2001 Volume 14 Issue 4 Pages 603-611
The development of sufficiently transparent resin systems is one of the key elements required for a successful and timely introduction of 157nm lithography. This paper reports on the "Simple Transmission Understanding and Prediction by Incremental Dilution" (STUPID) model, a quick back-of-the-envelope increment scheme to estimate the absorption of polymers at 157nm. A number of promising candidate resins based on norbornenes are discussed, and results with a first 157nm resin system developed at the University of Austin are presented. The new system is based on copolymers of norbomene-5-methylenehexafluoroisopropanol (NMHFA) and t-butyl norbornene carboxylate (BNC), formulated with an acetal additive obtained by copolymerization oftbutyl norbomene-5-trifluoromethyl-5-carboxylate (BNTC) with carbon monoxide. Lithographic performance of this system extends to 110nm dense features using standard illumination and a binary mask, or 80nm semi-dense and 60nm isolated features with a strong phase shift mas . The dry etch resistance of this resist is found to be slightly lower than APEX-E DUV resist for polysilicon but superior to it for oxide etches.
