Study of alternating phase shift mask structure for 65nm node devices

摘要

To extend 193nm lithography for 65nm node devices, optimization of alternating phase-shift mask (alt. PSM) structures has been performed. A rigorous electro-magnetic field simulation of light scattering in 3D mask topographies, which is well known for optimization of alt. PSM structures, was used. The structures with a single and a dual trench were evaluated by evaluating the optical image of fabricated masks using AIMS fab 193 (Carl Zeiss). Prior to the optimization, limitation of shallow trench depth and undercut size was considered from the standpoint of mask making. Maximum undercut size was defined in order to prevent the Cr pattern peeling in cleaning process. In the optimized structure, CD difference between adjacent patterns with 0-space and π-space is within +/-10nm with 300nm focus margin for different pattern pitches.