Paper PS1-ThM1
Coupled Ion, Photon and Electron Synergies in Plasma-Surface Interactions for Organic Materials

Thursday, November 12, 2009, 8:00 am, Room A1

Recent experimental and simulation studies have revealed that plasma-organic surface chemistry can be strongly affected by synergistic interactions among ions, vacuum ultraviolet (VUV) photons and electrons at surfaces. In this talk, I summarize our recent studies of these synergies, focusing on various polymer and SiCOH low-k dielectric materials. When plasma and vacuum beam measurements, coupled with molecular dynamics (MD) simulations, are compared for various materials and various exposure conditions, certain patterns emerge. MD shows that (~ 100 eV) ion effects are restricted to several nm near the surface, but that their effects can depend strongly on the type of polymer and other species present. The synergistic effects of plasma-generated ions, photons and electrons can be understood in terms of a competition between bond-breaking scissioning reactions and bond-forming cross-linking and other reactions. The complexity of the results is due in part to the fact that these species have different depths of penetration, and that their bond breaking and bond forming reactions depend on the structure of the material. However, even greater complexity results from the fluence- or dose-dependent nature of electrons and ions: low dose result in scissioning and higher doses result in cross-linking. The effects of simultaneous exposure depend on both position relative to the surface and time. I illustrate these ideas with examples taken from PMMA-based 193 nm photoresists; poly-alpha methyl styrene (PaMS) and poly-four methyl styrene (P4MS); and ultra low k, nanoporous SiCOH. MD simulations and models of VUV photon penetration into polymers are used to interpret both plasma and vacuum beam experimental results.