Several fundamental aspects of the oxidation-induced redistribution of Ge in thin films of SiGe are studied. This includes the incorporation of Ge into the oxide and the formation of what is alternatively referred to as pileup , snow-plow, or a germanium-rich layer. Experimental data from the present work shows longer oxidation times leading to an increase of Ge content in the pileup region and eventually creating a single high Ge content pileup layer by entirely consuming the initial SiGe layer. The pileup effect was shown to occur at the oxidation interface, with the highest Ge content occurring at the same interface. For a given oxide thickness, the redistribution of Ge and the formation of a pileup region was shown experimentally to be independent of temperature in the range between 800 C and 1000 C. Simulations using common models for the oxidation of Si and diffusion of Si in SiGe indicate that temperature does have an influence on the composition of the pileup layer, though the range of achievable compositions is limited. The flux of Si due to diffusion of Si in SiGe relative to the oxidation-induced flux of Si out of the SiGe is integral to the formation and dimensions of a pileup region. Two predictive relations were derived for describing the dynamics of oxidation of SiGe. The first relation is given for determining the pileup layer thickness as a function of oxide thickness and the composition of the pileup layer. The second relation assumes a limited supply of Si and is for determination of the minimum initial thickness of a SiGe layer to avoid oxidation of Ge. The validity of these equations was confirmed experimentally by RBS and XPS data from the present work. The proposed models may be used in nanostructuring of thin films of SiGe by oxidation and in the design of core-shell structures and transistors. This is all done with a focus on oxidation of epitaxial thin films (< 100 nm) of Si 1-X Ge X in dry O 2 at 1 atm between 800 C and 1000 C. V

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 Si 1-X Ge X . This model may also be used for determination of the diffusivity of Si in Si 1-X Ge X 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.

In order to evaluate the role of Ge as a catalyst or inhibitor for the oxidation process in SiGe, oxidation rates for sub‐100‐nm films of SiGe are examined and compared to previous reports and established models for Si oxidation. Values for the Ge concentration in the pile‐up layer at the oxidation interface are considered as well as the more traditional approach of considering the Ge content in the as‐grown SiGe film. The experimental results presented here indicate that oxidation rates for 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. This comparative analysis is performed with a focus on oxidation of epitaxial thin films of Si1−xGex in dry O2 at 1 atm at 800, 850, 900, 950, and 1000 °C.

The present study examines the kinetics of dry thermal oxidation of (111), (110), and (100) silicon-germanium (SiGe) thin epitaxial films and the redistribution of Ge near the oxidation interface with the aim of facilitating construction of single and multi-layered nano-structures. By employing a series of multiple and single step oxidations, it is shown that the paramount parameter controlling the Ge content at the oxidation interface is the oxidation temperature. The oxidation temperature may be set such that the Ge content at the oxidation interface is increased, kept static, or decreased. The Ge content at the oxidation interface is modeled by considering the balance between Si diffusion in SiGe and the flux of Si into the oxide by formation of SiO 2. The diffusivity of Si in SiGe under oxidation is determined for the three principal crystal orientations by combining the proposed empirical model with data from X-ray diffraction and variable angle spectroscopic ellipsometry. The orientation dependence of the oxidation rate of SiGe was found to follow the order: ð111Þ > ð110Þ > ð100Þ. The role of crystal orientation, Ge content, and other factors in the oxidation kinetics of SiGe versus Si are analyzed and discussed in terms of relative oxidation rates. V

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