利用殘餘應力研製CMOS製程相容之射頻微型開關

Use residual stresses to develop MEMS switches with CMOS process

指導教授 : 黃榮堂、施勝雄 研究生 : 許中勇  機電整合研究所94年


摘要

  本論文採用CMOS 標準製程配合幾項微機電(MEMS)的後製程,來研製出微型開關。開關驅動的方式,在此是採用「靜電力」,根據電壓的增加,使得電壓極板對懸臂樑的吸引力慢慢變大。目前微型開關的研究皆碰到電壓過大以致於不能與CMOS結合運用,且CMOS製程技術會產生殘餘應力並造成懸臂樑翹曲嚴重等問題,故本文利用CoventorWare微機電模擬軟體驗證能量法分析殘餘應力所造成懸臂樑翹曲等問題的可行性,再藉由懸臂樑翹曲作為主要的設計方式,將微型開關電壓控制在3.3V,並透過CIC做RLS製程,將基材掏空以減少Substrate Loss、增加Isolation及後製程步驟僅需ㄧ道蝕刻過程即可將結構釋放,最後利用厚光阻作為自我封裝以降低製作晶片成本。
  利用此一微型開關特性運用於被動元件,例如可變電感及可變電容。本設計之微型開關可達到小面積、驅動電壓小、製作容易且能夠與CMOS 製程相容。因為僅使用CMOS 製程的插銷層(Via)、金屬層(Metal)、多晶矽層(Poly)等來實現,實際製作上,透過CIC 下線TSMC0.35um CMOS製程,以濕蝕刻後製程完成懸臂樑的釋放,預期可成為積體電路元件之一。


關鍵詞:標準CMOS製程、微機電製程、微型開關、可變電感、可變電容

ABSTRACT

 In this thesis, we present a novel MEMS-switch fabricated with CMOS process and extra post-process techniques of MEMS. A MEMS-switch includes controllable structure and two steady electrodes. The switch is driven by using electrostatic force. The force of attraction form electrode to cantilever beam increases while enlarging the voltage.
 So far, the problem we encountered is that the driving voltage of MEMS switch is too large to combine with CMOS technique. Besides the residual stress produced from CMOS process caused such a serious problem as deflection of cantilever beam. Therefore, in this research, we use CoventorWare to inspect the feasibility of Energy Method. Subsequently, the driving voltage can be set below 3.3V. The region of RLS should be defined preliminarily, and Silicon should be excavated to reduce Substrate Loss and increase Isolation. Only one etching process is needed in post-process to form the structure. Finally, use thick photoresist to complete self-packaging to lower down the cost of chip fabrication.
 The property of MEMS switches can be applied to such passive components as variable capacitances and variable inductors. The advantages f MEMS switches are as follows: small area, low driving voltage, uncomplicated fabrication, and compatible with CMOS process. We only use via layer, metal layer and poly layer of CMOS process to fabricate our design. Therefore, our MEMS switches are fabricated by the TSMC 0.35um 2P4M process commissioned by CIC.

Key Words: CMOS、MEMS、MEMS switches、Variable Inductor、Variable Capacitor