MECHANISM OF SUBMONOLAYER OXIDE FORMATION ON SILICON SURFACES UPON THERMAL-OXIDATION

We present the results of an experimental and theoretical investigation of the initial oxidation of Si(100). Oxidation kinetics were measured in real time by x-ray-photoelectron spectroscopy. In the pressure and temperature regime studied, we observed the following kinetic phenomena: a decrease of the initial oxidation rate with increasing temperature, kinetic curves (i.e., coverage vs time) showing saturation with the saturation value increase for the higher temperatures, and a transition from ''passive'' to ''active'' oxidation. To account for the experimental results a phenomenological first-order phase-transition theory was used. On comparing the experimental and theoretical results, we suggested a physical mechanism for submonolayer silicon oxide formation.