Activation mechanism of implanted boron in a Si substrate

Abstract

The recrystallization and dopant activation in the BF2+ implanted samples with a 110 keV/5×1015 cm−2 condition into a Si substrate and annealed with different heating rates to various preset temperatures for zero holding time have been studied. A higher heating rate yielded a higher carrier mobility and a better crystallinity. A statistical model was proposed to characterize the dopant activation. The activated dopant concentration n was expressed as γ exp(−Ea/kT). The pre-exponential term γ is a function of critical temperature Tc, due to a finite melting point of Si, and heating rate. Both the effective activation energy Ea and Tc values decreased with increasing heating rate. With increasing heating rate, the γ term rapidly decreased at low rates due to the shortened effective annealing time, but showed slight increase at high rates due to the decreased Tc value. Low heating rates facilitated the dopant activation via the γ term, while high heating rates enhanced the activation efficiency via the Ea term.