Comparative study on EOR and deep level defects in preamorphised Si implanted with B+, BF2+ and F+–B+

The evolution of EOR defects and deep level traps, upon annealing and their effect on the junction leakage currents have been studied for low (10 keV) and high (70 keV) energy Ge-preamorphised (PAI) n-type silicon samples, that were boron implanted in several ways: B-ions, BF2+-ion and B+–F+ co-implantation, in order to fabricate ultra shallow p+n junctions. Transmission electron microscopy (TEM) revealed that the EOR defects change in type and density, depending upon annealing conditions and Ge energy. The traps, detected by deep level transient spectroscopy (DLTS), were analyzed and it has been found that they are due to interstitial-clusters; also, their evolution upon annealing is related to the evolution of the EOR defects. In the case of 70 keV Ge energy, the high leakage currents in the B+, BF2+ and B+–F+ implanted samples are very similar, due to similar evolution of EOR and deep level defects upon low temperature annealing. However, in the case of B+–F+ co-implantation for the 10 keV PAI samples, it has been found from TEM and SIMS results that F stabilizes the EOR defects and it also inhibits the dissolution of the electrically active deep level defects. These two facts lead to dramatically increased leakage currents in these B+–F+ co-implanted samples. In contrast, these phenomena have not been observed with the BF2+ and B+ implanted samples.