A comprehensive physics-based modeling framework for electromigration (EM) in copper nano-interconnects is presented. It combines the three stages of stress evolution, void nucleation, and void dynamics in a single fully coupled and consolidated platform. Mechanical stress evolution, pre- and post-void nucleation, and its impact on void dynamics are deciphered, which enables accurate predictions of EM aging processes as validated by dedicated EM experiments. Subsequently, the experimentally validated model is utilized to shed light on the impact of a number of manufacturing variables, namely, line extension, via taper angle, and the effectiveness of the via bottom flux divergence point. A linear correlation between the ion leakage through the via bottom barrier and the peak tensile stress at the cathode was observed in long lines. In short lines, a blocked cathode end with atomic leakage through the anode end weakens the back-stress effect and threatens the Blech effect induced interconnect immortality. Increasing the line extension length was shown to increase the EM lifetime by about 40%. This impact was saturated beyond 1 critical dimension of line extension. On the other hand, the via taper angle increased the upstream EM lifetime by about twofold when the taper angle was increased from 0° to 30°, which indicates that the change of via taper angle has a stronger impact on EM lifetime compared to the line extension.

As electronic devices continue to shrink in size and increase in complexity, the current densities in interconnects drastically increase, intensifying the effects of electromigration (EM). This renders the understanding of EM crucial, due to its significant implications for device reliability and longevity. This paper presents a comprehensive simulation framework for the investigation of EM in nano-interconnects, with a primary focus on unravelling the influential role of microstructure, by considering the impact of diffusion heterogeneity through the metal texture and interfaces. As such, the resulting atomic flux and stress distribution within nano-interconnects could be investigated. To this end, a novel approach to generate microstructures of the conductor metal is presented, whereby a predefined statistical distribution of grain sizes obtained from experimental texture analyses can be incorporated into the presented model, making the model predictive under various scales and working conditions with no need for continuous calibration. Additionally, the study advances beyond the state-of-the-art by comprehensively simulating all stages of electromigration including stress evolution, void nucleation, and void dynamics. The model was employed to study the impact of trench dimensions on the dual damascene copper texture and its impact on electromigration aging, where the model findings were corroborated by comparing them to the available experimental findings. A nearly linear increase in normalized time to nucleation was detected as the interconnect became wider with a fixed height for aspect ratios beyond 1. However, a saturation was detected with a further increase in width for lines of aspect ratios below 1, with no effective enhancement in time to nucleation. An aspect ratio of 1 seems to maximize the EM lifetime for a fixed cross-sectional area by fostering a bamboo-like structure, where about a 2-fold of increase was estimated when going from aspect ratio 2 to 1.

With scaling of nano-interconnect linewidth toward a 3 nm technology node, electromigration in copper nano-interconnects is becoming a major limitation. In this context, the increase of texture polycrystallinity plays a major role and necessitates better understanding of the impact of void dynamics and its interaction with texture at operating conditions. To this end, comprehensive, yet efficient, physics-based numerical models are warranted given that electromigration experiments at low operating temperatures are not feasible. Albeit, development of such models has been a challenge since it involves large length-scale discrepancy between features, i.e., from wire dimensions (hundreds of micrometers) down to grains and voids (tens of nano-meters and below) leading to substantial computational cost. To this end, in this study an efficient multi-scale physics-based electromigration modeling approach is demonstrated, where an experimentally calibrated Korhonen-type 1D model solves electromigration at the global scale (entire interconnect), and a 2D local model simulates void dynamics considering the impact of electron wind, void surface energy, and stress gradients. The role of copper texture, i.e., grain boundaries, grain orientation and anisotropic properties is thoroughly investigated. We demonstrate that by tailoring the copper grain structure, void behavior and thus resistance evolution of nanowires can be effectively controlled. Compared to wider interconnects, in scaled nanowires, surface energy is found to play a dominant role on void morphology compared to electron wind. Strong anisotropy of diffusivity of copper's FCC lattice fosters faceted morphologies and emergence of slit morphology during void transition through the polycrystalline texture. Bamboo segments are shown to effectively pin the voids migrating toward the cathode in cases with cobalt cap. In addition, voids migrating from low diffusivity to high diffusivity regions adopt a longitudinally elongated morphology, which can be detrimental in a down-stream operation mode.

The combined effect of thermomigration (TM) and electromigration (EM) on the reliability of Cu interconnects is investigated. Package-level EM+TM tests were conducted to understand the impact of temperature gradients on void nucleation and void growth in the presence of electrical currents. Through failure analysis, void nucleation at the via bottom followed by subsequent void growth toward adjacent vias is confirmed. An analytical model is developed to quantify the impact of temperature gradients on EM lifetime. Results indicate that thermal gradients have a more pronounced impact at lower ambient temperatures, reducing EM lifetime by approximately 50% at 100 ∘C, compared to a 42% reduction at 300 ∘C. This work enhances the understanding of EM+TM coupling mechanisms and provides a practical model for predicting

This paper presents a comprehensive simulation framework for the investigation of electromigration (EM) in nano-interconnects, with a primary focus on unravelling the influential role of microstructure. To this end, a novel approach to generate conductor metal’s microstructures is presented, whereby a predefined statistical distribution of grain sizes obtained from experimental texture analyses can be incorporated into the developed EM modelling framework. The framework considers the impact of diffusion heterogeneity through the metal texture and interfaces. As such, the intricate interplay between microstructural/interfacial properties, and the resulting atomic flux and stress distribution within nanointerconnects could be investigated. Additionally, the study advances beyond the state of the art by comprehensively simulating all stages of electromigration, including stress evolution, void nucleation, and void dynamics while considering the impact of microstructure. Specifically, the model was employed to study the impact of trench dimensions on dual damascene copper texture and its subsequent impact on electromigration aging, where the model findings were corroborated by comparing to available experimental findings. A nearly linear augmentation in normalized lifetime was detected for aspect ratios equal to or greater than 1. However, a saturation is detected for wider lines with no effective enhancement in lifetime. An aspect ratio of 1 seems to maximize EM lifetime for each cross-sectional area by fostering a bamboo-like structure, where about 2-fold of increase is estimated when going from aspect ratio 2 to 1.