多晶硅双端固支梁高周循环下疲劳特性的分析

多晶硅固支梁是MEMS器件中较常见的可动部件,通过静电激励的方式对其进行疲劳振动加载;所用结构为面外运动结构,为了测试样品的加速疲劳特性,通过在固支梁面内引入缺陷的方式来增大应力水平值;器件在经历了1.72×1011次循环之后,微梁的谐振频率、振动幅度发生了较大偏移,其谐振频率的偏移量达到14.531 kHz,器件性能发生了严重的退化.研究结果表明,利用谐振频率的改变来表征材料性能的退化是一种准确、可行的方法,同时本文进一步分析指出,器件上引入凹槽缺陷的方法确实可起到加速疲劳的作用;可利用此方法制作不同应力水平幅度的结构进行振动载荷疲劳加载实验,从而得到固支梁结构疲劳加速因子.

Analysis of Polysilicon Fixed-fixed Beam under High-cycle Fatigue

Polysilicon fixed-fixed beam is familiar in MEMS devices as a movable part, and in this paper it is actuated by the way of electrostatic as fatigue vibration loading. The structure used here is out-of-plane movement ones, notch is fabricated in the beam to increase the level of stress which is employed to study the accelerated life test of the fixed-fixed beam. The resonant frequency and amplitude of vibration of the beam increase visibly after it suffers the vibration loading more than 1.72×1011 cycles, and the offset of the resonant frequency is 14.531 KHz. The performance of device decreases severely. The results show that it is an accurate and feasible method to characterize the changes of material performance of beam. The method that the beam with notch which is employed to study the accelerated life test of the fixed-fixed beam is feasible. Different levels of stress can be generated for accelerated life experiment under vibration fatigue loading by this way, and the acceleration factor can be got at the same time.