A new precursor for the chemical vapor deposition of tantalum nitride films

Abstract

A new precursor system for the deposition of tantalum nitride films has been developed. The tantalum(IV) complexes Ta(NEt₂)₂Cl₂(p-Me₂Npy)₂ and Ta(NEt₂)₂(NCy₂)₂ were synthesized and their structures were determined by X-ray crystallography. Ta(NEt₂)₂Cl₂(p-Me₂Npy)₂ has an octahedral structure with trans chloride and cis amido ligands, and Ta(NEt₂)₂(NCy₂)₂ has a distorted tetrahedral geometry. Tantalum nitride films were prepared from Ta(NEt₂)₂(NCy₂)₂ and ammonia at 340 °C using aerosol-assisted chemical vapor deposition. The films on glass had resistivities of 2.5 ± 0.1 × 10⁵ μΩ cm. Rutherford backscattering spectrometry, forward recoil spectrometry, and X-ray photoelectron spectroscopy data suggest the films have a composition of approximately TaN_1.5H_0.3–0.5. The X-ray photoelectron spectroscopy data also indicate that the average tantalum oxidation state is +4 and that each hydrogen atom in the film is associated with two nitrogen atoms on average. The films were a barrier to diffusion between copper and silicon at 500 °C for one hour. The results of this study suggest that the oxidation state of the metal in the precursor controls the oxidation state of the metal in the film, and thereby the film stoichiometry and properties.