Kinetics and Mechanism of the Surface Reaction During Silicon Oxidation

In previous work^2, we have shown that a surface reaction is important during initial oxidation of silicon for ultra thin gate oxides under certain conditions. The region of this reaction completely mixes with the interface growth when the oxide thickness is smaller than 20 ÅThe present work(Supported by NSF, PRF, and NJ-AIMS) is to study the kinetics and mechanism of this surface reaction and its possible role played in accelerating the oxidation rate during initial oxidation. High-resolution medium energy ion scattering (MEIS) with isotopic (^16O and ^18O) labeling (E.P. Gusev, H.C. Lu, T. Gustafsson, and E. Garfunkel, Phys. Rev. B 52 (1995) 1759; Appl. Phys. Lett. 67 (1995) 1742.) was used to monitor the distributions of the two oxygen isotopes. Silicon samples with 30 - 60 Å oxide films were reoxidized in 0.1 - 100 Torr ^18O₂ at 720 - 1050^o C. The surface reaction was found to be an exchange reaction and saturates very fast at lower temperatures. The kinetics and mechanism derived from studying the concentration of the oxygen isotope at the surface under various processing conditions will be discussed.