Iridium thin films deposited by radio-frequency magnetron sputtering

Abstract

Deposition of metallic iridium thin films has been achieved by sputtering an Ir target with argon. The deposition of the Ir films was investigated at argon gas pressures in the (10–40) mTorr range with various rf power densities. The stress, resistivity, and structure of the Ir films were systematically determined as a function of both the Ar pressure and the rf power density. While all the deposited Ir films are polycrystalline with a preferred (111) orientation, not only their stress but also their resistivity were found to be particularly sensitive to the Ar gas pressure. As for many sputtered metal thin films, the stress of Ir films, deposited at a power density of 5 W/cm2, drastically changes from highly compressive (−2 GPa) to highly tensile (+1.2 GPa) in a relatively narrow range of Ar pressure (10.5–25.5 mTorr). Likewise, the room-temperature resistivity of Ir sputtered films changes by a factor of about 5 when the Ar pressure is increased from 22.8 to 36.0 mTorr. Deposition conditions yielding Ir films which combine the lowest resistivity (17 μΩ cm) and very low stress levels (few tens of MPa) are identified. Finally, it is established that the stress of Ir films scaled linearly with the lattice-parameter dilatation of the (111) preponderant phase.