Characterization of ArF immersion process for production

Abstract

ArF immersion lithography is essential to extend optical lithography. In this study, we characterized the immersion process on production wafers. Key lithographic manufacturing parameters, overlay, CD uniformity, depth of focus (DOF), optical proximity effects (OPE), and defects are reported. Similar device electrical performance between the immersion and the dry wafers assures electrical compatibility with immersion lithography. The yield results on 90-nm Static Random Access Memory (SRAM) chips confirm doubling of DOF by immersion as expected. Poly images of the 65-nm node from a 0.85NA immersion scanner are also shown.