In this work, we have studied the formation of ultra-shallow p-type junctions by rapid vapor phase doping. The doping process was performed in an ultra high vacuum rapid thermal processing system using 0.1 l/min of a B2H6/H2 mixture. The B2H6 content of the mixture was only. 500 ppm corresponding to a B2H6 flow of 50 μl/min. In contrast, previous work in conventional and rapid thermal processing systems used B2H6 flows as high as 0.1 l/min which tend to form either pure boron or boron silicide layers depending on the processing conditions. In this study we exposed 4″, (100) oriented, n- and p-type silicon wafers to the B2H6/H2 mixture for varying growth conditions. Boron junction profiles were obtained at temperatures ranging from 650°C to 850°C. Boron dose, peak concentration, and junction depth were found as a function of growth temperature and time. Our results show that ultra-shallow (≤ 500 Å) boron profiles with surface concentrations above 1020 cm−3 can be obtained in Si at temperatures as low as 650°C. Typical process times range from 15 to 90 seconds making the process a good candidate for single wafer manufacturing in rapid thermal processing systems.