Activation annealing of ultra-low-energy implanted boron in silicon: a study combining experiment and process modeling

We present our investigations on the clustering, diffusion and electrical a ctivation of ultra-low-energy (<1 keV) implanted boron in crystalline silic on during annealing in the temperature range between 900 and 1200<degrees>C , We show that during the initial stage of the annealing, boron is bound to non-diffusing clusters. The formation and the dissolution in dependence of temperature are analyzed. We determine a dissolution time constant with an average activation energy of 2.3 eV, The depth-dependent electrical activa tion as measured by spreading resistance profiling was used to determine th e fraction of electrically active boron. From the analysis of the time depe ndence of the electrically active fraction? a time constant was determined which is faster compared with the boron cluster dissolution time constant i n the investigated temperature range. We have simulated the annealing proce ss to demonstrate the influence of the boron clustering on the broadening o f the boron profile. (C) 2000 Elsevier Science Ltd. All rights reserved.