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 fundamental performance limits. It has been proposed that drain current is ultimately limited by the rate at which carriers can be thermally injected from the source into the channel. In this work, we show that commonly used techniques for experimentally determining carrier velocity are insufficient to determine how close modern MOSFETs operate to the ballistic or "thermal limit." We propose a new technique and show that an advanced 1 V NMOS technology with L/sub eff/<50 nm operates at no more than /spl sim/40% of the limiting thermal velocity.