Trapping of Si interstitials in boron doping background: Boron clustering and the “+1” model

Abstract

Boron transient enhanced diffusion (TED) in Si predoped with boron isotope atoms has been studied using secondary ion mass spectroscopy and channeling nuclear reaction analysis. Si crystal was first implanted with B11 ions of various doses and subsequently annealed at 1100 °C for 2 h to produce a uniform B11 doping concentration. The B11-doped sample and a Si control sample were then implanted with 40 keV B10 ions. Compared to the B11-free sample, B10 TED in the B11-doped sample is much retarded during the initial anneal at 750 °C for 1 h, while more broadening in the B10 profile occurs for the B11-doped sample after a second anneal at 950 °C for 15 min. The effect of B11 doping on B10 TED is discussed in terms of the trapping of Si interstitials in B11 doping background. The amount of trapped Si interstitials, for a certain B10 dose, increases with B11 doping concentration, but no “missing” Si interstitials are found for a B11 doping level of 7.8×1017 cm−3. From our data we show that it is also possible to test the “+1” model from the knowledge of B clustering mechanisms.