Evidence of the carrier mobility degradation in highly B-doped ultra-shallow junctions by Hall effect measurements

Abstract

In this paper, we present an empirical method for the self-consistent interpretation of SIMS and Hall effect measurements of boron-doped ultra-shallow junctions that allows to estimate the activation level of the doped layers (maximum active dopant concentration, active dose fraction) and, for the case of partially activated structures, to assess whether or not the carrier mobility is affected by the electrically inactive BICs. Epitaxial structures realized by chemical vapour deposition (CVD) were studied. We found that, for partially electrically active structures, a degradation of the drift mobility due to the presence of BICs is shown, which is experimentally confirmed by low temperature Hall effect measurements, indicating the existence of an additional Coulomb-type scattering mechanism. In addition, the post-deposition annealing steps (either 1050 °C spike or 1300 °C flash) are found to improve the activation level and induce a corresponding improvement of the carrier mobility, which is clearly associated to the progressive dissolution of the BICs during annealing.