Adhesion of ductile films and coatings: scratch test using a wedge blade indenter
Scratch testing with a spheroconical indenter to evaluate adhesion of ductile metallic coatings on brittle substrates often results in unclear critical load identification. This report shows how a wedge blade indenter overcomes this limitation. Its special geometry promotes distinct failure events, enabling easier and more reliable determination of critical loads and coating adhesion.
Ductile metals such as gold (Au), platinum (Pt), and palladium (Pd) are widely used in semiconductor, optoelectronic, and electronic applications due to their excellent electrical conductivity, oxidation resistance, and optical properties. Because of their high cost, they are typically deposited as thin films or multilayer systems on brittle substrates such as GaAs, GaSb, silicon, glass, or ceramics using PVD, CVD, or ALD processes. However, thin ductile layers are prone to delamination, making reliable adhesion measurement essential for device performance and product quality. The nanoscratch test is a widely used method for evaluating thin film adhesion. However, when ductile metallic films are tested with a spheroconical indenter, pronounced plastic deformation often obscures failure events, making critical load determination difficult and unreliable.
To address this limitation, a patented method was developed using an NST³ nanoscratch tester equipped with a wedge blade indenter (Figure 3). Its special geometry promotes more distinct coating failure, enabling clearer interpretation and more reliable adhesion assessment than conventional spheroconical indenter.
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