Advanced metal and dielectric barrier cap films for Cu low k interconnects

Multi-layer SiN barrier film with high breakdown and low leakage is developed for Cu low k interconnects and is compared with the SiCNH barrier film used at previous technology nodes. Ultra-thin SiN barrier cap film also provides high conformality and fills recess in Cu lines observed post CMP. A significant enhancement in electro migration (EM) performance was obtained by selectively depositing Co on top of Cu lines followed by conformal multi-layer SiN barrier film. Further EM lifetime improvement is obtained by using a Co liner to form a wrap around structure with completely encapsulated Cu. An integrated in-situ preclean/ metal/dielectric cap chamber was used to avoid any oxidation of Cu/Co layers. Kinetic studies of CVD Co liner/Co cap samples show significant increase in EM activation energy (1.7 eV) over samples with dielectric only barrier film (0.9-1 eV). The complete wrap around structure with Co liner and Co cap shows improved device reliability.