W-Cu sputtered thin films grown at oblique angles from two sources: Pressure and shielding effects

Abstract

International audienceTwo series of W-Cu thin films were developed by the GLAD co-sputtering technique. The films were producedwith two separated W and Cu targets. Both targets were focused on the centre of the substrate and were simultaneouslysputtered using opposite and oblique angles of 80° from the substrate normal. In the first series, theW and Cu target currents were inversely changed from 50 to 140 mA in order to tune the elemental concentrationsand the microstructure. For the second series, a shield was added between W and Cu targets, perpendicularlyto the substrate surface in order to prevent the cross-contamination of the targets. The targetcurrents were varied similarly to the first series. Two argon sputtering pressures were used (0.42 and 1.0 Pa) ineach series, with and without the shield.Microstructure showed a tuneable inclined columnar microstructure, which become normal to the substrateat high pressure. The crystallographic structure was not significantly influenced by the shield implementationbut rather by the sputtering pressure. The W/Cu atomic concentration ratio varied between 0.2 and 5.5 as afunction of the sputtering pressure and target currents and an anisotropic chemical composition was measuredinside the columns. The wide range of DC electrical resistivities (3.6 ×10−7 to 5.7×10−5 Ωm) was discussedconsidering W and Cu target currents, high and low sputtering pressures and the use of a cross-contaminationshield. The role of the microstructure was clearly shown since significantly higher resistivity was obtained athigh pressure, as a function of the W/Cu atomic concentration ratio