蓝宝石衬底化学机械抛光的机理研究

利用磨料为SiO2的碱性抛光液对蓝宝石衬底材料进行了化学机械抛光，并对蓝宝石衬底化学机械抛光（简称CMP）的机理进行了深入的研究，指出了蓝宝石CMP的主要的动力学过程，并详细分析了影响各动力学过程的诸要素。结果表明，蓝宝石衬底的CMP过程是一个复杂的多相反应过程，是化学作用与机械作用互相加强和促进的过程，影响它的各要素间既相互促进，又相互制约。     

用于蓝宝石材料加工的新型超精密抛光技术及复合抛光技术研究进展

超精密抛光是一种降低表面粗糙度,获得高表面质量和表面完整性的加工技术.蓝宝石作为典型的难加工硬脆材料,传统抛光方法存在表面会产生崩碎、划痕等损伤,表面质量难以得到保证以及加工效率低等问题.本文综述了应用于蓝宝石材料的磁流变抛光、水合抛光、化学机械抛光和激光抛光等技术的原理与特点及其研究现状,并分析了各抛光技术的优缺点;从表面质量、磨料与磨液、效率与成本等方面对各抛光技术进行比较;介绍了复合抛光技术在蓝宝石材料中的应用;最后重点展望了蓝宝石材料超精密抛光技术的下一步研究.     

用于蓝宝石材料加工的新型超精密抛光技术及复合抛光技术研究进展

超精密抛光是一种降低表面粗糙度,获得高表面质量和表面完整性的加工技术。蓝宝石作为典型的难加工硬脆材料,传统抛光方法存在表面会产生崩碎、划痕等损伤,表面质量难以得到保证以及加工效率低等问题。本文综述了应用于蓝宝石材料的磁流变抛光、水合抛光、化学机械抛光和激光抛光等技术的原理与特点及其研究现状,并分析了各抛光技术的优缺点;从表面质量、磨料与磨液、效率与成本等方面对各抛光技术进行比较;介绍了复合抛光技术在蓝宝石材料中的应用;最后重点展望了蓝宝石材料超精密抛光技术的下一步研究。     

精细雾化抛光氮化硅陶瓷的抛光液配制参数优化

采用超声精细雾化施液抛光对氮化硅陶瓷基体进行抛光,研究了不同的pH值、磨料浓度以及氧化剂含量对氮化硅陶瓷基体抛光的材料去除率的影响,优化了pH值、磨料浓度及氧化剂含量,并与传统的化学机械抛光进行了对比。结果表明:当二氧化硅磨粒质量分数为5wt%,氧化剂含量为1wt%,pH值为8时,材料去除率MRR为108.24nm/min且表面粗糙度Ra为3.39nm。在相同的抛光参数下,传统化学机械抛光的材料去除率MRR为125nm/min,表面粗糙度Ra为2.13nm;精细雾化抛光的材料去除率及表面粗糙度与传统抛光接近,但精细雾化抛光所用抛光液用量仅为传统抛光所用抛光液用量的1/9。     

蓝宝石衬底的化学机械抛光工艺研究

系统地分析了蓝宝石抛光工艺过程的性能参数,通过大量实验总结出了其影响因素并提出了优化方案。结果表明,采用粒径为40nm、低分散度的SiO2溶胶磨料并配合以适当参数进行抛光,可以获得良好的表面状态和较高的去除速率,能够有效提高蓝宝石表面的性能及加工效率。     

Material removal in grinding sapphire wafers with brazed–diamond pellet plates

Grinding is an important abrasive machining process in many manufacturing chains. In order to improve the material removal in the grinding of sapphire wafers, this study presents two brazed-diamond pellet (BDP) plates developed with different BDP surface textures, i.e., a non-grooved BDP plate and a grooved BDP plate. Their performances were tested in the coarse grinding of sapphire wafers. The surface topography, surface roughness, material removal rate (MRR) were comprehensively investigated. The experimental results show that sapphire is removed in its brittle mode. However, the grooved BDP plate can produce lower surface roughness under a higher MRR. The improvement in surface roughness is mainly due to the better coolant flowability and chip removal facilitated by the grooves. The higher MRR is partly due to the increased pressure in the sapphire-plate contact zone. It is found that the grooved BDP plate can increase MRR by about 45.7%.     

Macroscopic and microscopic investigation on chemical mechanical polishing of sapphire wafer

Sapphire (alpha-Al2O3) is an important ceramic material that is widely used in substrate material for electronics. We investigate the chemical reaction layer on a sapphire wafer using X-ray photoelectron microscopy (XPS) and atomic force microscopy (AFM). The frictional characteristics of sapphire chemical mechanical polishing (CMP) was studied using in-situ friction force monitoring system. From XPS analysis and AFM experiment, a chemically-reacted layer was verified on the sapphire surface through a chemical reaction between the sapphire and chemicals in a slurry. During sapphire CMP, the friction force mainly depended on the applied pressure. The material removal efficiency per unit friction energy in sapphire CMP was 6.18 nm/kJ.     

Influence of Processing Techniques on the Surface Microstructure of V<Subscript>85</Subscript>Ni<Subscript>15</Subscript> Membrane Alloy

Vanadium-based alloys with a BCC structure are considered to be an alternative to palladium alloys for hydrogen purification. Since the performance of membranes is influenced by not only their bulk characteristics but also their surface condition, we have investigated the effect of different surface preparation techniques (abrasive grinding and polishing, electrolytic polishing, and ion etching) on the surface microstructure of V₈₅Ni₁₅ membrane alloy using X-ray photoelectron spectroscopy. After electrolytic polishing and ion etching, we observed an increase in the percentages of vanadium and nickel metals in the surface layer of the alloy in comparison with its state after abrasive polishing. Such changes are expected to be favorable for an increase in the rate of hydrogen dissociation and recombination on the surface of the membrane material, eventually improving hydrogen transport efficiency.     

CVD金刚石膜高效超精密抛光技术

CVD金刚石膜作为光学透射窗口和新一代计算机芯片的材料,其表面必须得到高质量抛光,但是现存方法难以满足既高效又超精密的加工要求.本文提出机械抛光与化学机械抛光相结合的方法.首先,采用固结金刚石磨料抛光盘和游离金刚石磨料两种机械抛光方法对CVD金刚石膜进行粗加工,然后采用化学机械抛光的方法对CVD金刚石膜进行精加工.结果表明,采用游离磨料抛光时材料去除率远比固结磨料高,表面粗糙度最低达到42.2 nm.化学机械抛光方法在CVD金刚石膜的超精密抛光中表现出较大的优势,CVD金刚石膜的表面粗糙度为4.551 nm.     

Mechanism of high selectivity in ceria based shallow trench isolation chemical mechanical polishing slurries

dl-aspartic acid as a removal rate selectivity enhancer for shallow trench isolation chemical mechanical polishing slurries was investigated over a pH range. The effects of downward pressure, rotational speed of the turntable as well as the ceria abrasive loading were also examined. The selectivity is very sensitive to changes in the pressure but not to changes in the rotational speed. Select experiments were also conducted with other types of abrasives with and without the additive. A comparison of the pK_a values of the amino acid with the variation of the selectivity with pH indicates that the form of amino acid plays a vital role in determining the polishing behavior and the selectivity. Further, the results corroborate the hypothesis that chemically active sites on the abrasive may be blocked by certain forms of the amino acids, leading to changes in the selectivity.     

一种提高光学零件沥青盘修形抛光稳定性的新方法

材料去除的时不变性是计算机控制光学修形的基础.为了提升沥青盘数控抛光的材料去除稳定性,采用抛光液喷淋添加方式进行光学零件沥青盘数控抛光.从沥青盘的力学特性出发,根据沥青材料针入度与温度的规律确定抛光液喷淋添加方式能够有效控制加工区域的温度,从而显著提高了抛光稳定性和大幅度延长了沥青盘使用寿命.同时,提出了最佳喷淋温度的选取策略来指导加工,研究结果对提升光学零件沥青盘抛光收敛效率和抑制误差具有重要意义.     

Synthesis of Zn-doped colloidal SiO<Subscript>2</Subscript> abrasives and their applications in sapphire chemical mechanical polishing slurry

In this paper, Zn-doped colloidal SiO₂ composite abrasives were synthesized by seed-induced growth method and used to polish sapphire substrates. Time of flight secondary ion mass spectroscopy and scanning electron microscopy analyses show that element zinc has been doped into colloidal SiO₂, and the prepared Zn-doped colloidal SiO₂ composite abrasives are all ideal spherical and have good dispersibility. Chemical mechanical polishing (CMP) performances of Zn-doped colloidal SiO₂ composite abrasives on sapphire substrates were investigated using UNIPOL-1502 CMP equipment. Experimental results show that, under the same testing conditions, the surfaces of sapphire polished by Zn-doped colloidal SiO₂ composite abrasives exhibit lower root mean square roughness and higher material removal rate (MRR) than those of pure colloidal SiO₂ abrasive. Especially, the composite abrasive shows the maximum MRR at 1.0 wt% Zn(OH)₂ content. Furthermore, the acting mechanism of Zn-doped colloidal SiO₂ composite abrasives in sapphire CMP was analyzed by X-ray photoelectron spectroscopy, and analytical results show that element zinc in composite abrasives can react with sapphire substrate to form aluminum zincate (Al₂ZnO₄) during CMP, which promotes the chemical effect in CMP and leads to the improvement of MRR.     

Polishing techniques for optical grade sapphire

Abstract

Sapphire is an important crystal that finds application in a number of high technology optical applications. For optical applications a high transparency is essential. Several defects/imperfections are present in the surface layer of ‘as grown’ sapphire crystal. These defects/imperfections can be removed by polishing the sapphire crystals. The high hardness and strength of sapphire necessitates the use of high machining and polishing forces. Conventional polishing techniques are unable to meet this requirement. Specialised techniques have been developed to obtain optical flatness and low scatter surface finish. These techniques are reviewed and compared in this article.     

Surface integrity and removal mechanism in grinding sapphire wafers with novel vitrified bond diamond plates

In order to improve machining efficiency of sapphire wafer machining using the conventional loose abrasive process, fixed-abrasive diamond plates are investigated in this study for sapphire wafer grinding. Four vitrified bond diamond plates of different grain sizes (40?µm, 20?µm, 7?µm, and 2.5?µm) are developed and evaluated for grinding performance including surface roughness, surface topography, surface and subsurface damage, and material removal rate (MRR) of sapphire wafers. The material removal mechanisms, wafer surface finish, and quality of the diamond plates are also compared and discussed. The experiment results demonstrate that the surface material is removed in brittle mode when sapphire wafers are ground by the diamond plates with a grain size of 40?µm and 20?µm, and in ductile mode when that are ground by the diamond plates of grain sizes of 7?µm and 2.5?µm. The highest MRR value of 145.7?µm/min is acquired with the diamond plate with an abrasive size of 40?µm and the lowest surface roughness values of 3.5?nm in Ra is achieved with the 2.5?µm size.     

Improving efficiency of finishing natural stone using diamond-polymer fiber tools

The paper describes methods for improving efficiency of finishing natural stone using diamond-polymer fiber tools during a preparatory operation prior to polishing. The authors have identified the parameters that have an influence on the production of calibrated fibers. Prototype tools have been prepared and tested. A tool design has been put forward which ensures uniform wear of the abrasive layer. Quality of the machined surface has been analyzed.     

Effect of abrasives on the glossiness and reflectance of anodized aluminum alloys

Blasting can eliminate or change the surface texture of as-rolled aluminum alloy by indentation to roughen the alloy’s surface. We investigated the effects of the blasting conditions on the glossiness and reflectance of Al1050-H16 and Al5052-H32 alloys in this study. As-rolled sheets were blasted at various pressures, and then removed for sequential cleaning, chemical polishing, and anodizing steps. After each step the samples were measured by micro-TRI-gloss meter and spectrophotometer to compare the effects produced by the abrasive powders and processing variables. Polyhedral alumina and round iron powders were used as the blasting media. The glossiness (Gs(60°)) decreased as the root mean square roughness (Rq) increased, regardless of the shape of the abrasive powders. The abrasives powders could cause wear and/or fracturing during the blasting process as well as fine debris, which could become embedded in the blasted surface. When an aluminum alloy was blasted with iron powders, the glossiness value after alkaline etching and chemical polishing was greater than that after being blasted with alumina; while the anodized Al5052-H32 alloy’s surface became more yellowish in color.     

Nanoindentation hardness of particles used in magnetorheological finishing (MRF)

Knowledge of the hardness of abrasive particles that are used in polishing is a key to the fundamental understanding of the mechanisms of material removal. The magnetorheological-finishing process uses both magnetic and nonmagnetic abrasive particles during polishing. The nanohardnesses of the micrometer-sized magnetic carbonyl iron and nonmagnetic abrasive particles have been measured successfully by use of novel, to our knowledge, sample-preparation and nanoindentation techniques. Some of the results reported compare favorably with existing microhardness data found in the literature, whereas other results are new.     

Removal rate model for magnetorheological finishing of glass

Magnetorheological finishing (MRF) is a deterministic subaperture polishing process. The process uses a magnetorheological (MR) fluid that consists of micrometer-sized, spherical, magnetic carbonyl iron (CI) particles, nonmagnetic polishing abrasives, water, and stabilizers. Material removal occurs when the CI and nonmagnetic polishing abrasives shear material off the surface being polished. We introduce a new MRF material removal rate model for glass. This model contains terms for the near surface mechanical properties of glass, drag force, polishing abrasive size and concentration, chemical durability of the glass, MR fluid pH, and the glass composition. We introduce quantitative chemical predictors for the first time, to the best of our knowledge, into an MRF removal rate model. We validate individual terms in our model separately and then combine all of the terms to show the whole MRF material removal model compared with experimental data. All of our experimental data were obtained using nanodiamond MR fluids and a set of six optical glasses.     

Abrasive Flow Polishing of Micro Bores

Micro bore finishing for metal and ceramic materials has been a challenge in the manufacturing industry. Unfortunately, little is understood about how to polish a micro bore and how to assess its inner wall quality because it is difficult to access the micro bore for either polishing or measurement. This article reports on a feasibility study of the abrasive flow polishing of micro bores of 260 ~ 500-µm diameters and 25 ~ 50 length/diameter ratios for both metal and ceramic materials. An abrasive flow polishing machine was designed and built with turbulent flow characteristics. Polishing of steel S45C bores of 400- and 500-µm diameters, stainless steel 304 bores of 500-µm diameter, and zirconia bores of 260-µm diameter was conducted. Surface roughness and topography of the polished inner walls of micro bores were characterized using profilometry and optical interferometry from the three-dimensional point of view. Significant reduction in surface roughness of the micro bore inner walls has been made in the polishing processes. The results indicate that it is feasible to apply the abrasive flow polishing technology for metal and ceramic micro bores of diameters of 260 µm or larger and the length/diameter ratios of 25 or higher. It is found that surface roughness of the polished micro bore inner walls decreases with an increase of the abrasive flow passes.     

Development of surface finish during the polishing of porcelain ceramic tiles

Polishing tests on a laboratory scale have been used to simulate and study the industrial polishing process for unglazed porcelain ceramic tiles. Tile surface quality was assessed in terms of roughness and optical gloss. Tests with a sequence of progressively smaller silicon carbide abrasive particles showed a general trend of decreasing roughness and increasing gloss during the process. The coarser abrasives (larger than 400 grit number) caused the major change in surface roughness, while the finer abrasives (smaller than 400 grit number) produced the major change in gloss. In these materials the maximum gloss achievable by polishing is limited by the porosity of the ceramic. The rate of material removal during polishing with a coarse abrasive obeyed an Archard-type wear law, being linearly proportional to applied load, although load had little effect on the surface roughness attained after different durations of polishing. In contrast, load had a significant effect on gloss, with higher loads leading to higher values of gloss. The development of both roughness and gloss with polishing time is well described by quantitative empirical models involving a simple exponential function. The same model for gloss evolution is also shown to apply to data reported from industrial-scale polishing experiments in previous work.