Electromigration characteristics of high-temperature sputtered Al-alloy metallization

Electromigration (EM) characteristics have been investigated in the TiN/Al-alloy/TiN systems formed with two types of high-temperature sputtered Al-alloy metallizations. The Al-alloy films were prepared with and without a Ti glue layer before Al-Si-Cu film high temperature-sputter deposition. Using the Ti glue layer, an Al-Ti-Si product layer having a resistivity of 43 /spl muspl Omega/cm, instead of giant Si precipitates, grew during interfacial reaction between the Ti film and the growing Al-Si-Cu film. As the result, a bilayer structure of Al-alloy/Al-TiSi product was formed on the TiN layer. The EM resistance was drastically improved using the Ti underlayer. The high quality of the Al-alloy film (the increase in {111} orientation and the decrease in the standard deviation of the grain distribution) as well as the absence of Si precipitates will contribute to the suppression of void formation. Moreover, the EM-induced failure proceeds gradually because the Al-Ti-Si product layer will act effectively as a current bypass. This effect is supported by good electrical characteristics of the Al-Ti-Si product layer and the interface between the Al-alloy layer and the product layer. The local temperature increase is not essential to the subsequent growth of voids in the high-temperature sputtered Al-alloy metallization with the Ti glue layer.<>