Tungsten oxide–silicon dioxide (WOx–SiOy) composite thin films were deposited for the first time via the remote oxygen plasma-enhanced atomic layer deposition (ALD) process using a novel metal-organic heteronuclear and heteroleptic precursor, bis(tert-butylimido)bis(trimethylsilylmethyl)tungsten. Self-limiting ALD growth was demonstrated over a wide temperature window of 203–328 °C with growth per cycle decreasing with increasing temperature from 0.75 to 0.4 Å/cycle, respectively. Residual gas analysis revealed ligand competition and showed that ligand reaction during ALD nucleation and growth was a function of deposition temperature, thereby affecting the film composition. As the temperature increased from 203 to 328 °C, the film composition [W/(Si + W)] ranged from 0.45 to 0.53. In addition, the carbon impurity content was reduced and the refractive index increased from 1.73 to 1.96, the density increased from 4.63 to 5.6 g/cm3, and the optical bandgap decreased from 3.45 to 3.27 eV. Grazing angle x-ray diffraction indicated that as-deposited films were amorphous. Upon annealing in O2 at 500 °C or higher, depending on deposition temperature, films are crystalized into the triclinic WO3 phase. At the same time, WO3 is sublimed from the surface and films are reduced in thickness.
Plasma-enhanced atomic layer deposition of WO3-SiO2 films using a heteronuclear precursor
Kamesh Mullapudi, Konner E. K. Holden, Jessica L. Peterson, Charles L. Dezelah, Daniel F. Moser, Ravindra K. Kanjolia, Douglas J. Tweet, John F. Conley; Plasma-enhanced atomic layer deposition of WO3-SiO2 films using a heteronuclear precursor. J. Vac. Sci. Technol. A 1 January 2023; 41 (1): 012406. https://doi.org/10.1116/6.0002214
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