Dynamic delamination of patterned thin films

Abstract

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Laser-based Determination of Decohesion and Fracture Strength of Interfaces and Solids by Nonlinear Stress Pulses

“…The controlled delamination of a film is more difficult to achieve, but has been reported recently (Kandula et al, 2008a). In the following results obtained for some characteristic systems are selected to illustrate the potential of this laser-based method to study pure and mixed-mode decohesion of thin films in layered systems.…”

“…It is important to note that in most practical situations thin films tend to fail under mixed-mode I+II conditions. Controlled dynamic delamination of thin films has been achieved recently by insertion of a weak adhesion region below the film to be delaminated (Kandula et al, 2008a). While spallation experiments characterize the interface strength or critical stress for microvoid or microcrack initiation the delamination process can be more closely associated with the propagation of cracks.…”

“…Mixed-mode failure was studied in this particular work using a silicon wafer of 730 nm thickness covered with a Si x N y passivation layer (400 nm) and an Au film of thickness of 300 nm, 600 nm, or 1200 nm reported recently (Kandula et al, 2008a). The back side of the silicon substrate was bonded to a fused silica prism equipped with an Al layer (400 nm) and a confining waterglass layer.…”

Dynamic delamination of patterned thin films: a numerical study

“…100 μm) was too small to reliably extract interfacial energy. Kandula et al (2008b) recently enhanced the edge delamination test by introducing a weak adhesion region, which essentially served as a precrack upon loading. This new thin film pattern geometry, shown schematically in Fig.…”

“…The entire debonding process lasted over 800 μs and the crack extended over 9 mm, substantially longer than the 10 ns duration of the loading pulse and the 330 μm initial pre-crack length. Kandula et al (2008b) extracted the interface toughness G c by assuming the kinetic energy (K ) trapped in the thin film at the onset of spallation of weak interface of length a 0 (pre-crack length) must equal the energy required for final crack extension a f − a 0 ,…”