Detection of Sub-Design Rule Physical Defects Using E-Beam Inspection

E-beam inspection provides an alternative approach to brightfield inspection for detection of otherwise difficult to detect physical defects. Advantages of E-beam inspection include superior resolution, the ability to classify defects using patch images, automatic filtering of prior level defects, and beam conditions for material contrast. For extremely small defects, which are becoming more common with each technology, brightfield inspection can fall short because of resolution limits. Either the defects are too small to even be detected or the defects are hidden among nuisance or other types of defects and cannot be binned out without SEM review. We present four examples of challenging defects that could not effectively be monitored with brightfield inspection and, therefore, were monitored with E-beam inspection. Throughput is a key limitation of E-beam inspection. Therefore, brightfield inspection should always be used for defection of physical defects when effective. To maximize the chance of success with brightfield inspection, E-beam inspection data may be used as a gold standard for development of the best optical inspection conditions. A methodology to do this is described and illustrated.