PROCESS-CONTROL OF MAGNETRON SPUTTERING OF TIN COATINGS STUDIED BY IN-SITU AES AND PLASMA DIAGNOSTICS

The understanding of reaction mechanisms during reactive sputtering requires the knowledge of the flux and energy of the various particles impinging on the substrate and their effects on the growth rate and composition of the coating. Experiments have been performed in an ultrahigh vacuum receiver equipped with an in situ Auger electron spectroscopy system for chemical analysis of the substrate composition and instruments for plasma diagnostics. TiNx films were deposited on high speed steel substrates in an Ar-N-2 atmosphere by planar magnetron sputtering in the d.c. mode. The composition of the TiNx coatings was determined as a function of the Ar and N-2 partial pressure, bias voltage, d.c. power and substrate temperature. Mass spectrometer measurements were used to determine the ion fluxes to the substrate and their energies during film deposition. The flux of neutral titanium atoms was measured by optical spectrometry. Most of the experiments were carried out in a transition region for the composition of TiNx, with 0 < x < 1, in order to get a sensitive response of the composition to changes in sputter parameters. Relevant reaction mechanisms occurring in the plasma, on the target and on the substrate surface are discussed.