Radiation degradation of poly(methyl methacrylate) in the soft x‐ray region

Abstract

AbstractThe molecular weight distribution change has been measured for the photoresist poly(methyl methacrylate) [PMMA] after in‐vacuo exposure to monochromatic soft x‐rays from the Canadian Synchrotron Radiation Facility [CSRF]. The experimental changes in the mo‐lecular weight distribations derived from gel permeation chromatography [GPC], were compared to a simple Monte Carlo simulation model that assumes random main chain scission. Using this model a scission radiation chemical yield of G(S) = 1.28± 0.10 at room temperature was found to give the best fit at a photon energy of 621 eV. This value is similar to values reported previously in the literature using electron beam and γ‐ray sources, but significantly larger than those reported for fast neutrons, α‐particles, or energetically charged particles. It was found that in this soft x‐ray energy regime, that degradation of PMMA involves primarily a random scission process of the main chain. The results of a least‐squares fit of this soft x‐ray G(S) data and all available literature values from other radiation sources, to the linear energy transfer [LET] dE/dx are discussed. © 1993 John Wiley & Sons, Inc.