- 學位論文
微機電式數位類比轉換反射鏡模組之研製及在白光干涉系統之應用
A Micromirror Module using a MEMS Digital-to-Analog Converter and its Application for White-Light Interferometry System
摘要
本研究發展了一種微機電式數位類比轉換(digital-to-analog converter)之反射鏡模組，可將數位輸入訊號轉換成類比位移量，並且應用在非接觸式的光學式表面輪廓量測系統中。在設計上，採用了電子電路中的二進位權重數位類比轉換概念，應用於機械結構的轉換中，並且以物理模型的推導配合數值模擬的結果來進行設計。在製程上，分別以SOI 晶圓和玻璃晶圓為基材，並採用氫氧化鉀非等向性溼蝕刻、深式反應離子蝕刻、氫氟酸/鹽酸濕蝕刻和金屬蒸鍍等技術，成功地將微反射鏡面、數位類比轉換機構和8 組靜電式平行板致動器整合於單一晶片中。除此之外，也同時克服了傳統微機電製程中，對於大面積的懸浮結構中，必須佈滿蝕刻孔以移除犧牲層之限制，製作出直徑1.2 mm 的完整反射鏡面。此元件的驅動電壓為60 V，暫態的切換時間為80 ms。在數位類比的轉換功能方面，此元件能將4位元的數位輸入訊號，轉換成奈米尺度的位移量。微反射鏡的位移量隨著輸入的數位訊號呈現線性的增加，單一的步階位移量為72 mm，總行程為1050 nm。此元件不僅具備了體積小和高精準度等優點，更容易以簡單的電路來進行控制。除此之外，本研究亦將此元件安裝於白光干涉系統中，以取代傳統所使用的參考反射鏡和壓電致動平台模組，有效地簡化了系統的複雜度和成本。同時，以光柵結構和光學透鏡作為樣本，配合七步相移演算法進行量測和分析，並與接觸式表面輪廓儀量測的結果相比較，平均誤差在10 nm 以內，顯示此元件已可成功應用在白光干涉系統中。
並列摘要
In this work, we develop a microelectromechanical digital-to-analog converter mirror module (M-DACMM), and demonstrate its application for non-contact optical surface profiling systems. The proposed device generates nano-scale step motions that are proportional to input digital signals. The M-DACMM device, which consists of a large-area mirror, a digital-to-analog converter and 8 electrostatic parallel-plate actuators, can be monolithically fabricated by using a proposed micromachining process. Also, the process is suitable for releasing a large-area mirror (1mm in diameter) without the need of etching holes on the mirror surface. The transient responses of the mirror module are also measured and discussed. The switching time between two input binary states is less than 80 ms. The measured full-scale displacement is 1050 nm, and the motion step is 72 nm. The M-DACMM device has advantages of high position accuracy, high repeatability, and small size. Also, the device can be easily controlled by a simple actuation circuit. The M-DACMM is successfully installed on a white-light interferometry system as a reference mirror module. The surface-profiling results measured by the system are also presented.