seasoning

Seasoning runs dummy wafers after PM or chamber clean to stabilize chamber conditions before resuming production, establishing a consistent wall state. Purpose: (1) Coat chamber walls with process-representative film, (2) Stabilize plasma conditions, (3) Establish thermal equilibrium, (4) Reduce first-wafer effects. Seasoning types: (1) Full seasoning—after wet clean or major PM, typically 25-50 dummy wafers; (2) Mini-seasoning—after in-situ clean, typically 1-5 wafers; (3) Recovery—after extended idle, stabilize temperature and wall state. Process: run actual production recipe on unpatterned wafers, monitor key parameters (uniformity, rate, particle counts). Seasoning endpoints: (1) Fixed wafer count (conservative); (2) Parameter stabilization (rate, uniformity within control limits); (3) Particle count acceptable. First-wafer effect: initial wafers after clean often show different characteristics (rate, uniformity) until walls equilibrate. Seasoning wafer allocation: tracked separately from production, not counted against tool uptime. Optimization: minimize seasoning wafers while achieving stable process—balance cost (dummy wafers) vs. quality risk. Chamber wall condition: affects radical recombination, gas phase chemistry, and ultimately process results. Critical step often overlooked but essential for reproducible semiconductor manufacturing.