throughput

Throughput measures the number of wafers processed per unit time (typically wafers per hour, WPH) by a semiconductor manufacturing tool or production line, serving as the fundamental productivity metric that determines fab capacity, cycle time, and manufacturing cost per wafer. Tool-level throughput: determined by process time per wafer (or per batch), overhead time (wafer loading/unloading, recipe set-up, alignment), and simultaneous processing capacity. Single-wafer tools: throughput = 3600 / (process_time + overhead_time) WPH—a tool with 60-second process time and 30-second overhead achieves 40 WPH. Batch tools: throughput = batch_size × 3600 / (process_time + load/unload_time)—a furnace processing 150 wafers in a 4-hour cycle achieves ~37.5 WPH. Throughput by equipment type: (1) lithography scanners: 200-300 WPH (highest throughput tools, also highest cost—$100-350M each), (2) etch tools: 15-40 WPH per chamber (multi-chamber platforms multiply this), (3) CVD tools: 10-30 WPH per chamber, (4) PVD tools: 20-60 WPH per chamber, (5) CMP tools: 30-60 WPH per platen, (6) wet benches: 100-200 WPH (batch processing of 25-50 wafer cassettes), (7) metrology tools: 10-30 WPH (measurement time per site × number of sites limits speed). Fab-level throughput: the total wafer output of the entire fab, measured as wafer starts per month (WSPM) or wafer outs per month. A modern 300mm logic fab produces 40,000-100,000 WSPM. Fab throughput is limited by the bottleneck tool group (the process step with the least excess capacity relative to demand). Throughput improvement methods: (1) process time reduction (optimize recipes without quality impact—faster etch rates, higher deposition rates), (2) overhead reduction (faster wafer handling, parallel processing, optimized scheduling), (3) equipment utilization improvement (reduce PM time, reduce qualification time, improve MTBF/MTTR), (4) add tool capacity at bottleneck steps, (5) batch size optimization (fill every slot in batch tools). Throughput directly impacts cost—manufacturing cost per wafer is approximately total fab operating cost / total throughput, making throughput maximization a primary manufacturing objective.