A Novel Fracture Mechanics Technique on Studying Passivation Crack Behavior for Advanced Si Package with Aluminum Redistribution Layer (AL-RDL) Routing

In the last several years, “Super-High-Density Metal-Insulator-Metal” (SHDMIM) technology development had represented a significant advancement in advcaned Si node electronic packaging, particularly in the realm of integrated circuits (ICs) and semiconductor devices. This innovative approach focuses on enhancing package performance by leveraging the unique properties of metal-insulator-metal (MIM) structures, which are known for their excellent electrical characteristics. Typically, SHDMIM structures are embedded between the Passivation-1 and Passivation-2 layers to achieve electrical isolation. However, it is important to note that passivation, being a brittle material, is susceptible to the cracking, particularly under the conditions of reliability temperature cycling tests. Such cracking may compromise the integrity of the passivation layers, potentially leading to SHDMIM failure. This study investigates the fracture analysis in the Al-RDL U-shaped passivation-2 structure using both simulation and experimental methods. Initially, the critical fracture energy $\left(G_{c}\right)$ for both of Pass2-1 and Pass2-2 that composing the passivation-2 layer is determined using the nanoindentation method. Subsequently, using developed fracture model incorporating both static and dynamic crack analysis to elucidate the fracture phenomena and provide insights into crack initiation and propagation. In the static crack modeling, the energy release rate (Err) is evaluated using the J-integral method. The simulation model validates against test data, thereby providing the critical crack length by establishing the relationship between $G_{c}$ and Err. Parametric studies on geometry and process conditions reveals that the energy release rate is enhanced by smaller AP spacing, thinner Pass2-1 layers, and higher processing temperature. In the dynamic crack modeling, the eXtended Finite Element Method (XFEM) with traction-separation laws was utilized, the crack initiation at the Pass2-1 corner, its penetration through the Pass2-1/Pass2-2 interface, and subsequent propagation to the Pass2-2 bottom edge are simulated, which aligns closely with experimental observations. The developed fracture mechanism technique has been validated and provided a design guideline to mitigate the crack driving force in Al-RDL passivation structures. This study provides critical insights and methodologies to enhance the reliability of SHDMIM capacitor devices by addressing crack-related failures in passivation structures.