A 0.15 /spl mu/m KrF lithography for 1 Gb DRAM product using highly printable patterns and thin resist process

In order to realize the 1 Gbit DRAM product, 0.15 /spl mu/m photolithography will be necessary. Recently, off-axis illuminations and phase shift masks have been studied for realizing 0.175-0.25 /spl mu/m lithography. Even if these technologies are used, 0.15 /spl mu/m lithography is difficult. Investigating various lithographic approaches by optical simulation including the effect of photoresist processing, we found that a thin resist (300 nm thick), highly printable memory cell patterns, and optical proximity correction are very useful for realizing the 0.15 /spl mu/m rule DRAMs with KrF laser stepper (NA=0.6).