Study on Fabrication of MEMS Cantilevers for Photoacoustic Spectroscopy Gas Sensors

[[abstract]]本研究利用微機電系統技術開發高靈敏度之懸臂樑光聲光譜感測器，進行懸臂樑感測器元件設計、製作與測試。使用絕緣層上矽晶片中的氧化層當作犧牲層，利用感應耦合電漿離子蝕刻定義懸臂樑輪廓，並蝕刻背基板直到氧化層，最後使用氫氟酸掏空氧化層，完成懸臂樑感測器元件之製作。完成後針對懸臂樑元件特性進行分析，利用白光干涉儀量測懸臂樑的三維表面輪廓，以得知懸臂樑距離水平面之高度差，再經由雷射都卜儀測量出懸臂樑的第一振模頻率，代入公式計算懸臂樑之楊氏係數、彈性常數與離面位移。此微機電懸臂樑將可應用在高靈敏度光聲光譜氣體偵測上。[[abstract]]In this study, micro-electromechanical system (MEMS) cantilevers for the photoacoustic spectroscopy (PAS) gas sensing applications were designed and fabricated. The cantilevers were fabricated on a silicon-on-insulator (SOI) wafer with the buried oxide layer (BOX) as the sacrificial layer. The deep-reactive-ion etching (DRIE, ICP) was used to define the shape of cantilever, and for the through wafer etching. The structure was then released, removing the BOX layer, in hydrofluoric acid solution. The cantilevers were measured under a white light interferometer to determine the static out-of-plane displacement. In order to analyze the physical properties (resonance frequency, Young’s modulus, spring constant, displacement amplitudes) of cantilevers, the measurement was then taken using a laser Doppler vibrometer. This device can achieve better analytical sensitivity, highly linear response, and greater physical movement than that the conventional membrane microphone does.[[note]]碩