Femtosecond ultraviolet (248 nm) excimer laser processing of Teflon (PTFE)

We have investigated by X-ray photoelectron spectroscopy (XPS) the surface of poly(tetrafluoroethylene) (PTFE) films, which were subjected to processing by femtosecond (fs) UV radiation from an excimer laser (KrF: λ=248 nm, tp∼380 fs) in air. Bulk characterization of processed PTFE films by Fourier transform infrared spectroscopy (FTIR) permit an investigation of the laser induced modifications in the material at energy densities below the ablation threshold. No features in XPS and FTIR spectra indicated the incorporation of hydrogen and/or oxygen, or the formation of a cross-linked network of carbon indicating chemically clean processing in contrast to nanosecond excimer laser processing which chemically degrades the surface. Scanning electron microscopy (SEM) of the micrometer size vertical interconnect (microvia) indicated mechanically and thermally damage free processing of PTFE with good edge quality, in contrast to nanosecond excimer laser processing.