環形偏軸發光與調細式相移光罩最適化模擬與應用

Abstract

偏軸發光應用於微影成像技術有多項優點,最大優點為在不改變i-線 (365 奈米)的原有製程條件下,可大幅改善聚焦深度;其次包括應用簡單, 最簡單的方法為曝光步進機加裝遮光板即可. 偏軸發光的缺點為四孔,二 孔及直縫型的改善效果有圖案方向的依存性. 另外,光源均勻性亦尚待改 善. 環形偏軸發光對於解像度與聚焦深度的改善雖非最佳,但無圖案方向 性的限制,所以在生產線上之實用性較高.本論文以田口玄一實驗計劃法, 針對0.35微米製程,利用L9, L18直交表研究相關光學參數對製程的影響. 模擬結果發現,對於0.35微米密集線 /隙而言,最適化設計是數值光圈 為0.5,環形發光外環相擾度當量值為0.70 ,環形發光內環相擾度當量值 為0.35,光罩設計為負偏差0.03微米. 聚焦深度可增加0.4微米左右.面對 眾多的微影製程變因,不同製程相關參數之最適化,將是微影成像技術成敗 的關鍵. 以電腦模擬配合田口實驗計劃法可經濟而有意義地對眾多的變因 進行研究. Off-Axis Illumination (OAI) has several merits when applied to microlithography. The most important merit is that depth of focus could be largely improved while conventional i-line process remain unchanged. Next, the application of OAI is quite easy, the simplest way to apply OAI is the adding of an aperture stop in stepper. The disadvantage of OAI is that the improvement is dependent of pattern orientation from types of quadrupole, dipole and slit. The homogeneity of illumination beam also needed to be improved. Annular OAI is not the best OAI for the improvement of resolution and depth of focus, however, annular OAI is independent of pattern orientation, therefore, its applicability to production line is higher than others. In this thesis, the Taguchi Genichi methodology of experimental design has been applied by using L9 and L18 orthogonal array to study the effects of optical parameters on the processes for 0.35 um linewidth patterns. Simulation study found out that NA 0.5, outer ring sigma equivalent 0.70 in annular OAI, inner ring sigma equivalent 0.35 in annular OAI and negative mask bias 0.03 um are the optimum design for 0.35 um dense line/space. The depth of focus improved by about 0.4 um. Faced with many variances in lithographic processes, the optimization of related factors for varied processes is the key issue. Simulation combined with Taguchi method could study such many variances economically and significantly.