Comparative Study of HfTa-based gate-dielectric Ge metal–oxide–semiconductor capacitors with and without AlON interlayer

Abstract

The electrical properties and high-field reliability of HfTa-based gate-dielectric metal-oxide-semiconductor (MOS) devices with and without AlON interlayer on Ge substrate are investigated. Experimental results show that the MOS capacitor with HfTaON/AlON stack gate dielectric exhibits low interface-state/oxide-charge densities, low gate leakage, small capacitance equivalent thickness (∼1.1 nm), and high dielectric constant (∼20). All of these should be attributed to the blocking role of the ultrathin AlON inter- layer against interdiffusions of Ge, Hf, and Ta and penetra- tion of O into the Ge substrate, with the latter effectively suppressing the unintentional formation of unstable poor- quality low-k GeOx and giving a superior AlON/Ge inter- face. Moreover, incorporation of N into both the interlayer and high-k dielectric further improves the device reliability under high-field stress through the formation of strong N- related bonds.