An investigation of the pulse characteristics on deposition rate of reactively sputtered titanium dioxide films synthesised with a low-frequency modulation of the discharge current

Among the problems related to target poisoning in reactive magnetron sputtering is the drastically low deposition rate of stoichiometric ceramic coatings deposited in the reactive mode. New techniques have recently Seen proposed to improve the process by modulating, at low frequency, either the reactive gas flow rate or the discharge power. This paper presents investigations relating to the deposition of TiO2 for both stable and unstable sputtering conditions, as well as the influence of a low-frequency modulation of the discharge current. The investigations show that high magnitude and low duty of the modulation are favourable parameters, whereas the optimum frequency can vary by approximately one order of magnitude, which should however be adapted to the pumping suction of the reactor. Investigations regarding the shape of the modulation indicate that three stages are required in order to improve the deposition rate of stoichiometric coatings: deoxidation, deposition and oxidation. (C) 1997 Elsevier Science S.A.