模擬探討以散條提升32奈米線幅禁止間距焦深

Abstract

本論文使用美國KLA-Tencor之微影模擬軟體Prolith v. 9.0，探討以正偏差、遮光全條及減光全條散條消除32奈米線幅禁止間距相關問題。 本論文重要發現如下: 1.在32奈米線幅，減光全條利用透射度(T)與相位差(ϕ)的調變，其寬度可較遮光全條增加約一倍。在散條寬度32奈米、透射度(T)=0.4、相位差(ϕ)低於30度，可改善禁止間距，且不會成像。 2.在間距較小時，加入散條易影響主線條空間影像，造成正規化成像對數斜率(Normalized Image Log-Slope, NILS)與像比(Contrast)降低，焦深減少，最大照射寬容度(Maximum Exposure Latitude, ELmax)與最大焦深(Maximum Depth of Focus, DOFmax)皆降低；隨著間距增加，在加入散條的前與後，EL對DOF圖中二條曲線開始出現交點，交點隨著間距增加而升高，若EL的設定低於交點值，焦深可增加，所以當交點高於EL=6%，達到論文中設定需求，焦深即可增加，此時ELmax減少，DOFmax增加；間距再增加，主線條不受影響，NILS反而增加，此時ELmax與DOFmax皆增加。 3.在32奈米線幅，間距較小時加入減光全條散條，隙的空間影像，如邊端效應干涉波主極大重疊，相對光強較高，自身較不易成像；間距較大時，如邊端效應干涉波主極大分離，相對光強較低，自身較易成像。

The lithographic simulation software of Prolith v. 9.0 from USA KLA-Tencor was used in this thesis, the positive bias, chromium whole scattering bar (CSB) and attenuated whole scattering bar (ASB) were used to study the relative issues of eliminating the forbidden pitches for 32 nm linewidth. Some important findings of this thesis are reported as following: 1. For 32 nm linewidth, by the modulation of transmittance (T) and phase change of ASB, the width of ASB can be nearly doubled if compared to CSB. At the ASB width 32 nm, transmittance (T)=0.4, and phase change <30 degree, the forbidden pitches can be improved, and also, image of ASB will not be formed. 2. At the smaller pitches, the adding of scattering bars will easily affect the aerial images of main lines, resulted the decreasing of NILS, contrast and depth of focus (DOF), and decreasing of both maximum exposure latitude (ELmax) and maximum DOF (DOFmax). As the pitches increased, before and after the adding of scattering bars, crossing point from 2 curves showed up in the EL vs. DOF plots, rising of position of crossing point followed the increasing of pitches. If the setting of EL is lower than the crossing point, DOF can be increased. So, when crossing points are higher than EL=6%, meet the requirement of this thesis, DOF can be increased, under these conditions, ELmax decreased, and DOFmax increased. As the pitches increased further, the aerial images of main lines will not be affected, however, NILS increased, under these conditions, both ELmax and DOFmax increased. 3. For 32 nm linewidth, the adding of ASB at the smaller pitches, if the main maximum of interference formed by edge effect overlapped, the relative intensity of aerial image from space is relatively high, image of ASB itself will not be easily formed. At the larger pitches, if the main maximum of interference formed by edge effect separated, the relative intensity of aerial image from space is relatively low, image of ASB itself will be easily formed.