Dissolution kinetics and PAG interaction of phenolic resins in chemically amplified resists

Abstract

This paper describes the dissolution behavior of phenolic resins and resists in aqueous base solutions as measured with a quartz crystal microbalance. The dissolution kinetics of poly(4-hydroxystyrene) is linear with time, irrespective of molecular weights and polydispersities (including tandem blends). The effects of the composition of poly(4-hydroxystyrene-co-t-butyl acrylate) (ESCAP resin) and the loading of triphenylsulfonium triflate on the dissolution kinetics have been studied, revealing that the dissolution rate exponentially decreases with increasing the acrylate and triflate contents. A longer induction period is observed at a higher acrylate and triflate concentration. The dissolution inhibition effect of acid generators has been correlated with an interaction between the phenolic OH group and an acid generator molecule as studied by 13C NMR. The strong interaction of onium salts with phenol is clearly observed also in IR spectra of the above copolymer films. The quartz crystal microbalance has provided valuable information on the dissolution kinetics of exposed Shipley UVIIHS resist films, which exhibit a very fast dissolution of 30,000 Å/sec. The dissolution rates of the exposed resist films have been correlated with the degrees of deprotection as determined by thickness measurements, IR, and 13C NMR, and also with the rate values of authentic terpolymers of 4-hydroxystyrene, t-butyl acrylate, and acrylic acid, which had been prepared from an ESCAP copolymer. © 1997 TAPJ.