Effect of annealing conditions on a hafnium oxide reinforced SiO2 gate dielectric deposited by plasma-enhanced metallorganic CVD

Hafnium oxide thin films for gate dielectric were deposited at 300degreesC on p-type Si(100) substrates by plasma-enhanced metallorganic chemical vapor deposition (PE-MOCVD) and annealed in O-2 and N-2 ambients at various temperatures. As-deposited HfO2 films showed an almost amorphous structure, but samples annealed at 800degreesC in O-2 showed an increase of crystallinity compared with those in the N-2 ambient. The flatband voltage shifts and interface trap densities of HfO2 capacitors annealed in an O-2 ambient are larger and lower, respectively, than those in N-2 ambient. Interface trap densities of HfO2 thin films annealed at 800degreesC in O-2 were about 5.5x10(11) cm(-2) eV(-1). The capacitance equivalent oxide thicknesses of HfO2 thin films annealed at 800degreesC were approximately 30 Angstrom independent of N-2 and O-2 ambients. Hysteresis of as-deposited gate dielectric was quite large, but that of gate dielectric annealed at 800degreesC in O-2 and N-2 ambients was reduced to a negligible level of about 20 mV without increase of the equivalent oxide thickness. The leakage current densities of HfO2 thin films annealed at 800degreesC in O-2 and N-2 ambient were about 8x10(-5) and 3x10(-26) A/cm(2), respectively, at -1 V.