Evaluation of a deep-UV bilayer resist for sub-half micron lithography

摘要

A chemically amplified silicon-containing resist has been formulated and evaluated as a thin imaging layer in a positive tone deep UV (DUV) bilayer scheme. The key component is a silicon-containing polymer which has been characterized by GPC, UV, and dissolution rate studies. Dose and focus latitudes were determined for 0.4 and 0.5 $mu@m patterns exposed on a SVGL Micrascan I step and scan system and on KrF excimer laser steppers. The dose latitude on a GCA (0.35 NA) excimer was found to be 20% for 0.4 $mu@m features and about 30% for 0.5 $mu@m features ($POM 10% CD variation). Focus latitude was at least 2 $mu@m for 0.5 $mu@m patterns. Wafer to wafer LW uniformity as well as within water uniformity is shown. Typical processing involves 5 - 10 mJ/cm$+2$/ exposure doses, employing a 90$DGR@C post-expose bake (PEB) and a 60 sec 0.21 N TMAH develop. The dependence of linewidth upon PEB was found to be about 13 nm per degree C for 0.5 $mu@m features. Pattern transfer into the hardbaked i-line resist underlayer was done in an MLR chamber on an AME 5000. A low pressure etch is preferred to eliminate residue but this can lead to a higher non-uniformity across the wafer. Sidewall roughness was prevalent and this could be partially attributed to `feet' on the silicon-containing imaging layer.