No abstract

Via delamination, a novel electromigration failure mechanism, has been investigated and understood. The mass transport model, in conjunction with environmental, thermal, and mechanical stresses was proposed to explain this failure mechanism. Process enhancements, which include lowering the thin film stresses and strengthening the adhesion between the tungsten plug/metal stack and metalhnter-level dielectric interfaces, have effectively eliminated this reliability failure mode.

This paper presents a novel stressing technique for investigating via quality and integrity in tungsten-AICu interconnect systems. This stressing technique induces a new manifestation of the stress induced voiding failure mechanism for a tungsten-AICu interconnect system. This voiding is caused by the cycling of the mechanical stress at the tungsten-metal interface. This mechanical stress cycling results from the Joule heating induced by the AC current stress. Finite element analysis numerical simulations were performed, and the simulated mechanical stress results correlated well to physical failure analysis results. The interaction of these mechanical stresses with localized aberrations in interfacial quality causes the metal voiding to occur. It will be demonstrated that utilizing cleaner ILD and metal etching techniques will reduce the failure rate due to this mechanism.

No abstract