The Characterization of Chromeless Phase Shift Mask Technique for Sub-45nm Lithography

Abstract

In this study, theoretical background of Chromeless Phase Lithography (CPL) is investigated. Simulation and experimental results are compared and discussed. The study covers CPL data generation, mask fabrication and wafer printing verification. Four areas of process window optimization are investigated. CPL data handling optimization, which includes three-zone layout decomposition, optical proximity correction and sub-resolution assist feature placement rules are studied. 2D overlap region of diffraction orders within the entrance pupil is analyzed. The investigation shows that depth of focus can be improved through background noise reduction and illumination optimization. 3D mask effects and quartz depth optimization are also verified. The investigation shows that effective phase for CPL mask in 193 nm lithography should be set at 205 degree. High NA vector effects are introduced. Simulation results show depth of focus can be improved by migrating lithography system from dry to wet system and through the effect of polarization.