Lower sheet/contact resistance in shallower junction obtained by F+B mixed implant

Further reduction of sheet/contact resistance is observed and shallower junction is obtained using F+B implant instead of conventional B, BF2, or BF2+B implant. A deeper fluorine implant to increase the distance between F and B causes a higher retained boron dose while making the junction depth shallower upon annealing. Junction depth reduction is achieved by making the junction boundary abrupt near the junction depth, and higher retained boron dose leads to a reduction of sheet and contact resistance. Even if our experimental scheme practically focuses on the deep contact junction, the abrupt junction profile with high activation efficiency obtained by shifting the F implant deeper than B implant is also attractive for the ultrashallow source/drain extension technology for sub-0.1 mum p-type metal-oxide-semiconductor devices. (C) 2002 American Vacuum Society.