Low-energy implantation was one of the most promising options for ultra-shallow junction formation for the new generation of bipolar complementary metal oxide semiconductor (BiCMOS) Si technology. Boron was one of the dopants to be implanted, but was the most problematic because of its low stopping power, and its tendency to undergo transient enhanced diffusion and clustering during thermal activation. An experimental contribution was made here, using secondary defect profiles, to the understanding of low-energy B implants in crystalline Si. Shallow p+n junctions were formed by low-energy B implantation - 1015/cm2 at 3keV - into n-type crystalline Si pre-amorphized with Ge - 1015/cm2 at 30keV, 60keV and 150keV. Rapid thermal annealing (15s, 950C) was then performed to achieve electrical activation of the dopant and implantation damage removal. A reliable approach was proposed for the measurement of secondary defect profiles, induced by this process, using the isothermal transient capacitance associated with deep-level transient spectroscopy. The approach could be generalized to the profile measurement of any defect in a Si or III-V semiconductor substrate. In the present case, a relatively high concentration of electrically active B-related defects extended to a depth of 3.5µm into the crystal bulk.

Reliable Measurements of Defect Profiles in Low-Energy Boron Implanted Silicon. H.Benchenane-Mehor, M.Idrissi-Benzohra, M.Benzohra, F.Olivie: Japanese Journal of Applied Physics, 2004, 43[11A], 7572-5