Recent aspects concerning DC reactive magnetron sputtering of thin films: A review

In this paper, attention is paid to DC reactive magnetron sputtering and its implications, such as the hysteresis effect and the instability in the reactive gas pressure, differential poisoning of magnetron cathode, as well as the methods which are used to control the process. These methods include: (a) increasing the pumping speed, which requires considerable additional costs; (b) increasing the target-to-substrate distance, which requires larger vacuum chambers (hence, higher costs) and also results in lower deposition rates; (c) obstructing reactive gas flow to the cathode with the resultant reduction of deposition rate and the need for complicated arrangements; (d) pulsed reactive gas flow, which requires an extensive amount of process optimisation and a continuous monitoring and adjustment of the process parameters; (e) plasma emission monitoring; and (f) voltage control, which are inexpensive and have proved to be powerful techniques for monitoring and controlling the reactive sputtering processes, in real time without disturbing the discharge, for the deposition of high-quality films, reproducibly. In addition, arcing and methods to avoid it are reviewed; this includes, are initiations and their destructive effects (e.g. driving the process to become unstable, reducing the target lifetime and creating defects in the sputtered films), time required for arcs to occur, and finally, methods of avoiding arcs. The latter includes the use of unipolar or bipolar pulsing techniques at frequencies in the range 10-70 kHz. (C) 2000 Elsevier Science S.A. All rights reserved.