Effects of O3 and H2O as oxygen sources on the atomic layer deposition of HfO2 gate dielectrics at different deposition temperatures

Variations in the growth behavior, physical and electrical properties, and microstructure of the atomic layer deposited (ALD) HfO2 gate dielectrics were examined with two types of oxygen sources: O-3 and H2O for the given Hf-precursor of Hf[N(CH3)(C2H5)](4). The ALD temperature windows for O-3 and H2O were 240-320 degrees C and 200-280 degrees C, respectively, with the growth rate of HfO2 using O-3 being higher than that of the films using H2O within the ALD window. While the film density of HfO2 using O-3 decreased, the film density of HfO2 using H2O increased with the decreasing ALD temperature. As the deposition temperature decreased, the amount of impurity in the HfO2 film with the O-3 oxidant increased due to the insufficient reaction, which led to the crystallization of the HfO2 film into the tetragonal structure after the post-deposition annealing at 600 degrees C. The films with a lower density and a higher carbon-impurity concentration retained the portion of the tetragonal phase (similar to 30%) to the highest annealing temperature of 1000 degrees C. However, the HfO2 films grown at 200 degrees C with H2O showed the best electrical performance, which could be ascribed to the highest density, low impurity concentration, and negligible involvement of the interfacial low dielectric layer.