Etching-enhanced Ablation and the Formation of a Microstructure in Silicon by Laser Irradiation in an SF₆ Atmosphere

Sequential pulsed-laser irradiation of silicon in SF⁶ atmospheres induced the formation of an ensemble of microholes and microcones. Profilometry measurements and direct imaging with an intensifying charge-coupled device camera were used to study the evolution of this microstructure and the laser-generated plume. Both the partial pressure of SF⁶ and the total pressure of an SF⁶-inert gas mixture strongly influenced the maximum height that the microcones attained over the initial surface. The cones first grew continuously with the number of pulses, reached a maximum, and then began to recede as the number of laser pulses increased further. The growth of the cones was closely connected with the evolution of the laser-generated plume.