Effect of background-gas impurities on the formation of sputtered β-tantalum films

Abstract

The effect of the gas background in argon glow discharges on the structure of sputtered tantalum films has been studied. The films were deposited in a 240-liter chamber of a conventional oil-diffusion pump system, and in 2-liter chambers of two sputter-ion ultrahigh-vacuum systems. Initial vacua before static sputtering ranged from 1.5×10-10 Torr to 2×10 -7 Torr. The gas background generated by the desorption effect of the glow discharge was minimized by presputtering periods of varying duration. The films were found to be mostly beta tantalum, with varying contents of bcc tantalum. The results indicate that the appearance of beta tantalum depends on the substrate temperature, and that the formation of beta tantalum and its resistivity are independent of the gas-background impurities in deposition systems with ultimate pressures between ∼10-10 and ∼10 -7 Torr. © 1967 The American Institute of Physics.