設計與製作半色調光罩以製作具任意外形之微結構在微元件光學上的應用

Abstract

本論文提出了以半色調網點(half-tone)的方式發展灰階光罩(gray-scale masks)，並結合準分子雷射微加工系統之技術。利用此技術我們可以使用準分子雷射微加工系統以及僅只一道半色調光罩直接地在一般的透明聚合物（polymer），例如polycarbonate上製作出具有連續而平滑之表面的微光學元件。因此利用此技術可以大幅地降低如在傳統半導體中利用多道光罩、多次曝光顯影、蝕刻來製作微光學元件的繁複製程,並減少在多次半導體製成中所導入的對準誤差並獲得較高的光學效率。另外此技術比起高光能量感應玻璃（HEBS）光罩法較為經濟實用。 從模擬以及實驗的結果中,我們發展出一套方便而可靠的方式以設計半色調光罩來製作可具任意外型的微光學元件，利用此方法設計出來的半色調光罩已成功地製作出雙稜鏡以及微透鏡等微光學元件。而製作出來的微光學元件其表面平整度之方均根值可達到在小於十分之一的波長程度，因此製作出之元件將可提供相當好的功能與光學效率。根據應用上的需求我們可以設計半色調光罩來製作出所需的元件，元件的大小可以從數百微米到數微米，和通用的高深寬比。 實驗結果亦展示了雙稜鏡及微透鏡分別在半穿透半反射式液晶顯示器及固態沈浸透鏡（Solid Immersion Lens）上之應用，這樣的結果顯示出半色調光罩技術可以成功地用於製作各種應用上如顯示器技術、光資訊儲存、光纖通訊及微機電等領域所需之微光學元件。

We have developed a new technique of gray-scale masks by using half-tone techniques combined with the excimer laser micromachining. This technique can directly produce the microoptical elements with continuous surface relief on transparent polymer substrate, such as polycarbonate substrate by only one half-tone mask. Thus, this technique can reduce the complexity in fabrication, such as the complex process of multiple lithographic processes and alignment errors in traditional multi-binary masks method and yield higher optical efficiency. Beside, this technique is more cost-effective compared with HEBS (High Energy Beam Sensitive) glass technology. From the simulated and experimental results, we developed a convenient and reliable method to design the half-tone mask for forming arbitrary 3-dimentional microstructure. By using this method, the microoptical elements such as biprism and microlens with continuous profile are fabricated by designed half-tone mask. The RMS (Root Mean Square) value of surface roughness is within one-tenth of wavelength for fabricated microoptical elements, yielding high optical performance. The dimension of fabricated microoptical elements can range from a few to hundreds of micron with high aspect ratio according to the applications. The applications of fabricated biprism and microlens in transflective LCD and SIL (solid immersion lens) were demonstrated, respectively. Microoptical elements fabricated by using half-tone mask used for display, optical storage, optical fiber communication, MEMS, and etc. shall be very promising.