Role of loading mode on crack propagation behavior and adhesion at Cu–SiCN interface

Interfacial failure between copper (Cu) and dielectric materials in back-end-of-line (BEOL) interconnects is often attributed to various loading modes applied during the manufacturing processes and device operation. In this work, we investigate the role of loading modes on crack propagation behavior and adhesion at the Cu–silicon carbon nitride (SiCN) interface. Two types of surface-treated specimens, without SiH₄ gas inflow (WOS) and with SiH₄ gas inflow (WS), are examined using double cantilever beam (DCB) and four-point bend (FPB) fracture test methods, which introduce pure mode I and mixed mode loadings, respectively. The results demonstrate that WOS-treated specimens exhibit interfacial fracture in the DCB and FPB tests, whereas WS-treated specimens show alternating crack paths in the DCB test and interfacial fracture in the FPB test. These different crack propagation behaviors are explained by considering the loading modes, selectively enhanced interfacial bonds, and material properties, and they are verified through comprehensive experiments and numerical simulations. Finally, it is revealed that the measured adhesion energy significantly depends on the loading mode and crack propagation behavior.