EFFECT OF FREE-CARRIER ABSORPTION ON THE ANNEALING OF ION-IMPLANTED SILICON BY PULSED LASERS

The temperature rise in an ion-implanted silicon sample illuminated by a pulsed laser (ruby or Nd: YAG) is determined by numerical solution of the heat-diffusion equation. The temperature dependence of the thermal conductivity and the free-carrier absorption are included in the calculations. The latter was found to have a very significant effect when the laser is operated in the Q-switched mode. The analysis shows that annealing in this mode almost certainly involves melting of the sample surface. In the free-oscillation mode, however, free-carrier absorption is negligible, and this mode may therefore provide a method of melt-free annealing.