Effective Work Function Computation of HfO2/TiN/W Bi-metal System: Role of Barrier-TiN

Using ab-initio simulations, we compute the effective work function of TiN/W bi-metal system interfaced with a high-k layer. We study the dependence of the effective work function of HfO2/TiN/W stack on (i) the thickness of the barrier-TiN layer and (ii) the amount of W intermixing in TiN layer. Our simulations show that the barrier-TiN layer plays a significant role in impacting the effective work function: beyond a thickness of three Ti-N layers (approximately 0.6nm), the effective work function is predominantly determined by the barrier-TiN layer for both Ti- and N-terminated HfO2/TiN interfaces. When W atoms are intermixed in the Ti-layer closest to the HfO2/TiN interface, we find that the effective work function changes with W concentration and converges to the value for HfO2/W stack at 50% W concentration.