Nanopatterning with 248 nm photolithography by photostabilizing bilayer photoresists

The authors demonstrated patterning of 35 nm isolated lines with 248 nm photolithography by photostabilizing a bilayer photoresist structure with a postdevelopment UV exposure. Overcoming the limitations of the conventional single-layer resist structure, the bilayer structure allowed the resist lines to drastically shrink in dimensions by similar to 70% upon photostabilization, while maintaining their critical attributes including sidewall profile, dry etch resistance, and ability to be stripped, and eliminating the need for high-temperature baking during the process. Comparing two types of photoresists, environmentally stable chemically amplified positive (ESCAP) and acetal, as the top layer in the bilayer structure, the ESCAP-type resist's shrinkage was similar to 67% that of the acetal-type resist, as a result of its lower free-volume reduction and extent of cross-linking, C-13 solid-state nuclear magnetic resonance spectra indicated. that the photostabilized resists were cross-linked through bonding between the polymer backbones and between the backbones and the phenol side groups. The applicability of this photostabilization technique to device processing was confirmed with the fabrication of a similar to 35 nm insulator-metal-insulator junction, a structure similar to that of a typical giant magnetoresistive reader. Their technique may be readily extendable to other applications requiring nanopatterning. (c) 2007 American Vacuum Society.