Design Guidelines for Sub-12 nm Nanowire MOSFETs

Abstract

Traditional thinking assumes that a light effective mass ( $m^*$ ), high mobility material will result in better transistor characteristics. However, sub-12-nm metal-oxide-semiconductor field effect transistors (MOSFETs) with light $m^*$ may underperform compared to standard Si, as a result of source to drain (S/D) tunneling. An optimum heavier mass can decrease tunneling leakage current, and at the same time, improve gate to channel capacitance because of an increased quantum capacitance ( $C_q$ ). A single band effective mass model has been used to provide the performance trends independent of material, orientation and strain. This paper provides guidelines for achieving optimum $m^*$ for sub-12-nm nanowire down to channel length of 3 nm. Optimum $m^*$ are found to range between 0.2–1.0 $m_0$ and more interestingly, these masses can be engineered within Si for both p-type and n-type MOSFETs. $m^*$ is no longer a material constant, but a geometry and strain dependent property of the channel material.