Evaluation of interfacial toughness and bond strength of sandwiched silicon structures

Abstract

Results of a study to measure the interfacial strength and toughness in sandwiched silicon structures, using sol–gel processing as the bonding method, are examined. The interfacial bond strength was determined using a standard uniaxial tensile test, while a relative measure of interface toughness was ascertained using exploratory Vickers indentations. The specimens were positioned and aligned so that the indentations were made directly on the interface region, with the cracks emanating from one set of the impression diagonals at the free surface coinciding with the trace of the interface. The length of these radial cracks, having a penny-like configuration, required to cause debonding at the interface was measured in order to provide relative fracture toughness and fracture energy values. Indications of ‘local’ bond toughness were obtained by indenting at locations near the interface and following the path of the radial cracks. The applicability of the technique with reference to material interfaces is discussed.