High Mobility Ge pMOSFETs with ZrO₂ Dielectric: Impacts of Post Annealing

This paper investigates the impacts of post metal annealing (PMA) and post deposition annealing (PDA) on the electrical performance of Ge p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs) with ZrO₂ dielectric. For the transistors without PDA, on-state current (I_ON), subthreshold swing (SS), and capacitance equivalent thickness (CET) characteristics are improved with PMA temperature increasing from 350 to 500 °C. Crystallization of ZrO₂ dielectric at the higher PMA temperature contributes to the increase of the permittivity of ZrO₂ and the decrease of the density of interface states (D_it), resulting in a reduced CET and high effective hole mobility (μ_eff). It is demonstrated that Ge pMOSFETs with a PDA treatment at 400 °C have a lower CET and a steeper SS but a lower μ_eff compared to devices without PDA.