wafer starts

Wafer starts measures the **number of raw wafers entering the fabrication process** per unit time (typically per month). It's the primary metric for fab production volume and capacity planning. **Typical Fab Wafer Starts Per Month (WSPM)** • **Small/specialty fab**: 5,000-15,000 WSPM • **Mid-size fab**: 20,000-40,000 WSPM • **Large high-volume fab**: 50,000-100,000 WSPM • **TSMC mega-fab (e.g., Fab 18)**: 100,000+ WSPM **Wafer Starts vs. Wafer Outs** **Wafer starts** = wafers entering the fab. **Wafer outs** = wafers completing all process steps and shipping. The difference is the **WIP** (work-in-progress) in the fab. During ramp-up, starts exceed outs as the fab fills with WIP. At steady state, starts ≈ outs (with a lag of ~2-3 months cycle time). **Why Wafer Starts Matter** **Revenue forecasting**: More wafer starts → more wafer outs → more die production → more revenue (with yield factored in). **Capacity planning**: Wafer starts relative to installed capacity determines utilization rate. **Customer commitments**: Foundries commit capacity to customers as wafer starts per quarter. **Supply chain signal**: Industry-wide wafer start data indicates overall semiconductor demand health. **Wafer Start Decisions** Fabs don't blindly maximize starts. **Customer orders** drive starts at foundries. **Demand forecasts** drive starts at IDMs. During downturns, companies deliberately reduce starts to avoid building excess inventory. During shortages, fabs run at maximum starts and customers compete for allocation.