Wirelike growth of self-assembled hafnium silicides: oxide mediated epitaxy

Abstract

A wirelike shape of Hf silicides, which is not observed in silicides directly grown on Si (0 0 1), has been obtained by oxide mediated epitaxy (OME). Hafnium deposition (similar to0.4 and similar to0.2 ML) onto ultrathin (similar to1 nm) SiO2 and annealing at 900degreesC resulted in the formation of self-assembled wirelike silicides via a silicate phase (Hf-O-Si bonding units) in the 600-800degreesC temperature range. Silicide nanowires were found to be encapsulated in the bundle aggregates. The number density of OME-grown silicides apparently decreased as a form of nanowire bundles along with an increasing aspect ratio compared with the directly grown disilicides on Si (0 0 1). This finding has an implication for the use of an ultrathin SiO2 layer in controlling the tradeoff between the number density and the aspect ratio of self-assembled silicides. (C) 2004 Elsevier B.V. All rights reserved.