1. Purpose of the gate
Last wafer start is the final gate in the node's life. It closes the Node End of Life stage. After it, no new wafers start on the node, so any order not covered by the final start plan cannot be filled from new production. The gate checks that the plan covers every confirmed order, that the tools, spares, consumables and materials needed to process those wafers to completion are secured, and that the knowledge of how the process was run is preserved in an archive.
The archive matters more than it may seem. Customers will keep products built on the node in the field for long after the last shipment, and questions about failures, reliability or traceability will continue to arrive. The archive must let someone who never worked on the node answer those questions: the final process baseline and recipes, control plans, qualification reports, change history, design kit versions and the records that link each lot to its processing.
The criteria are: final wafer start plan covers every confirmed order; equipment and materials supply secured to the last start; and process archive complete.
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