3D X-ray microscopy: A near-SEM non-destructive imaging technology used in the development of 3D IC packaging

In this paper, we describe the novel technique of using leading edge X-ray microscopy (XRM) technology to replace physical cross-sectioning in failure analysis (FA) and 3-dimensional integrated circuit (3DIC) process development. Contrary to general consensus that 3D X-ray is too slow, we explain how XRM can be used to obtain high quality cross-section images within 5-300min per measurement depending on the physical properties (materials, feature sizes, and outer dimensions) of the sample and the minimum tolerable image quality needed to visualize a defect. The specifics of the inspection technique itself and how X-rays interact with the sample to achieve high-quality images will be discussed and contrasted with conventional 3D microCT technology. Furthermore, understanding the effects that imaging parameters, such as voltage, power, exposure time, resolution, number of projections, etc., have on the quality of an image, can help the user reduce the 3D X-ray inspection time considerably. A test vehicle package is used to illustrate the effects of inspection time in image quality, and to compare and contrast the quality of an optical image taken from a physical cross-section and a virtual cross-section image taken from an XRM tomography.