Abstract
In a study of the surface reaction of molecular and atomic chlorine on Si(100) and Si(111) using X-ray photoemission spectroscopy and molecular beam scattering, we have found only SiCl in the chlorinated layer formed by the molecular chlorine exposure, with no change in this bonding configuration after annealing. Most desorption products were SiCl2. SiCl desorbed above 900°C, probably due to the recombinative desorption of SiCl+Cl→SiCl2. SiCl desorbed directly from the surface without any reaction. Heavily chlorinated species, such as SiCl2, SiCl3 and SiCl4, were observed on Si(100) and Si(111) surfaces exposed to atomic chlorine. These heavily chlorinated species quickly desorbed from the surface after annealing at 300°C. No heavily chlorinated species were observed on the silicon surface exposed to molecular chlorine. The chlorinated layer on Si(111) was thinner than that on Si(100), explaining the appearance of the <111> facet reported in photo-enhanced etching.