具有双应变梁的硅微机械倾角传感器结构设计

提出了一种能抗侧向耦合干扰的微机械硅倾角传感器的敏感结构设计,它由两个不同大小的质量块和连接它们的两个相互平行的硅应变梁组成.文中通过推导给出了硅应变梁上所受的应变与倾角及位置的解析关系,并计算了在两个不同质量块作用下硅梁上的应力分布,最后提出了制作该结构的工艺设计.     

具有双应变梁的硅微机械倾角传感器结构设计

提出了一种能抗侧向耦合干扰的微机械硅倾角传感器的敏感结构设计，它由两个不同大小的质量块和连接它们的两个相互平行的硅应变梁组成。文中通过推导给出了硅应变梁上所受的应变与倾角及位置的解析关系，并计算了在两个不同质量块作用下硅梁上的应力分布，最后提出了制作该结构的工艺设计。     

硅微机械二维倾角传感器结构设计

提出了一种结构简单,制造工艺容易实现的硅微机械二维倾角传感器结构设计,它由蝶形质量块和连接它们的四个成十字形的硅应变梁以及具有过载限位保护功能的硼硅玻璃衬底构成.传感器能同时检测出绕两轴的倾角变化.分析了硅应变梁的受力情况,得到了与倾角的解析关系,并用有限元方法验证了结果,理论灵敏度为0.75 mV/ °.     

基于光纤光栅应变花的平面应变状态实验分析

提出并实现了直角与三角形两种光纤光栅(FBG)应变花方案,分别由在1根光纤上实现准分布的3个FBG制成。将之粘贴存等强度梁上,判断主应变方向及大小,研究其平面应变测量性能。试验结果显示,测量主应变方向同实际方向符合,两种应变花测量结果一致。     

应变硅技术在纳米CMOS中的应用

应变硅技术具有迁移率高、能带结构可调的优点,且与传统的体硅工艺相兼容,在CMOS工艺中得到广泛地应用,尤其是MOS器件的尺寸进入纳米节点。文章综述了应变硅技术对载流子迁移率影响的机理,并从全局应变和局部应变两个方面介绍了应变硅在CMOS器件中的应用。同时,将多种应变硅技术整合在一起提升MOS器件的性能是未来发展的趋势。     

固定载荷下光纤光栅应变传感阵列检测裂缝悬臂梁损伤的研究

介绍了光纤光栅分布式传感原理,推导了悬臂梁受载荷时的应变计算公式,以金属悬臂梁为研究对象,以光纤光栅应变传感阵列为传感工具,实验研究了固定载荷下裂缝悬臂梁的光纤光栅检测的新方法.金属悬臂梁上光纤光栅应变传感阵列粘贴的位置和预制裂纹的位置由有限元模拟确定,固定载荷的加载是在金属悬臂梁的自由端悬挂标准砝码.记录金属悬臂梁在无损伤、一条裂缝、两条裂缝和三条裂缝的光纤光栅应变传感阵列检测到的实验数据,以无损伤的实验数据为初始数据,分别与有损伤的实验数据进行比较,得到悬臂梁在各个损伤情况下的应变变化量,根据应变变化量的不同,确定出悬臂梁上损伤的位置.     

纳米CMOS电路的应变Si衬底制备技术

应变硅衬底材料——弛豫SiGe层作为应变硅技术应用的基础,其质量的好坏对应变硅器件性能有致命的影响。综述了近年来用于纳米CMOS电路的各类弛豫SiGe层的制备技术,并对弛豫SiGe层中应变测量技术进行了简单的介绍,以期推动应变硅技术在我国芯片业的应用。     

一种具有应力隔离结构的扭摆式电容加速度计

基于硅-玻璃键合工艺的扭摆式加速度计,其信号输出对扭转梁上的应力极敏感,而微加工过程中由于硅、玻璃两种材料热膨胀系数不匹配,会在扭转梁上引入较大的热应力,进而引起加速度计温度漂移。为此,提出一种具有应力隔离结构的扭摆式电容加速度计。通过缓冲折叠梁和内支撑框架的优化组合,使热应力难以传递到扭转梁上,从而有效降低加速度计的温度漂移。使用ANSYS软件对加速度计进行了模态和热应力分析,结果表明:工作模态的固有频率为1 352 Hz,远小于其他干扰模态的频率;加速度计的灵敏度为0.386pF/g(g=9.8m/s2);相同条件下,不带隔离结构的扭摆加速度计的热应力主要集中在扭转梁的末端,其最大应力约100 MPa;具有应力隔离结构的加速度计,其热应力主要集中在缓冲折叠梁上,而扭转梁上的应力约为1.7 MPa,仅为前者的1.7%。采用硅-玻璃键合和电感耦合等离子体(ICP)刻蚀工艺,完成了加速度计芯片的制作。     

选择性腐蚀Si1-xGex与Si制备绝缘体上超薄应变硅

基于应变硅以及绝缘体上超薄应变硅(SSOI)工艺,使用氢氟酸、硝酸和醋酸的混合溶液与质量分数为25%的四甲基氢氧化铵(TMAH)溶液选择性腐蚀Si1-xGex与Si以制备绝缘体上超薄应变硅。研究了质量分数为0.5%～5%的HF和Si1-xGex中Ge的含量对选择性腐蚀的腐蚀速度与选择比的影响,优化了选择性腐蚀工艺。采用氨水、过氧化氢和水的混合溶液处理选择性腐蚀后的Si1-xGex与Si表面,得到了高应变度、高晶体质量的超薄SSOI。采用原子力显微镜(AFM)测试腐蚀速度以及腐蚀后的表面粗糙度;使用喇曼光谱仪表征Si1-xGex以及应变硅的组分以及应变度;使用透射电子显微镜(TEM)对SSOI的晶体质量进行了表征。结果表明,超薄SSOI的表面粗糙度(RMS)为0.446 nm,顶层Si的应变度为0.91%,顶层应变硅层厚度为18 nm,且具有高的晶体质量。     

螺旋倾斜复合技术对光纤布拉格光栅传感器的减敏作用北大核心CSCD

降低光纤布拉格光栅(FBG)应变传感器的应变灵敏度是解决传感器量程小、无法监测大应变问题的一种重要方法。为了监测构件在使用过程中的应力应变变化,提出了螺旋倾斜式光栅复合技术,建立了光栅实测应变与试样实际应变间的理论关系,在不同螺旋倾角下进行了光栅应变灵敏度的测量试验。试验结果表明,该方法能有效降低光栅应变灵敏度,增大光栅应变测量量程。     

Bridge configurations in piezoresistive two-axis accelerometers

In piezoresistive two-axis accelerometers with two proof masses suspended by cantilever beams, there are generally many ways to configure the Wheatstone bridges. The configurations are different both with respect to functionality and performance. The main distinction is between bridges that contain resistors belonging to both proof masses, and the one bridge that doesn’t. We compare the different bridge configurations by analytical calculations of bridge non-linearity, robustness towards manufacturing variations and electronic noise. We consider accelerometers where the ratio between the sensitivity to acceleration normal and parallel to the chip plane vary over a wide range. For numerical examples we use representative values for p-type silicon. The performance of the configuration with one bridge connected to each proof mass is superior to those that combine resistors belonging to different proof masses.     

激光全息法制备二维硅基图形衬底

理论上模拟了全息光刻法制备二维硅基图形阵列的光强分布和显影过程,通过改变激光波长及入射光与样品表面的夹角即可得到不同周期的二维图形.在此基础上,采用三束光一次曝光和湿法腐蚀图形转移技术,在n型(100)硅衬底上制备出了周期在亚微米量级的均匀二维图形阵列.该方法适合大面积硅基图形阵列的制作.     

3D Free‐Form Patterning of Silicon by Ion Implantation,Silicon Deposition,and Selective Silicon Etching

A method for additive layer‐by‐layer fabrication of arbitrarily shaped 3D silicon micro‐ and nanostructures is reported. The fabrication is based on alternating steps of chemical vapor deposition of silicon and local implantation of gallium ions by focused ion beam (FIB) writing. In a final step, the defined 3D structures are formed by etching the silicon in potassium hydroxide (KOH), in which the local ion implantation provides the etching selectivity. The method is demonstrated by fabricating 3D structures made of two and three silicon layers, including suspended beams that are 40 nm thick, 500 nm wide, and 4 μm long, and patterned lines that are 33 nm wide.     

Design of mechanical band-pass filters with large frequency bands for energy scavenging

In this paper, the design of mechanical band-pass filters to be used in energy scavengers is studied. For such filters an ensemble of cantilever beams is proposed where at the tip of each beam a mass, known as the proof mass, is mounted. It is shown that such an ensemble can be made into a band-pass filter with a large frequency band when dimensions of the beams and masses of the proof masses are chosen appropriately. Several systematic procedures for designing mechanical band-pass filters with large frequency bands are given.     

A 1024-element high-performance silicon tactile imager

A 32×32-element capacitive silicon tactile imager, for use in precision robotics applications where high density and high resolution are important, is discussed. The silicon chip measures 1.6 cm×1.6 cm, and is organized in an X-Y matrix of 1024 capacitor elements on 0.5-mm centers. The process uses two boron diffusions (deep and shallow) followed by a silicon-to-glass electrostatic bonding step and subsequent unmasked wafer dissolution. This results in a thick center plate for the sense capacitor supported by thinner beams. Only four noncritical masking steps for silicon and two for glass are required. A measured force sensitivity of 0.27 pF/gmf/element, temperature sensitivity of less than 3o p.p.m./°C, and maximum operating force of ≈1 gm/element has been obtained. A discrete data acquisition system used with the device offers over 6 b of force resolution, and the imager can be read at a rate of 15-20 μs/element, offering an effective frame rate of 5.1 ms     

Failure analysis method by using different wavelengths lasers and its application

We succeeded in an accurate detection for failure locations on a silicon semiconductor device (hereafter called “IC”) by applying the failure analysis method in which two kinds of laser beams having different wavelengths are simultaneously irradiated on a surface of IC. Short wavelength laser beam (λ=1083nm) causes potential changes in an internal circuit of IC due to generating many electron-hole pairs in the semiconductor. On the other hand, long wavelength laser beam (λ=1360 run) causes an easy operation of parasitic bipolar elements due to increasing temperature of IC by irradiation heat. By combining these effects of two laser beams, the accurate detection of latch-up locations on internal circuits of IC (has been recognized to be difficult up to now) has come possible.     

A study of residual stress distribution through the thickness of p+ silicon films [thermal oxidation effects]

The effect of thermal oxidation on the residual stress distribution throughout the thickness of heavily-boron-doped (p⁺ ) silicon films is studied. The deflection of p⁺ silicon cantilever beams due to residual stress variation throughout the film thickness is studied for as-diffused and thermally oxidized films. Cantilevers of as-diffused p⁺ silicon films display a positive curvature (or a negative bending moment), signified by bending up of the beams. Thermal oxidation of the films prior to cantilever fabrication by anisotropic etching modifies the residual stresses in the p⁺ film, specially in the near-surface region (i.e. the top 0.3 to 0.5 μm for the oxidation times used here), and can result in beams with a negative curvature even when the oxide is removed from the p⁺ silicon cantilever surface subsequent to cantilever fabrication     

A 94-GHz aperture-coupled micromachined microstrip antenna

This paper presents an aperture-coupled micromachined microstrip antenna operating at 94 GHz. The design consists of two stacked silicon substrates: (1) the top substrate, which carries the microstrip antenna, is micromachined to improve the radiation performance of the antenna and (2) the bottom substrate, which carries the microstrip feed line and the coupling slot. The measured return loss is -18 dB at 94 GHz for a 10-dB bandwidth of 10%. A maximum efficiency of 58±5% has been measured and the radiation patterns show a measured front-to-back ratio of -10 dB at 94 GHz. The measured mutual coupling is below -20 dB in both E- and H-plane directions due to the integration of small 50-μm silicon beams between the antennas. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies     

Amorphous silicon as a resist material

Lithographic properties of amorphous silicon films exposed to glow-discharge hydrogen plasma and ion beams have been investigated. The rate of film etching by a CF₄ plasma is lowered by exposure, giving rise to a negative resist behavior of the material. The sensitivity and contrast are ~10¹⁸ ions/cm² and 1.1, respectively. The effect of exposure time on etching characteristics was also studied     

Transient effects during dynamic hologram formation in BSOcrystals: theory and experiment

A model is presented for the time dependence of energy transfer between two incident beams and the concomitant grating formation in photorefractive materials. The theory includes the effects of birefringence, optical activity, and absorption of light. The predictions of the model are compared in detail with sets of experimental measurements performed with bismuth silicon oxide (BSO) crystals. Good agreement of the measured values and theory was found