Semi E90.1

SEMI E90.1 defines the SECS-II message set that carries SEMI E90's substrate-tracking data between equipment and host — E90 defines the substrate ID, location, and processing-history data model a tool must maintain per wafer, while E90.1 defines the actual wire-level messages that move that per-substrate data over the SECS-II link automatically. Without E90.1, E90's substrate-tracking model would describe what a tool needs to know about each wafer in the abstract, but a host would have no standardized way to actually read which substrate currently occupies which process position, or receive a notification the moment a substrate's tracked location changes — E90.1 is the protocol binding that turns substrate tracking into real-time, automatic data exchange rather than a periodic manual query.

The reason substrate tracking needed its own SECS-II protocol spec rather than a generic status message is that per-wafer location data has to update in near-real time and at fine granularity — a host tracking lot genealogy or diagnosing a mis-process needs to know exactly which chamber or slot held which specific wafer at which moment, and a generic equipment-status message carries no guarantee of that granularity or timing across different tool vendors. A fab correlating a yield excursion back to a specific chamber exposure needs every tool's substrate-location reporting to use the same message structure and update cadence, which is exactly the integration cost E90.1 eliminates — standardizing the SECS-II layer underneath E90's tracking model the same way E87.1 did for carrier data and E58.1 did for ARAMS.

E90.1 is what makes wafer-level traceability actually real-time across a mixed-vendor fab rather than a batch-reconciled approximation — the protocol layer is what turns E90's tracking model into data a host can trust the moment something changes, not just after the fact.