Impact of high-/spl kappa/ dielectric HfO/sub 2/ on the mobility and device performance of sub-100-nm nMOSFETs

Abstract

Scaling of Si MOSFETs beyond the 90-nm technology node requires performance boosters in order to satisfy the International Technology Roadmap for Semiconductors requirements for drive current in high-performance transistors. Amongst the preferred near term solutions are transport enhanced FETs utilizing strained Si (SSi) channels. Additionally, high-/spl kappa/ dielectrics are expected to replace SiO/sub 2/ around or after the 45-nm node to reduce the gate leakage current problem, facilitating further scaling. However, aside from the many technological issues such as trapped charge and partial crystallization of the dielectric, both of which are major issues limiting the reliability and device performance of devices employing high-/spl kappa/ gate stacks, a fundamental drawback of MOSFETs with high-/spl kappa/ dielectrics is the mobility degradation due to strong soft optical phonon scattering. In this work we study the impact of soft optical phonon scattering on the mobility and device performance of conventional and strained Si n-MOSFETs with high-/spl kappa/ dielectrics using a self-consistent Poisson Ensemble Monte Carlo device simulator, with effective gate lengths of 67 and 25-nm. Additionally we have also briefly investigated the effect (the percentage change) that a trapped charge within the gate oxide will have on the drive current for both a SiO/sub 2/ oxide and an equivalent oxide thickness of high-/spl kappa/ dielectric.