The biggest challenge for the failure analysis engineer is to physically expose and identify exactly which feature of the failed cell structure is responsible for the measured failure problem. With ever-shrinking device geometries, that task has become even more difficult because the defects are even subtler and smaller, resulting in some new characteristics of modern FA. Microanalysis of semiconductor devices often deals with defect identification in a very small region. This region can be a failed gate or “hot spot” area detected with various techniques. Such analysis is especially important for RAM memory devices because bit-related failures are the most prevalent failure mode, from both yield and reliability perspectives.
More than ever, high-resolution equipment, such as Focused Ion Beam (FIB), Field Emission Scanning Electron Microscope (FESEM), and Transmission Electron Microscope (TEM) has been used for failure analysis. Such high-resolution equipment is not only used for final observation of the defect, but also during prior analysis steps, when its location has not yet been fully identified.
Energy Dispersive X-ray Spectroscopy and Electron Backscatter Diffraction tools attached to the SEM have been a popular choice for compositional analysis of defects. |
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