Effects of treatment parameters in electric-field-enhanced postexposure bake

This article demonstrates the improved lithographic performance of Shipley UVIIHS with an electric-field treatment during postexposure bake (PEB) for KrF optical exposures. Linewidth trends with treatment are given and explained through simulation of the acid motion. An upward electric field of approximately 10 V/mum was applied during the first 7 s of PEB to crack the surface inhibition, and thereafter the field polarity was altered every 7 s to enhance the acid-catalyzed reactions. Compared with standard PEB, the electric-field treatment resulted in deeper trenches, wider openings and significant compensation for underexposure. In some cases, electric-field-enhanced PEB led to more profile tapering, indicating that a larger downward direct electric field is needed to enhance the deprotection reactions in the lower half of the resist. (C) 2003 American Vacuum Society.