Layer thickness effect on fracture behavior of Al/Si3N4 multilayer on Si substrate under three-point bending

The fracture behavior of multilayers in the nanometer thickness range has attracted an increased attention due to microelectronics and high-speed technologies. In this work, Al/Si3N4 multilayers fabricated by magnetron sputtering on the silicon substrate were subjected to three-point bend testing. It was investigated that the fracture behavior of Al/Si3N4 multilayers with different individual layer thickness λ (50, 100, 250 nm) but with the same total thickness (1.0 µm). There is a significant layer thickness effect on the fracture behavior of the whole multilayer-substrate system: when the individual layer thickness is large (250 nm), the failure of the whole system was dominated by the fracture of the substrate, while the failure of the whole system was dominated by the fracture of the multilayer with smaller individual layer thickness (50 nm). This effect is clearly obvious, although the total thickness of the multilayer is very small compared with that of the substrate. As the individual layer thickness decreased from 250 nm to 50 nm, the fracture strain on the Al/Si3N4 multilayer decreased from 0.073% to 0.026%.