A new procedure for measuring the decohesion energy for thin ductile films on substrates

A novel testing technique has been developed capable of measuring the interfacial fracture resistance, Γ_i, of thin ductile films on substrates. In this technique, the thin film on the substrate is stressed by depositing onto the film a second superlayer of material, having a large intrinsic stress, such as Cr. Subsequent processing defines a precrack at the interface between the film and the substrate. The strain energy available for driving the debond crack is modulated by varying the thickness of the Cr superlayer. Spontaneous decohesion occurs for superlayers exceeding a critical thickness. The latter is used to obtain Γ_i from elasticity solutions for residually stressed thin films. The technique has been demonstrated for Cu thin films on silica substrates.