Impact of the surface treatment on the redistribution of low energy implanted boron atoms is investigated for the deep sub-micron ULSI processing. It is of importance to control the ambient and temperature, in respect to encapsulation, during annealing, as well as screen oxide thickness and post-implant cleaning for dose retention and profile tailoring. An optimization of these factors is demonstrated for BF2 + implantation to form a shallow bipolar transistor base.