Deep Vertical Etching of Silicon Wafers Using a Hydrogenation-Assisted Reactive Ion Etching

A novel hydrogenation-assisted deep reactive ion etching of silicon is reported. The process uses sequential hydrogen-assisted passivation and plasma etching at low-density plasma powers to stimulate the vertical removal of the exposed Si substrate. The main feature of this technique is the sequential alternation of the electrodes while switching between different gases. Three-dimensional structures with aspect ratios in excess of 40:1 and features as small as 0.7 mum have been realized. The net etch rate is about 0.25 mum/min, although higher rates are expected to be achievable.     

二氧化硅的干法刻蚀工艺研究

主要研究了二氧化硅的干法刻蚀工艺.运用反应离子刻蚀设备(RIE150×4)进行了一系列的刻蚀实验,采用不同的工艺条件对二氧化硅进行选择刻蚀工艺研究,得出了不同工艺条件对应的刻蚀速率、均匀性、选择比等刻蚀参数,并对结果进行了比较与分析,得到了相对最佳的工艺条件.     

Vertical Mirror Fabrication Combining KOH Etch and DRIE of (110) Silicon

This paper presents fabrication of MEMS-actuated optical-quality vertical mirrors as the key active optical components in a silicon optical bench (SOB) technology. The fabrication process is based on a combination of potassium hydroxide (KOH) etch and deep reactive ion etching (DRIE) of (110) SOI wafers. The process starts by creating optical-quality vertical surfaces by KOH etch, followed by an oxidation step to protect them. The patterned wafer is then etched by DRIE to define actuators. The process is designed to allow the KOH etch and DRIE to be independently optimized without compromising either while at the same time meeting the challenge of lithography on high-aspect-ratio structures. Three variations of the fabrication process are demonstrated, two that use double masking layers and one that uses a silicon masking layer. We demonstrate in-plane scanners and fast translational vertical mirrors fabricated using these processes. In addition, we propose extensions of the fabrication process to account for DRIE aspect-ratio limitations. Mask layouts of key SOB building blocks, including vertical mirrors, beam splitters, and parallel-plate actuators, are also presented.$hfill$ [2008-0146]      

Free-Form Simulation of Sequential Etching and Surface Characterization for 3-D MEMS Fabrication

A new diffusion-based simulation model of isotropic wet etching and free-form surface characterization method for 3-D free-form microelectromechanical systems (MEMS) fabrication is presented in this paper. To simulate the etching process, a diffusion-based model solved by the finite-element method (FEM) has been developed, allowing extraction of more accurate etch-front data at discrete time steps. In the developed method, free-form MEMS objects are modeled as B-spline functions with material concentration. Finite elements are generated by discretization in the parametric domain of the free-form object and mapping back to the Euclidean space. Points on the etch front are extracted using a Z-map method. The extracted point data are characterized to obtain a B-spline representation of the etch-front surface. Examples from the isotropic etching simulation of 2-D and 3-D objects with both regular and free-form geometry are presented. The developed method allows the simulation of 3-D objects with free-form input and free-form mask opening and facilitates the simulation of sequential etching of free-form objects with irregular mask openings. This paper also discusses applications of the developed method in MEMS process planning that can be realized by taking advantage of the better control of geometry that it provides in MEMS fabrication.     

The Parametric Differential Method: An Alternative to the Calculation of Form Factors

The parametric differential method calculates the form factors without using approximations by polygons. Because of this it contributes to the improvement of the realism of the images synthesised through the radiosity method. This paper presents the most important characteristics of the parametric differential method as well as the results concerning its accuracy. Comparison of the form factors found using the new algorithm has been made with those analytically found.     

一种改进的CHRIS/PROBA垂直条带去除方法

多角度高光谱高空间分辨率的CHRIS数据是新一代小卫星PROBA平台上的CHRIS传感器获取的又一卓越的遥感数据源,虽然其数据有诸多优势,但也有一个缺陷:在图像上垂直条带噪声污染严重。本文在San-dra Mannheim提出的去除此类噪声的方法基础上,对该方法进行了另一种途径的探索,基于图像分割的原理,将图像分成灰度相近的几个片段,逐片断应用最小二乘法的多项式拟合,然后将去过条带的片段整合成一幅完整的图像。通过试验证明,用该途径实现的这种方法在地物复杂图像灰度变化剧烈的影像上取得了优越于其他方法的效果,并且证实,对于具有同类条带噪声的OMIS(Airborne Operational Modular Imaging Spectrometer),该方法也取得了比较好的效果,因而值得推广。     

ElastIC: An Adaptive Self-Healing Architecture for Unpredictable Silicon

With continued technology scaling, silicon is becoming increasingly less predictable. Recent years have brought an acceleration of wear-out mechanisms, such as oxide breakdown and NBTI, which occur over a part's lifetime. Manufacturing device failure rates will increase significantly with decreases in device sizes, possibly reaching one in thousands or even hundreds of devices. Process variations will increase significantly in future technologies because fundamental laws of physics drive certain parametric variations, such as random dopant fluctuation (RDF) and line edge roughness, making their increased contribution to variability almost inevitable. The combination of wear-out mechanisms, RDF, and line edge roughness leads to an unpredictable silicon fabric that poses a major obstacle to reliable computing in future technologies. The authors present a broad vision of a new cohesive architecture, ElastIC, which can provide a pathway to successful design in unpredictable silicon. ElastIC is based on aggressive runtime self-diagnosis, adaptivity, and self-healing. It incorporates several novel concepts in these areas and brings together research efforts from the device, circuit, testing, and microarchitecture domains. Architectures like ElastIC will become vital in extremely scaled CMOS technologies.     

TPMS硅基压阻式压力传感器的研制

:轮胎压力监测系统(TPMS)对压力传感器越来越大的市场需求使得这类传感器再次成为一个研究热点.商业领域对新一代压力传感器的要求是小尺寸、高性能、低价格,针对在30 μm厚度的硅杯方形薄膜上采用新型折线形状和位置的压敏电阻,设计并制作了一系列压阻式压力传感器.分析和讨论了膜的面积、电阻形状和位置等参数对压力传感器的灵敏度和线性度的影响.测试得到1000 kPa量程下边长为370μm的压力传感器灵敏度和线性度分别为15.5 mV/V·FS、0.012%/FS;边长为470μm的传感器的灵敏度和线性度分别为32.2 mV/V·FS、0.078%/FS,满足TPMS应用标准.这种器件体积小、成品率高,灵敏度和线性度均得到提高,也可用于医学、航空等其他领域.     

一种基于区间数偏离度的方案排序方法

针对特征取值为区间数的方案排序问题,提出两个区间数的偏离度概念用以构造方案间的偏离度矩阵,并给出一种基于总体偏离度优化的特征权重确定方法。利用提出的区间数向量的相对贴近度概念刻画一个方案接近于另一个方案的程度,进而对候选方案的优劣排序。该方法提出的各种度量较直观、易于理解,并通过实例验证方法的有效性和实用性。     

An Interactive Satisfying Method Based on Alternative Tolerance for Multiple Objective Optimization With Fuzzy Parameters

An interactive satisfying method based on alternative tolerance is presented for the multiple objective optimization problem with fuzzy parameters. Using the $alpha $ -level sets of the fuzzy numbers, all the objectives are modeled as the fuzzy goals, and the tolerances of the objectives are iteratively changed according to a decision maker for a satisfying solution. Via a specific attainable point programming model, the membership functions can be modified, and then, a lexicographic two-phase programming procedure is constructed correspondingly to find the final solution. In a special case, the objective constraint is added instead of changing the membership functions; therefore, the dissatisfying objectives for the decision maker can be improved step by step. The presented method not only acquires the $alpha $ -Pareto optimal or weak $alpha $-Pareto optimal solution of the fuzzy multiple objective optimization, but also satisfies the progressive preference of the decision maker. A numerical example shows its power.      

A Si/Glass Bulk-Micromachined Cryogenic Heat Exchanger for High Heat Loads: Fabrication, Test, and Application Results

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a $1 times 1hbox{-cm}^{2}$ footprint and a length of up to 3.5 cm. It is intended for use in Joule–Thomson (J–T) coolers and can sustain pressure exceeding 1 MPa. Tests at cold-end inlet temperatures of 237 K–252 K show that the heat exchanger effectiveness is 0.9 with 0.039-g/s helium mass flow rate. The integrated Pt RTDs present a linear response of 0.26%–0.30%/K over an operational range of 205 K–296 K but remain usable at lower temperatures. In self-cooling tests with ethane as the working fluid, a J–T system with the heat exchanger drops 76.1 K below the inlet temperature, achieving 218.7 K for a pressure of 835.8 kPa. The system reaches 200 K in transient state; further cooling is limited by impurities that freeze within the flow stream. In J–T self-cooling tests with an external heat load, the system reaches 239 K while providing 1 W of cooling. In all cases, there is an additional parasitic heat load estimated at 300–500 mW.$ hfill$[2009-0093]      

Fabrication of Integrated Vertical Mirror Surfaces and Transparent Window for Packaging MEMS Devices

A scheme for creating metal-coated vertical mirrors in silicon, along with an integrated transparent package lid for assembling, packaging, and testing microelectromechanical systems (MEMS) devices is presented. Deep reaction ion etching (DRIE) method described here reduces the loading effect and maintains a uniform etch rate resulting in highly vertical structures. A novel self-masking lithography and liftoff process was developed to ensure that the vertical mirrors undergo uniform metallization while leaving a transparent window for optical probing. Front side of a Si wafer was shallow-etched using DRIE to define an eventual optical window. This surface was then anodically bonded to a Pyrex wafer. Backside Si was then patterned to define thin channels around the optical window. These channels were vertically etched using DRIE, after which the unattached portions of the window region were removed. Negative photoresist was spun on the remaining vertical structures and the stack was exposed from the Pyrex side using Si structures as a self-mask. Subsequent metal sputtering and liftoff results in the metallized top and mirror sidewalls while leaving a clear window. These integrated mirrors and lids are then bonded to the active MEMS mirrors. Various processes and results are illustrated with an example of packaged corner cube retroreflectors (CCRs)     

A Method for Fabrication of Polycarbonate-Based Bioactive Platforms

Surface-based assays have been used extensively for the functional and structural analysis of biomolecules such as DNA or proteins. These experiments are established by the analysis of binding between acceptor molecules and immobilized receptors on a platform. Site-specific printing of receptor molecules on gold, glass, or polycarbonate (PC) surfaces is conventionally performed by the chemical derivatization of a surface, priming it to covalently bind to subsequently deposited receptor molecules. Unlike conventional methods, we have developed a new fabrication method for bioactive PC surfaces by directly molding PC granules doped with receptor molecules. PC-based receptor molecules were synthesized and commercially available PC granules were doped with these synthesized molecules. In our proof-of-concept study, PC doped with dye 1 (Fig. 1) was used as the receptor molecule. Using an aluminum mold and a hot press machine, PC-based objects were manufactured through compression molding using doped PC granules. Affinity analysis was evaluated by monitoring the localization of a monoclonal antibody elicited against dye 1 to the surface of the molded platforms by fluorescence microscopy. The results illustrated effective binding of an anti-dye 1 monoclonal antibody to the surface, substantiating successful display of assemblies of molecular receptors on the surface through compression molding. Although conventional surface functionalization methods impose limited applications and alter desired opto-mechanical properties of the polymer, our investigation provides a versatile means for the fabrication of bioactive PC-based platforms. It can also be used for engineering and imbedding receptor arrays within three-dimensional objects with applications to the production of opto-medical devices or biosensors.     

Direct Fabrication of Nanoscale Light Emitting Diode on Silicon Probe Tip for Scanning Microscopy

We have fabricated a silicon microprobe integrated with a nanometer-sized light emitting diode (Nano-LED) on the tip. This paper describes the fabrication procedure and preliminary topographic testing results. The silicon probe with electrode pattern was made by wet-etching a silicon-on-insulator wafer using oxide as the mask. Subsequently, the probe tip was cut using a focused ion beam (FIB) to form a 150 nm-wide gap. Semiconductor nanoparticles (CdSe/ZnS core-shell nanoparticles) were electrostatically trapped and excited within the electrode gap made on the probe tip. The LED-tip is approximately 150 nm 150 nm. The nano-LED light intensity and current were measured as a function of the driving voltage up to 25 V. In addition to the electroluminescence peaks from the CdSe particles, possible emission from silicon dioxide doped in the FIB milling process was also observed in the measured spectra. Basic mechanical characteristics of the silicon probe were measured by mounting the probe on a tuning fork in a standard near-field scanning optical microscopy (NSOM) set up. It was observed that the drag force reduces the probe oscillation as the vibrating tip approached the near-field of the sample surface. The topographic images of a chromium test pattern on a glass substrate were successfully acquired by keeping the probe tip within roughly 5 nm from the sample surface. Although the probe tip shape and the location of the Nano-LED are yet to be further optimized before realizing near-field optical scanning experiment, the result showed its great promise as a new type of NSOM tip with the ldquoon-proberdquo light-source.     

高速船垂向运动控制方法研究

高速船在波浪中高速航行时,由海浪引起的船舶垂向运动,包含纵摇和垂荡,可能会使船上的乘客晕船。此外,如果船舶的垂向运动达到某种程度还会对船舶的安全性构成极大的威胁,如砰击、甲板淹湿。利用控制水翼（T型水翼和艉压浪板）实现姿态控制可有效减少船舶垂向运动。为了研究在顶浪情况下,安装T型水翼和艉压浪板后的船舶垂向运动,利用MATLAB/SIMULINK建立船舶垂向运动行仿真模型并进行仿真,采用遗传算法为姿态控制系统设计控制器,并对控制效果进行分析。仿真表明,控制器具有良好的控制效果,可减小船舶的垂荡和纵摇。     

IDD:DDE编码改进方法

编码技术是XML查询处理的基础,为适应XML更新需要,近年来提出很多动态编码方法,大致可分为基于位串的编码和基于向量的编码.当XML更新时,动态编码方法应该产生最短位长新编码分配给插入节点.位串编码具有这个性质,而对于向量编码,却是一个难点.以DDE为例,提出了向量编码的最短位长新编码计算方法.该方法将问题建模为整数规划,通过构造所有不可约分数求得最短位长新编码.和原有简单利用向量相加计算新编码相比,优点包括了重用已删编码,降低编码长度,提高查询性能,具有更好查询支持等.     

Custom Development as an Alternative for ERP Adoption by SMEs: An Interpretive Case Study

There have been few studies of the adoption of custom-developed enterprise resource planning (ERP) systems. An interpretive case study of a SME in the agri-food industry was thus conducted to analyze this phenomenon. The study shows that custom ERP seems to represent a credible alternative for ERP adoption by small and medium-sized enterprises (SMEs) and that to minimize risk at the adoption stage, a SME can proceed in a rather intuitive and unstructured manner, based however upon certain principles, policies, and practices.     

Alternative scenarios of green consumption in Italy: An empirically grounded model

Any transition towards a more environmentally sustainable world will strongly depend on people's willingness to adopt the best available practices. We present here the Consumption Italy (CITA) model, an empirically grounded agent-based model designed to represent household consumption in Italy and to estimate the related greenhouse gas emissions under different environmental policy scenarios. We explored the effect of a price increase for high impact goods and services (e.g., because of the introduction carbon taxes) and of a change of agents' environmental concern (e.g., because of information campaigns). We found that both kind of actions can orient people consumption in the desired direction. However, their target and intensity should be carefully calibrated to produce significant effects at an acceptable cost.