Dopant enhanced solid phase epitaxy in silicon and germanium

Johnson, B. C.; Oshima, Takeshi; McCallum, J. C.*

Solid phase epitaxy (SPE) is an efficient process to activate implanted dopants on a low thermal budget. Although SPE is a common processing step in the formation of shallow junctions, a complete model is still lacking. Here, we reassess the dominant SPE model describing the dopant dependence of SPE to include factors related to the strain introduced by high dopant concentrations. A range of parameters cause the SPE regrowth rate to deviate from its intrinsic value, characterized by an activation energy of 2.7 eV for Si and 2.15 eV for Ge, This includes the dopant concentration, pressure and the presence of impurities. It is assumed that the defects are in thermal and electronic equilibrium and that the concentrations of positively or negatively charged defects are determined by the band structure and density of states of the bulk crystal. The SPE regrowth rate is then expected to be proportional to the concentration of these defects. The free parameters of the model are the SPE defect energy level and degeneracy. A comprehensive data set for both Si (As, P and B) and Ge (As, Sb and Al) over a wide range of dopant concentrations and SPE anneal temperatures is used to test this model.