Ensuring long-term stability of process and film parameters during target lifetime in reactive magnetron sputtering

Reactive magnetron sputtering of a metallic target in a mixture of inert and reactive gas is now widely applied for compound deposition at high rates. It has been shown that problems due to arcing and the hysteresis of the process can be overcome by pulse sputtering and appropriate process control. Another important aspect is the shift of deposition parameters and reactive working point due to target erosion. For industrial applications, compensation of the shift is desired to achieve constant deposition conditions and homogeneous film properties during the target life. For this, different possibilities exist. In this paper, reactive sputtering of alumina films using stationary sputtering with the Double-Ring Magnetron (DRM) is reported. Ongoing target erosion is compensated using the movable magnet systems of the DRM to keep magnetic field strength at the target constant during target erosion. This technique has the advantage of constant electric discharge parameters during target life, and therefore ensures constant energetic substrate bombardment. Results with respect to constancy of deposition rate, film thickness distribution and film properties are discussed. Furthermore, the process stability and efficacy of the hidden anode are evaluated throughout target life.