Swing effects in alternating phase shift mask lithography: Implications of low σ illumination

Abstract

We develop sub-100-nm resist patterns with alternating phase shift mask (alt PSM) using 0.68 numerical aperture KrF lithography scanner at a partial coherence factor σ of 0.31, the lowest available in our tool - a need of alt PSM technique. Although we achieve resist lines down to 65 nm, the standing wave and critical dimension (CD) swing effects are immense on big patterns. The 180 nm lines show CD swings two times to that of 90 nm lines. The sidewall profiles of 180 nm lines are also more susceptible to swing inflection point selection than 90 nm lines. The finding on the use of alt PSM is that the higher standing wave, larger CD swing, and more degradation of sidewall profiles on big patterns than small patterns are the implications of low σ illumination. We suggest the inclusion of big patterns for swing studies while setting up the lithography process using alt PSM. © 2006 American Vacuum Society.