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August Technology has been granted United States Patent No. 6,947,588 for a method that detects defects on the circumferential edge of a semiconductor wafer.
"Progress in finding an edge inspection solution has moved slowly due to the complexity of curved surface inspection," said Cory Watkins, chief technology officer at August Technology. How many killer defects actually originate at the wafer edge?  "As much as 30% in some processes," said Watkins.  "Consequently, many killer edge defects escape detection and continue to damage front-side devices by migrating to the front-side or causing gross device failure through a secondary mechanism such as a popping blister or broken wafer."

Included in the patent is an optical method that overcomes the problems of variable wafer edge surface topographies. August has broken up the collected image into smaller grids during capture time and stores the information for off-line analysis.