Effective work-function control technique applicable to p-type FinFET high-k/metal gate devices

In this work, we investigated the effect of so-called WF (Work Function) setting anneal (high temperature annealing on TiN/HfO2 stack) on gate stack properties. It was found that intermixed layer created in-between TiN and HfO2 during WF setting anneal has negative fixed charge and reduces pFET Vt (positive Vt shift). In addition, higher anneal temperature further reduces pFET Vt while keeping nFET Vt almost unchanged. This could be explained by passivation of oxygen vacancies in HfO2 with diffused oxygen from TiN layer. By combining these effects, one can further push effective work function towards valence band edge which enables wider coverage of transistor Vt option.