Electromigration lifetime enhancement for lines with multiple branches

With clock or power supply interconnect “trees” there is often a very high current “trunk” feeding current to multiple branches. This work demonstrates and discusses increased “trunk” lifetime with increasing numbers of current branches in a plug-via metal system. The branches act as reservoirs or sources of additional Al and Cu ions, which can re-fill portions of voids and/or slow void growth. It is discussed that any area of metal at a lower current density might be considered a reservoir or source of metal ions for higher current density regions, and can effectively extend the lifetime of the higher current density region. Comparative Black´s model parameters are developed and failure analysis is described