| Aluminum has been applied for interconnections in integrated circuits since their invention because of its low resistivity and silicon compatibility; however, with the scaling of integrated circuits, pure aluminum has become unsuitable. Aluminum alloyed with copper and silicon reduces the problems of electromigration, hillock growth, and junction spiking but, because of continued size reductions, such alloying is also becoming less effective.;Because interlevel failures are caused by stresses that develop in the aluminum films during high-temperature processing, mechanical stresses are examined by means of a highly sensitive laser-based measurement apparatus. Stress as a function of temperature is measured for several alloys and layered films consisting of aluminum with silicon, copper, titanium, tantalum, vanadium, tungsten, and/or titanium silicide. Several variations in the film stress of these alloys during thermal cycling are observed, and models are proposed to explain these results.;Scaling theory for interconnection resistivity and electromigration is also developed and used to formulate guidelines. Recent electromigration results are then compared to theoretical predictions.;The synthesis of films via sputtering facilitates the deposition of many materials in one process cycle. This approach was used to fabricate a multilayered metal structure for a single level of interconnection. When these structures are fabricated with aluminum-silicon and titanium, failures such as interlevel shorts and electromigration are reduced and interconnection resistivity remains low which is important for maximum performance in micron and submicron integrated circuits. Interconnections are treated as if they are a device that can be designed to reliably perform a function in the analyses presented. |
