Removal Processing of Transparent Thin Film by Lasers

Abstract

A new drilling technique is proposed for removing polymeric layer formed on conductive layer using IR laser light, which is not absorbed by the polymeric layer sufficiently for ablation. In this technique, a piece of polymeric film was blown off after a single shot of radiation. To apply this process to laser drilling, we have systematically measured changes in size of the resulting hole with the fluence, the irradiation area and the thickness of a polymeric layer. We also investigated the mechanism of this process by luminescence spectroscopy of the irradiated samples. We observed sharp peaks in the spectrum in the case of single laser irradiation of 8.6 J/cm² while such intense peaks could not be seen when the irradiation pulse energy decreased to 1.2 J/cm². Thus, the polymeric film was removed without violently decomposition to atomic species. Advantages of this technique are (1) the polymeric layer can be completely removed within a certain area by a single shot of laser pulse, and (2) it is possible to escape from problems such as debris, smear and delamination, which occurs when CO₂ lasers or UV laser is used.