MICROSTRUCTURE AND MORPHOLOGY OF ALN COATINGS ON SAPPHIRE DEPENDING ON NITROGEN CONCENTRATION AND CONDITIONS AT THE INITIAL STAGES OF DUAL MAGNETRON SPUTTER DEPOSITION

The influence of nitrogen proportion and two-stage modes on parameters a and c of the unit cell, dimensions of germs and grains, slope of grains and their relative concentration, surface morphology and thickness of AlN coatings deposited on c -oriented sapphire by dual magnetron reactive sputter deposition, is studied in this paper. It was found that coating structure is ultimately determined by the state of the surface of sputtering targets and the flow of impurities into the chamber. Growth in N 2 concentrations in the region where the target surfaces remain partly coated by AlN x , is accompanied by the increase in parameter c and the concentration of grains with planes (002) substantially parallel to the coating surface, the decrease in parameter a and the proportion of inclined grains. In case of a completely closed AlN x target parameters a and c increase with the decrease in concentration of grains of both orientations. It is noted that multi-stage magnetron sputter deposition can be a powerful tool for controlling the structure of AlN coatings on sapphire