Depth profiling of Al diffusion in silicon wafers by laser-induced breakdown spectroscopy

Abstract

Al diffusion in silicon wafers at different temperatures was detected by laser induced breakdown spectroscopy (LIBS) in this work. An Al thin film with a thickness of about 800 nm was deposited on silicon wafers by magnetron sputtering and then post-annealed in air at 300 and 610 °C (or without post-annealing) to achieve different depth profiles. The depth profile of Al in the wafers was measured using energy dispersive spectroscopy (EDS) and LIBS. EDS almost can not distinguish between the different Al concentrations at deeper positions of the different samples due to its low detection limit. The LIBS experiment was performed in an atmospheric environment. The pulse fluence was fixed at 16 J cm⁻² to cause an average ablation rate of 200 nm per pulse. LIBS can distinguish between the depth profiles of different diffusion samples very well. The results confirm that LIBS is very well suited for the detection of metal diffusion in silicon wafers.