Enhanced dielectric properties of ZrO2 thin films prepared in nitrogen ambient by pulsed laser deposition

Abstract

ZrO2 thin films were fabricated in O2 ambient and in N2 ambient by pulsed laser deposition (PLD), respectively. X-ray diffraction revealed that films prepared at 400°C remained amorphous. The dielectric properties of amorphous ZrO2 films were investigated by measuring the capacitance–frequency characteristics of Pt/ZrO2/Pt capacitor structures. The dielectric constant of the films deposited in N2 ambient was larger than that of the films deposited in O2 ambient. The dielectric loss was lower for films prepared in N2 ambient. Atom force microscopy investigation indicated that films deposited in N2 ambient had smoother surface than films deposited in O2 ambient. Capacitance–voltage and current–voltage characteristics were studied. The equivalent oxide thickness (EOT) of films with 6.6 nm physical thickness deposited in N2 ambient is lower than that of films deposited in O2 ambient. An EOT of 1.38 nm for the film deposited in N2 ambient was obtained, while the leakage current density was 94.6 mA cm−2. Therefore, ZrO2 thins deposited in N2 ambient have enhanced dielectric properties due to the incorporation of nitrogen which leads to the formation of Zr-doped nitride interfacial layer, and is suggested to be a potential material for alternative high-k (high dielectric constant) gate dielectric applications.