A new testing technique for the characterization of the mechanical behavior of the interconnect structures of integrated circuit devices is introduced in this paper. Modified crosssectional nanoindentation (MCSN) is the result of extending cross-sectional indentation (CSN) to patterned structures. As in conventional CSN, a Berkovich indenter is used to initiate fracture in the silicon substrate beneath the interconnect structure. The cracks propagate through this structure, preferentially along the weakest interfaces in the system. A FIB (Focused Ion Beam) is used for sample preparation, machining a trench parallel to the indentation surface. In this way, the crack growth can be better controlled and the problem may be modeled in two dimensions.
The technique has been used to study crack propagation in patterned structures as a function of thin film composition and processing. The results obtained, in terms of crack length along each interface studied, correlate well with the fracture energy measured by four-point bending (4 PB) in blanket films of the same materials. Finite element modeling of the stress fields in the vicinity of the crack tip has been carried out to understand the crack paths observed.