Grain-Orientation Induced Quantum Confinement Variation in FinFETs and Multi-Gate Ultra-Thin Body CMOS Devices and Implications for Digital Design

This paper identifies and investigates a new source of random threshold voltage variation, which is referred to as Grain-Orientation-induced Quantum Confinement (GOQC) in emerging ultra-thin-body metal-gate complementary metal-oxide-semiconductor (CMOS) devices including FinFET, tri-gate, and nanowire field-effect transistors. Due to the dependence of the work function of the metal gates on their grain orientations, different parts of the gate in multigate CMOS devices can have different work functions, resulting in a high electric field in the channel (body) of these devices and, hence, in electrical confinement of the carriers. GOQC effect is shown to be the dominant source of the quantum threshold voltage variation in all emerging ultra-thin multi-gate devices including FinFETs. It is also highlighted for the first time that such variations can have significant implications for the performance and reliability of minimum-sized digital circuits such as static random-access memory cells.