Interfacial Adhesion and its Impact on Cu Interconnect Reliability

Incorporation of disparate metallization and dielectrics in microelectronic devices presents a number of challenges related to their overall robustness and reliability. Often a metal/dielectric interface, such as Cu/SiN, or a semi-noble metal/reactive metal interface, such as Cu/Ta, is required in the device build. Because these materials have different reactivities (Cu/Ta) or form nonmetallic interfaces (Cu/SiN), the properties of the bimaterial interface is determined by the bonding at the interface which in turn is influenced by the deposition environment and the segregation of impurities to the interface. In addition, understanding of phenomenon such as plasticity and stress corrosion cracking is necessary to properly assess overall dielectric reliability. Accordingly, this tutorial reviews mechanisms which contribute to interfacial adhesion and uses selected pieces of the literature to illustrate how each mechanism plays a role in Cu interconnect reliability.