Real-time analysis of volatiles formed during processing of a chemically amplified resist

The analysis of vapors desorbing from resist films during processing provides important information on impurity content, loss of resist components, and available decomposition pathways that complements data obtained by film composition studies. We have constructed an instrument for in-situ sampling and identification of volatiles from both bulk polymers and cast films by tandem mass spectrometry. We have used this instrument to identify volatile products from thermal and acid catalyzed deprotection of p-(t-butyloxycarbonyloxy)styrene (PTBOCST) to form p-hydroxystyrene (PHOST). The results show that the two reaction pathways have markedly different chemistry, and that the generally accepted deprotection mechanism oversimplifies what is actually happening in the film.