Modifying Threshold Voltages to n- and p- Type FinFETs by Work Function Metal Stacks

Abstract

High-k metal gate technology improves the performance and reduces the gate leakage current of metal–oxide–semiconductor field-effect transistors (MOSFETs). This study investigated four different work function metal (WFM) stacks in the gate of fin field-effect transistors (FinFETs) on the same substrate. These devices not only successfully produced distinct levels of threshold voltages (|Vt|) but also converted n- to p-type features merely by adding p-type WFM in the gate of the MOSFETs. All of the devices satisfied short-channel effects with shrinking channel length. The gate-to-body electric field induced drain leakage due to the nature of bulk FinFETs. However, the n- and p-type gate stacks presented different gate current leakage. For reliability, hot carrier injection (HCI) could have a higher reliability impact than the negative-bias temperature instability (NBTI) for p-MOSFET, although the stress voltage of HCI was roughly half that of the NBTI test. This multi-threshold voltage tuning allows designers to design CMOS and choose the trade-off between low power consumption and high performance on the same platform.

Keywords

• Work function metal
• threshold voltage tuning
• energy-dispersive X-ray spectroscopy
• FinFETs
• reliability