Environmentally stable chemically amplified positive resist containing vinyllactam terpolymers

In this paper we report here on lithographic performance of high resolution, environmentally stable and aqueous base developable positive tone resist for DUV lithography. There have been a lot of efforts to prevent the resist from suffering from the deactivation of acid during the delay time between exposure and post exposure bake(PEB). The new design of matrix resin containing amide functional group has advantages over current lithographic techniques. The effect of amide functional group as a basic additive in a chemically amplified resist was investigated. A new class of matrix resin containing amide functional group, poly(hydroxystyrene-co-t-butyl acrylate-co-3-(t-butoxycarbonyl)-1-vinyl-2-caprolactam), was developed. It showed 0.20μm lines/spaces patterns of this resist using KrF excimer stepper (NA 0.55, partial coherence factor 0.55) with a exposure dose of 25mJ/cm^2. This resist showed no change of pattern profile after 2 hours post exposure delay in which ammonia concentration is 5ppb. 3-(t-butoxycarbonyl)-1-vinyl-2-caprolatam(BCVC) unit as a basic additive can not only solve amine contamination effectively, but also improve the resolution of the resist. BCVC unit reduces the diffusion of acid and it results in sharp contrast at the interface between the exposed and unexposed areas. Therefore, adding BCVC unit in matrix resin leads to the stabilization of the pattern profile and higher resolution.