A lithographic and process assessment of photoresist stabilization for double-patterning using 172-nm photoresist curing

Abstract

We have developed a unique resist stabilization process for double patterning that uses 172 nm UV curing to 'freeze' a first photoresist pattern prior to application and patterning of a second photoresist film. 172 nm cure offers many potential advantages over other resist stabilization processes, including improved pattern fidelity vs. other cure processes and track-based implementation scenarios that are relatively simple, compact, and inexpensive. Assessment of 172 nm double imaging process requirements and limitations indicates that pattern distortions in the 'frozen' first photoresist may arise during all 2nd patterning steps, including coating, exposure, and development. Careful optimization to maximize overall pattern fidelity is needed. Process optimization using a conventional 193 nm photoresist suggests that pattern freeze approaches based on resist cure are best suited to extremely regular structures due to line-end and other resist distortions. Nevertheless, the method allows cross-grid contact printing at lithographic k1 = 0.385.