The anomalous diffusion behavior of ultra low-energy implants was investigated. It was noted that transient enhanced diffusion was minimal at such low energies, since excess interstitials were very close to the surface. Instead, interface-induced up-hill diffusion was found, for the first time, to predominate during low-temperature thermal cycles. The interface pile-up dynamics could be exploited so as to produce shallower junctions. Attempts to minimize transient enhanced diffusion before spacer deposition, by the inclusion of extra rapid thermal anneals, were shown to be detrimental to the formation of B ultra shallow junctions.

Interface-Induced Up-Hill Diffusion of Boron: an Effective Approach for Ultra-Shallow Junctions. H.C.H.Wang, C.C.Wang, C.S.Chang, T.Wang, P.B.Griffin, C.H.Diaz: IEEE Electronic Device Letters, 2001, 22[2], 65-7