Reducing Alternating Phase shift Mask (Alt-PSM) write- time through mask data optimization

Resolution enhancement techniques (RETs) such as optical proximity correction (OPC), phase-shifting masks (PSM), sub-resolution assist features (SRAF) have become essential components in the sub-90nm silicon manufacturing process. For the 65nm generation, alternating phase shift masks (Alt-PSM) is recognized as a proven wafer imaging technique. The large process window and hence stable process control is one of the key properties which make it the most viable approach for 65nm production compared with other RET approaches. On the mask making side, the good mask error enhancement factor (MEEF) performance of the Alt-PSM is a big plus as it makes the wafer CD control less susceptible for CD errors on the mask. Even though the benefits of Alt-PSM are well known, the reticle cost and manufacturing challenges have impeded its extensive adoption. In this work, we explore a methodology to reduce the Alt-PSM mask write time vis-a-vis cost, through certain data optimization techniques.