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.