Sensitivity of Positron Annihilation Spectroscopy to Energy Contamination in Low Energy Boron ion Implantation

摘要

We describe the development of a positron-based, non-destructive energy contamination monitor for use with low energy boron implantation. Using a simple model describing the effect of intrinsic electric fields on positron diffusion we show that for junction depths (X{sub}j) in the range of 50-500nm, beam-based positron annihilation spectroscopy (PAS) has sensitivity to changes in X{sub}j of 10nm. Corroborating experimental measurement of fully-formed p-n junctions fabricated by implantation of boron in n-type silicon at energies of 2,10 and 25keV, all to a dose of 1×10{sup}14cm{sup}(-2), are also described. Further, it is shown that PAS can distinguish B{sup}+ implanted wafers which have been deliberately poisoned with higher energy implants, from those which received no contaminating implantation.