Copper–dielectric cap interface with enhanced reliability for 45 nm technology and beyond

A production capable preparation of a Cu–dielectric cap interface with a significantly enhanced reliability robustness has been developed for the 45 nm dual damascene technology and beyond. The electromigration (EM) lifetime could be improved by a factor of 2 with an advanced in situ cleaning process (ACP) including a soft silicidation step of the Cu metallization prior to the Cu–cap deposition. The increase of the Cu metal line resistivity can be controlled and limited to <6%. Anneal experiments at high temperature underline a high thermal stability of the Cu–cap interface including the copper-silicide (CuSi) intralayer. The new ACP is applicable to Cu interconnects built with dense or porous ultra-low-k (ULK) dielectrics because the process minimizes the surface damage. This yields in a doubled dielectric breakdown strength of a Cu damascene structure with a ULK inter-level dielectric by implementation of the ACP.