Ultrafast pump-probe microscopy reveals the mechanism of selective fs laser structuring of transparent thin films for maskless micropatterning

作者：Rapp Stephan^*; Rosenberger Janosch; Domke Matthias; Heise Gerhard; Huber Heinz P; Schmidt Michael

来源：Applied Surface Science, 2014, 290: 368-372.

DOI：10.1016/j.apsusc.2013.11.086

• Laser ablation
• Pump-probe microscopy
• Thin film
• Ultra-short pulse laser

Maskless patterning of biocompatible Ta2O5/Pt/glass sensor chips can be realized by ultra-short laser pulse ablation. At a fluence of 0.2 J/cm(2), the thin Ta2O5 film is selectively lifted-off by indirectly-induced ablation at laser wavelenghts where the Ta2O5 is transparent and the Pt absorbing. This enables precise and very fast structuring. Here, 660 fs laser pulses at a center wavelength of 1053 nm are applied. The driving physical effects of this ablation mechanism are revealed by pump-probe microscopy. This technique allows the observation of the whole ablation process ranging temporally from femtoseconds to microseconds. An ultrafast heat-expansion in the absorbing Pt, initiating a shock-wave to the Ta2O5 within the first 10 ps, bulges the Ta2O5 film after some nanoseconds. Bulging velocities of 750 m/s are determined corresponding to an extreme acceleration of about 10(10) g. Exceeding the stress limit in the Ta2O5 causes film disintegration after 50 ns. A model, describing essential reaction steps, is developed. This model is also applicable to other industrial important layer systems, where thin transparent films have to be removed.

• 出版日期2014-1-30