Chemical Vapor Deposition of HfO₂ Thin Films Using the Novel Single Precursor Hafnium 3-Methyl-3-pentoxide, Hf(mp)₄

Abstract

Hafnium oxide films have been deposited on silicon substrates by metal organic chemical vapor deposition using the novel single precursor, hafnium 3-methyl-3-pentoxide {Hf[OC(CH3)(C2H5)2]4, Hf(mp)4}, with no additional oxygen source, and the deposition mechanism was elucidated. Hf(mp)4 is a liquid at room temperature and has a moderate vapor pressure comparable to that of hafnium tert-butoxide, Hf(OtBu)4, and a lower residual weight (<10%) in thermogravimetric analysis. The deposition rate was found to be ∼27 Å/min at 400 °C, and the activation energy was 68.1 kJ/mol, which is higher than those of other hafnium alkoxide and hafnium amide precursors. By gas chromatography/mass spectroscopy and nuclear magnetic resonance analyses of the thermally decomposed vapor phase products collected during the deposition of HfO2 films, it was clearly found that they are grown via β-hydrogen elimination processes of the Hf(mp)4 single precursor. Negligible carbon incorporation of the HfO2 films, examined by X-ray photoelectron spectroscopy and depth-profiling Auger electron spectroscopy, indicates that, except for the β-hydrogen elimination processes, no additional decomposition and/or recombination processes contributed to the HfO2 film growth. The morphology, crystallinity, and electrical properties of the HfO2 films were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, and capacitance−voltage and current−voltage measurements.