Particle Re-Deposition During Ultrashort Pulse Laser Ablation of ITO Thin Films Using Single- and Multi-Beam Processing

The processing of transparent conductive oxides (TCO) using ultrashort laser pulses (USP) is of interest for an increasing number of applications. Among other things, the coupling of the energy into the workpiece is crucial for the precise machining of materials. To this intent, the effects of pulse duration, fluence, numerical aperture (NA), pulse overlap, beam shaping, and a suction system on particle re-deposition are investigated during partial ablation of a 100 nm thick indium tin oxide (ITO) layer on fused silica. It is shown that in particular, a large NA and therefore a small spot diameter as well as a high pulse overlap significantly infiluence the re-deposition of particles regarding their amount, size and local distribution on the sample surface. Furthermore, the beam shaping and the resulting multi spots show an effect on the particle dynamics during a machining process. Keywords: materials processing, transparent conductive oxides, particle re-deposition, ultrashort pulse, energy coupling, shielding