Low resistive and highly reliable Cu dual-damascene interconnect technology using self-formed MnSixOy barrier layer

Copper (Cu) dual-damascene interconnects with self-formed MnSi_xO_y barrier layer using a copper-manganese (Cu-Mn) alloy seed layer is successfully fabricated for the first time. No delamination is found in the chemical mechanical polishing process, probably because of better adhesion strength between the MnSi_xO_y barrier and dielectric. More than 90% yield is obtained for a 1 million via chain. Microstructure analysis by transmission electron microscopy shows that an approximately 2 nm thick and continuous MnSi_xO_y layer is formed at the interface between Cu and dielectric of the via and trench and there is no barrier at the via bottom. This via structure without the bottom barrier provides these essential advantages: reduced via resistance; significant via-electromigration lifetime improvement due to there being no flux divergence site at the via; excellent stress-induced voiding performance.