A Novel Model for Boron Diffusion in SiGe Strained Layers Based on a Kinetics Driven Ge-B Pairing Mechanism
A new temperature dependant model for the Ge-B pairing mechanism has been established and implemented in a process simulator. The combination of both lattice strain effects and GeB clustering has been successfully applied to various anneals. The match with experimental SIMS profiles is excellent.
Boron diffusion across silicon–silicon germanium boundaries
Most boron diffusion studies in Si–Ge have been made in regions of uniform germanium content. In this paper diffusion is observed from a boron-doped epitaxial silicon layer across surrounding Si–Ge layers. Pileup of boron in the Si–Ge layers shows that the activity coefficient for boron in Si–Ge is lower than that for pure silicon. A simple pairing model for Si–B interaction fitted the pileup quite well, with the same equilibrium constant applying to both Si0.9Ge0.1 and Si0.97Ge0.03 layers. The effect of this was simply to immobilize a significant fraction of the boron while retaining its acceptor qualities, the ratio of immobile boron to normal substitutional boron being proportional to the germanium content. Quasielectric field effects at the Si–SiGe interface have a strong effect on the results obtained.
Strain and interdiffusion in semiconductor heterostructures.
It is often suggested that the rate of interdiffusion at semiconductor heterostructure interfaces may be strongly dependent on elastic strain in the structure. Experimental and theoretical results show that strain does not, and should not, affect interdiffusion.