On-Device Overlay is the measurement of overlay directly on functional device structures — rather than using dedicated overlay targets in the scribe line, on-device overlay extracts registration information from the actual product features, providing the truest representation of overlay at the device location.

On-Device Overlay Methods

• e-Beam: SEM-based measurement of overlay on actual device features — high resolution but slow.
• In-Die Targets: Small overlay targets placed within the die area (near devices) — better than scribe-line targets.
• Computational: Extract overlay from design features using pattern matching or machine learning.
• Hybrid: Combine scribe-line target measurements with in-die corrections.

Why It Matters

• Accuracy: Scribe-line targets may not represent actual device overlay — target-to-device offset varies.
• Intrafield Variation: On-device captures intrafield overlay variation that scribe-line targets cannot.
• Advanced Nodes: At <5nm, overlay budgets are ~1-2nm — target-to-device differences can consume the entire budget.

On-Device Overlay is measuring what matters — extracting overlay from actual device features instead of proxy targets for the most accurate registration measurement.