Investigation of postoxidation thermal treatments of Si/SiO2 interface in relationship to the kinetics of amorphous Si suboxide decomposition

Interfacial Si suboxides (SiOx , x,2) are detrimental to transistor performance and are typically minimized during postoxidation anneals. To study the kinetics of SiOx decomposition, thick films ~;2000 Å! of amorphous Si:O:H alloys (0.7,x,1.4) were deposited by remote plasma enhanced chemical vapor deposition and subjected to rapid thermal anneals. Films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, ellipsometry, photoluminescence ~PL!, and transmission electron microscopy. At temperatures .500 °C initially there is a rapid segregation into amorphous Si (a-Si) surrounded by a SiO2 shell which acts as a diffusion barrier decelerating the reaction. Phenomenological modeling of kinetics with a one-dimensional Avrami– Erofe’ve treatment gives an upper limit for a-Si lateral growth rates of 1.2 Å/s at 900 °C with an activation energy of 120 kJ/mol. PL, Raman, transmission electron microscopy and ellipsometry confirm this segregation model in the amorphous state. Due to the rapid initial decomposition and relatively large diffusion coefficients, a simple kinetic hindrance explanation for the 4–8 Å of SiOx at the SiO2 /Si interface is unlikely. © 1998 American Vacuum Society. @S0734-211X~98!09104-5#