Alternating phase shifted scattering bars for low k[sub 1] trench pattering

Abstract

This article studies the resolution enhancement for sub-120nm isolated trench patterns using alternating phase shifted scattering bars. Through simulation, we found that three sets of 40nm alternating phase shifted scattering bars with separation of 120nm are the best aerial image provider in terms of higher peak intensity, lower side lobe intensity, and smaller full width of half maxima. Simulation results are verified experimentally, and we achieved isolated trench at patterned critical dimension (CD) target of 120nm±10% with manufacturability process window for nominal design CD of 125nm. The patterned CD target 120nm corresponds to k1 factor of 0.33 for exposing wavelength of 248nm, sigma of 0.31, and maximum numerical aperture (NA) of 0.68. Three sets of alternating phase shifted scattering bars showed good mask linearity up to 115nm nominal design CD. We compared isolated trench process condition with dense patterns. Our experimental results show that both isolated and dense patterns can be printed at the same process condition.