The progress and challenges of threshold voltage control of high-k/metal-gated devices for advanced technologies (Invited Paper)

This paper discusses recent progress in and challenges of threshold voltage control for advanced high-k/metal-gated (HKMG) devices. It presents the impact on threshold voltage (V"t) control of incorporating La and Al into HKMG devices. A dipole moment model explaining V"t tuning of HfSiON/metal-gated MOSFETs is proposed. In addition, a dual channel scheme that allows La"2O"3 capping in NMOS and a SiGe channel in PMOS to achieve acceptable V"t for HKMG CMOS devices will be discussed. Also shown is the impact of the robustness of the SiO"2/Si interface on the HKMG MOSFET V"t-equivalent oxide thickness (EOT) roll-off. Finally, techniques to improve the interface quality of a HKMG stack will be discussed.