Investigation of a model for the segregation and pile-up of boron at the SiO/sub 2//Si interface during the formation of ultrashallow p/sup +/ junctions

We have quantitatively investigated how boron segregates to regions dose to the surface, and what controls this phenomenon, using XPS and Backside SIMS measurement techniques. We found that, on the contrary to the equilibrium segregation, the pileup of boron are mainly on and within 0.6 nm of the Si side of the interface, and that there is no difference between the kind of encapsulation. This also suggests that the pileup of boron is mainly on the Si side, and implies that the main factor in this segregation is the existence of the Si surface. From the viewpoint of device fabrication, this result seems to be useful in terms of the fabrication of side-walls. The possibility for boron pileup to occur in the interstitial state was also shown.