Photolithography at 0.10 and 0.13 μm using ArF excimer laser lithography in combination with resolution enhancement techniques

Abstract
ArF (193 nm) excimer laser lithography was evaluated for production of 0.10- to 0.15-μm-size line widths. For near-term (0.13- to 0.15-μm line widths) work, an emphasis was placed on resolution enhancement strategies not requiring new mask processes or materials and was limited to consideration of binary masks in combination with annular (σi=0.4, σ0=0.6) illumination. Using a 0.5 numerical aperture lens, silylation resist, and a binary mask, a 0.8-μm depth of focus was obtained for 0.14-μm dense lines and 1.0 μm for 0.15-μm lines. However, the lack of resist linearity required almost 50% lower dose for the isolated lines, suggesting the need for optical proximity correction. For smaller features (0.10- to 0.12-μm line widths), chromeless phase-shifting masks were used. Using a partial coherence of 0.6, a 1.8-μm depth of focus and ∼3% exposure latitude was achieved for 0.11-μm isolated lines at spatial periods as small as 0.24 μm. However, aerial image modelling suggests a limitation in this approach is focus-dependent image distortion as a result of lens aberrations. These aberration-induced effects may limit the practical depth of focus for this approach and must be considered for extension of optical lithography to near the Rayleigh resolution limit.

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