Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma

A plasma-enhanced atomic layer deposition (ALD) process using the Ag(fod)(PEt 3 ) precursor [(triethylphosphine)(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)silver(I)] in combination with NH 3 -plasma is reported. The steady growth rate of the reported process (0.24 ± 0.03 nm/cycle) was found to be 6 times larger than that of the previously reported Ag ALD process based on the same precursor in combination with H 2 -plasma (0.04 ± 0.02 nm/cycle). The ALD characteristics of the H 2 -plasma and NH 3 -plasma processes were verified. The deposited Ag films were polycrystalline face-centered cubic Ag for both processes. The film morphology was investigated by ex situ scanning electron microscopy and grazing-incidence small-angle X-ray scattering, and it was found that films grown with the NH 3 -plasma process exhibit a much higher particle areal density and smaller particle sizes on oxide substrates compared to those deposited using the H 2 -plasma process. This control over morphology of the deposited Ag is important for applications in catalysis and plasmonics. While films grown with the H 2 -plasma process had oxygen impurities (∼9 atom %) in the bulk, the main impurity for the NH 3 -plasma process was nitrogen (∼7 atom %). In situ Fourier transform infrared spectroscopy experiments suggest that these nitrogen impurities are derived from NH x surface groups generated during the NH 3 -plasma, which interact with the precursor molecules during the precursor pulse. We propose that the reaction of these surface groups with the precursor leads to additional deposition of Ag atoms during the precursor pulse compared to the H 2 -plasma process, which explains the enhanced growth rate of the NH 3 -plasma process.