New chemical information has been obtained which explains "footing" and "bottom pinching" effects in chemically amplified (CA) resists on a silicon nitride surface. X-ray photoelectron spectroscopy measurements indicate that the residual alkaline molecules on the nitride surface play a major role in the formation of nitride footing. It appears that the organic contaminants are not responsible for nitride footing. O-2 and N2O/SiH4 plasma treatment are used to modify the silicon nitride surface. Less severe footing is observed if the nitride surface is treated with N2O/SiH4 plasma. This is attributed to the deposition of a thin oxide cap on the nitride substrate, which Suppresses the surface basicity. However, extended N2O plasma treatment causes resist bottom pinching. This is ascribed to the surface acidity of a newly formed oxide cap which enhances the CA resist development process. Results show that the N (1s) peak, after extended N2O/SiH4 plasma treatment, has shifted to a higher binding state which suggests that the nitride surface becomes acidic, causing bottom pinching.