Electromigration Induced Leakage at Shallow Junction Contacts Metallized with Aluminum/Poly-Silicon

An Al/poly-Si metallization prevents thermally induced Al/Si interpenetration at shallow junction contacts while simultaneously compensating for Al thinning at steps. However, the devices remain susceptible to junction leakage by the electromigration of Si from the substrate. The lifetimes are shown to be a function of the contact current, temperature, window size and the junction depth. The relative failure rates of small-geometry contacts and fine-line Al interconnects are such that if the interconnect current density is maintained constant at ~105 Acm-2, Al/poly-Si contacts will remain electromigration resistant despite a scale-down in device geometry.