Activation and deactivation in heavily boron-doped silicon using ultra-low-energy ion implantation

Abstract

A shallow p+∕n junction was formed using an ultra-low-energy implanter. Activation annealing exhibited both solid phase epitaxy, in which the sheet resistance dropped rapidly, and reverse annealing. Deactivation phenomena were investigated for the shallow source/drain junction based on measurements of the postannealing time and temperature following the rapid thermal annealing treatments. We found that the deactivation kinetics were divided into two regions. In the first region the rate of deactivation increased exponentially with the annealing temperature of up to 850°C. In the second region it decreased as the annealing temperature exceeded 850°C. We believe that the first region is kinetically limited while the second one is thermodynamically limited. In addition, we observed “transient enhanced deactivation,” an anomalous increase in the sheet resistance during the early annealing stage where the the temperatures were higher than 800°C. The activation energy for transient enhanced deactivation was measured to be between 1.75 and 1.87eV, while that for normal deactivation was between 3.49 and 3.69eV.