Electron Mobility Limited by Remote Charge Scattering in Thin (100)- and (110)-Oriented Silicon Body Double-Gated Metal--Oxide--Semiconductor Field-Effect Transistors with High-k Gate Dielectrics

We have investigated the electron mobility limited by the remote charge scattering, mu(RCS), in the thin silicon body (<= 8 nm) double-gated metaloxide-semiconductor field-effect transistors (MOSFETs), focusing on its dependency on the body thickness and the silicon surface orientation. In order to predict the mu(RCS) in such an unprecedented MOSFET system, the adequacy of physical models used in the computation was verified by comparing the computational results with the experimentally determined mu(RCS) from the actual bulk MOSFETs with high-k dielectric fabricated on the (100) and (110) silicon substrates. It has been discovered for the first time that the mu(RCS) is dropped to less than half of the bulk device's mu(RCS) when the body thickness is 5 nm and that the mu(RCS) lowering derived from the body thickness reduction is more serious in the (110)-oriented surface than in the (100)-oriented surface. These mobility trends have been quantitatively explained by the effective mass difference between the two surfaces as well as by the carrier confinement in the metallurgically defined narrow silicon body. These observations indicate the great importance of the systematic reduction of charged traps in high-k gate dielectrics in the advanced devices. (C) 2012 The Japan Society of Applied Physics