Frequency doubling and resolution enhancement technique exploration for chrome-less phase shift mask

As increasing complexity of devices and scaling have continued to push the lithography to low k1 limit, lithographic scientists have been developing various resolution enhancement techniques (RET) to extend 193nm immersion lithography. The EUV scanners have become increasingly expensive. Thus, gaining extra value and performance from immersion tools through RET is an appealing approach. Phase shift mask (PSM) is one of the RET techniques. Chrome-less PSM can produce frequency doubling to half the pitch. In this paper, we have investigated the resolution limit of the frequency doubling. The conditions to generate frequency doubling have been studied, too.