| AVS 66th International Symposium & Exhibition | |
| Thin Films Division | Tuesday Sessions |
| Session TF+AP-TuM |
| Session: | ALD and CVD: Precursors and Process Development |
| Presenter: | Neha Mahuli, University of Colorado at Boulder |
| Authors: | N. Mahuli, University of Colorado at Boulder J.M. Wallas, University of Colorado at Boulder S.M. George, University of Colorado at Boulder |
| Correspondent: | Click to Email |
Metal oxyfluoride films are chemically robust and resistant to plasma corrosion. This study explored the atomic layer deposition (ALD) of various metal oxyfluorides including aluminum oxyfluoride (AlOxFy), hafnium oxyfluoride (HfOxFy) and zirconium oxyfluoride (ZrOxFy). Different deposition techniques were developed to obtain tunable stoichiometry of these metal oxyfluoride films. The complicating factor was fluorine/oxygen exchange and the diffusion of fluorine in the oxyfluoride film.
For the metal oxyfluoride deposition, H2O and HF were used as the oxygen and fluorine sources. Al(CH3)3 was used as the Al source. Hf and Zr alkylamide precursors were used as the Hf and Zr sources. The metal oxyfluorides were deposited using either (1) the halide-exchange method or (2) the nanolaminate method. These two methods gave rise to tunable stoichiometry from pristine metal oxide to adjustable oxyfluoride to pristine metal fluoride.Both methods were evaluated using in situ quartz crystal microbalance (QCM) measurements and ex situ X-ray photoelectron spectroscopy (XPS) analysis.
The halide-exchange method is based on the facile exchange of oxygen by fluorine from HFbased on following equation (MOx + yHFàMFy + xH2O). HF exposures after deposition of the metal oxide easily replaced oxygen with fluorine. The fluorine also diffused into the underlying metal oxide film as a function of time and temperature. The compositional control is achieved either using metal oxide layers of various thicknesses or different HF pressures. The rate of fluorine diffusion determined by in-situ QCM as well as ex-situ XPS was assigned as AlOxFy>ZrOxFy>HfOxFy.
The stoichiometry was also tuned using the nanolaminate method with different numbers of metal oxide ALD and metal fluoride ALD cycles. One supercycle (of ratio n:m) here consists of ‘n’ layers of metal oxide followed by ‘m’ layers of metal fluoride. The F:O ratios in the metal oxyfluoride films using this mechanism could be controlled over the full range of compositional ratios. The rate of fluorine diffusion in these systems was also found to be AlOxFy>ZrOxFy>HfOxFy.