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.