The effect of implant dose rates and two step anneals on p/sup +/-n ultra-shallow junctions

Ultra-shallow junctions are obtained using low energy BF/sub 2/ (5 keV) implants in crystalline Si. The variation in junction depth as a function of dose rate and two-step anneals is studied for doses of 1/spl times/10/sup 14/ and 1/spl times/10/sup 15/ cm/sup -2/. B diffusion is retarded in the tail region for the higher dose rates and consequently the junction depth decreases as compared to the lower dose rates. Junction depth is further reduced for the two-step anneals as compared to the single-step RTA.