A Study of Effects of Metal Gate Composition on Performance in Advanced N-Mosfets

This work investigates the effects of HfO2 layer defects, formed by the Al atoms in the metal gate, on performance and reliability in advanced n-type metal-oxide-semiconductor field-effect transistors (n-MOSFETs) with different Al content in the gate stacks. Many groups have proposed theories (e.g., Si-H bond dissociation, trapped in high-k defects and impact ionization) to explain the degradation mechanisms in MOSFETs, with most focusing on the dissociation of the Si-H bond at the Si/SiO2 interface and the carrier trapping in the high-k layer. However, for multi-V-th devices, experimental results indicate that the formation of defects by Al atoms in the HfO2 layer is the main reason for degradation in advanced n-MOSFETs. Therefore, we propose a mechanism to clarify the deterioration in advanced n-MOSFETs with different Al content in the gate stacks, and this mechanism is confirmed by positive bias temperature instability (PBTI), hot carrier instability (HCI), HCI power-law fitting and the gate-induced drain leakage (GIDL) measurement.