Liquid Mediated Pulsed Laser Processing of Silicon

Abstract

We have investigated the formation of thin layers of carbides and nitrides by irradiating silicon (100) single crystal immersed in clear organic solvents or liquid ammonia. The liquids were transparent to the excimer laser (λ=308 nm, τ45 ns) used, at energy densities from 0.5 to 3.0 Jcm−2. Most of the laser energy was absorbed by the silicon specimens above a certain threshold to cause melting of the surface to a depth of approximately 250 nm. The pool of liquid silicon reacts with the solvents or ammonia in a saturated high pressure vapor phase for a duration of approximately 200 ns per pulse. The specimens were irradiated with a number of pulses ranging from 1 to 50. The films were then analyzed for structure and composition using TEM, AES, and IR spectroscopy. We report here calculations of laser-solid interactions, microstructure, and properties of the resulting thin films.