超精密晶圆减薄砂轮及减薄磨削装备研究进展

在芯片制程的后道阶段,通过超精密晶圆减薄工艺可以有效减小芯片封装体积,导通电阻,改善芯片的热扩散效率,提高其电气性能、力学性能。目前的主流工艺通过超细粒度金刚石砂轮和高稳定性超精密减薄设备对晶圆进行减薄,可实现大尺寸晶圆的高精度、高效率、高稳定性无损伤表面加工。重点综述了目前超精密晶圆减薄砂轮的研究进展,在磨料方面综述了机械磨削用硬磨料和化学机械磨削用软磨料的研究现状,包括泡沫化金刚石、金刚石团聚磨料、表面微刃金刚石的制备方法及磨削性能,同时归纳总结了软磨料砂轮的化学机械磨削机理及材料去除模型。在结合剂研究方面,综述了金属、树脂和陶瓷3种结合剂的优缺点,以及在晶圆减薄砂轮上的应用,重点综述了目前在改善陶瓷结合剂的本征力学强度及与金刚石之间的界面润湿性方面的研究进展。在晶圆减薄超细粒度金刚石砂轮制备方面,由于微纳金刚石的表面能较大,采用传统工艺制备砂轮会导致磨料发生团聚,影响加工质量。在此基础上,总结论述了溶胶–凝胶法、高分子网络凝胶法、电泳沉积法、凝胶注模法、结构化砂轮等新型工艺方法在超细粒度砂轮制备方面的应用研究,同时还综述了目前不同的晶圆减薄工艺及超精密减薄设备的研究进展,并指出未来半导体加工工具及装备的发展方向。     

New tool concept for grinding a plateau-like surface for tribological applications

One of the most important factors for energy efficiency is the reduction of friction in machine elements. The grinding process is often the final machining process in machining hardened steel parts and the resulting surface finish influences the tribological behavior. The combination of grinding with a honing process can generate a plateau-like surface to reduce friction and create an oil reservoir to decrease abrasive wear and improve the fluid film stability. Additional processes like laser machining, micro milling or etching are able to generate micro dimples to improve the reduction of friction. Today, grinding processes are limited to machine plateau-like surfaces. Within this paper, a new tool concept will be presented, composed of a grinding tool with two different grain sizes and a metallic bonding. The use of small abrasive grains generates a smooth surface with low roughness values. A few additional larger grains induce stochastic scratches and create the plateau-like surface. Grinding experiments are conducted to analyze the effect of feed rate, feed angle and ratio between small and large grains on the resulting surface.     

在线电解修整(ELID)超精密磨削中的金刚石磨具特性研究

ELID(Electrolytic In-process Dressing)磨削技术是在电化学加工、电解磨削原理基础上发展起来的一项磨削新技术,主要用于硬脆材料超精密磨削过程中金属基结合剂超硬微细磨粒砂轮的在线修整.本文以金刚石微粉砂轮在线电解修整(ELID)磨削氮化硅陶瓷为例,着重研究了磨具特性对硬脆材料超精密磨削过程的影响.研究表明,磨具组织沿砂轮圆周的不均匀性将会导致砂轮表面钝化膜状态的不一致,这将直接影响砂轮局部参与切削的磨粒数量,影响单个磨料的实际磨削厚度.这首先将对工件表面的磨削质量,特别是对表面粗糙度产生直接影响,同时也非常不利于实现材料的高效去除.     

Tool path generation for ultra-precision machining of free-form surfaces

The generation of tool paths for ultra-precision machining is still a limiting factor in the manufacturing of parts with complex optical surfaces. In conventional machining as well as in complex five axes machining the application of CAD- and CAM-software for the generation of tool paths is state of the art. But these software solutions are not able to generate tool paths according to the high requirements of ultra-precision machining. This paper describes possible ways to generate tool paths for ultra-precision machining when the optical surface can be analytically described or when the surface data is derived from optical design software. Ultra-precision milling experiments with different tool paths have been carried out and the quality of the machined geometry has been evaluated concerning the achievable form accuracy.     

A study on optimum grinding factors for aspheric convex surface micro-lens using design of experiments

As the consumer market in the optics, electronics and aerospace industries grows, the demand for ultra-precision aspheric surface micro-lens increases. To enhance the precision and productivity of ultra-precision aspheric surface micro-lens, we present an ultra-precision grinding system and process for the aspheric surface micro-lens. In this paper, an ultra-precision grinding system for manufacturing the aspheric surface micro-lens was developed by considering the factors affecting the grinding surface roughness and profile accuracy. This paper deals with the mirror grinding of an aspheric surface micro-lens by resin-bonded diamond wheel and with the spherical lens of BK7. The optimization of grinding conditions with respect to ground surface roughness and profile accuracy is investigated by design of experiments.     

An active tool holding device

The machine tool industry has to overcome many challenges to produce efficient, high performance and precise machine tools. These requirements are directly from the customers, who want the ability to produce more cost-effective. In order to achieve this, the machine parameters such as the feed rate or the depth of cut of grinding machines are increased. These new parameters affect the dynamic behavior of the machine tool, and in some cases can result in extreme vibrations. These vibrations can generate chatter marks on the workpiece surface or limit the ability to obtain a stable process. This article deals with an active approach to reduce possible vibrations within machine tools. Here the tool holding device of a surface grinding machine has been extended to create an active tool holding device. The active design allows the manipulation of the dynamic behavior of a surface grinding machine, allowing the implementation of a better parameter set.     

Precision and micro CVD diamond-coated grinding tools

Both for ultra-precision and for micro-machining diamond is used very often as tool material. The reason is the very high dimensional stability of diamond due to its extreme hardness. Diamond is used for two kinds of machining processes: for cutting, like turning, drilling or milling, as well as for abrasive processes, like grinding. Diamond cutting tools can be made with massive diamond (monocrystal, CVD diamond, PCD) or with diamond coatings. Standard diamond abrasive tools are made by bonding diamond monocrystals onto a base body. A new grinding layer technology is presented: chemical vapour-deposited microcrystalline diamond layers have crystallite tips with very sharp edges that can act for grinding processes. Base body materials and coating technology is presented. Application results of grinding experiments show that very high workpiece quality can be reached, e.g. a roughness Ra of 5 nm with glass workpieces. Truing and recoating techniques are discussed for reuse of worn CVD diamond grinding wheels. Micro grinding tools (abrasive pencils, burrs) can be manufactured with the same coating technology. Very small tools with diameters of 50 μm have been made and successfully tested.     

Development of monitoring system on the diamond tool wear

Recently, ultra-precision machining using a single crystal diamond tool has been developing very rapidly, especially in the fields of production processes for optical or magnetic parts such as magnetic discs, laser mirrors, polygon mirrors and copier drums. As a result, it has been successfully extended to machine various soft materials, generating mirror-like surfaces to sub-micron geometric accuracy with the ultra-precision CNC machine and the single crystal diamond tool. With the real cutting operation, the geometric accuracy and the surface finish attainable in machined surfaces are mainly determined by both of the sharpness of a cutting tool and stability of the machine vibration. In this study, for monitoring the progress of machining state for assuring the machining accuracy and the surface quality, a new monitoring method of machining states in face-cutting with diamond tool is proposed, using the frequency response of multi-sensors signal, which includes wear state of tool in terms of the energy within the specific frequency band. A magnetic disc is machined on the ultra-precision lathe.     

天然金刚石刀具前刀面的表面粗糙度控制技术

介绍了金刚石刀具的发展和技术特点,设计了一种天然金刚石刀具前刀面表面粗糙度修磨控制方法,并通过工艺实验完成了对金刚石刀具的修磨。结果表明:验证了(100)面的金刚石的难磨方向,沿此方向加工后金刚石的表面粗糙度值较低、磨削热较多;易磨方向表面粗糙度较差、磨削热较少。优化修磨角度修磨后,金刚石刀具前刀面表面粗糙度R_a值可达0.3 nm,将其应用在超精密切削中效果良好。      

应用ELID技术进行微晶玻璃超精密磨削

由于微晶玻璃具有优良的物理、机械性能，在光学等领域得到了越来越多的应用。ELID磨削利用在线．电解的方法修整超细粒度的金刚石砂轮，可以有效地实现硬脆材料的超精密加工。本文将ELID磨削技术应用于微晶玻璃的超精密加工，通过改进ELID磨削的关键技术，包括砂轮电火花整形、电解修整电源和ELID磨削液的改进，实现了微晶玻璃的超精密磨削加工，同时通过采用原子力显微镜对不同磨削参数下的工件表面进行分析，以保证在塑性状态下对微晶玻璃进行磨削。因此提高了ELID磨削的质量。获得了Ra2．308nm的较好表面质量。     

磨削划伤成因分析与工程控制

磨削加工是现代装备制造业发展的重要支撑之一。但是，在磨削加工特别是精密、超精密磨削加工过程中，磨削划伤却时有发生，严重困扰着磨削技术的应用与发展。为此，通过大量磨削现场及零件表面磨削划伤查寻与测量，结合切削学、摩擦学、物理学、材料学、影像学相关知识，对磨削工程中各种磨削划伤进行了全面梳理及分析。探究了磨削划伤的主要技术特征；基于砂轮周边磨削和端面研磨二种磨削方式，揭示了单颗磨粒磨削划伤和团聚磨粒磨削划伤形成过程；归纳了影响磨削划伤的主要因素，提出了应对技术措施。     

Abrasive processes for micro parts and structures

The demand for miniaturized products and functionalized parts is increasing, and many such products are made of hard and brittle materials machined by abrasive processes. The first part of this keynote paper is dedicated to a discussion of micro parts and micro structures machined – at least in part – by abrasive processes, followed by a discussion of the associated abrasive processes. The strengths and limitations of these processes, among which include dicing, micro grinding, micro abrasive blasting, and vibration and magnet field assisted finishing are discussed. The paper concludes with a discussion of future trends in the field.     

Application potential of coarse-grained diamond grinding wheels for precision grinding of optical materials

Fine-grained resin bonded diamond tools are often used for ultra-precision machining of brittle materials to achieve optical surfaces. A well-known drawback is the high tool wear. Therefore, grinding processes need to be developed exhibiting less wear and higher profitability. Consequently, the presented work focuses on conditioning a mono-layered, coarse-grained diamond grinding wheel with a spherical profile and an average grain size of 301 µm by combining a thermo-chemical and a mechanical-abrasive dressing technique. This processing leads to a run-out error of the grinding wheel in a low-micrometer range. Additionally, the thermo-chemical dressing leads to flattened grains, which supports the generation of hydrostatic pressure in the cutting zone and enables ductile-mode grinding of hard and brittle materials. After dressing, the application characteristics of coarse-grained diamond grinding wheels were examined by grinding optical glasses, fused silica and glass–ceramics in two different kinematics, plunge-cut surface grinding and cross grinding. For plunge-cut surface grinding, a critical depth of cut and surface roughness were determined and for cross-grinding experiments the subsurface damage was analyzed additionally. Finally, the identified parameters for ductile-machining with coarse-grained diamond grinding wheels were used for grinding a surface of 2000 mm² in glass–ceramics.     

大型钢坯低倍试样加工与缺陷检测的新装备、新技术

以公司研发的重型超精密镜面铣磨一体化数控机床和金属表面综合检验仪为基础,介绍对钢坯低倍试样进行镜面加工、表面缺陷及纯净度检测的新技术、新装备,如大型钢坯全端面镜面加工技术与装备;利用机器视觉检测技术,通过高像素扫描相机获取全端面图像;通过图像识别技术查找疑似缺陷,再通过高倍显微镜对疑似缺陷进行甄别。通过对低倍与高倍检测合二为一检验方法的介绍,证明这种在试样镜面状态下的机器视觉检测将成为钢铁材料表面检验的关键技术,理化检测将逐渐前移到钢坯检验。     

Injection molded spherical grinding tools: manufacture and application of a novel tool concept for micro grinding

Micro grinding offers the possibility of machining micro structures in hard and brittle materials producing small-scaled parts. Novel micro grinding systems and machines require miniaturized tools and spindles to meet the demands of small or desktop machines providing a small working space. This paper introduces a novel grinding module called ’GrindBall’, with highly integrated tool drive and bearing functions as well as a shaft-free, spherical grinding tool for micro machining applications in small-scaled machine tools. One of the challenges within the development of the GrindBall module is the manufacture of spherical grinding tools, which are not commercially available. A promising method to produce such grinding tools, the injection molding of micro particle filled polymers, is demonstrated in this paper. Injection molding and grinding experiments show that such spherical grinding tools meet the main requirements of this novel grinding technique and show significant material removal rates.     

非球面垂直磨削法的砂轮误差分析与实验研究

针对垂直磨削法中砂轮误差对超精密磨削非球面加工质量的影响,通过对多种砂轮误差的逐一理论分析,阐述了各种砂轮误差对非球面磨削加工质量的影响状况,并对部分砂轮误差进行校正和补偿,以提高磨削加工质量。最后,通过非球面磨削加工实验验证了砂轮误差补偿的正确性。该研究为非球面超精密磨削加工中砂轮误差的补偿提供技术参考。      

非球面超精密磨削误差建模与补偿研究

为提高课题组自研的超精密磨床加工精度,基于多体系统理论,运用齐次坐标变换原理,分析该超精密磨床37项几何误差来源,对非球面超精密磨削的综合误差建模。超精密磨床的多项几何误差元素已在制造阶段标定、补偿,取砂轮对刀误差和砂轮轮廓半径磨损误差作为主要面形误差来源,分别推导其对综合误差的传递函数,分析误差辨识方法,建立误差修正补偿模型,提出基于直接补偿的点补修正法。试验结果表明：建立的综合误差模型正确,根据误差辨识方法和修正补偿模型,修正误差后面形误差显著降低,有效提高面形精度。     

Advances in Modeling and Simulation of Grinding Processes

In the last decade the relevance of modeling and simulation of grinding processes has significantly risen which is caused by industrial needs and is indicated by the number of publications and research activities in this area. This keynote paper results from a collaborative work within the STC G and gives an overview of the current state of the art in modeling and simulation of grinding processes: Physical process models (analytical and numerical models) and empirical process models (regression analysis, artificial neural net models) as well as heuristic process models (rule based models) are taken into account, and outlined with respect to their achievements in this paper. The models are characterized by the process parameters such as grinding force, grinding temperature, etc. as well as work results including surface topography and surface integrity. Furthermore, the capabilities and the limitations of the presented model types and simulation approaches will be exemplified.     

现代超精密加工机床的发展及对策

超精密加工机床是实现超精密加工的重要机械装备。介绍了当前国内外超精密机床的发展现状,从系统的角度分析了影响机床加工精度的因素,并对我国超精密加工机床的研发提出了一点建议。     

An investigation into surface generation in ultra-precision raster milling

This paper presents a study of the factors that affect surface generation in ultra-precision raster milling. A series of experiments was conducted to study the effect of different factors on surface generation in ultra-precision raster milling. The results indicate that machining parameters, tool geometry, cutting strategy, and tool wear are the critical factors for achieving super mirror finish surfaces, while cutting strategies, tool path generation, and kinematic errors of the slides are vital to the form accuracy of freeform surfaces. The experimental results are useful for the diagnosis of systematic errors in machine tools, and the control of machining errors. Compensation strategies can be devised, and improvement can be made in the optimization of surface generation and hence the surface quality when using ultra-precision raster milling can be improved.