Die Attach in Hi-Rel P-Dips: Polyimides or low chloride Epoxies?

Advancements in the speed and input/output (I/O) density of integrated circuits (IC's) used in computers and other high performance systems are creating a need for new designs, materials, and processes capable of providing high density multilayer interconnections with controlled electrical characteristics. To meet these needs, we selected an interconnect materials system consisting of multiple layers of thin film copper conductor patterns separated by polyimide (PI) dielectric layers, fabricated on a ceramic substrate. We developed processes for depositing films and patterning high resolution features in both conductor and dielectric films, and established a process sequence for filling vias and building up multilayer structures. We investigated the stability of the Cu/ PI materials system by determining the effects of cure conditions and humidity aging on the dielectric properties, internal stress, mechanical properties, and adhesion of PI. We then fabricated multilayer test structures, including a functional multichip ring oscillator circuit, to demonstrate process feasibility and the electrical performance of Cu/PI interconnections.