Optimization of plasma polymerized methylsilane process for 248 and 193 nmlithography applications.

Optical lithography continues to be investigated as the most interesting ap proach for achieving sub 0.18 mu m design rules. Currently an important eff ort is going on for single layer resist optimization at 193 nm, while some work is also performed to investigate the potential of top surface imaging schemes. A CVD photoresist currently known as Plasma Polymerized Methylsila ne (PPMS) can provide a completely dry photolithographic process, useful at 248 and 193 nm. Negative tone patterns can be developed using Cl-2-based p lasma development allowing the resulting PPMSO patterns to be used as SiO2 patterns. Up to now, PPMS film deposition and development have been achieved using si ngle step recipes. A single step CVD deposition process provides a film who se composition is identical through out the all thickness whereas the photo -oxidation process induces a gradient of oxidation in the PPMSO film. In th is work, we show that a significant improvement of the development can be a chieved using a multi-step etching recipe which takes into account the oxid ation gradient (and therefore etching resistance) throughout the PPMSO film thickness. Similarly, a significant improvement is performed using a two s tep CVD recipe. A very photosensitive PPMS film can be deposited on top of a non photosensitive PPMS film, allowing the oxygen incorporation to be lim ited to the photosensitive film, and therefore limiting the partial oxidati on between dense lines in the top photosensitive layer. Comparison between single and bi-layer CVD processes and single and multi-step etching recipes will be presented at 248 nm.