Erlangen 2022 – scientific programme
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K: Fachverband Kurzzeit- und angewandte Laserphysik
K 2: Poster
K 2.11: Poster
Tuesday, March 15, 2022, 16:30–18:30, P
Ultra-short laser micro-machining by spatially shaped ps- and fs-pulses for depth-selective µ-TLM resistivity test structures of sputter-deposited metal/oxid/semiconducting contact layers — •Stephan Krause1,2, Stefan Lange2, Hardik Vaghasiya1, Christian Hagendorf2, and Paul-Tiberiu Miclea2,1 — 1Centre for Innovation Competence SiLi-nano, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany — 2Fraunhofer Center for Silicon Photovoltaics CSP, Halle (Saale), Germany
In this work, we applied spatially shaped ultra-short pulse laser micro-machining for a new processing approach of µ-TLM test structures. These structures are used for resistivity measurements of multilayer systems with highly resistive interface layers, e.g. in oxide passivation layers for solar cells. For precise measurements of electrical sheet and contact resistivity of the individual layers, isolating trenches and homogenous ablation areas are required. Ultrashort pulses with 10 ps and 200 fs of different laser wavelength (532 nm, 1030 nm) as well as optical beam shaping elements for a redistribution of the intensity from gauss to top-hat profiles enables a selective removal of top metallic Ag and oxide layers on the multilayer stack. At the same time thermal damage is minimized in underlying material and adjacent region of the laser trenches. Small effective optical penetration and sub µm-adjustable ablation depth were achieved by an ultrafast ablation mechanism via absorption at the several multilayer interfaces. Morphology and microstructure of heat affected zones (HAZ) at the laser structures are characterized by scanning electron microscopy.