Characterisation of the silicon nitride thin films deposited by plasma magnetron

Silicon nitride thin films were deposited by reactive DC magnetron sputtering on different substrates in a home-made planar DC sputtering system. The sputtering was performed from a silicon target in a sputtering atmosphere of (Ar, H-2, N-2) mixture. The gas composition could be varied from 0 to 100% for Ar and N-2, and from 0 to 10% for H-2. The structure and purity of the coatings have been investigated as a function of the process parameters, such as the composition of the sputtering atmosphere and the total pressure. The deposited films were characterised by optical interferometry (thickness measurement), Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and XPS. The XPS spectra indicated that Si3N4 was obtained for a molar fraction of nitrogen larger than 0.1, and also indicated that the sputtered silicon nitride films were uncontaminated with oxygen and carbon. The N/Si ratio of the nitride films could be tuned between 0.56 and 1.33 depending on the deposition conditions. The presence of the transverse optical (TO) and longitudinal optical (LO) phonons in infrared reflection absorption spectroscopy (IRRAS) attest for the presence of Si-N bonds. For the stoichiometric films no change in the LO phonon peak position was observed, indicating that there is no variation in the film composition. Copyright (C) 2008 John Wiley & Sons, Ltd.