High-Resolution X-Ray Imaging of Controlled Microcrack Steering in BEoL Stacks (Invited)

Microcrack propagation through a BEoL stack is visualized by positioning a miniaturized micro double cantilever beam test in the beam path of a laboratory full-field X-ray microscope. Imaging the propagation of microcracks with sub-100nm resolution, the controlled steering of microcracks in the BEoL stack of dies manufactured in advanced technology nodes is demonstrated. The capability to steer microcrack propagation in a controlled way and to observe this process simultaneously provides a powerful tool for studying the efficacy of guard rings and of upper metallization layers in the BEoL stack, where the Cu plasticity is toughening the region due to size effects, to arrest cracks. In addition, the experiments can provide valuable input for the design of guard rings. This new approach has important implications for risk mitigation strategies in semiconductor industry and for the manufacturing of silicon dies used as chiplets in heterogeneous integration/advanced packaging for reliable and sustainable products.