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(Color online) (a) Load-displacement curves from dummy-Si/epoxy/Ta/1-μm-Cu/SiO2/Si with Cu-silica interfaces having corrugations of aspect ratio AR = 0.34 oriented either parallel (∥) or orthogonal (⊥) to the crack path. Inset schematics and SEM micrographs illustrate the two loading geometries and the crack propagation direction (arrows) for each corrugation orientation. (b) Core level XPS spectra from fracture surfaces indicating that fracture occurs at the copper-silica interface.
(Color online) (a) Fracture toughness of Cu-silica interfaces with different aspect ratio corrugations and 1-μm-thick Cu films. The inset SEM micrographs reveal the crack path from the notch to the weakest interface (left) and through orthogonal corrugations (right), and the top schematic depicts the debond morphology. (b) Fracture toughness of a planar Cu-silica interface with a 15-nm-thick Cu film plotted as a function of the loading phase angle Ψ. The asymmetric curve is due to different extents of plasticity due to crack kinking towards SiO2 and Cu, for +Ψ and −Ψ, respectively.
(Color online) The top schematic captures key contributors to the fracture toughness of corrugated Cu-silica interfaces. Fracture toughness of Cu-silica interfaces having corrugations with aspect ratios (a) AR = 0.34 and (b) AR = 0.13 oriented either parallel or orthogonal to the crack path. (c) Fracture toughness for orthogonally corrugated interfaces as a function of aspect ratio. The contributions of the different processes are shown. Empty and filled bars denote interfaces with 15-nm and 1-μm Cu films, respectively.
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