Oxidation of silicon surface with atomic oxygen radical anions

The surface oxidation of silicon (Si) wafers by atomic oxygen radical anions (O^- anions) and the preparation of metal--oxide--semiconductor (MOS) capacitors on the O^--oxidized Si substrates have been examined for the first time. The O^- anions are generated from a recently developed O^- storage-emission material of Ca₂₄Al₂₈O₆₄]⁴⁺.4O^- (C12A7-O^- for short). After it has been irradiated by an O^- anion beam (0.5\mu A/cm²) at 300⁰C for 1--10 hours, the Si wafer achieves an oxide layer with a thickness ranging from 8 to 32nm. X-ray photoelectron spectroscopy (XPS) results reveal that the oxide layer is of a mixture of SiO₂, Si₂O₃, and Si₂O distributed in different oxidation depths. The features of the MOS capacitor of x/Si> are investigated by measuring capacitance-voltage (C-V) and current-voltage (I-V) curves. The oxide charge density is about 6.0 \times 10¹¹cm² derived from the C-V curves. The leakage current density is in the order of 10^-6A/cm² below 4MV/cm, obtained from the $I-V$ curves. The O^- anions formed by present method would have potential applications to the oxidation and the surface-modification of materials together with the preparation of semiconductor devices.