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Alternating phase shift mask (A1tPSM) is considered as one of the most promising technique in leading-edge lithography. Its optical performance can be verified by sub-lOOnm gate generation and guaranteed device properties, indicated as depth of focus (DOF) and on chip CD variation (OCV). Nevertheless, continuous gate reduction in logic device demands more high-qualified mask process and optimization of illumination to overcome resolution limit. As one of the solution, appropriate mask structure and OPC rule dependent on illumination condition are evaluated. Issues out of mask manufacturing and Cr-less PEPSM as substitution of PEPSM are also discussed. Besides, interrelation between issues of mask and optical characteristics are investigated and compared mutually. In the end of this paper, we propose the optimum mask type and opportune time for ArF lithography