The use of SiGe barriers during the formation of p+ shallow junctions by ion implantation

Ultra-shatlow p(+) junctions are required for next generation electronics. We present a technique for the formation of ultra-shallow p(+) junctions that increases the thermal stability of the junctions formed by ion implantation. By using a 10 nm Si1-xGex barrier layer, the diffusion of B is inhibited during high temperature processes. Alloys having a composition from x = 0 to 0.4 were investigated and it is shown that the most effective barrier had the maximum Ge fraction. The junction depth decreased to 36.7 nm for a 5x10(15)/cm(2) 1 kV BF3 plasma implant spike annealed at 1050 degreesC, compared to a junction depth of 48 nm for a Si control sample having the identical implant and anneal. It is hypothesized that the inhibition of B diffusion in the alloy layer is caused by a reduction of the Si self-interstitials in the alloy.