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.

This presentation covers the challenges associated with IC package inspection and shows how two nondestructive techniques, scanning acoustic microscopy and X-ray imaging, are being used to locate and identify a wide range of defects, particularly those in 3D packages and multilayer boards. It reviews the basic principles of scanning acoustic microscopy (SAM), X-ray imaging, and 3D X-ray tomography and the factors that affect image resolution and depth. It demonstrates the current capabilities of each method along with different approaches for improving resolution, contrast, and measurement time.

This paper assesses the capabilities of scanning acoustic tomography (SAT) for the analysis of bonded silicon wafers. In order to quantitatively evaluate detectability and resolution, the authors acquired images from samples prepared with artificial voids. The samples consisted of two wafers, a cap wafer and a base wafer with dry-etched pits on a silicon-oxide layer. Cap wafers of different thicknesses were used along with transducers of appropriate focal length. The paper describes the experimental setup and test procedures in detail as well as the results.