Surface defects and arc generation in reactive magnetron sputtering of aluminium oxide thin films

Abstract

Arcing phenomena and defect density on the surface of aluminium oxide thin films have been investigated as a function of process parameters such as pulsing frequency, substrate bias voltage, target voltage and sputtering gas pressure. The thin films were deposited by direct current reactive magnetron sputtering techniques. The deposition of the thin films was controlled by target voltage. A pulsed power supply at low and medium frequency range (2–50 kHz) was used to improve the stability of the deposition process and to reduce the surface defect density. Target poisoning led to arcing and an unstable deposition process, which, in turn, resulted in defects on the surface of the thin films. Target poisoning was minimised by depositing the thin films at high target voltages at a pre-set target power density. Mainly microarcing during the deposition was observed. Strong arcing resulted in rough coating surfaces and metallic aluminium droplet contamination. The changes in the appearance of the thin films from transparent colourless to transparent opaque were observed.