The effects of ambient and dissolved oxygen concentration in ultrapure water (UPW) on native oxide growth were studied at room temperature using a silicon (100) surface. Studies focused on the initial stage of the surface oxidation immediately after the HF cleaning. The silicon surfaces were exposed at a fixed duration to the UPW with different dissolved oxygen concentrations, open air, and dry nitrogen, respectively. The SiO2 equivalent thicknesses of the native oxides formed were then measured and compared. Results indicate that the ambient and the dissolved oxygen concentration in UPW dramatically affect the growth rate of the native oxide. Decreasing the dissolved oxygen concentration in UPW and using an inert and dry atmosphere for the ultracleaning is shown to reduce or eventually prevent the native oxide from growing on silicon surfaces. The SiO2 equivalent thicknesses of the native oxide formed on these surfaces were characterized by a rapid acid extraction followed by a determination for extractable silicon. The extractable silicon was determined by a high-resolution magnetic-sector ICP mass spectrometer. This analytical method has been demonstrated for measurement of an oxide thickness on a silicon wafer surface down to a monolayer range with a possible 0.1 angstrom resolution. (c) 2005 The Electrochemical Society. All rights reserved.