Ultrathin HfO2 gate dielectric grown by plasma-enhanced chemical vapor deposition using Hf[OC(CH3)3]4 as a precursor in the absence of O2

Abstract

Hafnium oxide thin films for use in a gate dielectric were deposited at 300 °C on p-type Si(100) substrates using a Hf[OC(CH3)3]4 precursor in the absence of oxygen by plasma-enhanced chemical vapor deposition. A comparison of films deposited in the absence and presence of oxygen indicated that oxygen was an important determinant in the electrical properties of HfO2 films, which were subsequently annealed in N2 and O2 ambients. The capacitance equivalent oxide thickness of the as-deposited Pt/HfO2/Si capacitor was approximately 17 Å and abruptly increased at an annealing temperature of 800 °C in both N2 and O2 ambients. The hysteresis of the as-deposited gate dielectric was quite small, about 40 mV, and that of the gate dielectric annealed at 800 °C in an O2 ambient was reduced to a negligible level, about 20 mV. The interface trap density of the Pt/HfO2/Si capacitors was approximately 1012 eV−1 cm−2 near the silicon midgap. The leakage current densities of the as-deposited Pt/HfO2/Si capacitor and those annealed at 800 °C in N2 and O2 were approximately 8 × 10−4, 8 × 10−5, and 3 × 10−7 A/cm2 at –1 V, respectively.