Structure and oxidation kinetics of the Si(100)-SiO2 interface

We present first-principles calculations of the structural and electronic p roperties of Si(001)-SiO2 interfaces. We first arrive at reasonable structu res for the c-Si/a - SiO2 interface via a Monte Carlo simulated annealing a pplied to an empirical interatomic potential, and then relax these structur es using first-principles calculations within the framework of the density- functional theory. We find a transition region at the interface, having a t hickness on the order of 20 Angstrom, in which there is same oxygen deficie ncy and a corresponding presence of suboxide Si species (mostly Si+2 and Si +3). Distributions of bond lengths and bond angles, and the nature of the e lectronic states at the interface, are investigated and discussed. The beha vior of atomic oxygen in a-SiO2 is also investigated. The peroxyl linkage c onfiguration is found to be lower in energy than interstitial or threefold configurations. Eased on these results, we suggest a possible mechanism for oxygen diffusion in a-SiO2 that may be relevant to the oxidation process. [S0163-1829(99)08115-1].