NOVOLAK RESIN-BASED POSITIVE ELECTRON-BEAM RESIST SYSTEM UTILIZING ACID-SENSITIVE POLYMERIC DISSOLUTION INHIBITOR WITH SOLUBILITY REVERSAL REACTIVITY

This paper deals with a novel novolak resin-based positive resist system designed for practical direct electron-beam fabrication. The novel positive resist system, which has a solubility reversal mechanism, consists of an acid-sensitive polymeric dissolution inhibitor, an acid generator, and a novolak matrix resin. Various kinds of polymers, which can be converted to dissolution promoters by acid-catalyzed reaction, are investigated as the dissolution inhibitor of the system. A tetrahydropyranyl-protected poly(p-vinylphenol) (THP-M) is selected as the polymeric dissolution inhibitor. THP-M is insoluble in aqueous base solutions and compatible with novolak resins. The acid-catalyzed deprotection of THP-M results in poly(p-vinylphenol), which is soluble in aqueous base solutions and can be a dissolution promoter in the system. It is found that a methanesulfonic acid ester is the most effective acid generator for this resist system. Aryl onium salts, well-known acid generators, are not effective because of their strong dissolution-inhibition behavior results in negative tone patterns. High-resolution patterns (0.4-mu-m lines and spaces) are achieved with high sensitivity (2.5-mu-C/cm2 at 30 kV).