The influence of target erosion on the mass spectra of clusters formed in the planar DC magnetron sputtering source

The present paper reports on target erosion as one of the crucial parameters influencing the cluster size distribution. Size distributions of nanosized Cu clusters produced by a DC magnetron sputtering source during the lifetime of several different targets were monitored using a quadrupole mass filter. It is indicated that, during the target lifetime, cluster size distribution continuously shifts towards larger cluster sizes and becomes broader. After a certain operation time the cluster size distribution changes abruptly and the cluster formation is stopped. This happens much earlier than the point at which the erosion groove depth reaches the target thickness. It is suggested that a change in the mass spectra during the target lifetime is caused by the variation of the free metal atom density in the aggregation region. This may be due to the alteration of the sputtering yield. It is shown that the variation of the mass spectra correlates with the angular dependence of the sputtering yield.