Failure Analysis Issues/Techniques

Die/Wafer Visual Examination: Die/wafer examination can be achieved using optical microscopes or the scanning electron microscope (SEM). SEMs have the additional ability to perform voltage contrast and electron-beam-induced current analysis of devices under biased conditions. Biased devices can also be examined with high-magnification infrared thermography, which can identify hot spots that command interest as possible failure sites. An ultraviolet microscope can be used for the evaluation of organic contamination.

X-ray Radiography: X-ray radiography is a method for nondestructive analysis of most types of die. The investigator would inspect for internal open circuits and shorts, and changes in alignment due to the mounting or bonding of the die. X-ray analysis would not alter or affect either the device or its failure mode.

This technique offers two helpful benefits for the failure investigator: (a) a graphic representation of internal characteristics of the die under inspection prior to any sectioning or handling. (b) A pictorial representation of how the device is constructed.

Infrared Screening: Using a sensitive radiometer and advanced software, this imaging technique can detect patent and latent defects such as dewets/voids, substrate delaminations, and weak or misaligned components.

Micro Sectioning: During the course of failure analysis, it's often necessary to cross-section the sample. The goal of cross-sectioning or micro sectioning is to expose internal features of the die or wafer.

Surface Analysis: An energy-dispersive X-ray analysis (EDXA) attachment to the scanning electron microscope (SEM) is a valuable tool in failure analysis as it can use the X-rays of the SEM to analyze the material makeup. When a high-energy beam of electrons bombards the sample under observation, X-rays are given off that impinge on the silicon surface of the EDXA detector. Along the penetration track, interaction occurs between the X-ray and silicon atoms, creating hole-electron pairs. The currents generated are sampled and the magnitude of pulses related to signal output is usually a multichannel spectral output with peaks at specific energies, representing X-rays for the various elements present in the specimen being observed in the SEM. The major advantage of the EDXA system is the detection of the entire energy/elemental spectrum simultaneously.


		A Few Tools of the Trade