Progress in top surface imaging process

A top surface imaging (TSI) process is one of the approaches for 0.10 mum or smaller pattern fabrication using photolithography. We have been evaluating the different types of bilayer resist processes, such as a bilayer silylation process, a bilayer process using a Si-containing resist and an improved silylation process which applies vapor phase silylation treatment after alkaline wet development (SILYAL). In this paper, we review the current status of these processes, specifically focusing on the progress in the bilayer silylation process. In addition, we evaluated the critical dimension (CD) controlability of the bilayer silylation process for 193 nm lithography and found that this process can already be compared with the wet-development single-layer resist process. We found that the resist stripping technique, which has been the main problem of the TSI process, is practically feasible with the application of a plasma ashing treatment followed by a subsequent wet cleaning using a fluorine-containing chemical stripper. We also evaluated the characteristic properties using a 157 nm frame exposure tool and confirmed that this process is extendible to 157 nm lithography.