Comprehensive study and control of oxygen vacancy induced effective work function modulation in gate-first high-k/metal inserted poly-Si stacks

We report the crucial impact of “Reductant Controlled MIPS (RC-MIPS) process” to obtain a sufficiently high effective work function (EWF) of poly-Si/TiN/HfSiON stacks in the gate-first process. It was found that carbon impurity, the strongest reductant element in the gate stack, dominates oxygen vacancy (V
_o
) formation kinetics and markedly enhances Fermi level pinning (FLP) phenomenon. We designed a high EWF gate-first RC-MIPS technology that uses both in situ metal/high-k fabrication and reduction suppressing processes, which leads to improved EOT-J
_g
characteristics and EWF stability.