An in situ method for measuring acid loss from polymer films

This article reports an in situ approach to studying acid loss from polymer (films of the type used in microlithiography. We developed a method which makes use of the dye coumarin 6 (C6) which has absorption characteristics w hich change dramatically as a result of acid-induced changes in its prototr opic forms. Acid loss from polymer films containing C6 is accompanied by it s deprotonation, which is signaled by a change in the absorption of the fil m. This technique provides kinetic data describing acid loss from polymer f ilms. Acid loss is a function of both acid volatilization from sites at the surface of the film as well as diffusional processes within the film. Unde r controlled conditions, acid loss obeys first-order kinetics, and the half -lives, tau(1/2), of acids in phenolic and acrylate polymer films were dete rmined. We studied the effects of temperature, acid structure, polymer stru cture, and T-g on the tau(1/2) values obtained. (C) 2000 John Wiley & Sons, Inc.