AFM measurement of atomic-scale Si surface etching by active oxidation

Atomic-scale etching of a clean Si surface by active oxidation with oxygen molecules was examined using exsitu atomic force microscopy (AFM). The etch rate was directly determined by measuring the etch depth with AFM. A SiO(2) anti-etching mask was used on a H-terminated Si(001)-2 x 1:H surface prepared by low pH HF treatment followed by annealing in H(2). The etch rate under active oxidation conditions was almost proportional to the O(2) pressure, which was consistent with previous reports. The etch rate exhibited a weak temperature dependence with an apparent activation energy of 0.2 eV. A distinct transition of the reaction mode from etching to oxide formation was observed in detail as an abrupt decrease of the etch rate by lowering the temperature near the boundary condition between the etching and oxide formation conditions. (C) 2010 Elsevier B.V. All rights reserved.