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

Abstract

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 GeO2 and SiO2 interfacial layers. Large capacitance density of 3.3 μF/cm2, 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 SiO2 interfacial layer, while the device with ultrathin interfacial GeO2 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 GeO2 interfacial layer is due to the severe Ge outdiffusion, thinned interfacial GeO2 and thicker gate dielectric after 550 °C rapid-thermal anneal.