Numerical simulations were investigated that used a non-linear interdiffusion solver and dynamic X-ray diffraction calculations to predict the local composition evolution in low Ge concentration Si/SiGe superlattices and their diffraction patterns during annealing. Superlattice satellite peak decay rates were compared with experimentally measured values and simulated diffraction patterns were matched directly to data with good success. The simulations were used to test the sensitivity of X-ray diffraction to various uncertainties commonly encountered when measuring interdiffusion at Si/SiGe interfaces. It was found that the most serious errors result from variations in the Ge content across the surface of the wafer. For example, the resolution limit of most experimental techniques used to measure Ge concentration in a SiGe film was ±1at%, for a film with 11% mean Ge concentration annealed for 5h at 870C, this level of error will cause the observed interdiffusivity values to deviate by –25% or +50%. The simulations were further used to show that for Si/SiGe interdiffusion, superlattice diffraction produces valid measurements when applied to 004 superlattice satellite peaks and square wave composition modulations even though it was only exactly applicable to satellite peaks about 000 reflections and to sinusoidal composition modulations. Finally, it was shown that proper interpretation of X-ray scattering data to extract Si/SiGe interdiffusivity values must account for the strong dependence of the interdiffusivity on Ge concentration.

Analysis of X-ray Diffraction as a Probe of Interdiffusion in Si/SiGe Heterostructures. D.B.Aubertine, N.Ozguven, P.C.McIntyre, S.Brennan: Journal of Applied Physics, 2003, 94[3], 1557-64