Low-resistance bandgap-engineered W/Si/sub 1-x/Ge/sub x//Si contacts

Bandgap-engineered W/Si/sub 1-x/Ge/sub x//Si junctions (p/sup +/ and n/sup +/) with ultra-low contact resistivity and low leakage have been fabricated and characterized. The junctions are formed via outdiffusion from a selectively deposited Si/sub 0.7/Ge/sub 0.3/ layer which is implanted and annealed using RTA. The Si/sub 1-x/Ge/sub x/ layer can then be selectively thinned using NH/sub 4/OH/H/sub 2/O/sub 2//H/sub 2/O at 75/spl deg/C with little change in characteristics or left as-deposited. Leakage currents were better than 1.6/spl times/10/sup -9/ A/cm/sup 2/ (areal), 7.45/spl times/10/sup -12/ A/cm (peripheral) for p/sup +//n and 3.5/spl times/10/sup -10/ A/cm/sup 2/ (peripheral) for n/sup +//p. W contacts were formed using selective LPCVD on Si/sub 1-x/Ge/sub x/. A specific contact resistivity of better than 3.2/spl times/10/sup -8/ /spl Omega/ cm/sup 2/ for p/sup +//n and 2.2/spl times/10/sup -8/ /spl Omega/ cm/sup 2/ for n/sup +//p is demonstrated-an order of magnitude n/sup +/ better than current TiSi/sub 2/ technology. W/Si/sub 1-x/Ge/sub x//Si junctions show great potential for ULSI applications.