靜電式光相位調制器陣列

Abstract

本論文提出兩種光相位調制微鏡面陣列，兩者針對512nm波長的光源，皆可以達到使鏡面出平面方向的四分之一波長(128nm)位移，除此之外也可保持鏡面的平整度在十分之一波長(51nm)以內的最大彎曲量。兩設計利用台灣積體電路公司的0.35um CMOS製程來製作元件的主結構，並且在元件製作完成後進行自行設計的後製程。後製程中，一道雙面對準黃光微影步驟與兩道ICP非等向性背後矽蝕刻步驟，此三步驟在微鏡面下方留下40um厚的矽塊材，這將會使得在結構懸浮後，200um×200um大小的微鏡面可抵抗殘餘應力產生的變形。之後兩元件各自使用RIE非等向性乾蝕刻與HF Vapor等向性乾蝕刻來當作完成懸浮的最後一道後製程。而此兩個光相位調制微鏡面陣元件是以靜電力所驅動，其中，以高低梳狀致動器的光相位調制器需要以38V來驅動微鏡面到四分之一波長的位移，且擁有65%的Fill Factor，另一個結合梳狀致動器與平行板靜電致動器的光相位調制器對於四分之一波長位移只需要3V的驅動電壓，但卻在不外加任何覆晶封裝技術下，達到有90%高的Fill Factor。

Two phase shifting micro mirror arrays that can achieve λ/4 vertical displacement and make the mirror peak-to-valley deformation within λ/10 (514nm light source) have been designed, fabricated and tested. These phase shifter arrays are fabricated using TSMC 0.35 2P4M CMOS process. By utilizing in-house developed post processes which consisted of one double side alignment lithography step and two ICP anisotropic silicon backside etching steps. We are able to preserve 40um thick silicon under the 200um×200um mirror which can be used to decrease the mirror deformation after release. Finally two phase shifters use RIE anisotropic etching and HF vapor isotropic etching to release micro structures respectively. The present phase shifting micro mirror arrays are driven by electro-static forces. Note that the comb drive phase shifting micro mirror array with 65% fill factor required 38V to achieve λ/4 displacement. However, the comb drive plus parallel plate phase shifting micro mirror array with 90% fill factor which needs only 3V to reach the λ/4 displacement without the need of flip-chip bonding technology.