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Abstract: Developing a robust predicting methodology on the interfacial fracture energy of dissimilar materials is urgently needed to meet the mechanical strength requirements for investigating novel materials and subsequent device structures with the bonded types of multi thin films. Thus, this paper provides an overview of useful approaches according to linear-elastic interfacial fracture mechanics, such as J-integral method, modified virtual crack closure technique (MVCCT), and analytical solutions derived from the relationship between the stress field of delaminated tip and crack tip opening displacements to compare their estimated capability of cracking energy. A popular technique for determining the interface adhesion of thin coatings is the four-point bending test (4-PBT). The testing vehicles of 4-PBT allow a more thorough validation of the foregoing predicted approaches based on finite element analysis compared with the simulated results with related experimental data. The critical energies of 18J/m2, 78.53J/m2, 52.01J/m2, and 71.02J/m2 for the bonded interfaces of SiO2/SiLK, Ta/SiLK, TaN/SiLK, and Si3N4/SiLK stacked nano-scaled thin films are precisely judged, respectively. The predicted results of the J-integral method match well with the MVCCT estimation. The results reveal that the opening fractured mode is dominant at the beginning of the crack advances along the bonded interface of Ta/SiLK, TaN/SiLK, and Si3N4/SiLK stacked films as the interfacial crack length increases. Moreover, the essential trends of dependences for the modulus ratio and thickness ratio of stacked thin films on interfacial energy release rate are logically identified and investigated. Therefore, this paper could be regarded as a design guideline of interfacial fracture behavior for stacked films utilized in the development of advanced device technologies. [Copyright &y& Elsevier]

Abstract: The integration of thin film technology into the fabrication of semiconductor transistors has given rise to significant challenges in the design of multi-level back-end-of-line interconnects. The interfacial adhesion between Al metal and TiN barrier is one of the major factors that affect interconnect reliability. Analyzing the effect of the interconnect structures of Al/TiN barriers on interfacial cracking energy under flexural loading is an interesting research direction. This work proposes a robust estimation of interfacial cracks by simulation-based methods to satisfy the mechanical design requirements for multi-level interconnect systems. A constant bending moment can be generated with the framework of the four-point bending test (4-PBT). A 4-PBT simulation model can be used in finite element analysis, combined with the J-integral method and the modified virtual crack closure technique, to accurately predict the interfacial fracture energy of Al/TiN films. Preliminary results indicate a considerable increase in energy release rate. Energy is released as a crack along the interface of the Al/TiN films passes through the region above the parallel metal lines of patterned interconnects, especially for a Cu/SiLK material system. The results also show that dielectrics can serve as stress buffer layers that inhibit crack growth. [Copyright &y& Elsevier]

Abstract: The interfacial adhesion of thin films between Al metal and TiN barrier is one of the major concerns dominating the mechanical reliability of semiconductor devices. The measured accuracy of cracking energy for stacked films with a nanoscale order is arduous to preserve because of the uncertainty in specimen preparations and instrumental operations. Consequently, the present research proposes a robust estimation of interfacial cracks using simulation-based methodologies to meet the requirement for mechanical designs in multi-level interconnected systems of electronic devices. According to the framework of the four-point bending test (4-PBT), the interfacial fracture energy of Al/TiN films is predicted via finite element analysis (FEA), combined with the J-integral method and modified virtual crack closure technique (VCCT). The foregoing simulated approaches are also verified by related analytical solutions and experimental data. Moreover, the effects of several patterned types of metal lines underneath the Al/TiN interface with various embedded cracks are analyzed. The primary results highlight a significant increase in the energy release rate (G) induced by the passing of a crack along the interface of Al/TiN films through the region below a metal line with a high degree of hardness. Dielectrics with a lower modulus would have the capacity to restrain progressive crack growth. Thus, a high G is expected to drop, as simultaneously demonstrated by the present simulated methodologies. [Copyright &y& Elsevier]

In order to resolve the issues of RC time delay and high power consumption, IC chips with Cu/low-k interconnects are developed to meet the foregoing requirements. However, there is a high potential that in doing so it may contribute to interfacial cracks occurring or propagating between the copper metal and the low-k dielectric material as a result of poor adhesion and lower fracture toughness, which results from the inherent mechanical imperfection of low-k materials. This fracturing problem is one of the most urgent issues for the thermomechanical reliability of Cu/low-k interconnects, and it needs to be resolved urgently. For this reason, we propose a prediction methodology of finite-element analysis (FEA) based on J-integral value estimation to investigate the interfacial fracture opportunity of low-k packages. However, the J-integral calculation is path dependent and so crucial in FEA for a crack on an interface between dissimilar materials. Therefore, various paths with an integral contour surrounding the crack tip are considered to avoid a misunderstanding of the cracking energy. All the analytic results indicate that a rectangular contour with a proper ratio of length/width, and multilayers of element close to the delaminating surfaces, is suggested for obtaining a stable J-integral value. On the other hand, the proposed methodology has been validated by a four-point bending test and compared with the relative experimental data of multi-low-k dielectric films. Moreover, under a reliable integral contour path that crack driving force predicted using the type of interfacial crack constructed by means of the element death technique, it shows good agreement with the simulated results of embedding actual crack. [ABSTRACT FROM AUTHOR]