Atomic H: A reagent for the extraction of chemical species from Si surfaces

Abstract

The surface chemistry of adsorbed halogen atoms on Si(100) has been studied using several surface science methods. It has been found that Cl atoms bond to dangling bonds on symmetric Si 2 dimer sites, and that the SiCl bond angle is titled 25 ±4° from the normal in the vertical plane containing the Si 2 dimer bond. The covalently bonded halogens Cl, Br, and I have been studied on Si(100) using atomic H bombardment at low substrate temperatures (300–630 K). In all cases, facile elimination of the hydrogen halide occurs, and the coverage of halogen may be driven to zero by moderate exposure to atomic H. The halogen extraction process is almost non-activated, suggesting that the chemical reaction to produce hydrogen halide species is driven by the potential energy carried by the atomic H species. This is an example of an Eley-Rideal reaction process and provides a potentially useful new approach for controlling atomic layer chemistry on semiconductors. Atomic H driven extraction of adsorbed methyl (CH 3) species on Si(100) is also observed to occur with lower efficiency than halogen extraction. Thermal desorption studies indicate that the C extraction process occurs as the result of atomic H induced etching of the surface, producing gas phase alkyl silanes such as CH 3SiH 3.