On the homogenization of multilayered interconnect for interfacial fracture analysis

The interface crack problem for Cu/low-k interconnect is considered using global-and-local finite element analysis. In the global analysis the thin film interconnect is represented by a homogenized layer with equivalent material properties. Local model around the interface crack tip is analyzed with displacement boundary condition extracted from the global modeling result to determine the fracture mechanics parameters. It is shown that, for the global-and-local modeling approach, interconnect homogenization using representative volume element (RVE) approach provides accurate prediction on the fracture mechanics parameters for an interface crack under either thermal or mechanical loads, while significant error occurs when the interconnect, even though having thickness less than 1/100 of the whole component thickness, is neglected in the global analysis. The problem of an interface crack between low-k dielectric and etch-stop thin film in a flip-chip package under thermal excursion is also investigated as an application example of the global-and-local modeling approach.