It was noted that a better understanding of B diffusion behavior within, and in the vicinity of, SiGe was necessary in order to optimize the extension and the source/drain in pMOSFETs. In order to achieve this goal, the effects of both mechanical strain and Ge doping upon B diffusion were investigated. Most previous research had investigated these two effects under the conditions of low B concentration in which an equilibrium state of point defects had been achieved. These were not the conditions used in aggressive CMOS technologies. An experiment was therefore designed in order to investigate B diffusion in both strained and relaxed SiGe including ultra-low energy, high-concentration B implantation and spike rapid thermal annealing. Models were proposed and the retardation factors corresponding to Ge concentration and stress effect were successfully extracted. Experiments on calibration, and the resultant diffusion constants for an ultra-shallow B junction in SiGe, were presented.

Boron Diffusion in Strained and Strain-Relaxed SiGe. C.C.Wang, Y.M.Sheu, S.Liu, R.Duffy, A.Heringa, N.E.B.Cowern, P.B.Griffin: Materials Science and Engineering B, 2005, 124-125, 39-44