Retardation of boron diffusion in silicon by defect engineering

By judiciously placing vacancy and interstitial defects at different depths, we are able to enhance or retard boron diffusion. This opens up a new approach for the formation of shallow P(+)n junction in silicon. After preimplantation with 50 or 500 keV Si+ ions to produce a surface vacancy-rich region, we studied the diffusion of deposited B on predamaged samples with annealing between 900 and 1010 degreesC. Boron diffusion retardation was observed in both implantation conditions after low temperature annealing with enhancement occurring in a 50 keV implanted sample at high temperature. Choosing high energy implantation to separate vacancies and interstitials can reduce the boron diffusion significantly. Such suppression became more obvious with higher implant doses. A junction less than 10 nm deep (at 1 X 10(17) cm(-3) according to carrier concentration profiles) can be formed. (C) 2001 American Institute of Physics.