Influence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions

Hole mobility degradation has been studied in high-dose boron-implanted ultrashallow junctions containing high concentrations of boron-interstitial clusters (BICs), combining an empirical method based on the self-consistent interpretation of secondary-ion-mass spectrometry (SIMS) and Hall measurements and liquid-nitrogen (⁠$LN2$⁠) to room temperature (RT) hole mobility measurements. It has been found that BICs act as independent scattering centers which have a strong impact on hole mobility in addition to the other scattering mechanisms such as lattice and impurities scattering. A mobility degradation coefficient $α$ has been introduced, which gives information on the mobility degradation level in the analyzed junctions. In the case of very high concentrations of BICs (containing a boron density up to $8×1014cm−2$⁠), measured hole mobilities were found to be $∼40%$ lower than corresponding theoretical values. BICs dissolution through multiple Flash anneals at high temperature $(1300°C)$ reduces the observe mobility degradation.