Framework to extract cohesive zone parameters using double cantilever beam and four-point bend fracture tests

This paper focuses on extracting cohesive zone modeling (CZM) parameters for ultra low-k (ULK) interlayer dielectric (ILD) layers present in back end of line stack (BEOL) of flip-chip (FC) semiconductor devices. Unlike other fracture-mechanics based approaches, CZM can simulate crack initiation and propagation at several locations. However, additional parameters need to be determined to enable cohesive zone (CZ) elements to reliably predict the failure region. In this paper, we present a methodology, combing fracture experiments and finite-element (FE) simulations to extract CZM parameters under mixed-mode loading conditions. Using load vs. displacement data from the double cantilever beam (DCB) test and four-point bend test (FPBT) experiments, we have characterized all the parameters necessary for CZM. The developed cohesive zone failure criteria can then be applied to interfaces in BEOL stack models to identify the locations of crack initiation and propagation.