電化學蝕刻停止之研究

Abstract

本論文對國內鮮少人深入，在微機電領域卻又勢在必行之電化學蝕刻停止製程進行探討研究，從已發展完成之非等向蝕刻技術（anisotropic etching）的基礎上，建構具有高精準度、製程便利及高重現性的電化學蝕刻停止製程技術（Electrochemical Etch-stop Technology），以期在微機電系統元件研發上，具備完成良好特性的元件之關鍵製程能力。 首先，我們建構一可進行三電極與四電極電化學蝕刻設備，並設計以多種附加方式改善蝕刻後表面粗糙度的蝕刻槽體。使用此設備進行電化學蝕刻特性之參數萃取，完成與N+磊晶層厚度20um接近，其厚度為21.96um的薄膜，並討論各種方式對蝕刻後矽晶片表面粗糙度的影響。最後，研究對鋁、氧化矽與氮化矽對矽均具有極高蝕刻選擇率之特殊TMAH溶液配方與電化學蝕刻停止技術結合，以期在已完成CMOS電路製程的矽晶片上完成具有良好特性之微機電元件，整合為智慧型微機電系統晶片(SOC)。

A study of the electrochemical etching stop process is presented in this thesis. Based on the well-developed anisotropic etching technology, we set up the electrochemical etch-stop technology equipment which is higher precision, less process step, higher reproducible. Therefore, we can realize the precisely controlled ultra thin membrane after accomplishing this research to have the key process of advanced devices with high performance. First, we set up the electrochemical etch-stop equipment that can work by three and four electrode electrochemical etch-stop methods and designed a etching tank with ultrasonic shaking, oxygen adding and circulating solution flow of etching solution to improve the surface roughness. Second, we extracted the parameters of electrochemical etching characteristics and fabricated the membranes with the thickness of 21.96 um near the 20 um epitaxy layer using this equipment. Third, We discussed several ways how to improve the surface roughness. Finally, special composition of TMAH solution that has good selectivity of aluminum, silicon oxide and silicon nitride between silicon combined with the electrochemical etch-stop technology. For the reason, we can fabricate the micromachining devices with good performances in the same silicon wafer after CMOS circuit process completed. It is the trend of system of chip (SOC) of MEMS.