Adhesion enhancement of norbornene polymers with lithocholate substituents for 193-nm resists

Norbomene copolymers having derivatives of lithocholic acid were synthesized as matrix polymers for 193-nm lithography. Norbornene with a succinic acid ester group was introduced into the matrix polymers in order to improve adhesion to a silicon substrate without causing cross-linking during the post-exposure bake process. Dry-etching resistances of the polymers to CF4-reactive ion etching are comparable to that of poly(4-hydroxystyrene), a typical matrix resin for 248-nm lithography. The resists formulated with the polymers gave 0.15 mum line and space patterns at a dose of 14 mJ/cm(2) using an ArF excimer laser stepper and a standard 2.38 wt% tetramethylammonium hydroxide aqueous solution.