Application of optical emission spectroscopy to predict the composition of films during reactive magnetron sputtering of Ti-Al composite targets

Abstract

The processes of reactive magnetron sputtering of Ti-Al composite targets with different Al/Ti ratios have been studied. The dependences of the deposition rate, discharge voltage, elemental composition, and intensity of the control lines of optical plasma radiation on the oxygen concentration in the Ar/O2 gas mixture are established. It is shown that during reactive sputtering of Ti-Al composite targets, the discharge voltage is determined by the effective ion-induced secondary electron emission coefficient (SEEC) which depends on the area occupied by metals on the target, the degree of their oxidation, and the SEEC of these metals and their oxides. The rate of the deposition of TixAl1-xOy films in the metallic and transition sputtering modes increases proportional to the concentration of Al in the target, but the relative concentration of metals in the deposited films depends on the oxygen concentration in the Ar/O2 gas mixture and is determined by the reactivity of the target materials. It has been shown by optical emission spectroscopy (OES) that the ratio of the atomic concentrations of Al and Ti in deposited TixAl1-xOy films unambiguously depends on the ratio of the intensity of the control optical lines of aluminum AlI and titanium TiI in plasma. This makes it possible to use the OES method to predict the content of metals in a film during reactive magnetron sputtering of Ti-Al targets.