run-to-run control

**R2R Control** (Run-to-Run Control) is a **supervisory process control method that adjusts recipe parameters between consecutive runs (lot-to-lot or wafer-to-wafer)** — using an EWMA controller to track process drift and automatically compensate by modifying setpoints. **How Does R2R Control Work?** - **Measure**: After each run, measure the critical output (CD, thickness, uniformity). - **EWMA Update**: $hat{y}_{n+1} = lambda y_n + (1-lambda) hat{y}_n$ (exponentially weighted estimate of process level). - **Correction**: $u_{n+1} = u_n + G^{-1}( ext{target} - hat{y}_{n+1})$ where $G$ is the process gain matrix. - **Apply**: Updated recipe parameters are applied to the next run. **Why It Matters** - **Industry Standard**: R2R control is the most widely deployed APC method in semiconductor manufacturing. - **Drift Correction**: Automatically compensates for chamber aging, consumable wear, and environmental drift. - **Multi-Variable**: Advanced R2R controllers handle multiple correlated parameters simultaneously. **R2R Control** is **the autopilot for semiconductor processes** — automatically adjusting recipes between runs to keep output on target despite continuous process drift.