Ge concentrations in pile-up layers of sub-100-nm SiGe films for nano-structuring by thermal oxidation

Abstract

The data and analysis presented herein aims to facilitate the design and manufacture of SiGe based nanostructures and devices by describing the enhancement of Ge concentration in sub-100-nm thin films of SiGe by dry thermal oxidation. Thin films of SiGe were restructured by using thermal oxidation induced self-organization of Si and Ge atoms to create a layer of enhanced Ge concentration. The dry thermal oxidations were carried out at temperatures between 800 °C and 1000 °C. The influence of temperature on the Ge content at the oxidation front, as measured by x-ray diffraction, is examined and supported by simulation results. A model for determination of the Ge content in the pile-up layer is presented along with appropriate values for the activation energy and pre-exponential constant for diffusion of Si in Si1-XGeX. This model may also be used for determination of the diffusivity of Si in Si1-XGeX by fitting the model results to the measured Ge concentration in the pile-up layer. It is observed that the Ge content at the oxidation front is a function of temperature and varies linearly between 64% at 800 °C and 36% at 1000 °C. However, the Ge content is largely independent of oxide thickness and the Ge content in the initial SiGe layer. When the Ge concentration at the oxidation front is considered, the experimental results presented here indicate that the oxidation rates of SiGe closely match those of Si and provide evidence that the presence of Ge in very thin films of SiGe does not lead to enhanced or retarded oxidation rates as compared to Si.