Interfacial layer dependence on device property of high-κ TiLaO Ge/Si N-type metal-oxide-semiconductor capacitors at small equivalent-oxide thickness

We have investigated the device property dependence of high dielectric-constant (high-κ) TiLaO epitaxial-Ge/Si n -type metal-oxide-semiconductor (n-MOS) capacitors on different GeO ₂ and SiO ₂ interfacial layers. Large capacitance density of 3.3 μF/ cm ² , small equivalent-oxide thickness (EOT) of 0.81 nm and small C-V hysteresis of 19 mV are obtained simultaneously for MOS capacitor using ultrathin SiO ₂ interfacial layer, while the device with ultrathin interfacial GeO ₂ shows inferior performance of larger 1.1 nm EOT and poor C-V hysteresis of 93 mV. From cross-sectional transmission electron microscopy, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy analysis, the degraded device performance using GeO ₂ interfacial layer is due to the severe Ge outdiffusion, thinned interfacial GeO ₂ and thicker gate dielectric after 550 °C rapid-thermal anneal.