On experimental determination of carrier velocity in deeply scaled NMOS: How close to the thermal limit?

Continued success in scaling bulk MOSFETs has brought increasing focus on f undamental performance limits. It has been proposed that drain current is u ltimately limited by the rate at which carriers can be thermally injected f rom the source into the channel [1], In this work, we show that commonly us ed techniques for experimentally determining carrier velocity are insuffici ent to determine how close modern MOSFETs operate to the ballistic or "ther mal limit." We propose a new technique and show that an advanced 1 V NMOS t echnology with L-eff < 50 nm operates at no more than <similar to>40% of th e limiting thermal velocity.