Fabrication and performance studies of multilayer polymer/metal interconnect structures for packaging applications

Multilayer copper/polyimide interconnect structures were fabricated using a reactive-ion-etching-based lift-off technique. Conductor cross-sectional area control, planarity, and a gap-free structure were made possible by the use of a novel siloxane-polyimide. The resultant structure consisted of two signal wiring layers between two ground planes with a nominal impedance of 40 Ω. Although redundant metallization processes were found to repair open lines, they resulted in an increase of the number of processing steps and could result in an increase of defects. Stud chain structures were found to survive cooling to 77 K with very little change in their characteristics, while heating of the copper interconnections to 350°C in a reducing environment reduced their resistance by 3%