Wafer Mapping Sensor

Wafer mapping sensors, identification readers, and OCR readers each confirm a different fact about a wafer before anything happens to it — whether a slot actually has a wafer in it, which specific wafer that is, and whether that wafer's own printed identifier matches what the system expects.

OCR reading the wafer's own laser-marked ID directly is the one check that catches a mix-up no electronic carrier tag could ever catch. A FOUP's RFID tag identifies the carrier itself, and a mapping sensor confirms a slot is occupied — but neither one proves that the physical wafer sitting in that slot is actually the wafer the system's records say it is. OCR reads the permanent ID laser-marked directly onto the wafer at manufacture, verifying the wafer's own identity independent of which carrier or slot it happens to be riding in right now — the only one of these three checks that can catch a wafer that's been physically swapped or misplaced into the wrong slot.

Mapping sensors run earliest in this sequence, because every later check depends on first knowing exactly which slots actually have a wafer present at all. A mapping scan happens at FOUP docking, before any ID or OCR reading, since those later checks only make sense for slots confirmed to hold a wafer — reading an ID off an empty slot isn't a meaningful operation, so the mapping check sets the baseline that the ID and OCR checks build on.

Wafer mapping, ID reading, and OCR together build a complete, verified picture of exactly what's physically present before a tool commits to processing it — occupied-slot confirmation, carrier identity, and the wafer's own permanent identity each closing a different gap the other two checks leave open.