Scrap Wafer

A scrap wafer is a non-product wafer used for process testing, equipment qualification, or experimental runs where the wafer will not become saleable product. Types: Previously failed product wafers recycled for non-critical uses. Virgin test-grade wafers purchased for specific testing needs. Applications: New recipe development and optimization, equipment qualification after maintenance, process troubleshooting and experiments, contamination testing, destructive analysis. Cost advantage: Using scrap wafers instead of expensive prime product wafers reduces cost of testing and development. Reclaim: Some used wafers can be reclaimed (stripped, polished, cleaned) and reused as scrap wafers for further testing. Reclaim services reduce waste and cost. Traceability: Even scrap wafers must be tracked to prevent accidental mixing with product wafers. Clear labeling and segregation required. Quality considerations: Scrap wafer quality (contamination, surface condition) may differ from prime wafers. Results may not perfectly represent production conditions. Wafer grades: Prime (highest quality for product), test grade (adequate for most testing), reclaimed (reprocessed used wafers), dummy grade (fill wafers). Disposal: Wafers that cannot be reclaimed are disposed of per environmental regulations. Silicon recovery possible. Consumption: Fabs consume significant quantities of non-product wafers for all testing and qualification activities. Budget: Scrap and test wafer costs included in fab operating budget as indirect manufacturing cost.