Microwave Evaluation of Electromigration Susceptibility in Advanced Interconnects
Yaw S. Obeng, Kin P. Cheung, Dmitry Veksler, Christopher E. Sunday
Traditional metrology has been unable to adequately address the needs of emerging integrated circuits (ICs) at the nano scale; thus, new metrology and techniques are needed. For example, the reliability challenges in fabrication need to be well understood and controlled to facilitate mass production of through-substrate-via (TSV) enabled three-dimensional integrated circuits (3D-ICs). This requires new approaches to the metrology. In this paper, we use microwave propagation characteristics to study the reliability issues that precede physical damage caused by electromigration in Cu-filled TSVs. The pre-failure microwave insertion losses and group delay are dependent on both the device temperature and the amount of current forced through the devices-under-test. The microwave insertion losses increase with increasing test temperature, while the group delay increases with increasing forced direct current magnitude. The microwave insertion losses are attributed to defect mobility at the Cu-TiN interface, and the group delay changes are due to resistive heating in the interconnects which perturbs dielectric properties of the cladding dielectrics of the copper fill in the TSVs.