Experimental and numerical evaluation of interfacial adhesion on Cu/SiN in LSI interconnect structures

The local interfacial strength is a key factor in designing and fabricating advanced three-dimensional large-scale integration interconnect structures. In this paper, both local fracture tests and three-dimensional elastic-plastic crack propagation analysis for a 10 μm × 10 μm specimen were performed, and the local interfacial adhesion between a Cu interconnect and a SiN cap layer were evaluated. The three-dimensional elastic-plastic crack propagation simulation was developed to evaluate the interfacial adhesion that eliminated the effect of progressive plastic dissipation energy during crack propagation. The results show that the average interfacial adhesion for Cu/SiN is 4.46 ± 0.17 J/m². The crack propagation behavior and fracture pattern depend on the interfacial adhesion, and these differences are due to the plastic yielding of the side edge of the specimen. The critical interfacial adhesion for the onset of shear fracture is 4.92 J/m², which is the upper bound of the interfacial adhesion evaluation for the 10 μm × 10 μm specimen.