Current trends in 157 nm dry lithography

Lithography at 157 nm using F2 laser is the next step after 193 nm for ULSI fabrication with dimensions below 50 nm. However, there are certain issues to be addressed before the acceptance of the technology by the industry. The most important are: (1) design of resists with low absorption and outgassing at 157 nm, (2) improved line edge roughness and resolution and (3) defect-free resist surface following illumination at 157 nm. In this communication it has been confirmed theoretically and experimentally that outgassing of resists at 157 nm is an intrinsic molecular property and does not depend on the laser parameters. Based on a theoretical model, a new method for measuring outgassing of resists has been developed by measuring the thickness loss, following illumination at 157 nm, using vacuum ultraviolet absorption spectroscopy and atomic force microscopy.