Effects of donor concentration on transient enhanced diffusion of boron in silicon

Abstract

The effects of substrate donor concentration on transient enhanced diffusion (TED) of boron implanted into silicon wafers predoped with arsenic or phosphorus have been investigated by using secondary ion mass spectroscopy and theoretical simulations. Boron ions have been implanted at low energy (10–20 keV) and successively annealed in the temperature range 700–1000 °C. No detectable boron TED (TED<10×) has been observed in samples uniformly predoped with P at the concentration of 1.2×1020 cm−3. The B TED is strongly reduced even in the samples predoped with As. However, for the highest As concentration (1.3×1020 cm−3) an exponential high diffusivity tail has been detected in the B profiles at all the examined annealing temperatures. This anomalous effect has been attributed to the interstitials produced by an As clustering reaction occurring during the low temperature annealing. The main effects responsible for the vanishing of the B TED, i.e., ionization of the interstitials (Fermi level effect), competitive behavior of P in the interaction with the interstitials, and donor-acceptor pairing have been examined and discussed.