Mechanism for the Reduction of Interstitial Supersaturations in MeV-Implanted Silicon

We demonstrate that the excess vacancies induced by a 1-MeV Si implant reduce the excess interstitials generated by a 40-keV Si implant during thermal annealing when these two implants are superimposed in silicon. The experiment presented in this work demonstrates that this previously observed reduction is dominated by vacancy annihilation and not by gettering to deeper interstitial-type extended defects. Interstitial supersaturations were measured with the use of B doping superlattices (DSL) grown on a silicon-on-insulator (SOI) substrate. Implanting MeV and keV Si ions into the B DSL/SOI structure eliminated the B transient enhanced diffusion normally associated with the keV implant. The buried SiO2 layer in the SOI substrate provides a barrier that isolates the deep interstitials-type extended defects of the MeV implant, thereby eliminating the possibility that these defects getter the interstitial excess induced by the keV Si implant.