Femtosecond laser-induced removal of silicon nitride layers from doped and textured silicon wafers used in photovoltaics

The removal of a 75- to 90-nm-thick passivating silicon nitride antireflection coating from standard textured multicrystalline silicon photovoltaic wafers with a typical diffused 90-ohm/sq-emitter upon irradiation with near-infrared femtosecond laser pulses (790 nm central wavelength, 30 fs pulse duration) is studied experimentally. The laser irradiation areas are subsequently characterized by complementary optical microscopy, scanning electron microscopy and depth profiling chemical analyses using secondary ion mass spectrometry. The results clarify the thin-film femtosecond laser ablation scenario and outline the process windows for selective antireflection coating removal.