Photostimulated desorption in laser-assisted etching of silicon

Photodesorption of ${\mathrm{SiF}}_3$ groups, which are the principal adsorbates on a silicon surface during etching by ${\mathrm{XeF}}_2$, is found to be responsible for the etch-rate enhancement observed under illumination by low-power, cw band-gap radiation. It is proposed that desorption is stimulated by photogenerated-charge-carrier–mediated chemical reaction, and not the simple charge trapping and recombination mechanism usually invoked for desorption from semiconductor surfaces.