Preparation of hafnium oxide films from oxygen-free Hf[N(C2H5)2]4 precursor and their properties

Hafnium oxide films were deposited on silicon substrates at the deposition temperature ranging from 190 to 450 °C by metalorganic chemical vapor deposition (MOCVD). An oxygen-free precursor, Hf[N(C2H5)2]4, and O2 gas were used as starting materials. Deposition rate increased by the addition of O2 gas but was centrally decreased by the excess O2 addition due to the gas phase reaction at the temperature of 360 to 400 °C. Hafnium oxide films deposited at 400 °C consisted of amorphous phase and noticeable carbon and nitrogen contamination was not detected by X-ray photoelectron spectroscopy (XPS). From the relationship between the reciprocal of accumulation capacitance and physical thickness, and the cross-sectional high-resolution transmission electron microscope (HRTEM) observation, the relative dielectric constant of the hafnium oxide layer and the interfacial layer were estimated to be 16.4 and 7.8, respectively. The relative dielectric constant of the interfacial layer was much higher than silicon oxide and was closely related to the oxygen-free characteristics of hafnium precursor. This high dielectric constant (high-κ) interfacial layer is beneficial in decreasing the equivalent oxide thickness value.