Surface modification of polymeric thin films with vacuum ultraviolet light

Spin-coated poly(methyl methacrylate) (PMMA) thin films on SiO2 substrate were chemically modified with laser light at 157 nm in nitrogen. Film changes involve bond breaking of polymeric chains, etching, and surface morphological changes. The 157 nm photons mainly dissociate the C-O, C=O, and C-H bonds, and catalyze the formation of new C-N bonds. The surface roughness of the irradiated films was changed with the formation of elongated patterns. The film thickness during irradiation was reduced with the rate of 0.005 nm at 1 mJ/cm(2). Furthermore, the PMMA film forms a thin interface layer with the SiO2 substrate. Its thickness was reduced following vacuum ultraviolet (VUV) irradiation due to photodissociation of molecules inside the interface layer. Copyright (C) 2008 John Wiley & Sons, Ltd.