Abstract

Fault isolation is an important initial component of the failure analysis investigation as it provides the first indicator of the defect physical location. The most broadly familiar fault isolation techniques include photoemission microscopy (PEM), optical beam induced resistance change (OBIRCH) and liquid crystal analysis (LCA). Each of these techniques has their own strengths but also drawbacks which can impede the analysis by either not providing a well isolated defect location or causing damage to the defect region. For some types of defects, photoemission and liquid crystal analysis may create local heating of the device which can distort the defect and mask the root cause of the failure. These techniques also rely on optical microscopy which has low resolution compared to the feature size of current technologies. In addition, each technique may not highlight the defect site itself; only pointing the analyst to the defective circuit within the sample. Electron Beam Induced Current (EBIC) and Electron Beam Absorbed Current (EBAC) microscopy provides solutions to these complications. In this paper we describe some very effective approaches by using these beam-based techniques in conjunction with traditional methods. As introduction, we have provided some interesting case studies whereby EBIC/EBAC have been used in conjunction with FIB circuit edits and scan diagnostic results to narrow the defect search areas. We focus the paper on some less common applications of cross sectional EBIC/EBAC as well as utilizing an AC coupled configuration to activate more subtle defect sites. We conclude with two examples where AC coupled cross-sectional EBIC is needed to highlight the cause of the failure.

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