Selective removal of transparent conductive oxide layers with ultrashort laser pulses: Front- vs. back-side ablation

Abstract

High average power, high repetition rate ultrashort pulse (pulse duration < 10 ps) laser systems with µJ pulse energies [1, 2] are increasingly used for bio-medical and material processing applications. Interesting applications for the ultrashort pulse laser systems are in the field of selective structuring of thin-films. Thin-film solar cells have shown a big potential to decrease cost of manufacturing for photovoltaic generation. Despite many research attempts to optimize materials the mass production of thin-film solar cells is still looking for versatile tools for the structuring of the thin-film coated area, where thin films with a thickness of ca. 1 µm have to be line structured with galvanic separation without damaging the substrate or any other layers.In this paper we report on recent results on the selective ablation of transparent conductive oxide (TCO) thin film, i.e. Boron-doped ZnO. The multi-pulse process thresholds were determined for direct and induced (lift off) laser-processing. From comparison of the process thresholds for both methods we can conclude that the induced ablation is more suitable for the structuring of the TCO layer. On the other hand, structuring of the TCO layers by induced ablation is more complicated due to its strong dependence on the quality of the glass substrate.High average power, high repetition rate ultrashort pulse (pulse duration < 10 ps) laser systems with µJ pulse energies [1, 2] are increasingly used for bio-medical and material processing applications. Interesting applications for the ultrashort pulse laser systems are in the field of selective structuring of thin-films. Thin-film solar cells have shown a big potential to decrease cost of manufacturing for photovoltaic generation. Despite many research attempts to optimize materials the mass production of thin-film solar cells is still looking for versatile tools for the structuring of the thin-film coated area, where thin films with a thickness of ca. 1 µm have to be line structured with galvanic separation without damaging the substrate or any other layers.In this paper we report on recent results on the selective ablation of transparent conductive oxide (TCO) thin film, i.e. Boron-doped ZnO. The multi-pulse process thresholds were determined for direct and induced (lift off) laser-processing. From com...