Femtosecond pulsed laser ablation of 3CSiC thin film on silicon

Abstract

A femtosecond pulsed Ti:sapphire laser (pulse width=120 fs, wavelength=800 nm, repetition rate=1 kHz) was employed to perform laser ablation of 1-μm-thick silicon carbide (3CSiC) films grown on silicon substrates. The threshold fluence and ablation rate, useful for the micromachining of the 3CSiC films, were experimentally determined. The material removal mechanisms vary depending on the applied energy fluence. At high laser fluence, a thermally dominated process such as melting, boiling and vaporizing of single-crystal SiC occurs. At low laser fluence, the ablation is a defect-activation process via incubation, defect accumulation, formation of nanoparticles and final vaporization of boundaries. The defect-activation process reduces the ablation threshold fluence and enhances lateral and vertical precision as compared to the thermally dominated mechanism. Helium, as an assistant gas, plays a major role in improving the processing quality and ablation rate of SiC thin films due to its inertness and high first ionization energy.