Studies on Reaction Mechanisms of EB Resist by Pulse Radiolysis

For development and improvement of chemically amplified resists, the mechanisms of acid-generation reactions and the matrix effects were studied by using a pulse radiolysis technique. Ionic and nonionic acid generators act as electron scavengers when irradiated with an ionizing radiation in methanol solutions, resulting in the formation of Brφnsted acids. Rate constants for the reactions of the acid generators with a solvated electron have been determined. The rate constants of the onium salts were in the range of (1.6-2.7)x1010M-1 s-1. The nonionic acid generators were also found to be highly reactive to the solvated electron. Regardless of the structures and the polarities, the acid generators contribute to the acid generation by scavenging the solvated electron with the rates close to the diffusion-controlled limit. The reaction of acid generator with electrons trapped by base polymer was clarified. It would appear that electron scavenging reaction by acid generator in chemically amplified EB resist have two processes, and both process contribute to acid generation mechanism.