Via Electromigration Lifetime Improvement of Aluminum Dual-Damascene Interconnects by Using Soft Low-k Organic SOG Interlayer Dielectrics

<jats:title>Abstract</jats:title><jats:p>The via electromigration(EM) reliability of aluminum(Al) dual-damascene interconnects by using Niobium(Nb) new reflow liner is described. It has been found that the via EM lifetime was improved by introducing low-k organic spin on glass(SOG)-passivated structure than the conventional TEOS-SiO<jats:sub>2</jats:sub>/SiN-passivated structure. Higher EM activation energy of 1.08 eV was obtained for the SOG-passivated structure than the conventional TEOS-passivated structure of 0.9 eV, even though no significant Al micro-crystal structure difference was found for both structures. It has been turned out that the low-k SOG material has the 1/7 Young's modulus (8 GPa) of TEOS-SiO<jats:sub>2</jats:sub> (57 GPa) or thermal SiO<jats:sub>2</jats:sub>(70 GPa). The small Young's modulus means that SOG is more elastically deformable and/or softer than TEOS or thermal SiO<jats:sub>2</jats:sub>. This elastic deformation of the low-k SOG could retard the tensile stress evolution due to the Al atom migration near the cathode via, and elongated the time until the Al interconnect tensile stress exceeds the critical stress value for void nucleation. It has been concluded that the small-RC and reliable multi-level Al interconnect can be realized by the Nb-liner reflow-sputtered process with soft and low-k SOG dielectric materials.</jats:p>