以光學超解析法製作光碟母模之研究

Abstract

本研究的目的在於探討一種運用熱致超解析效應的新式雷射微影(laser lithography)技術，並且證明此技術能有效地縮小光阻層上的記號寬度。 此技術是將一層薄薄的金屬遮罩層鍍在光阻層之上，經過聚焦雷射的曝光之後，遮罩層將在雷射光點中心附近開啟一個融熔區域。因為此區域的大小遠小於雷射聚焦光點，而且其光學性質不同於其他未融熔的固態區域，穿透光之光強度分佈將會較入射光之光強度分佈來得小，因而形成小於光學繞射極限的光點。 本論文的實驗方式是採用現今商用之光碟母模製程，加上一鍍膜的手續，來進行光碟母模的製備。厚度範圍由5到15 nm的銦薄膜被鍍到光阻膜之上，經過雷射刻版以及顯影的步驟之後，以原子力顯微鏡來量測及評估母膜表面情況。根據模擬及實驗的結果，光阻層上的記號寬度可以比雷射刻版機所能達到的極限還要小40%以上。

The objective of this research is to study an innovative lithography using the effect of thermal-induced super resolution, and to demonstrate that the technique can effectively reduce the exposed pit width on the photoresist layer. The technique makes use of a thin metallic mask layer deposited on the top of the photoresist layer. After illuminating with a focused laser beam, the mask layer opens an aperture in melting temperature area around the center of the laser spot. Because the aperture size is much smaller than the laser spot and the optical properties of solid mask layer are different from those of melting one, the intensity distribution of the transmission light would become narrower than that of the incident light and forms a below-diffraction-limit spot size. Our experimental processes were based on the commercial CD mastering procedure and added a mask layer deposited by evaporation. Indium thin film with a range of thickness from 5 to 15 nm was evaporated on the photoresist layer as metallic mask layer. After recording and development processes, the profile of pits on the glass master disc was measured by atomic force microscope (AFM) to evaluate the experimental results. According to the simulation and experimental results, the pit width on the photoresist layer could be shrunk by more than 40% of the diffraction limit of the laser beam recorder.