PHOTOLITHOGRAPHY AT 0.10 AND 0.13 MU-M USING ARF EXCIMER-LASER LITHOGRAPHY IN COMBINATION WITH RESOLUTION ENHANCEMENT TECHNIQUES

ArF (193 nm) excimer laser lithography was evaluated for production of 0.10- to 0.15-mu m-size line widths. For near-term (0.13- to 0.15-mu m line widths) work, an emphasis was placed on resolution enhancement strategies not requiring new mask processes or materials and was limit ed to consideration of binary masks in combination with annular (sigma (i) = 0.4, sigma(0) = 0.6) illumination. Using a 0.5 numerical apertur e lens, silylation resist, and a binary mask, a 0.8-mu m depth of focu s was obtained for 0.14-mu m dense lines and 1.0 mu m for 0.15-mu m li nes. However, the lack of resist linearity required almost 50% lower d ose for the isolated lines, suggesting the need for optical proximity correction. For smaller features (0.10- to 0.12-mu m line widths), chr omeless phase-shifting masks were used. Using a partial coherence of 0 .6, a 1.8-mu m depth of focus and similar to 3% exposure latitude was achieved for 0.11-mu m isolated lines at spatial periods as small as 0 .24 mu m. However, aerial image modelling suggests a limitation in thi s approach is focus-dependent image distortion as a result of lens abe rrations. These aberration-induced effects may limit the practical dep th of focus for this approach and must be considered for extension of optical lithography to near the Rayleigh resolution limit. (C) 1997 Am erican Vacuum Society.