System LSI multi-vth transistors design methodology for maximizing efficiency of body-biasing control to reduce vth variation and power consumption

Abstract

In this paper, we describe newly developed multi-Vth transistors design scheme operable for body-biasing control for 65nm-node and beyond. The major issue of body-biasing control on system LSI comprising multi-Vth is that different Vth transistor exhibit different body-biasing sensitivities rendering body-biasing control scheme unfeasible. We have successfully solved the issue by Hf-based dielectric work-function (WF) modulation combined with optimal channel design, with which Vth shift amount under the same body-biasing is equalized among transistors having different Vth. The net result is the excellent body-biasing controllability as well as well-suppressed GIDL and Vth variation. Moreover, die to die Vth variation has been effectively reduced even for dies with multi-Vth transistors using body-biasing. We believe that this methodology is the most suitable for future low power system LSI application due to its simplicity and bulk-design inheritability