Investigation on the Ablation of thin Metal Films with Femtosecond to Picosecond-pulsed Laser Radiation

Ultrafast-pulsed laser radiation enables defined removing of different materials with very high processing accuracy due to the short interaction time of the radiation with the material, and the reduced heat affected zone compared to the removal with nanosecond laser radiation. For further processing improvements, a deep understanding of the involved processes of the laser radiation material interaction, especially the complex ablation phenomena, is necessary. Therefore, the ablation of metal films (d = 0.3-2 μm) of gold, platinum, aluminum, nickel and molybdenum was investigated using single-pulsed focused laser radiation (λ = 1030 nm) in dependence on the pulse duration (τH = 200 fs-15ps). The metals were chosen due to their different thermophysical properties, especially their electron-phonon-relaxation time. Two different ablation regimes, so called strong- and gentle-ablation, are observed for all investigated materials. To explain the experimental results, theoretical investigations based on the thermophysical properties as well as on the Two-Temperature-Model, including a temperature dependent reflectance, were performed.