Wafer in Foup

Wafer-in-FOUP loading is the handoff moment where a wafer physically enters or leaves its shipping pod — the step that turns a sealed, sensor-tracked cassette into 25 individually addressable wafers the fab's automation can act on. It happens at the load port, before the FI robot does anything else, and every later automation record (slot history, lot genealogy, carrier-to-tool traceability) is anchored to what gets logged during this one step.

The slot map is the whole point of this step. A FOUP can arrive with wafers missing, double-slotted, or tilted from a rough ride on the OHT, and the mapping sensor — usually a through-beam or reflective laser pair that sweeps the full slot range — has to catch all three before the FI robot ever reaches in. A cross-slotted or tilted wafer that gets picked anyway is a near-certain wafer break or a scraped carrier, so most load ports refuse to proceed past mapping until the scan comes back clean.

The record this step writes outlasts the wafer's time at this tool. Every downstream question a fab asks — which FOUP was this wafer riding in three process steps ago, did it ever get flagged cross-slotted, which load port logged the exception — traces back to the carrier ID and slot map captured right here. Losing or corrupting a wafer-in-FOUP record doesn't just affect the current tool stop; it breaks the genealogy chain for every step the wafer visits afterward.

Wafer-in-FOUP loading looks like a formality bolted onto the front of FI-robot handling, but it's the only point in the automation chain where the physical state of the pod — what's actually in which slot — gets reconciled against what the MES thinks is there, and every later handling decision inherits whatever this step got right or wrong.