1.6  Failure Mechanisms in Interconnects

In interconnects, failures are the variation of parameters beyond critical values which prevents the designated function of integrated circuits. The typical parameters are the resistance of the interconnect and the resistive and capacitive isolation to neighboring components like interconnects, devices, or to the bulk. Differences between the experienced parameters and the designed parameter can be caused by defect-related problems or by wear-out.

Defect-related problems are caused by the fabrication process. Missing process steps and especially dirt contamination can be responsible for regions where the conducting material is missing, leading to higher resistance than designed [92, 109]. Furthermore, the isolating layers can be thinner than engineered, leading to higher leakage currents and capacitive coupling into other system parts, affecting there function.

Wear-out, in contrast, is a failure phenomenon, which occurs or evolves under the operation of the devices. This can even occur under normal operating conditions. Wearout phenomena are for example material diffusion from the metal into the semiconductor or the isolation/dielectric leading to a change in the electrical characteristics, or temperature induced phenomena leading to stress induced failure (e.g. cracking or delamination) [134].