Processing and microwave characterization of multilevel interconnects using benzocyclobutene dielectric

Interconnection density is one of the most significant factors affecting cost, performance, and reliability of integrated circuits (ICs) and multichip modules (MCMs). In this paper, high density multilayer interconnect structures were fabricated using gold metallization and polymer interlayer dielectric. A number of polymers were investigated and benzocyclobutene (BCB) was selected for its electrical, mechanical, and thermal properties. A design of experiments was carried out to optimize plasma etching of vias in BCB. All metal depositions were done by lift-off techniques. A microwave characterization layout was designed to evaluate microstrip transmission lines, transmission line cross-overs, and multilevel spiral inductors. Two layers of metal separated by a layer of BCB were processed on a glass wafer. RF-on-wafer measurements were carried out at frequencies from 0.1 to 20 GHz. Equivalent circuit models fitted to the experimental data were used to derive the effective dielectric constant and characteristic impedance of the transmission lines, cross-over capacitance, and inductance and Q-factor for the multilevel spiral inductors