Clustering of ultra-low-energy implanted boron in silicon during postimplantation annealing

We report on the clustering behavior of ultra-low-energy (500 eV) implanted boron in silicon during the postimplantation activation annealing. The broadening of the boron concentration profile is found to be composed of a diffusing and a nondiffusing contribution. The nondiffusing part is attributed to clustered boron. The concentration of boron in clusters is found to be dependent on the annealing temperature and the annealing time. The amount of boron in clusters decreases with increasing annealing time. A dissolution time constant with an average activation energy of 2.3 eV is determined from this behavior.