Highly Reliable Cu Interconnect Using Low-Hydrogen Silicon Nitride Film Deposited at Low Temperature as Cu-Diffusion Barrier

Abstract

We demonstrated highly reliable Cu interconnects using a high-quality silicon nitride film grown at temperatures below 300 °C. The low-temperature silicon nitride (LT-SiN) film, which was used as a Cu-diffusion barrier layer and a final passivation layer, was deposited at 275 °C by plasma-enhanced chemical vapor deposition at a low SiH4 flow ratio. The low SiH4 flow ratio was due to the use of a highly dilute nitrogen flow, leading to the generation of many nitrogen radicals or ions in the plasma. These radicals or ions might reduce the hydrogen concentration and defect density of the film. As a result, a stoichiometric silicon nitride (Si3N4) film with a low hydrogen concentration was successfully obtained. By applying this LT-SiN film in 130-nm-node Cu interconnects for magnetoresistive random access memory, highly reliable via-hole electromigration (Via-EM) and line-to-line time-dependent dielectric breakdown (TDDB) characteristics were obtained.