We investigated the effect of post-exposure delay (PED) for poly[2-(2-hydroxyethyl)carboxylate-5-norbornene-co-2-carboxylic acid-5-norborene-co-maleic anhydride] [poly(HNC/BNC/NC/MA)] resist film, which formulated with photoacid generator (PAG) under the several solvents. The solvents used in this study mere propylene glycol methyl ether acetate (PGMEA), isobutyl methyl ketone (IBMK), 2-heptanone (2-H), and (alpha-methoxy)ethyl acetate (MEA). We have introduced a new concept of rheological approach to explain the solvent effect for PED by using rheometer and light scattering equipment. In the PGMEA solvent, the resist solution shows Newtonian behavior, but the other resist solutions show shear-thinning behavior. The resist film prepared by the shear-thinning solvent exhibited good FED stability. In order to explain these results, we conjectured that the resist polymer existed in long-rod shape under the specific solvent and high shear rate. Also, we could obtain 0.16 mu m L/S patterns in a severely amine-contaminated environment (about 35 ppb) after 30 min FED by using this method.