Feasibility of a CVD resist based lithography process at 193nm wavelength

Thin layer imaging can extend the optical lithography limit down to sub-0.18 mu m CD with 193nm wavelength tools. Thin layer imaging can be implemented in a bi-layer approach, in which a patterned thin layer is transferred into an underlying organic planarizing layer. It can also be implemented in a single-layer hardmask process, in which a photodefineable oxide precursor is used to directly pattern a device layer. In the first portion of our study, a plasma polymerized methyl silane (PPMS) bi-layer baseline process has been characterized for photospeed, resolution, and line edge roughness (LER). 1500 Angstrom thick organosilane films were patterned by a photo-oxidation process using a 193nm stepper (NA = 0.6). The process exhibits photospeeds that are easily tuned from 40 to 100 mJ/cm(2) in a well-controlled manner by adjusting the PPMS CVD deposition parameters. The process has demonstrated a resolution of 0.13 mu m. We show that the total dry-develop process time is critical in determining the lithographic process lattitude, photospeed, resolution and LER characteristics. The CVD resist process is most attractive if the thin layer can be directly converted into a thin oxide hard mask, useful for transferring the pattern directly into an underlying device layer. We demonstrate a CVD photoresist process in which patterned PPMS is converted into a silicon dioxide hardmask, and then transferred into underlying amorphous-Si layers with high selectivity. Using this technique, we have successfully demonstrated 0.15 mu m resolution amorphous-Si lines.