灰階光罩之設計與製作

Abstract

傳統的繞射光學元件大多採用二元光罩多道光罩曝光的方式來製作多步階的相位變化結構，對於2n個相位階分佈的繞射光學元件，需要進行n次的曝光與蝕刻。由於製程步驟繁複、不經濟，而且在製程中任一步驟發生誤差就會造成元件效能的降低，所以大家都期盼能有一種新型技術既能減少曝光顯影的步驟，又能維持繞射光學元件的高光學效率。 本論文以半色調網點(halftone)的方式發展灰階光罩(gray-scale masks)技術，將此一技術應用在新型微型繞射光學元件的製作上，以減少傳統二元式光罩在製作上所產生的光罩使用量、製程步驟及製程誤差，以提昇微型光學元件的應用性。

Conventionally, the diffractive optical elements（DOE’s）are produced with a binary multimask lithography-and-etch fabrication process. To generate a multilevel DOE structure with 2n phase level requires n binary masks, n photolithographic processing steps, and n etching steps. The multistep fabrication process is consuming, resulting in a low yield rate, and costly. It also places strict requirements on multimask alignment and etching error. Obviously, the binary multimask-and-etch technique is not practical for fabricating large numbers of DOE phase level for higher diffration efficiencies. In this thesis we have developed a new technique of gray-scale masks by using halftone techniques. This technique can be applied in micro-optical components fabrication to eliminate the multiple lithographic processes and alignment errors in traditional binary masks fabrication. As a result, the application of micro optical devices should be greatly extended.