微细电化学加工技术

介绍了微软电化学加工的原理及特点，详细介绍了基于电化学扫描探针显微镜进行的电化学微细加工技术，EFAB制作技术、刻蚀剂层技术（GELT）、超微细电极电化学加工技术等几种目前主要的微细电化学加工技术。     

Development of micropin fabrication process using tool based micromachining

A micropin fabrication process has been developed based on micromachining technology. One group of micromachining technology is microturning. It has the capability to produce three dimensional features on the micro scale. This paper deals with the CNC microturning process. Basically two types of microturning processes are used: straight microturning and taper microturning. Experiments were performed using a programmable multi-purpose miniature machine tool developed for tool based micromachining. NC codes were generated using Borland C++ Builder 6.0. Brass bars of 6 mm diameter have been machined to fabricate the micropin with carbide cutting tools. Work materials were clamped on the spindle which has the facility of three-axis movements. Unlike the conventional processes, the cutting tool has no movement. A step cutting process was applied to eliminate workpiece deflection in the microturning process. Finally a micropin was fabricated with 2 mm length. The larger and smaller diameter of the pin are 475 μm and 276 μm, respectively.     

Micro—nano electromechanical system by bulk silicon micromachining

MEMS(Micro ElectroMechanical System)based on semiconductor microfabrication plays im-portant roles for example in the periphery of IT systems.N EMS(Nano Elect roMechanical Sys-tem)contains nano-scale structures.Sop histicated and high performance systems based on the MEMS and the NEMS have been developed.Packaging and elect rical interconnection play an important role in realizing practically applicable systems.     

用体硅微加工工艺实现的微纳电械系统

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Ultrafast laser micromachining of 3C-SiC thin films for MEMS device fabrication

Femtosecond pulsed laser (800 nm, 120 fs) micromachining of thin films of 3C-SiC (β-SiC) semiconductor deposited on silicon substrate was investigated as a function of pulse energy (0.5 μJ to 750 μJ). The purpose is to establish suitable laser parametric regime for the fabrication of high accuracy, high spatial resolution and thin diaphragms for high-temperature MEMS pressure sensor applications. Etch rate, ablation threshold and quality of micromachined features were evaluated. The governing ablation mechanisms, such as thermal vaporization, phase explosion, Coulomb explosion and photomechanical fragmentation, were correlated with the effects of pulse energy. The results show that the etch rate is higher and the ablation threshold is lower than those obtained with nanosecond pulsed excimer laser ablation, suggesting femtosecond laser’s potential for rapid manufacturing. In addition, the etch rates were substantially higher than those achievable in various reactive ion and electrochemical etching methods. Excellent quality of machined features with little collateral thermal damage was obtained in the pulse energy range (1–10 μJ). The leading material removal mechanisms under these conditions were photomechanical fragmentation, ultrafast melting and vaporization. At very low pulse energies (<1 μJ), nanoscale material removal has occurred with the formation of nanoparticles that is attributed to Coulomb explosion mechanism. The effect of assist gas on the process performance at low and high energy fluences is also presented.     

Modeling and fabrication of microhole by electrochemical micromachining using retracted tip tool

Accurate microhole is a key feature for many kinds of micro parts widely used in diverse industries. But machining of microhole using traditional processes faces great challenges due to the thermal-mechanical effects. Electrochemical micromachining (EMM) is a potential technique to meet the requirement of high-quality microhole fabrication. However, the currently-used microtools suffer from some drawbacks such as stray dissolution, bell-mouth entrance and excess radial overcut. To overcome these limitations, a novel microtool with retracted tip structure is proposed in this work. A mathematical model has been developed to investigate the effect of retracted tip depth on machining accuracy. And an empirical formula is obtained based on the model to predict the diameter of the generated microhole. Experimental verification is performed on a home-made EMM system and reveals good correlation with the theoretical predictions. Using this novel microtool with optimum retracted tip depth, high-quality microholes have been fabricated on aluminum and 304 stainless steel sheets.     

The fabrication and preservation of nanostructures on silicon wafers with a native oxide layer

This study used nano‐oxidation lithography to create oxidized circular nanostructures on a silicon wafer with a native oxide layer (NOL). We also investigated the impact of wet etching on the size of circular oxidized nanostructures and examined how the method and duration of preservation affect them. Experimental results show that the height and width of oxidized circular nanostructures increase proportionally with applied voltage. After wet etching, an increase in applied voltage resulted in a marked increase in the width of the circular nanostructures, a decrease in the inner diameter, and little variation in height. We further demonstrated that in a moist environment, the oxidation process continues, resulting in a further increase in height and width. During the initial stages of preservation, these changes occurred rapidly; however, the increase was negligible after 30 days. We propose the concept of reaction area (RA) ratio to explain the above phenomenon and provide evidence to support these claims. Our results led us to a simple and yet effective method of preserving oxidized circular nanostructures, called the electrostatic patch preservation (EPP) method, to overcome problems associated with changes in size occurring during the preservation of silicon nanostructure molds. SCANNING 34: 347–356, 2012. © 2012 Wiley Periodicals, Inc.     

基于体硅工艺的定位平台制作工艺分析研究

介绍了一种基于体硅工艺的大尺寸、大深宽比的纳米级定位平台的制作工艺。对定位平台的制作中的关键工艺进行的分析,总结了导致器件失效的主要原因,探讨了减少失效的方法。同时介绍了一种可行的面内侧面压阻的加工方法。通过对深度反应离子刻蚀（DRIE）工艺参数的调整成功了刻蚀出了大尺寸、大深宽比的结构释放窗口,释放了最小线宽为2.5μm,厚度为50微米的梳齿结构。研制了一种良好性能的集成位移检测的纳米级定位平台。     

微细加工与装备技术进展

讨论微细加工与装备技术现状,介绍刻蚀技术、LIGA技术和准LIGA技术、微细特种加工等典型的微细加工工艺原理与技术特点,并指出各种加工方法的优缺点,分析微细加工技术的发展走向及装备技术的发展趋势。     

Some aspects of fabrication of micro devices by electrochemical micromachining (ECMM) and its finishing by magnetorheological fluid

Electrochemical micromachining (ECMM) is an advanced machining process for machining of electrically conducting materials. In the present work, a micro nozzle and a fluidic mixer having complex structures are made using masking technique by ECMM process. Mask is made of 50-μm transparent sheet and the micro nozzle and micro mixer are fabricated on an 800-μm thick copper sheet. The resulting rough inner walls and bottom surface of micro nozzle are finished using magnetorheological fluid-based finishing process. Surface finish of the nozzle is significantly improved after finishing. A comparison of width, depth, and surface roughness of the micro nozzle is also carried out before and after finishing. The mixing behavior of two fluids is visualized by microscope in micro mixer. The rough inner walls of the mixer’s channels act as obstructions and result in zigzag path of flowing fluid. Hence, mixing occurs at microscopic level because of rapid molecular diffusion.     

Nanostructure fabrication on germanium and silicon by nanocoining imprint technique

Germanium (Ge) and silicon (Si) material response to indentation with a nanostructured die is investigated. A diamond die attached to a high speed actuator previously used to create large arrays of nanofeatures on metallic surfaces was used to create nanofeatures on Ge and Si samples. The pressure induced transformation of Ge and Si from a diamond cubic brittle phase to a more ductile beta-tin metallic phase due to the nanofeatures on the die was investigated. Results using the dynamic nanocoining method showed chip-like deformation around the individual nanofeatures indicative of the beta-tin phase transformation at the nanofeature level. Micro-Raman measurements confirmed the metallic transition from evidence including metastable and amorphous phases after indentation. Indents created using a common linear indentation method exhibited similar behavior. The Si nanofeature deformation was compared to electroless (EL) nickel and the deformation differed as dictated by the mechanism of material flow. Although not observed in Si, fracture occurred in some Ge indents at higher loads as a result of the lower fracture toughness compared to Si.     

特种微型机械加工技术

综述微型机电系统/微型机械的三维形状加工及极限尺寸加工的研究开发现状.相对硅微细加工和LIGA工艺,不采用掩膜版的特种微细加工技术,如微细激光成型、微细电火花加工以及微细机械加工等近年来取得较大进展,在三维微小机械结构成型上有独到优势;同时扫描隧道显微加工技术的开发将微型机械向极限尺寸领域推进.微型机电系统/微型机械的长足发展有赖于融合已有先进技术和交叉学科思想的微型机械加工技术的进一步研究开发.     

Development of microelectrodes for electrochemical micromachining

Electrochemical micromachining (EMM) has become more and more important in micro machining in recent years. Microelectrode as the tool of EMM is an essential cell in the machining process. In this study, microelectrodes with various end shapes are fabricated by different processing techniques. First, the different end shape forming methods for microelectrode, such as electrochemical etching, single electric discharge, and electrochemical micromachining are investigated. Second, microelectrodes with various end shapes fabricated above are simulated, analyzed, and then used in EMM process. At last, micro holes array with diameter of less than 10???m, three micro holes with no taper and a 3D microstructure are machined on metallic materials by above three types of microelectrodes.     

Electrochemical micromachining with wet stamping: Instrument design and experimental investigation

This paper presents a novel micromachining approach named electrochemical wet stamping (E-WETS) for the fabrication of microstructures on metals and semiconductors. The E-WETS allows the direct imprinting of microstructures on an agarose stamp into workpiece through a selective anodic dissolution process. According to the characteristics of the E-WETS process, an optimized instrument which consists of a positioning stage and a force sensing module is developed. An orientation head is designed for the precise stamp-workpiece parallelism alignment, which ensures the uniform micropatterns on the workpiece. The technique of short voltage pulse is applied to the E-WETS to improve the surface roughness and precision of the fabricated microstructures. Experiments are conducted to investigate the influences of pulse duration on the machining performances. Then, micromachining experiments on aluminum and nickel are carried out under the optimum conditions. The experiment results indicate that the E-WETS is an effective method and the developed instrument can well meet the requirements of the E-WETS process.     

Effects of anisotropy during micromachining of cobalt

The effects of crystal orientation on the tribological characteristics of cobalt, during machining with a sharply pointed diamond, have been investigated. It has been found that the coefficient of friction and the width of the machined groove are both strongly dependent on the surface orientation, the normal load and the cutting direction. However, the actual tangential stress which is required for chip removal and therefore the energy required to remove unit volume of material are constant for a particular cutting geometry.     

A study of the characteristics for electrochemical micromachining with ultrashort voltage pulses

Electrochemical micromachining (EMM) has traditionally been used in highly specialized fields, such as those of the aerospace and defense industries. It is now increasingly being applied in other industries, where parts with difficult-to-cut material, complex geometry and tribology, and devices of microscopic-scale are required. EMM, which is not normally considered as a precision process, is presented in this paper. The application of voltage pulses between a tool electrode and a workpiece in an electrochemical environment allows the three-dimensional machining of conducting materials with micrometer precision. In this paper, tool electrodes (5 μm in diameter, 1 mm in length) are developed by EMM and microholes are manufactured using these tool electrodes. Microholes with a size of below 50 μm in diameter can be accurately achieved by using ultrashort voltage pulses (1–5 μs).