Low temperature oxidation of SiGe in ozone: Ultrathin oxides

X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SI MS), and spectral ellipsometry have been used to study ozone/atomic oxygen assisted direct oxidation of single crystalline SiGe. In situ Fourier trans form infrared spectroscopy is used to monitor changes in the gas phase comp osition of O-3/O-2 gas mixtures. At all temperatures studied, 125-530 degre es C, XPS results indicate that Ge is incorporated into the growing oxide a s GeO2. Increasing the oxidation temperature causes a decrease in the perce ntage of Ge incorporated in the growing oxide and an increase in the silico n content. Further, at oxidation temperatures of 400 degrees C and above, s ubstantial Ge segregation is observed using SIMS. The change in composition is described using a temperature dependent flux model. Also, as the oxidat ion temperature increases, the oxide/SiGe interface becomes more abrupt wit h 1.9 monolayer (ML) of suboxide (Si+1, Si+2, Si+3) detected at 125 degrees C and 0.8 ML of suboxide at 530 degrees C. Based on thickness measurements from XPS and spectral ellipsometry, initial growth rates of 5 and similar to 1 Angstrom/min were achieved for ozone oxidation of Si0.85Ge0.15 at 530 and 125 degrees C, respectively. For the ultrathin regime (oxide thickness < 25 Angstrom), the effective activation energy for SiGe oxidation in 950 p pm of O-3 is determined to be approximately 0.12 eV. (C) 2000 American Inst itute of Physics. [S0021-8979(00)08504-2].