Metallorganic chemical vapor deposition of hafnium silicate thin films using a dual source dimethyl-alkylamido approach

A low-temperature metallorganic chemical vapor deposition process has been developed for the growth of hafnium silicate thin films for advanced gate dielectric applications. In this process, a metallorganic hafnium precursor, tetrakis(dimethylamino)hafnium, and a metallorganic silicon precursor, tris(dimethylamino)silicon, were employed, using O2 as a co-reactant. Films were deposited at a substrate temperature in the range of 250-450°C. The films were subsequently annealed in oxygen and forming gas ambients to assess thermal stability. The resulting films were characterized by Auger electron spectroscopy to determine composition and X-ray diffraction to determine microstructure. Electrical test structures were fabricated with as-deposited and annealed hafnium silicate films, and C-V and J-V measurements were performed. As-deposited dielectric constant values ranging from 6.9 to 12.9 were achieved depending on processing conditions and resulting film composition. Leakage current density at flatband voltage minus 1 V for a 26 nm thick as-deposited film was measured to be 1.6× 10-1 A cm2 and was shown to decrease following an O2 anneal. The performance of these hafnium silicate films was also compared to hafnium oxide films deposited using the same Hf precursor and O2 oxidizer approach.