MODELING OF DEEP-SUBMICRON MOSFET DRIVE CURRENT

With already published MOSFET transistors of 25 nm gate length, the limit of the available current is a critical issue which must be clarified in order to guide the optimization of the transistor architecture. Leburton and Dorda¹ showed that the limitation of the drain current comes from the saturation of the electric field at the source, and not from the saturation of the carrier velocity. More recently, Lundstrom² compared the actual performance of the deep-sub-micron devices with their ballistic limit, and showed that the back-scattering at the source end of the channel is responsible for the limitation of the drain current. In both studies, the electric field, at the source end of the channel, plays a key part on the performances of the transistor. In this paper, we will review quantitatively this limitation, and, in addition, we are going to give a clear link between the drain current equations given by Lundstorm and the usual classical ones. Finally, we will examine the impact of the overshoot velocity on the transistor behavior.