Simulation of Electrical and Mechanical Properties of Air-Bridge Cu Interconnects

Several air-bridge type Cu interconnects, with air-gaps in the metal line level or extending to the via level, were modeled to evaluate their electrical performances and stress characteristics. It was found that the combination of fully-dense SiCOH dielectric and air-bridging down to the via level provides an effective dielectric constant of 2.27. This meets the ITRS need for the 45nm technology node and is extendable to the 32nm node. The stress levels of Cu line and via in the model structures depended on the dielectric material and air-gap configuration. For example, when air-gaps are extended into the via level, the stress levels for SiCOH were intermediate between those for TEOS and p-MSQ