Design of photoresists with reduced environmental impact. II. Water-soluble resists based on photocrosslinking of poly(2-isopropenyl-2-oxazoline)

The performance of water- and solvent-cast, two-component photoresist films containing poly(2-isopropenyl-2-oxazoline) or poly(2-isopropenyl-2-oxazoli ne-costyrene) with a photoacid generator has been investigated. These mater ials afford negative-tone images after deep-UV exposure and development in a suitable medium (water or toluene). Resist solutions prepared from polyme rs containing at least 80 mol % 2-isopropenyl-2-oxazoline may be cast from and developed in pure water. Features of higher quality can be obtained whe n the resist is cast from 2-methoxyethanol, probably because side reactions such as partial hydrolysis of the pendant oxazoline rings in aqueous envir onments are avoided. It was possible to resolve micrometer scale patterns u sing ca. 200 mJ/cm(2) of irradiation at 254 nm, followed by heating 2 min a t 130 degrees C and development in water alone. Image quality and etch resi stance were improved using copolymers containing up to 20 mol % of styrene repeat units. (C) 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37 : 1225-1236, 1999.