XPS and SIMS Study of Anhydrous HF and UV/Ozone‐Modified Silicon (100) Surfaces

Abstract

X‐ray photoelectron spectroscopy and secondary ion mass spectrometry are used to study the surface chemistry of silicon single‐crystal wafers. Anhydrous and UV/ozone processes modify the surface chemistry by altering the concentration and bonding environments of the most abundant surface atoms: Si, O, C, H, and F. Anhydrous in conjunction with water vapor removes the silicon native oxide. Native oxides with initial thicknesses of 11Å, four monolayers, are exposed to a rinse, , and an aqueous rinse and are reduced to 0.4, 0.2, and 0.1 monolayers, respectively. The carbon concentration exhibits an inverse relationship with the submonolayer oxide coverage. The process results in less than a monolayer of silicon fluorides. The silicon fluoride species decrease with air exposure resulting in mostly oxyfluorides after 1h. Rinsing the fluorinated surface with reduces the fluorine concentration, removes trace metal impurities initially bonded to the native oxide, and promotes initial formation. UV/ozone exposure reduces the hydrocarbon concentration on the surface while producing 8Å, three monolayers, of . Exposing the surface to UV/ozone removes the silicon fluoride species; only oxyfluorides are observed with the ozone‐induced. The cleanest silicon surface with respect to metallic and hydrocarbon impurities was achieved with a rinse‐UV/ozone oxidation process.