X-ray photoelectron spectroscopy studies on modified polyimide surfaces after ablation with a KrF excimer laser

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Abstract
The chemical properties of modified polyimide (PI) surfaces after ablation with a single laser pulse from a KrF excimer laser are studied by x‐ray photoelectron spectroscopy (XPS). Significant decreases in the atomic ratios (both oxygen to carbon and nitrogen to carbon) and bonding environment change are observed at the top ∼100 Å surfaces irradiated at laser fluences greater than 30 mJ/cm2 . The mechanism of formation of these modified surfaces is discussed in terms of the etching process based on the principal decomposition of imide groups of PI molecules, followed by rearrangement and recombination reactions. Furthermore, as a result of angular‐dependent XPS studies, an atomic concentration gradient is found to exist along the depth of the surfaces remaining after ablation. The possibility of surface oxidation after ablation is discussed.