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.