Contacts and junctions for the 45nm node

It is well accepted that one of the key parasitic resistances in ULSI transistors is the contact resistance between the silicide and the doped source/drain. In this paper, we investigate the individual components of this parameter. We show that the contact length is already a contributor at the 90 and 65nm nodes. Changing active doping in the Si via dose/energy modulations can reduce contact resistance in a low temperature flow, but not sufficiently to match results at high temperature. The largest knob is barrier height, leading some to consider moving to 2 different materials for contact to N+ and P+ regions (to replace a single silicide) which, although more complicated for processing may provide significant reductions in resistance. Using modifications to standard test structures and evaluation techniques, it becomes feasible to isolate the individual components of resistance, and to make significant progress in reducing this resistance.