Fracture characterization in patterned thin films by cross-sectional nanoindentation

A testing technique based on cross-sectional nanoindentation has been used to assess the mechanical reliability of interconnect structures. A Berkovich indenter was used to initiate fracture in a silicon substrate and cracks propagated through the structure. To better control crack growth and to convert the problem into two dimensions, a trench parallel to the indentation surface was previously machined using a focused ion beam. The crack lengths obtained for different material systems in the interconnect structure correlate well with the fracture energies measured for the same materials in blanket films. Finite element model simulations incorporating cohesive elements have been used to model the fracture processes and to explain the different cracking behaviour observed