Improvement an lithography pattern profile by plasma treatment

New chemical information has been obtained which explains "footing" and "bo ttom pinching" effects in chemically amplified (CA) resists on a silicon ni tride 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 obs erved if the nitride surface is treated with N2O/SiH4 plasma. This is attri buted to the deposition of a thin oxide cap on the nitride substrate, which Suppresses the surface basicity. However, extended N2O plasma treatment ca uses resist bottom pinching. This is ascribed to the surface acidity of a n ewly formed oxide cap which enhances the CA resist development process. Res ults show that the N (1s) peak, after extended N2O/SiH4 plasma treatment, h as shifted to a higher binding state which suggests that the nitride surfac e becomes acidic, causing bottom pinching. (C) 1999 American Vacuum Society . [S0734-2101(98)13104-X].