Extension of ArF lithography for poly gate patterning of 65nm generation and beyond

Due to the existing problems and delay of 157nm lithography tool, extension of the ArF (193nm) lithography process with resolution enhancement techniques (RET) should be considered for the 65nm generation lithography and beyond. The mature double-exposure lithography process based on dark-field alternating phase-shift mask (PSM) is one of the promising RET candidates, which is proven to be one of the production-ready strong phase-shifting techniques for current and future IC generations. In this paper, poly gate patterning with the minimum pitch of 160nm has been demonstrated with high numeric aperture (NA) and small partial coherence of ArF lithography along with a dark-field alternating PSM. For poly gate patterning of 65nm generation, optimum illumination settings are found for minimum pitch of 160nm. Through-pitch common process windows for gates with 65nm after-development-inspection (ADI) critical dimension (CD) at minimum pitch of 160nm can be reached larger than 0.30um depth of focus (DOF), which can be used for 65nm node production. Through-pitch proximity can be compensated by optical proximity correction (OPC). Line edge roughness (LER) can be improved a little by this dark-field alternating PSM technique. LER is found of strong aerial image contrast dependency. Shifter width is also chosen as optimum value to obtain the largest process windows and minimize the phase conflicts. 193nm Hi-NA or liquid immersion lithography is suggested to push the alternating PSM resolution limitation.