Impact of work function metal stacks on the performance and reliability of multi-Vth RMG CMOS technology

Multi-Vth CMOS device technologies have become standard for System-on-Chip designs. In Replacement Gate technologies, distinct device Vth’s are achieved by deploying different work function metal stacks, and thus concerns exist about the possible chemical interaction of different gate metals with the underlying dielectrics potentially affecting the device performance and reliability. We present a comprehensive study, comprising both electrical measurements and simulations, carried out on a planar transistor platform with state-of-the-art gate stacks. Two different metal stacks are deployed to fabricate low-Vth and ultra-high Vth pMOS and nMOS device flavors. The study provides fundamental insights on the impact of TiAl-based gate metal on EOT, gate leakage, interface quality, carrier mobility, short channel performance, PBTI and NBTI reliability.