An optimal liner for copper damascene interconnects

A liner for Cu-Damascene multilevel ULSI interconnects is described1,2 which satisfies all the important requirements for a high performance, reliable Cu interconnect technology. This liner has been implemented in the first CMOS/Cu manufacturing process,3 by now spanning four years in the field. The liner is a bilayer from a family of hcp/fcc-TaN followed by bcc-Ta (α-Ta). This bilayer is unique in that it simultaneously maximizes conductivity and adhesion on inner and outer interfaces; one or more of these attributes are compromised in single-component liners. The TaN/Ta bilayer is deposited sequentially in a single PVD or I-PVD chamber from a pure Ta target, using Ar and N2 sputtering gases. It is followed by a PVD Cu seed prior to electroplated Cu fill This process has high manufacturability attributes similar to typical single-layer PVD metal films. In all, the qualities of this bilayer liner produce high-yield, highly reliable, and electromigration-redundant Cu interconnects.