Electron microprobe compositional analysis of sputtered tantalum-aluminium films

Abstract

In the present paper the methods for measurement of the composition of two or more component tantalum-based thin sputtered films are summarized. The influence of the target construction on the composition of the films is discussed. The Ta-Al films were sputtered from composite Ta-Al targets. The composition of films was measured by means of the electron microprobe technique. From results it follows that using the composite targets for sputtering in argon at a pressure of 2×10⁻² torr and in its mixture with nitrogen (10⁻³ torr), the composition of Ta-Al films is proportional to the ratio of the Ta and Al exposed surfaces on the target. The proportionality factor equals to the ratio of “effective” sputtering yields of target components measured at given sputtering conditions. The presence of nitrogen in sputtering gas decreases the value of Ta yield 2.2 times. If a small Al surface is sputtered together with much larger Ta surface, the sputtering yield of Al remains unchanged. In Ta-Al films the occluded argon was qualitatively determined. The presence of nitrogen was not proved. This seems to be caused by the absorption of nitrogen characteristic radiation in the investigated films.