Modulating crack propagation in a multilayer stack with a super-layer

Quantitative characterization of interface adhesion and fracture properties of thin film materials is of fundamental and technological interests in modern technologies. Sandwich beam specimens used in fracture mechanics techniques, such as four-point bending and double-cantilever beam have been widely adopted, including the semiconductor industry. In this work, we highlight some of the challenges that these techniques are facing in characterizing ever thinner films and tough interfaces, and propose a simple strategy to address these challenges by engineering the stack structure of the specimen. We show that crack propagation in a multilayer stack can be controlled using a super-layer (SL) structure, and the dependence of the cracking behavior on the thickness and mechanical properties of the SL is studied. The effectiveness of the SL strategy is demonstrated for a range of technologically important material systems used in the on-chip interconnects of modern microprocessors, which represents one promising path to extend the industry-standard techniques to meet future characterization needs.