Initial oxidation of HF-acid treated Si(1 0 0) surfaces under air exposure studied by synchrotron radiation X-ray photoelectron spectroscopy

Initial oxidation of HF-acid treated Si(1 0 0) surfaces with air exposure has been studied by using synchrotron radiation X-ray photoelectron spectroscopy. We demonstrate that the initial oxidation is explained not by a layer-by-layer process, but by a non-uniform mechanism. Just after dipping a Si substrate in HF-acid and spin-drying, the Si surface is immediately oxidized partly with a coverage of 0.2. It is considered that the non-uniform oxidation takes place at surface defects on H passivated Si surfaces. With increasing the air exposure up to 1 week, we have found that the non-oxidized part is oxidized uniformly at slower rates compared to the beginning. IR absorption spectroscopy with a multiple-internal-reflection geometry clearly indicates the backbond oxidation of surface Si takes place despite the H passivation produced by the HF-acid treatment.