A Pyrazolate-Based Metalorganic Tantalum Precursor That Exhibits High Thermal Stability and Its Use in the Atomic Layer Deposition of Ta2O5

The atomic layer deposition (ALD) growth of Ta2O5 thin films was investigated using tert-butylimidotris(3,5-di-tert-butylpyrazolato)tantalum and ozone as precursors at deposition temperatures between 250 and 500 °C. The process provided uniform films and exhibited a large ALD window between 300 and 450 °C, in which a constant growth rate of 0.30 Å/cycle was observed. Surface-limited growth was confirmed at 325 °C, as evidenced by a constant growth rate with increasing precursor dose as delivered by longer pulse lengths. Furthermore, the thickness of films deposited at 325 °C varied linearly with the number of deposition cycles, which demonstrates good thickness control typical of ALD growth. The process provided stoichiometric Ta2O5 films with carbon, hydrogen, and nitrogen levels of ≤ 1.0 ≤ 1.9 and ≤ 0.9 atom %, respectively, within the ALD temperature window as determined by time-of-flight elastic recoil detection analysis. X-ray photoelectron spectroscopy measurements were consistent with the presence of Ta(V) and a stoichiometry of Ta2O5, with impurity elements below detection limits. All films were amorphous as deposited as determined by X-ray diffraction.