A new environmetally stable positive tone deep UV resist has been designed by incorporating basic units into a matrix polymer for stabilization toward airbone contaminants. Poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam) (poly(BCVC)), and poly(3-(t- butoxycarbonyl)-1-vinylcaprolactam-co-t-butyl acrylate-co-hydroxystyrene) (poly(BCVC-co- TBA-co-HOST)) were prepared and evaluated as potential deep UV photoresists. 0.2μm line/space patterns were obtained for these resist systems using a KrF excimer stepper (NA 0.55) with a dose of 25mJ/cm2. And these resists did not change pattern profile after 2 hours post exposure delay (PED) time in which ammonia concentration was 5 ppb. 3-(t-Butoxycabonyl)-1-vinyl-2-caprolactam (BCVC) unit as a basic moiety can not only solve the amine contamination problem effectively, bul also improve the resolution of the resists. 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 polymer leads to the stabilization of the pattern profile and higher resolution.