Simulation of the 45-nm half-pitch node with 193-nm immersion lithography—imaging interferometric lithography and dipole illumination

With immersion in water (n = 1.44), the highest spatial frequency available with ArF-based (193-nm) lithography tools with a numerical aperture (NA) = n×sin θ of 1.3 (1.44×0.9) corresponds to a half-pitch of 37 nm. This suggests that the 45-nm half-pitch node should be accessible. A detailed vector simulation study is reported for two approaches to printing for this node. Both imaging interferometric lithography (IIL, with a single mask and multiple exposures incorporating pupil plane filters) and dipole illumination (with two masks separating the x and y oriented small features) are shown to be capable of printing arbitrary structures under these conditions. There is a substantial loss of contrast for TM polarization at this NA that demands that different polarizations be used to capture the high spatial frequencies in the x and y directions. Both dipole and IIL schemes offer this capability; IIL provides more robust imaging results.