Scatterometry Overlay is the general term for using optical scatterometry (OCD) principles to measure overlay — encompassing both DBO (diffraction-based) and spectroscopic overlay methods that extract layer-to-layer registration from the spectral signature of overlay targets.

Scatterometry Overlay Methods

• DBO: Measure +1st/-1st diffraction order intensity difference — proportional to overlay.
• Spectroscopic: Measure full spectral response of overlay targets — fit overlay from spectrum shape changes.
• µDBO: Miniaturized targets for in-die measurement — multiple pads per target for X/Y overlay.
• 2D Targets: Measure X and Y overlay simultaneously from 2D grating targets.

Why It Matters

• Speed: Scatterometry-based overlay is faster than image-based — higher throughput for high-volume manufacturing.
• Accuracy: Achieves <0.5nm accuracy — competitive with or better than IBO for advanced nodes.
• In-Die: Small targets enable in-die overlay measurement — captures local variations that scribe-only targets miss.

Scatterometry Overlay is registration measurement through diffraction — using the spectral response of grating targets for high-throughput overlay metrology.