Laser-Induced Liquefaction of Tetrafluoroethane and Sulfur Hexafluoride Gases

Laser ablation is a significant industrial tool for material structuring; however, the quality of such physical processes is often hindered by the redeposition of ablated matter in the laser interaction zone. Laser-induced liquefaction (LIL) offers a novel approach to minimizing material redeposition by irradiating the target in a dry ambient and transporting the material away in a liquid medium. SEM, EDX, and real-time imaging provided evidence of the decomposition of the assist gases, tetrafluoroethane (C2H2F4) and sulfur hexafluoride (SF6), during nanosecond laser ablation of silicon and confirmed the presence of a transient liquid phase in the vicinity of the trench during laser ablation. The elemental composition and spatial characteristics of the redeposited ablated matter indicate that the liquefied species and chemistry of the ablated matter are important in the enhancement of the material removal processes. As a result, high aspect ratio trenches with low redeposition of material in the ablated feature were achieved. The identification of the LIL process now has potentially interesting applications in nanoparticle generation during laser ablation and to the improved understanding of silicon microstructures formed in these gases.