Tetragonal ZrO2-Gated Ge MOS Capacitors Fabricated on Si Substrate

Abstract

A tetragonal ZrO2 film stabilized by incorporating Ge atoms from an underlying Ge layer through a thermal annealing was investigated as the gate dielectric for Ge MOS devices. Formation of a tetragonal ZrO2 film and admixture of Ge atoms into a ZrO2 film were respectively confirmed by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) analysis. A sole tetragonal ZrO2 film was found to have a dielectric constant of 36.8 and demonstrated effective oxide thickness (EOT) down to 1.06 nm with good leakage current. However, it comes at the price of suffering poor interfacial quality. A more ideal gate stack for Ge MOS devices can be obtained by integrating a tetragonal ZrO2 film with an ultrathin thermal GeO2 layer to achieve a smaller EOT with satisfactory interfacial quality concurrently. Further improved gate stack performance can be accomplished by NH3 or H2 annealing to passivate grain boundaries.