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Internal stresses in titanium, nickel, molybdenum, and tantalum films deposited by cylindrical magnetron sputtering
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1977
Year
Thin Film PhysicsEngineeringTantalum FilmsSputtering‐pressure DependenceThin Film Process TechnologyChemical DepositionMagnetismLow Sputtering PressuresInternal StressesThin Film ProcessingThin-film TechnologyMaterials ScienceMaterials EngineeringHard CoatingPhysicsMaterial PropertyThin Film MaterialsPeening MechanismMicrostructureMaterial AnalysisCylindrical Magnetron SputteringNatural SciencesApplied PhysicsAlloy DesignThin Film DevicesThin FilmsChemical Vapor Deposition
Thin sputtered films of Ti, Ni, Mo, and Ta exhibit a transition to compressive stress at low working pressures, a behavior previously observed for Cr. The authors propose that energetic particle bombardment during deposition creates a peening mechanism responsible for the observed compressive stresses. Cylindrical magnetron sputtering was used to deposit 0.1–0.4 µm films at 1 nm s⁻¹ over 0.13–4.0 Pa Ar, enabling low‑pressure deposition with minimal substrate heating. The compressive‑stress transition occurs abruptly at a threshold pressure that rises with the coating’s atomic mass, and similar pressure‑dependent shifts are seen in electrical resistivity and optical reflectance, indicating a general deposition‑process change.
Measurements of internal stresses in thin sputtered films of Ti, Ni, Mo, and Ta confirm the onset of compression at low working pressures, as reported earlier for Cr [D. D. W. Hoffman and J. A. Thornton (in press) Thin Solid Films (Jan. 1977)]. Deposition from cylindrical magnetron sputtering sources gives access to a wide range of low working gas pressures with minimal substrate heating. The transition to compressive film stress at low sputtering pressures is abrupt, and occurs at threshold pressures that increase markedly with the atomic mass of the coating material. Moreover, the electrical resistivity and optical reflectance exhibit transitions in their sputtering‐pressure dependence that shift to higher pressures for the heavier elements. It appears therefore that the transitions in film stress, resistivity, and reflectance are general phenomena caused by an underlying change in the deposition process. A peening mechanism due to energetic particle bombardment is suggested. Data are presented for Ti, Ni, Mo, and Ta films, up to 0.4 μm thick, sputtered onto glass substates at a nominal deposition rate of 1 nm/s, over the pressure range 0.13–4.0 Pa of argon.