Experimental study of the ultrathin oxides on SiGe alloy formed by low-temperature ozone oxidation

Abstract

The ultrathin oxides (<1.2 nm) on SiGe are formed by directly oxidizing SiGe surface in 10% O3/O2 mixture in Beneq TFS 200 ALD system. The oxide compositions are characterized using X-ray photoelectron spectroscopy technology as a function of processing conditions, including oxidation time, temperature, and pressure. It is found that the oxide composition is very sensitive to ozone partial pressure. That is, under a lower pressure, Ge atoms can't be oxidized even over a long time and the oxides are pure SiOx. Until the temperature is increased to 300 °C, about 54% of the Ge atoms of the outermost atomic layer of SiGe are oxidized in the initial oxidation stage. Nevertheless, a slight increase in ozone partial pressure cause a rapid changeover to the formation of oxide mixture containing Si oxide and Ge oxide at all temperatures investigated, i.e. 100 °C–300 °C. Moreover, the oxidation rate of Ge atoms maintains almost unchanged from 100 °C to 230 °C, and decreases at 300 °C.