Vapor phase cleaning of Si(100) surface in a cluster tool was studied. Electrical properties of the SiO2/Si interlace and the integrity of 55 Angstrom SiO2 films formed by in situ pregate oxide cleaning and rapid thermal oxidation (RTO) were characterized. Pregate oxide cleaning included anhydrous hydrofluoride (AHF) vapor for etching of native or sacrificial oxide, UV/O-3 hydrocarbon removal, and UV/Cl-2 trace metallic contamination elimination. Compared with a conventional wet cleaning procedure, in situ cleaning results in an equivalent SiO2/Si interface and SiO2 film with higher charge-to-breakdown (Q(bd)). A two-step cleaning procedure consisting of AHF etching and UV/Cl-2 metal removal results in oxides with the highest Q(bd).