High activity of B during solid-phase epitaxy in a pre-amorphized layer formed by Ge ion implantation and deactivation during a subsequent thermal process

We have shown that ion-implanted boron (B) in an amorphous layer formed through Ge ion implantation becomes highly active during solid-phase epitaxy. The activated B concentration reaches about 10²⁰ cm^-3 and is almost completely independent of the temperature. This active concentration corresponds to the solid solubility at 900°C, hence the B becomes active at levels greater than the solid solubility below this temperature. This activated B was deactivated as a result of the subsequent thermal process in which the diffusion length reached about 10 nm. A low-resistance shallow junction can thus be realized in the low-temperature region provided we end the annealing before the onset of the rise in resistance.