Dynamics of void formation during implantation of Si under self-annealing conditions and their influence on dopant distribution

The formation and evolution of voids in Si implanted with P+ and As+ under the transient heating produced by high beam power density (of the order of some tens of W cm-2), are investigated and correlated with the observed anomalous redistribution of the implanted dopant. It is shown that in the advanced stage of irradiation, characterized by maximum transient temperatures in excess of 1100°C, the evolution of the defects is mainly related to the redistribution of dopant, rather than to the primary implantation parameters. In fact, voids, which in the earlier stage of irradiation are almost uniformly distributed up to a depth of about 0.8 of the ion projected range, tend afterwards to survive and grow in the regions of relatively high dopant concentration, while they disappear elsewhere. The segregation of dopants at voids seems to be the process which stabilizes the defects. It can be argued that the differences in void evolution observed for implantation with As+ or P+ ions are due both to the different mobility of the two impurities and to the different stability of the impurity-void complexes under irradiation