Overlay Fingerprint is the systematic, repeatable pattern of overlay errors across a wafer or across fields — decomposing the overlay error map into systematic components (translation, rotation, magnification, distortion) and residual random errors for targeted correction and process optimization.

Fingerprint Components

• Interfield: Wafer-level systematic errors — translation ($T_x, T_y$), rotation ($R$), magnification ($M_x, M_y$), trapezoidal, higher-order terms.
• Intrafield: Within-field lens distortion — third-order, fifth-order, and higher-order polynomial terms.
• Per-Exposure: Corrections applied by the scanner for each exposure field — correctables.
• Non-Correctable: Residual errors after all systematic corrections — the irreducible floor.

Why It Matters

• APC: Overlay fingerprints are the basis for advanced process control — systematic errors are corrected, reducing total overlay.
• Lot-to-Lot: Fingerprints vary by lot, wafer position in cassette, and process conditions — real-time correction needed.
• Tool Matching: Different scanners have different fingerprints — matching scanners requires fingerprint alignment.

Overlay Fingerprint is the signature of misalignment — the systematic, repeatable error pattern that can be characterized and corrected.