further enhance the material removal rate. Furthermore, through the X-ray photoelectron spectroscopy test, this study investigated the chemical effect mechanism of the alumina/metatitanic acid core–shell abrasives in sapphire CMP. The results show that solid-state chemical reactions occur between metatitanic acid shell and sapphire surface during CMP process. We also investigated the mechanical friction mechanism through abrasive wear and adhesive wear.     

抛光液pH值等对硬盘玻璃盘基片化学机械抛光的影响

随着硬盘存储密度的增大、转速的提高、磁头飞行高度的降低,对硬盘基板材料及基板表面质量提出了更高的要求。采用纳米SiO2作为抛光磨料,在不同抛光液条件下(pH值、表面活性剂、润滑剂等),对玻璃基片化学机械抛光去除速率和表面质量的变化规律进行了研究,并利用原子力显微镜(AFM)和光学显微镜观察了抛光表面的微观形貌。结果表明,玻璃基片去除速率在酸性、碱性条件下变化趋势相近,即随着pH值的升高,材料去除速率先增大后减小。加入一定量的表面活性剂和润滑剂使得去除速率有一定程度的下降,但是表面粗糙度明显降低,并且表面没有出现颗粒吸附现象。     

Polishing characteristics and mechanism in magnetorheological planarization using a permanent magnetic yoke with translational movement

Translational movement was integrated into a magnetorheological planarization process that uses a permanent magnet yoke with a straight air gap as magnetic source in order to improve surface planarity. The effects of the process conditions, including stroke and velocity of the translational movement, work and excitation gaps and concentration of carbonyl iron particles, on the polishing forces, surface roughness and volumetric removal rate were systematically investigated. The results showed that translational movement had insignificant effect on the polished surface finish, but considerably improved the surface planarity. The surface quality and volumetric removal rate were found to be affected by carbonyl iron particles concentration, and work and excitation gaps. Based on the parametric study, theoretical and empirical models were established for predicting the polishing forces, surface roughness and volumetric removal rate in this magnetorheological process.