How microalloying of the Al target can improve process and film characteristics of sputtered alumina

The outstanding thermo-mechanical and chemical stability of Al2O3 thin films attracts particular attention in academia and industry. Here we show that alloying of the powder metallurgically prepared Al targets with 2 as well as 5 at.% of Cr, Mo, or W significantly improves the process stability (e.g., reducing arcing events) for Al2O3, allowing their reactive magnetron sputtering in DC mode (substrate temperature was always 360 °C). Contrary to these microalloying elements, Nb did not change or improve the process characteristics of the Al target due to the relatively coarse Nb particles (<125 μm). Particularly the small (<10 μm) and fine-dispersed W particles are very effective in stopping the collision cascades to concentrate them to the near subsurface target-regions. This leads to a shift of the target-poisoning onset from O2/(Ar + O2) flow-rate-ratios of about 32 to 52%, specifically when adding 5 at.% to the Al target. Thereby also improved deposition rates are possible.