Comparison of HfO2 films grown by atomic layer deposition using HfCl4 and H2O or O3 as the oxidant

HfO2 gate dielectric thin-films were deposited on Si wafers using an atomic-layer deposition (ALD) technique with HfCl4 and either H2O or O-3 as the precursor and oxidant, respectively. Although the ALD reactions using either H2O or O-3 were successfully confirmed at a deposition temperature of 300degreesC, the structural and electrical properties of the HfO2 films grown using the two oxidants were quite different. The stronger oxidation power of the O-3 compared to H2O increased the oxygen concentration in the HfO2 film and the rate of interfacial SiO2 formation even at the as-deposited state. Because of the larger oxygen concentration, the decrease in the capacitance density of the film grown with O-3 after rapid thermal annealing at 750degreesC under N-2 atmosphere was slightly larger than that of the HfO2 film grown with H2O. Apart from this weakness, all the other electrical properties, including the fixed charge density, the interface trap density, the leakage current density and the hysteresis in the capacitance-voltage plot of the film grown with O-3 were superior to those of the film grown with H2O. Therefore, O-3 appears to be a better oxidant for the HfO2 film growth using the ALD method. (C) 2003 American Institute of Physics.