繞射光學元件應用於遠場繞射式微影技術之評估與研究

Abstract

本論文提出一種新式的無光罩光微影架構，藉由遠場光繞射的方式來達到微影的效果，應用此技術可以獲得次微米波長的特徵圖形，且整合無光罩技術的各項優點。可以免除製造傳統光罩的費用、縮短製程時間，快速產生光罩圖案、易於修正光罩設計、適合小量生產製造與實驗用途的多項優點。 論文中利用正型光阻(s1813)來描述在近場光微影下的震盪分佈，將近場下實驗的結果用來發展新式的遠場光微影技術。再利用連續相位式繞射元件模擬出類似近場光微影下的震盪分佈，並比較兩者的結果。 近場微影技術利用微機電製程製作晶圓母模，且搭配氣體輔助壓印技術製作出透明相位偏移光罩，可以達到相位偏移光罩般的次微米等級的線寬，且藉由近場接觸式相位偏移光罩微影技術，搭配光學顯微鏡、表面輪廓儀與原子力學顯微鏡，且利用感光阻劑與照光累積強度的高度相關性，可以研究在近場下光傳播分佈的物理行為。 研究中利用遞迴式傅立葉轉換法設計出連續相位式繞射光學元件，藉由純量理論，模擬出近場相位偏移微影實驗所到的光強度變化情形。 研究中所設計的繞射光學元件，其繞射結果在近場的光能量干涉情形與近場相位偏移微影實驗的結果呈現高度相關，有利於發展遠場繞射式光微影技術。

A new maskless optical lithography based on far-field diffractive lithography is proposed and evaluated in this thesis to achieve the sub wave-length results resolution enhancement method. In this thesis, the near-field perturbation of light passing through a phase mask was developed on a positive photoresist (s1813). The experiment will be used to obtain insights into the perturbation. A simulated far-field perturbation generated by a continuous-phase diffractive optical element (DOE) was attempted to achieve with the near-field perturbation obtained on the photoresist. The near-field lithography technique, used here, provides a means to achieve sub-micron features, typically accomplished by using the phase-shift mask technique with a LIGA process and gas assistant imprint process. The light intensity patterns observed using optical microscopy、surface profiler and AFM has provided detailed the near-field irradiance distribution of light intensity by using polycarbonate phase-shift mask. Then the continuous-phase DOEs were designed by IFTA (Iterative Fourier Transform Algorithm) to simulate the light perturbation. The IFTA design principle is to modulate incident light’s phase on element plane and to arrange the light phase and intensity distribution in diffractive plane, so that the final light intensity perturbation in diffractive plane be similar to the near-field perturbation distribution. The simulated patterns showed good agreement, demonstrating the design DOEs can be applied to the far-field optical lithography to achieve sub wave length results.