Degradation Mechanism in Si-Doped Al/Si Contacts and an Extremely Stable Metallization System

The resistance increase of diffused resistors with Si-doped Ai metallization was investigated under high current density. This degradation was caused by void formation at the Si-doped Al/Si interface. The resistance increase of the diffused resistor corresponded to the resistor length expanded by this void formation. The void formation resulted from a combination of Al and Si electromigration and diffusion of Si into the Al layer. This mechanism was confirmed by analyses of Cu-doped AI, which had excellent resistance to Al electromigration, and the AI/TiN/Ti metallization system, which should have a complete barrier effect against Si diffusion into Al. Based on these degradation analyses, an extremely stable Cu-doped Ai/TiN/Ti metallization system has been proposed for high current density applications..