Design Optimization of MEMS Comb Accelerometer
Design Optimization of MEMS Comb Accelerometer
复制标题
MEMS梳状加速度计的设计优化
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
X. Xiong
中科院分区：
文献类型：
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作者：
K. Sharma;Isaac G. Macwan;Linfeng Zhang;L. Hmurcik;X. Xiong
微机电系统（MEMS）是指将特征尺寸为1~1000微米的电气和机械部件集成在一起的技术。MEMS梳状加速度计已成功应用于汽车安全气囊展开系统。本文讨论了一种多晶硅表面微机械MEMS梳状加速度计的优化设计。该装置采用折叠光束结构，提高了灵敏度。可移动的质量通过折叠梁连接到两个锚。可活动的手指从可活动的肿块两侧伸出。每个活动手指周围都有左右固定的梳状指，从而形成差分电容对。任何沿敏感方向的加速度都会对可动质量产生惯性力，使梁发生偏转。因此差分电容间隙将发生变化。通过测量这种差分电容变化，可以测量所经历的加速度。通过ANSYS有限元仿真，提取出器件的灵敏度和谐振频率。通过在ANSYS仿真中逐渐改变设计参数，推导出器件灵敏度与各设计参数之间的关系。导出了器件灵敏度随光束宽度、光束长度和质量宽度的变化曲线，与理论预测吻合较好。从分析中得出结论，器件的性能很大程度上取决于各种设计参数。通过调整设计参数，可以获得所需的灵敏度。根据仿真结果，确定了一组梳状加速度计的优化设计参数。ANSYS仿真结果表明，该装置的位移灵敏度为3nm/g。提出的梳状加速度计可用于汽车安全气囊展开和导航等多种应用，并提出了梳状加速度计的制造工艺。该器件采用牺牲层表面微加工工艺制备。
MEMS (Microelectromechanical Systems) refers to the technology integrating electrical and mechanical components with feature size of 1~1000 microns. MEMS comb accelerometers have been successfully applied for air-bag deployment systems in automobiles. In this paper, the design optimization of a polysilicon surface-micromachined MEMS comb accelerometer is discussed. The device uses folded-beam structure to enhance the sensitivity. The movable mass is connected to two anchors through folded-beams. There are movable fingers extruding from both sides of movable mass. Each movable finger has left and right fixed comb fingers surrounding it, so that a differential capacitance pair is formed. Any acceleration along the sensitive direction will induce inertial force on movable mass and deflect the beams. Hence the differential capacitance gap will change. By measuring this differential capacitance change, the experienced acceleration can be measured. ANSYS FEM simulation is used to extract the device sensitivity and resonant frequency of the device. By gradually varying the design parameters in ANSYS simulation, the relationship between the device sensitivity and various design parameters is derived. The curves of device sensitivity versus beam width, beam length and mass width are derived and they are in good agreement with theoretical prediction. From the analysis it is concluded that the device behavior strongly depends upon various design parameters. By adjusting design parameters, desired sensitivity can be obtained. Based on the simulation results, a set of optimized design parameters for the comb accelerometer is decided. The ANSYS simulation results show that the device has displacement sensitivity of 3nm/g. The above-proposed MEMS comb accelerometer may be used for many applications, such as automobile airbag deployment and navigations, fabrication sequence of the comb accelerometer is also proposed. The device is to be fabricated using surface-micro machining process with sacrificial layer technique.