高灵敏度微机械薄膜的设计、模拟与优化

许多高性能微传感器和微执行器的实现都离不开高灵敏度的薄膜。使用微机械加工方法制备的薄膜一般有着不可忽视的残余应力。残余应力极大地降低了膜的机械灵敏度。文中提出的纹膜结构, 可在不改变工艺条件的前提下, 显著地降低残余应力的不良影响, 大幅度增加膜的灵敏度。理论分析的结果表明, 纹膜几何参数的设计是提高灵敏度的关键。文中提出了一种简单实用的纹膜制造工艺, 并结合此工艺设计出若干实际的结构,利用有限元分析(FEA ) 工具对结构进行了进一步的模拟和优化, 得到了各项设计参数的最优值。优化后纹膜的灵敏度较平膜提高了一个数量级, 可用于各种高性能M EM S 器件的制作。
关键词: 微机械; 残余应力; 灵敏度; 纹膜; 有限元分析
Abstract: A h igh ly sen sit ive m em b rane is essen t ial fo r m any devices based on m icroelec2 t rom echan ical system (M EM S). Fo r m icrom ach ined m em b rane, there is sign if ican t in ternal ( residual) st ress, w h ich st rongly decreases them echan ical sen sit ivity of m em b rane. The app li2 cat ion of co rrugated m em b rane offers the po ssib ility to increase the sen sit ivity of m em b rane w ithou t changing p rocess condit ion s, thu s elim inat ing the effect of in it ial st ress. A simp le ana2 lyt ical model p redict s that the imp rovem en t of sen sit ivity depends crit ically on the geom et ric param eter of the co rrugated m em b rane. A simp le and eff icien t p rocess to fab ricate the co rru2 gated m em b rane has been p resen ted and several co rrugated p rof iles are p ropo sed w ith th is p ro2 cess. To get the op t im al values of the designed param eters, F in ite Elem en t A nalysis (FEA ) m ethod has been u sed. The op t im ized co rrugated m em b rane show s the sen sit ivity mo re than one o rder larger than that of the f lat m em b rane w ith equal size and th ickness. M any h igh per2 fo rm anceM EM S devices can be realized w ith th is techn ique.
Key words: m icromach ine; res idua l stress; sen s itiv ity; corruga tedmembrane; FEA