Low temperature solution processed high-κ ZrO2 gate dielectrics for nanoelectonics

Abstract

The high-κ gate dielectrics, specifically amorphous films offer salient features such as exceptional mechanical flexibility, smooth surfaces and better uniformity associated with low leakage current density. In this work, ∼35nm thick amorphous ZrO2 films were deposited on silicon substrate at low temperature (300°C, 1h) from facile spin-coating method and characterized by various analytical techniques. The X-ray diffraction and X-ray photoelectron spectroscopy reveal the formation of amorphous phase ZrO2, while ellipsometry analysis together with the Atomic Force Microscope suggest the formation of dense film with surface roughness of 1.5Å, respectively. The fabricated films were integrated in metal–oxide–semiconductor (MOS) structures to check the electrical capabilities. The oxide capacitance (Cox), flat band capacitance (CFB), flat band voltage (VFB), dielectric constant (κ) and oxide trapped charges (Qot) extracted from high frequency (1MHz) C–V curve are 186pF, 104pF, 0.37V, 15 and 2×10−11C, respectively. The small flat band voltage 0.37V, narrow hysteresis and very little frequency dispersion between 10kHz–1MHz suggest an excellent a-ZrO2/Si interface with very less trapped charges in the oxide. The films exhibit a low leakage current density 4.7×10−9A/cm2 at 1V. In addition, the charge transport mechanism across the MOSC is analyzed and found to have a strong bias dependence. The space charge limited conduction mechanism is dominant in the high electric field region (1.3–5V) due to the presence of traps, while the trap-supported tunneling is prevailed in the intermediate region (0.35–1.3V). Low temperature solution processed ZrO2 thin films obtained are of high quality and find their importance as a potential dielectric layer on Si and polymer based flexible electronics.