Investigations and detections on a new BEOL dielectric failure mechanism at advanced technologies

The ultra-low k dielectrics have been widely used as semiconductor technology steps into 45 nm, 28 nm, and more advanced nodes. Combined with the rapid shrinks of critical dimensions, the ultra-low k dielectrics face challenges to retain the benefits of interconnect scaling both on their manufacturability and reliability performances. In this paper, abnormal failure phenomena were investigated on 28 nm ILD (Intra Level Dielectric) and IMD (Inter Metal Dielectric) qualifications and 40 nm mass production. A new failure mechanism of metal 1 to poly (M1-to-poly) leaky path was proposed based on theoretical investigations and experiments. Based on our newly proposed dielectric breakdown mechanism, a series of innovative test structures were designed for early detections and evaluations of reliability performances. These newly designed test structures have been proven to be useful due to better representing actual using profiles, more precise reliability evaluations, and more effective monitors on process variations at mass production.