Atomic Layer Chemical Vapor Deposition of Hafnium Oxide Using Anhydrous Hafnium Nitrate Precursor

Abstract

HfO₂ films have been deposited using anhydrous hafnium nitrate (Hf(NO₃)₄) as a precursor for atomic layer chemical vapor deposition (ALCVD). These films have been characterized using x-ray diffraction, x-ray reflectivity, atomic force microscopy, current vs. voltage, and capacitance vs. voltage measurements. An advantage of this precursor is that it produces smooth and uniform initiation of film deposition on H-terminated silicon surfaces. As deposited films remained amorphous at temperatures below ∼700°C. The effective dielectric constant of the film (neglecting quantum effects) for films less than ∼15 nm thick, was in the range of k_film ∼ 10-11, while the HfO₂ layer value was estimated to be kHfO₂ ∼ 12-14. The lower than expected dielectric constant of the film stack is due in part to the presence of an interfacial layer such as HfSiO_x. Excess oxygen may play a role in the lower than expected dielectric constant of the HfO₂ layer. Breakdown of HfO₂ films occurred at ∼5-7 MV/cm. Leakage current was lower than that of SiO₂ films of comparable equivalent thickness.