Sub-30 nm P/sup +/ abrupt junction formation in strained Si/Si/sub 1-x/Ge/sub x/ MOS device

For junction formation in strained Si on relaxed Si/sub 1-x/Ge/sub x/ substrates with x=15-30%, shallower and more abrupt boron P/sup +/ extension junction is achieved as the %Ge in the relaxed Si/sub 1-x/Ge/sub x/ is increased. At x=30%, a factor of 2 improvement in both junction depth Xj and abruptness Xjs is achieved over that formed in bulk Si. Further reductions in Xj and Xjs were achieved by vacancy injection during RTA anneal with NH/sub 3/ ambient. However, this approach was found effective only for Ge concentration below 30% above which the boron diffusion mechanism apparently changes over from interstitial to vacancy. With 6 nm Si cap on 30% Si/sub 1-x/Ge/sub x/ layer, it creates one of the shallowest and most abrupt boron junctions yet achieved with RTA; Xj=23 nm and Xjs/spl sim/4.5 nm/dec. Better boron junction activation (>10%) is also achieved in strained Si/Si/sub 1-x/Ge/sub x/ layer than in bulk Si.