Thermal dependence of leakage pathways in Cu/ULK advanced interconnects

Using Poole-Frenkel (PF) and variable range hopping modeling of transport, we show that the dielectric leakage pathways in advanced Cu/ULK interconnects can depend on temperature. The transport mechanism is consistent with bulk (3D) conduction in the [25-150] degrees C range and interfacial leakage above 150 degrees C. An important consequence is that accelerated reliability tests performed at too high temperatures should not be really representative of conduction mechanisms at real operating conditions ( < 130 degrees C). These results critically outline the growing importance of surface engineering with the unavoidable scaling down (1) of copper interconnects.