Magnetron sputtered carbon nitride: composition and chemical bonding of as-grown and post-annealed films studied with real-time and in situ diagnostic techniques

We prepared CNx films by reactive r.f. magnetron sputtering from a graphite target in a pure N2 plasma, with different substrate bias voltages (Vb). We studied the optical properties of CNx films by using the in situ spectroscopic ellipsometry (SE) in the energy region 1.5–5.5 eV. The differences in compositional and bonding configuration between CNx films, provided by the SE data analysis, are discussed and correlated with the results obtained by Fourier Transform IR SE (FTIRSE) measurements. Post-growth annealing experiments were performed in an ultra-high vacuum (UHV) chamber, up to 900°C. The film modifications and the nitrogen evolution, were monitored in real-time using an ultra-fast 16-wavelength ellipsometer and a quadropole mass spectrometer (QMS). In situ SE and FTIRSE measurements were also obtained on the completion of annealing. The nitrogen evolution is correlated with the carbon-nitrogen bonding and the compositional modifications in the films, as derived by FTIRSE and SE.