Lock-in thermal laser stimulation for non-destructive failure localization in 3-D devices

We report a new non-destructive method to localize interconnection failures in 3-D devices. The scanning optical microscopy (SOM) technique is based on lock-in thermal laser stimulation (LI-TLS) and uses thermal waves to non-destructively map the current path in a 3-D device. We validate the method with test structures and show how the magnitude and phase of a propagating thermal wave may provide valuable 3-dimensional information on the failure location. We apply the technique on a short failed chain structure in a four level chip stack with an intensity modulated laser as a thermal wave injector and the structure under test as a detector. We confirm our results by physical failure analysis through a selective cross sectioning process.