Resolution enhancement technology for ArF dry lithography at 65 nm node

The performance of ArF dry lithography at 65 nm node was studied together with RET. Commercial software Prolith 9.0 and in-house-software MicroCruiser 5.0 were used for simulation and mass data process. The combination of different phase shift mask (PSM), off axis illumination and patterns were chosen for this research. The image contrast, nominal image log-slope (NILS), depth of focus (DOF) and resist profile were considered to judge the lithography performance. The results show that the combination of small sigma conventional illumination and alternating phase shift mask (alt-PSM) is the best choice for Line/Space (L/S) patterns of different pitches. The isolate L/S pattern can be imaged with a large image contrast and DOF if alt-PSM and several kinds of illumination (such as small sigma, annular, and quasar illumination) are joined together. For semi-dense and dense L/S pattern, good lithography performance can be reached by using only small sigma illumination and alt-PSM. The impact of polarization illumination was also considered. Y-polarization illumination enhances the image contrast, NILS and the DOF for most conditions. The Z-orientation resist image fidelity was studied by optimization of the double bottom anti-reflection coating (DBARC) and resist thickness. This research predicts that 65 nm L/S pattern can be fabricated by current ArF dry lithography system.