Thermal analysis of the fusion limits of metal interconnect under short duration current pulses

Thermal analysis of the fusion limits of the IC metal under short duration current pulses has been performed using a quadruple level TiN/AlCu/TiN metallization system. A finite element (FE) simulation program has been calibrated to analyze the thermal effects in detail. The program can be used to predict self heating under DC and transient current conditions for various metal levels, geometries and current loading conditions. It is shown both experimentally and using FE simulations that the metal temperatures rise past 1000°C before open circuit failure under short duration current pulses. The critical failure current is strongly influenced by the metal thickness, thermal capacity and pulse width. Further, it is shown that the ratio of the critical energy causing open circuit conditions (fusion limit), to the theoretical melt energy increases with scaling. As a result, narrower metal lines can sustain higher current densities before failure