Structure formation in excimer laser ablation of stretched poly(ethylene therephthalate) (PET): the influence of scanning ablation
Multiple pulse laser ablation of stretched PET is performed with an ArF excimer laser (193 nm) in order to produce micro channels. The surface structure remaining after “scanning ablation”, in which the sample is moved during irradiation, is compared to the known results upon “static ablation”.
We observed that the debris contribution is enhanced upon scanning ablation, which has a major impact for the channels used in micro-fluidic applications. A more fundamental change of the channel floor structure, as seen by SEM, occurs at high fluences and short mask lengths. The channel floor structure originates from the structure on the irradiated ramp at the end of the channel. The “scanning structure” appears only if the irradiated end ramp forms an angle higher than 10.55(±0.15)° with the non-irradiated sample surface. The angle of light incidence is not responsible for the structure changes, in agreement with literature reports. Other possible mechanisms are briefly discussed.