Chemically amplified resists based on the norbornene copolymers with steroid derivatives

In order to develop a new series of chemically amplified photoresists for 193-nm lithography, norbornene substituted with a steroid derivative was copolymerized with maleic anhydride by free radical polymerization. The resulting polymers have excellent transmittance at 193 nm and possess good thermal stability up to 260 degrees C. The resist formulated with the polymers showed better dry-etching resistance than the conventional poly(hydroxystyrene) resist for Cl2/O2 plasma. With the standard developer, the resists from 0.15-0.20 micrometers patterns at doses of 5-18 mJ/cm2 using an ArF excimer laser stepper.