This presentation provides an overview of lock-in thermography and its application in semiconductor failure analysis. It begins with a review of direct thermal imaging, IR transmission and detection, and the fundamentals of lock-in measurements. It compares and contrasts steady-state IR imaging with lock-in thermography and shows how lock-in frequency and the shape of the excitation signal can be varied to increase signal-to-noise ratio and reduce acquisition time, thereby exposing a wider range of defects. It also presents several case studies in which lock-in thermography is used to diagnose shorts and hot spots in packaged devices, electronic systems, and 3D assemblies.

In thermal microscopy, temperature error arises whenever a constant emissivity value is assumed for different materials. In this paper, we propose a new approach to eliminate these undesirable effects resulting from the ambiguous surface emissivity of materials. This method enables the compensated (true) temperature distribution of a device under test to be obtained from the measured temperature image. A transfer function that relates the measured and true temperature is formed to estimate the actual temperature distribution of a biased device to an accuracy of approximately 0.3-0.7K.