Zirconium dioxide as a gate dielectric in metal-insulator-silicon structures and current transport mechanisms

This paper investigates the interfacial and bulk properties of zirconium dioxide as a high-k gate dielectric film and studies its current transport mechanisms. Aluminum gate/zirconium dioxide/n-type silicon (Al/ZrO₂/n-Si) metal-insulator-silicon (MIS) devices with equivalent-oxide-thickness (EOT) of ∼2.5 nm (with leakage current density of less than 2×10^-5 A/cm² at 1 V accumulation bias) were fabricated and characterized using electrical and structural analysis techniques. The simulated capacitance-voltage (C-V) curve, obtained by the self-consistent solution of Schrodinger and Poisson equations, was found to fit the measured C-V curve for the minimum (inversion) and maximum (accumulation) capacitances if dielectric constant values of 15 and 25 were used for the interfacial and bulk ZrO₂ layers. It was found that the Schottky emission mechanism fits a very narrow gate voltage (V_g) range of 0g<0.2 V (as this is an electrode-limited conduction) while the Frenkel-Poole (F-P) emission is the dominant current transport mechanism over 0.2 Vg<1.2 V in our devices.