Partial barrier free vias for cobalt-based interconnects and methods of fabrication thereof

Abstract

Partial barrier-free vias and methods for forming such are disclosed herein. An exemplary interconnect structure of a multilayer interconnect feature includes a dielectric layer. A cobalt-comprising interconnect feature and a partial barrier-free via are disposed in the dielectric layer. The partial barrier-free via includes a first via plug portion disposed on and physically contacting the cobalt-comprising interconnect feature and the dielectric layer, a second via plug portion disposed over the first via plug portion, and a via barrier layer disposed between the second via plug portion and the first via plug portion. The via barrier layer is further disposed between the second via plug portion and the dielectric layer. The cobalt-comprising interconnect feature can be a device-level contact or a conductive line of the multilayer interconnect feature. The first via plug portion and the second via plug portion can include tungsten, cobalt, and/or ruthenium.