Improved understanding of metal ion reservoirs within barrier-metal systems

Within integrated circuits there are many instances where low current density lines feed directly (without a via) into a single line of much higher current density, for example with clock or power supply distribution. This work demonstrates and discusses increased lifetime with increasing numbers of current feed lines in a barrier metal interconnect system. The low current density feed lines (branches) act as reservoirs or sources of additional Al and Cu ions, which can re-fill portions of voids and/or slow void growth in the high current density line (trunk). 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. Narrow lines may get more benefit than wide lines. Increasing reservoir size will increase lifetime, within limits.