Ultrathin HfO_2 gate dielectric grown by plasma-enhanced chemical vapor deposition using Hf[OC(CH_3)_3]_4 as a precursor in the absence of O_2

摘要

Hafnium oxide thin films for use in a gate dielectric were deposited at 300℃ on p-type Si(100) substrates using a Hf[OC(CH_3)_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 HfO_2 films, which were subsequently annealed in N_2 and O_2 ambients. The capacitance equivalent oxide thickness of the as-deposited Pt/HfO_2/Si capacitor was approximately 17 A and abruptly increased at an annealing temperature of 800℃ in both N_2 and O_2 ambients. The hysteresis of the as-deposited gate dielectric was quite small, about 40 mV, and that of the gate dielectric annealed at 800℃ in an O_2 ambient was reduced to a negligible level, about 20 mV. The interface trap density of the Pt/HfO_2/Si capacitors was approximately 10~(12) eV~(-1) cm~(-2) near the silicon midgap. The leakage current densities of the as-deposited Pt/HfO_2/Si capacitor and those annealed at 800℃ in N_2 and O_2 were approximately 8 x 10~(-4), 8 x 10~(-5), and 3 x 10~(-7) A/cm~2 at -1 V, respectively.