Some experiments that provide direct visualization of reactive sputtering phenomena

Abstract

Experiments using a reactive gas inlet tube laying directly on substrates during reactive sputtering of Al, Ti, and Zn have provided several insights into the mechanism of reactive sputtering and the efficiency of various gases for producing oxides. These effects can be visualized directly on the substrates. Reactive gases explored were O2, N2 O, CO2, and mixtures of O2 and H2 O. The experiments were conducted in the metallic target mode. The oxidized regions of the substrate near the reactive gas inlet tube are directly visible on the substrate. The size and shape of the oxidized regions allows one to visualize directly various reactive sputtering phenomena. From the data obtained one can (1) visualize directly that the reactive gas flow is molecular for low flows at pressures up to ∼20 m Torr and starts the transition to viscous flow at about that pressure, (2) separate the effects of local reactive‐gas concentration at the substrate and target oxidation on the efficiency of the reaction, (3) confirm directly the relation of metal oxidation efficiency and the free energy of oxide formation, and (4) rank order the efficiency of oxidation of the different gases investigated.