Measurement and simulation of boron diffusion in strained Si1-xGex epitaxial layers

Boron and germanium concentration profiles in rapid thermal annealed and furnace annealed Si and strained Si1-xGex in situ doped, epitaxial layers with both box-type and graded germanium (Ge) profiles were measured using secondary-ion-mass spectrometry (SIMS). A simple and accurate model that includes the modified strain, effect of trapping between B and Ge, the drift field due to bandgap narrowing, the intrinsic carrier concentration for Si1-xGex for boron diffusion in Si1-xGex, has been successfully implemented in simulation software. The model accurately simulates the measured boron as well as the Ge concentration profiles over a wide range of Ge fractions for box-type (0.06%, 0.2%, 4%, 10%, and 15%) and 15% for graded, and B peak concentrations for box-type (similar to3 x 10(18) cm(-3) to 1 x 10(19) cm(-3)) and 1 x 10(19) cm(-3) for graded, and various thermal budgets including rapid thermal and furnace annealing conditions. A comparison of the S1-xGex samples to the Si samples after both thermal anneals reveals a retarded B diffusivity inside the strained Si1-xGex layers. The Si1-xGex heterostructure model simulated the B diffusion in Si/Si1-xGex/Si heterostructures by incorporating both an enhanced B diffusivity and a Ge-dependent retardation. This retardation depends linear on the Ge concentration. Good agreement between the measured and simulated diffusion is obtained by including the model for strain and trapping effects.