Influence of gas flow oxygen content on discharge current in direct current cathode sputtering

A qualitative physical model is proposed to explain the influence of oxygen content in the gas flow on discharge current for reactive cathode sputtering in a direct current diod system. According to this model the increase of oxygen content affects the discharge current density in two ways: (1) by a sharp change in the coefficient of secondary ion-electron emission from the target surface as a result of its oxydation; and (2) by the influence of the oxygen content on the elementary ionization process in the discharge region near the cathode as a result of the transition from a glow discharge in a noble gas to a glow discharge in oxygen. The results of an experimental investigation with targets of different materials under different sputtering conditions are in good agreement with the conclusions from the proposed physical model. An additional experiment with two Si targets is carried out which shows a getter-pumping effect of sputtered material on active gases. (I.P.)