Extraction of Effective Carrier Velocity and Observation of Velocity Overshoot in Sub-40 nm MOSFETs

Abstract

Carrier velocity in the MOSFET channel is the main driving force for improved transistor performance with scaling. We report measurements of the drift velocity of electrons and holes in silicon inversion layers. A technique for extracting effective carrier velocity which is a more accurate extraction method based on the actual inversion charge measurement is used. This method gives more accurate result over the whole range of V<SUB>ds</SUB>, because it does not assume a linear approximation to obtain the inversion charge and it does not limit the range of applicable V<SUB>ds</SUB>. For a very short channel length device, the electron velocity overshoot is observed at room temperature in 37 ㎚ MOSFETs while no hole velocity overshoot is observed down to 36 ㎚. The electron velocity of short channel device was found to be strongly dependent on the longitudinal field.