應用光學近距效應修正之減光式相移光罩搭配環形偏軸發光與傳統發光最適化模擬與研究

Abstract

現今以i-線（365奈米）為光源之微影成像製程，由於圖案線寬越來越小與相互靠近，使得光學近距效應變得嚴重，同時聚焦深度與解像度亦嚴重受影響。為符合不同圖案之設計，i-線光學微影成像不易超越0.35微米解像度與1.25微米聚焦深度。應用相移光罩與偏軸發光等新技術可增加解像度與聚焦深度，另外，方可在光罩上利用光學近距修正技術來改善。 本論文以田口玄一實驗計劃法，針對0.35微米製裡，利用L9、L18直交表研究相關光學參數與光學近距修正對製程的影響。模擬結果發現，對於減光式相移光罩搭配環形發光的組合中，採用輔助線/隙之光學近距修正設計，其優點為提高曝光寬容度，密集線/隙增加∼11％、孤立線增加∼5％、孤立隙增加∼1％；聚焦深度改善上，密集線/隙增加∼6.7％、孤立線增加∼3.4％、孤立隙增加∼4.5％。如搭配傳統發光，於曝光寬容度上，密集線/隙增加∼8％、孤立線增加∼6％、孤立隙增加∼2％：於聚焦深度上，密集線/隙增加∼1.1％、孤立線增加∼2.8％、孤立隙增加∼2.8％。而使用光罩圖案偏差之光學近距修正設計，僅對密集線/隙之曝光寬容度具改善效果，曝光寬容度增加∼5％，對孤立線與孤立隙並無改善效果，此法對聚焦深度改善甚少。比較輔助線/隙修正與光罩固案偏差修正兩法，以前者為優，對各種圖案均有程度不一的改善效果。 在微影製程細線化要求下，變因不斷增加，不同製程相關參數之優選，將是微影技術成敗的關鍵。以電腦模擬軟體搭配田口實驗計劃法，可經濟而整合性的分析與研究眾多變因。

In i-line (365 nm) lithographic processes, denser and also narrower linewidth will generate serious proximity effect, decrease depth of focus (DOF) and resolution. It is not easy to have a resolution better than 0.35 μm and a DOF greater than 1.25 μm while still meet the design rules for all different patterns. The apphcation of phase-shifting Mask (PSM) and off-axis illurmnation (OAI) could increase both DOF and resolution, besides, optical proximity correction (OPC) on mask would also improve DOF and resolution. L9 and L18 orthogonal arrays of Taguchi method have been applied to the 0.35 μm processes to study the effects of optical parameters and OPC. Under the combination of attenuated PSM and annular OAI, the OPC by assisted line/space (L/S) resulted in the larger exposure latitude (EL), in which dense L/S increased ~11%, isolated line (IL) ~5%, isolated space (IS) ~1%. For improvement of DOF, dense US increased ~6.7%, IL ~3.4%, IS ~4.5 %. Under the combination of attenuated PSM and conventional illmnmation, regarding the exposure latitude (EL), dense L/S increased ~8%, IL ~6%, IS ~2%. regarding improvement of DOF, dense L/S increased ~1.1%, IL~2.8 %, IS~2.8 %. OPC by pattern bias indicated that only EL of dense L/S could be improved. EL increased ~5%. Pattern bias did not show improvement to both IL and IS. DOF was improved only slightly. The comparisons between assisted L/S and pattern bias indicated that assisted L/S is better method for OPC. Due to the demanding of narrower linewidth, the process parameters keep increasing. The optimization of related process parameters is the key issue for the success of lithography. Simulation combined with Taguchi method could study and analyze these parameters economically and integrately.