梳状电极双轴微机械加速度计的研制

提出了一种新型的基于体硅工艺的双轴加速度传感器,量程为±50 gn,采用全对称结构,其电容检测部分采用变面积、差分电容式的梳状电极结构.利用有限元分析软件分析得到本文所设计的双轴加速度传感器微结构整体质量为1.174 mg,X、Y轴的灵敏度皆为2.3 fF/g,模态分析结果表明,第一和第二模态振型为两敏感方向的振型,且谐振频率分别为2 774 Hz,2 775 Hz.经过MEMS加工工艺制作出的芯片尺寸为5 260 μm×5 260 μm.经过测试,此双轴加速度传感器的电学灵敏度为33.78 mV/g,谐振频率为2.4 KHz,带宽可达到1.5 KHz.     

基于LC谐振的无线无源应变传感器研究

研究一种平面螺旋电感和叉指电容并联结构的LC谐振无线无源应变传感器,利用LC谐振回路的谐振频率对不同应变的响应来表征传感器的应变特性,采用电感耦合的方式来实现无线检测.结果显示LC应变传感器的谐振频率随外加张应变增加而降低,沿电容电极长度方向谐振频率变化对应变的响应灵敏度约为0.3 kHz/με,垂直于电容电极长度方向...     

一种新型CMOS电容式绝对压力传感器的设计

提出了一种新型的采用标准CMOS工艺结合MEMS后处理工艺加工的电容式绝对压力传感器.传感器结构部分是由导体/介质层/导体组成的可变电容器.电容的上下极板分别为CMOS工艺中的多晶硅栅和n阱硅,中间介质层为栅氧化层.在CMOS工艺加工完之后,利用选择性的体硅腐蚀、pn结自停止腐蚀以及阳极键合等MEMS后处理工艺来得到传感器结构.与传统的电容式压力传感器相比,这种结构具有更大的初始固有电容,这样可以抑制寄生电容的影响,从而简化检测电路的设计.文中,应用多层膜理论模型分析了传感器的结构,并利用ANSYS有限元分析对模型进行了验证,并利用电容变化模型分析了传感器的灵敏度.对于边长为800 μm的敏感方膜,初始电容值为1 104pF,传感器灵敏度为46 fF/hPa.同时,本文给出了传感器的电容检测电路的设计.     

基于柔性电极结构的薄膜电容微压力传感器

基于柔性电极结构,本文设计、制作了薄膜电容微压力传感器,在阐述传感器工作原理的基础上,提出了两种设计思路,即基于柔性纳米薄膜的电容式微压力传感器和具有微结构的柔性电极薄膜电容式微压力传感器,并结合传感器的结构和柔性材料的加工特性,进一步提出了相应的力敏特性材料结构优化思路和加工流程,利用该流程得到了一种结构轻薄、工艺简单、高灵敏度的微压力传感器。经测试,本文制作的压力传感器的灵敏度能够达到218 fF/mmHg,在智能穿戴和可植入压力检测等领域显示出较好的应用前景。     

高灵敏度硅电容式压力传感器的研制

本文分析了圆形和方形硅杯的应力膜片在均匀压力下的弯曲,进而得到了电容式传感器的电容与压力的关系,指出当电极的半径与硅应力膜片的半径之比为0.6时,可以得到最高灵敏度。对非线性的改进,提出了通过改变电极的形状来实现,对器件的结构进行了设计。 文中介绍了硅电容式压力传感器的制作工艺,特别详细地研究了硅、玻璃的封接技术,提出了电流法实现静封过程的监控,整个静封装置仅用几十元,但静封样品的性能完全符合要求。     

电容式MEMS超声传感器设计与分析

目前电容式MEMS超声传感器（CMUS）多为收发一体结构,但二种工作模式对传感器结构要求存在很大差异,设计时为了兼顾收发性能往往不能使传感器性能达到最优;此外,传统的电容式MEMS超声传感器还存在寄生电容大的缺点。针对以上问题,基于收发分离的思想,设计了一种专用作超声接收的MEMS电容式传感器,结构上采用上下电极引线互错,单元间电极联线交错的方式来减小寄生电容。通过理论分析和ANSYS仿真得到所设计传感器的最佳工作电压为586V,灵敏度为174.2fF/Pa,满足现有超声接收传感器的应用要求。     

梳状电极电容式SO2 气体传感器􀀁

二氧化硫气体传感器由一组梳状电极和做为电介质覆盖其上的,对二氧化硫敏感的有机改性硅酸酯薄膜组成,梳状电极电容的基材为二氧化硅,铝电极以薄膜覆在其上,电极的厚度为1.6μm电极宽度和间隙和15μm,电极的长度为1200μm,电极总数为400个,采用溶胶－凝胶法和自旋涂覆技术形成气敏涂层,在室温和100Hz,1kHz,10kHz下,测定了梳状电极电容器的电容,探讨了二氧化硫浓度,测量频率和涂膜厚度对传感器灵敏度的影响,在本实验条件下,经有机改性的N,N－二乙基氨丙基－三甲氧基硅烷比其他同类的硅酸酯对二氧化硫有更高的灵敏度。     

测量压电式微压传感器灵敏度的新方法

研制了一套压电微压传感器的性能测量系统,它采用均匀声腔硅油介质中传播的声波作为压力源,标准传感器和被测传感器同时接收波动声压,比较两传感器的输出,测定被测传感器的灵敏度及频响.实验测试了3只压电式微压传感器,结果表明:传感器的灵敏度平均为3.0 mV/Pa,工作频率为20～2 000 Hz,灵敏度随频率波动小于0.5 mV/Pa,灵敏度重复偏差小于0.24 mV/Pa.     

一种单片集成电容式压力传感器的设计、制造和测试

提出了一种新型电容式压力传感器.在外加压力下,该传感器的极板面积、间距以及介质层介电常数均发生改变,并导致电容发生变化.同时介绍了接口电路的设计,该电路基于电容-频率转换原理.该传感器结构简单,实现了与CMOS接口电路集成.传感器采用标准CMOS工艺与后处理工艺相结合的方式制造.结果表明,在800 hPa到1 100 hPa的压力范围,传感器灵敏度约为44 fF/hPa,接口电路的分辨率为3.77 Hz/hPa.     

基于SON构造的电容式绝对压力传感器设计

针对空洞层上硅工艺在制作高质量的单晶硅感压膜和真空密封腔上的优势,提出了将其应用于制作电容式绝对压力传感器。应用板壳理论建立了传感器压力检测的理论膜型,对传感器的感压膜进行理论计算和有限元仿真,并利用电容变化模型分析了传感器的灵敏度。给出了基于Pcap01芯片的微电容检测系统的设计,对于半径为100μm,厚度为1. 7μm的圆形感压膜,初始电容值为0. 278 p F,传感器灵敏度为0. 86 f F/k Pa。     

A new measurement microphone based on MEMS technology

This paper presents a new type of measurement microphone that is based on MEMS technology. The silicon chip design and fabrication are discussed, as well as the specially developed packaging technology. The microphones are tested on a number of key parameters for measurement microphones: sensitivity, noise level, frequency response, and immunity to disturbing environmental parameters, such as temperature changes, humidity, static pressure variations, and vibration. A sensitivity of 22 mV/Pa (-33 dB re. 1 V/Pa), and a noise level of 23 dB(A) were measured. The noise level is 7 dB lower than state-of-the-art 1/4-inch measurement microphones. A good uniformity on sensitivity and frequency response has been measured. The sensitivity to temperature changes, humidity, static pressure variations and vibrations is fully comparable to the traditional measurement microphones. This paper shows that high-quality measurement microphones can be made using MEMS technology, with a superior noise performance.     

Membrane microcantilever arrays fabrication with PZT thin films for nanorange movement

Lead zirconate titanate (PZT) piezoelectric thin films have been prepared by sol-gel method to fabricate microcantilever arrays for nano-actuation with potential applications in the hard disk drives. In order to solve the silicon over-etching problem, which leads to a low production yield in the microcantilever fabrication process, a new fabrication process using DRIE etching of silicon from the front side of the silicon wafer has been developed. Silicon free membrane microcantilevers with PZT thin films of 1 μm in thickness have been successfully fabricated with almost 100% yield by this new process. Annealing temperature and time are critical to the preparation of the sol-gel PZT thin film. The fabrication process of microcantilever arrays in planar structure will be presented. Key issues on the fabrication of the cantilever are the compatible etching process of PZT thin film and the compensation of thin film stress in all layers to obtain a flat multi-layer structure.     

Fabrication of an S-shaped microactuator

We have developed a new fabrication process for electrostatic actuators having an S-shaped film element, which we previously invented for such applications as gas valves. The developed process allows batch fabrication of the actuator whose S-shaped structure height, which is equal to the amount of vertical film displacement, is of the order of a few hundred micrometers. The microactuators are fabricated by stacking three wafers. The middle wafer contains the sputtered Ni film strip which is buckled into an S-shape during the stacking process. The length of film necessary for the S-bend profile has a folded structure which is stretched after stacking. The size of the fabricated chip was 5 mm×5 mm, and the vertical film displacement was 220 μm. The actuator was operated by electrostatic force when the applied voltage was more than 70 V     

Residual stress influences on the sensitivity of ultrasonic sensor having composite membrane structure

Stress and sensitivity of arrayed ultrasonic sensors utilizing piezoelectric thin film (lead–zirconate–titanate film: Pb(Zr_0.52Ti_0.48)O₃) having composite membrane structure are demonstrated. Due to different thermal and elastic characteristics of each constitutive layer, a subsequent residual stress and deflection is generated on the resultant composite membrane. We present the influence of residual stress on the mechanical behaviors and sensitivities of a Si-based integrated sensor device. The design of sensor structure and the fabrication process especially relating to thermal treatment have significant effects on the stress state of the composite membrane, and the relationships among the stress states, deflections of membrane and sensitivities of sensor devices are considered. Tensile stress induced on the membrane consequently leads to sensitivity deterioration, while compressive stress improves sensitivity. Sensitivities of each sensor structure are expressed as the ratio of output voltage (V) to the acoustic pressure (P), and the variations of those are discussed relating to the residual stress states, PZT film properties and mechanical behaviors of each composite membrane.     

Design and modeling of a single-mass biaxial capacitive accelerometer based on the SUMMiT V process

This paper presents the design of a biaxial capacitive accelerometer that takes advantages of a single-mass configuration to provide two orthogonal axes of sensitivity. The accelerometer structure is based on the SUMMiT V fabrication process. A set of fixed electrodes provides reliable measurements of capacitance in the two orthogonal directions. An analytical model based on the Euler-Bernoulli stress theory is introduced for variable cross-sectional area beams and is validated with a finite element analysis. In order to avoid a short circuit between fixed and movable electrodes, four displacement limiters were designed. The displacement limiters prevent out-of-plane displacement of the seismic mass and can withstand an impact of 250,000 G. A two-dimensional transient analysis of the seismic mass was carried out to confirm a linear oscillation behavior for either direction on the operation plane. The natural frequencies in the vibration modes of the two axes of interest are 462.5 and 463.2 Hz. It is also shown that the principal stresses in the beams are smaller than the fracture strength of polysilicon.     

A Single-Crystal Silicon Symmetrical and Decoupled MEMS Gyroscope on an Insulating Substrate

This paper presents a single-crystal silicon symmetrical and decoupled (SYMDEC) gyroscope implemented using the dissolved wafer microelectromechanical systems (MEMS) process on an insulating substrate. The symmetric structure allows matched resonant frequencies for the drive and sense vibration modes for high-rate sensitivity and low temperature-dependent drift, while the decoupled drive and sense modes prevents unstable operation due to mechanical coupling, achieving low bias-drift. The 12–15-$mu m$-thick single-crystal silicon structural layer with an aspect ratio of about 10 using DRIE patterning provides a high sense capacitance of 130 fF, while the insulating substrate provides a low parasitic capacitance of only 20 fF. A capacitive interface circuit fabricated in a 0.8-$mu m$CMOS process and having a sensitivity of 33 mV/fF is hybrid connected to the gyroscope. Drive and sense mode resonance frequencies of the gyroscope are measured to be 40.65 and 41.25 kHz, respectively, and their measured variations with temperature are$+18.28~ Hz/~^circ C$and$+18.32~ Hz/~^circ C$, respectively, in$-40~^circ C$to$+85~^circ C$temperature range. Initial tests show a rate resolution around 0.56 deg/s with slightly mismatched modes, which reveal that the gyroscope can provide a rate resolution of 0.030 deg/s in 50-Hz bandwidth at atmospheric pressure and 0.017 deg/s in 50-Hz bandwidth at vacuum operation with matched modes.hfillhbox[1195]     

Integration of displacement sensor into bulk PZT thick film actuator for MEMS deformable mirror

Bulk PZT thick film actuator integrated with displacement sensor, the so-called self-sensing actuator, is presented in this paper. The PZT film is used as not only an actuating layer but also a displacement sensor, which is achieved by dividing the electrode on the top surface of the PZT film into two parts: central top electrode for actuating and outer annular sensor electrode for piezoelectric displacement detection. When the actuator moves, the piezoelectric charge is induced in the outer annular PZT due to the piezoelectric effect. The total amount of accumulated charge is proportional to the stress acting on the PZT, which is in turn proportional to the actuator displacement. By collecting the piezoelectric charge, the actuator displacement can be detected. A theoretical model is proposed to determine the structure parameters of the sensor and predict the sensor sensitivity. Experiments were performed on the micro-fabricated sensor integrated PZT thick film actuator, and the measured piezoelectric charge is close to the theoretical predictions. The integrated piezoelectric sensor has a displacement sensitivity of approximately 4 pC/nm. In addition, the integration of displacement sensor into the actuator needs no additional fabrication process and has no influence on the actuator performances.     

Fabrication of silicon and oxide membranes over cavities usingion-cut layer transfer

Silicon and oxide membranes were fabricated using an ion-cut layer transfer process, which is suitable for sub-micron-thick membrane fabrication with good thickness uniformity and surface micro-roughness. After hydrogen ions were implanted into a silicon wafer, the implanted wafer was bonded to another wafer that has patterned cavities of various shapes and sizes. The bonded pair was then heated until hydrogen-induced silicon layer cleavage occurred along the implanted hydrogen peak concentration, resulting in the transfer of the silicon layer from one wafer to the other. Using this technique, we have been able to form sealed cavities and channels of various shapes and sizes up to 50-μm wide, with a 1.6-μm-thick silicon membrane. As a process variation, we have also fabricated silicon dioxide membranes for optically transparent applications     

BESOI-based integrated optical silicon accelerometer

The design, simulation, fabrication and characterization of a new integrated optical accelerometer is presented in this paper. The reduction of fabrication, packaging and thermomechanical stresses are considered by keeping the weak mechanical parts free of stresses. The mechanical sensor consists on a quad beam structure with one single mass. In addition, there are two waveguides on the frame of the chip self-aligned to one on the mass of the accelerometer. Four lateral beams increase the mechanical sensitivity and allow the flat displacement of the optical waveguides on the mass. The working principle is based on the variation of the output light intensity versus the acceleration due to the misalignment of the waveguides. The devices have been optimized by the finite-element method to obtain a mechanical sensitivity of 1 /spl mu/m/g. The fabrication technology is based on BESOI wafers combining bulk an surface micromachining. Moreover, machined glass wafers with cavities are bonded to the silicon wafer for packaging and damping control. Special packaging considerations as dicing, polishing and alignment are also presented. Optical measurements at 633 nm shown an optical sensitivity of 2.3 dB/g for negative and 1.7 dB/g for positive acceleration. This difference in the sensitivity has been demonstrated as a consequence of the passivation layer located over the core of the waveguides.