Molecular beam studies of a gas-surface reaction: dynamics of laser-induced chemical etching of silicon (111) by chlorine

Abstract

Laser-induced chemical etching of Si(111) surface with molecular chlorine is investigated by use of a CW supersonic molecular beam under 355- and 560-nm pulsed laser irradiation. Two major desorbed reaction products, SiCl and SiCl{sub 2}, are observed by time-resolved mass spectrometry. The time-of-flight (TOF) spectra of the desorbed species are measured as a function of laser fluence and the translational energy of the incident chlorine molecules. The measured TOF spectra can be fitted to a Maxwell-Boltzmann distribution at laser fluences lower than 120 mJ/cm{sup 2}. The enhancement of the laser-induced gas-surface reaction on raising the normal component of the translational energy of the chlorine molecules is obvious for both laser wavelength cases. A reaction mechanism that mainly involves the dissociative chemisorption of Cl{sub 2}, the reaction of the adsorbed species, and the laser-induced desorption on the surface is proposed.