The unique physical phenomenon of photon emission from a variety of defects in ICs has long been exploited for failure analysis. This method provides a fast non-destructive inspection method for failure localization. Several functional failures have a distinctive emission signature that allows functional analysis of the design. The transition to flipchip packaging accelerated the use of Infrared Focal Plane Arrays (IR FPA) such as MgCdTe (MCT). It has been proven that systems that incorporate MCT arrays demonstrate higher sensitivity for emissions in comparison to the traditional Si CCDs; usually the higher sensitivity is compromised with inferior resolution. In this work we will review and demonstrate the optical limitations involved with the use of an MCT camera, yet we shall show a calibration procedure carried out by the analyst to bypass these limitations. By calibrating typical emissions, generated by typical functional defects, we generate calibration curves, which supply a fast reference for detection of the defective transistor, and the correlated current that results from the defect. The calibration of the array response is crucial for evaluation of its sensitivity. It will also enable a clear distinction between emissions, which correlate to small or negligible current flows, and emissions that correlate to significant current flows. We also classify logic failures that lead to emissions, and estimate the level of emission anticipated from these failures.

Infrared Micro Thermography can be applied as electrical fault identification in situations where photon emission is ineffective. Defects, such as certain types of stringers and particles, may conduct without emitting photons in the visible range. Arrayed infrared sensors such as an InSb 512x512 detector, coupled with the appropriate infrared optics can image the heat generated from the leakage site. Heating on the order of a fraction of a degree Kelvin can be observed. The heat signature can be superimposed on a normal optical image of the chip. Several practical examples using this fault identification technique are described.