許多高性能微傳感器和微執行器的實現都離不開高靈敏度的薄膜。使用微機械加工方法制備的薄膜一般有著不可忽視的殘余應力。殘余應力極大地降低了膜的機械靈敏度。文中提出的紋膜結構, 可在不改變工藝條件的前提下, 顯著地降低殘余應力的不良影響, 大幅度增加膜的靈敏度。理論分析的結果表明, 紋膜幾何參數的設計是提高靈敏度的關鍵。文中提出了一種簡單實用的紋膜制造工藝, 并結合此工藝設計出若干實際的結構,利用有限元分析(FEA ) 工具對結構進行了進一步的模擬和優化, 得到了各項設計參數的最優值。優化后紋膜的靈敏度較平膜提高了一個數量級, 可用于各種高性能M EM S 器件的制作。
關鍵詞: 微機械; 殘余應力; 靈敏度; 紋膜; 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