ENHANCED OXYGEN REACTIVE ION ETCHING RESISTANCE OF DIAZONAPHTHOQUINONE-POLY (FORMYLOXYSTYRENE) RESIST SYSTEM BY PHOTOACID CATALYZED PHOTO-FRIES REARRANGEMENT AND POTASSIUM-ION TREATMENT IN AQUEOUS-SOLUTION

Abstract

This paper presents a new process for the enhancement of oxygen reactive ion etching (RIE) resistance of a single-layer, deep UV resist system by selective incorporating of potassium ion with resist image in aqueous solution after exposure. A resist system of diazonaphthoquinone (DAQ) and poly(p-formyloxystyrene) (PFS) mixed with catalytic amount of triphenylsulfonium hexafluoroarsenate as a photoacid is exposed to deep UV. Photoacid catalyzes the photo-Fries rearrangement of PFS to form poly(p-hydroxystyrene) (PHS); DAQ rearranges to form indene carboxylic acid and grafts into PHS via S-O bond formation. A latent image is formed by selective reaction of carboxylic group with C5H11COOK in aqueous solution in exposed area which is resistant to oxygen RIE. There are no such reactions in unexposed area. The dry developed negative-tone patterns by oxygen RIE are obtained.