| As SiGe films are introduced into deeply scaled, ultra-fast MOS devices, it is increasingly clear that interdiffusion at Si/SiGe interfaces is a significant problem. Strained Si MOSFET's typically utilize a thin, epitaxial, strained Si channel grown onto a relaxed SiGe layer. For these structures, out-diffusion of Ge from the SiGe layer into the Si channel is a factor limiting the practical thermal exposure during processing. Predicting the degree of intermixing is difficult because the interdiffusion process is potentially influenced by the local Ge concentration, film strain, and non-equilibrium point defect concentrations.; Interdiffusion in SiGe is also important from a fundamentally scientific perspective. Systematic studies of the interdiffusion process in SiGe alloys will eventually lead to a deeper understanding of the many physical mechanisms involved. To date, interdiffusion studies in Si-rich SiGe alloys are anecdotal, focusing on interdiffusion at specific Si/SiGe interfaces. This thesis presents work that begins the process of generalizing these measurements by quantifying interdiffusivity in Si-rich alloys as a function of both Ge concentration and compressive biaxial film strain.; Interdiffusivity values are measured in SiGe alloys with Ge fractions of 0.075, 0.105, 0.128, 0.172, and 0.192. The activation enthalpy for interdiffusion is found to decrease linearly with Ge concentration by 4.05 +/- 0.25 eV/unit Ge fraction. The prefactor for interdiffusion is found to be proportional to exp(-35XGe). Extrapolating these trends to a Ge fraction of zero yields prefactor and activation enthalpy values of 450 +/- 100 cm2/s and 4.69 +/- 0.05 eV, consistent with accepted values for Si and Ge tracer diffusion in pure Si. Further, a change in compressive biaxial film strain of 0.002 is shown to have no detectable influence on the interdiffusion rates for alloys with Ge fractions of 0.075, 0.105, and 0.172. These results are incorporated into a model that is shown to successfully predict experimental results derived from both x-ray diffraction studies of a large amplitude Si/Si0.78Ge0.22 superlattice and secondary ion mass spectrometry studies of intermixing at the interfaces between Si capping layers and both Si0.9Ge0.1 and Si 0.78Ge0.22 blanket films. |
