Direct current reactive sputtering of aluminium

The influence of the oxygen content in the gas flow on the discharge current and on the chemical composition of sputtered AlO_x was investigated. Unlike SiO₂, Al₂O₃ films are formed on the substrate only for oxygen contents sufficient for full oxidation of the target surface. The minimum oxygen content can be determined by the sharp change in discharge current at constant working voltage and total gas pressure. Infrared spectra confirming this statement are given. The kinetics of the processes of forming and sputtering off of an oxide layer on the aluminium target surface were also investigated. Some speculations about the interrelation between oxide formation on the substrate and on the target for direct current reactive sputtering are given.