Normally, wafer must be held on vacuum wand to inspect wafer lot number at wafer edge to inspect correct lot number before DAF laminating.
Base on operator and technician interview, wafer lot can’t be inspected due to unclear alphabet of wafer lot at wafer edge. So, the problematic wafer was moved to do inspection under ring light (3X). Unfortunately, wire of ESD box touch problematic wafer during ring light catching. Finally, wafer dropping and broken wafer problem was found.