Proximity effects in dry developed lithography for sub-0.35 um a

摘要

Abstract: When printing at the resolution limit of the steppers, optical proximity effects become increasingly important and might limit the useful resist processing window. In this paper proximity effects have been studied for processes based on surface imaging and dry development. Proximity effect resulted in both linewidth and profile differences between dense and isolated lines at 0.35 $mu@m and below. Proximity is partly due to optical effects (NA, $sigma, wavelength, mask tonality) and partly due to processing conditions (silylation and development). To study the optical effects, aerial image simulations have been performed and a comparison with experimental results was carried out. Reduction in proximity is realized by a reduction in 'process offset', improvements in silylation contrast and a reduction in microloading effects during dry development. Positive tone resist processes show a reduced proximity effect as compared to negative tone resist processes and the feasibility for 0.30 $mu@m dimensions has been shown. At 0.25 $mu@m level, the process optimization should be accompanied with optical solutions in the form of selective mask biasing. !12