target value

**Target Value** in SPC is the **ideal, optimal value for a measured parameter** — the nominal design value around which specifications are set, representing the center of the specification range where the product performs best or the process is most robust. **Target Value Context** - **Design Nominal**: The intended value from the design — e.g., 28nm target CD for a 28nm gate. - **Best Performance**: The value that optimizes device performance — may differ from the spec center. - **Process Center**: Ideally, the process mean equals the target value — perfectly centered process. - **Offset**: Sometimes the target is intentionally offset from the spec center to account for downstream processing. **Why It Matters** - **Taguchi**: The Taguchi loss function says quality loss increases as the parameter deviates from target — even within spec. - **Centering**: Centering the process on target maximizes process capability (Cpk approaches Cp). - **APC**: Advanced Process Control (APC) systems target the nominal value — run-to-run controllers adjust recipes to maintain on-target. **Target Value** is **the bullseye** — the optimal nominal value that represents perfect process centering and best product performance.