ZrO2 Gate Dielectric Deposited by Plasma-Enhanced Atomic Layer Deposition Method

Abstract

Zirconium oxide (ZrO2) films were investigated as a potential replacement for a silicon dioxide (SiO2) gate dielectric and were successfully deposited by the atomic layer deposition (ALD) method using zirconium t-butoxide and oxygen as the Zr precursor and reactant gas, respectively. ZrO2 films exhibited a relatively smooth surface and interface layer, and a stoichiometric structure. The ZrO2 films deposited with the oxygen plasma state showed higher growth rate with lower carbon content than the films deposited with the oxygen gas phase. The leakage currents of the films deposited with the oxygen gas phase and oxygen plasma state were about 3.7×10-7 and 2.7×10-8 A/cm2 at the gate bias voltage of -1.0 V with calculated equivalent oxide thicknesses of about 2.85 and 3.31 nm, respectively. The calculated interface state densities were 1.16×1011 and 5.52×1012 eV-1 cm-2 for the films deposited with the oxygen gas phase and oxygen plasma state, respectively. ZrO2 films deposited with the oxygen plasma state showed generally improved film quality compared to the films deposited with the oxygen gas phase. This study demonstrated the possible application of the plasma-enhanced ALD technique for high-quality ZrO2 gate dielectric thin film deposition.