Altair 8920 Darkfield

The KLA Altair 8920 is a darkfield inspection system that processes 8-inch wafers.^[2][1]

Darkfield inspection works by directing a laser or broadband light source onto the wafer surface at an oblique angle. The specular reflection is blocked from reaching the detector, while light scattered by particles, pits, scratches, or pattern anomalies is collected and imaged. The system uses multiple collection channels, typically including forward-scatter and back-scatter optics, to capture different defect signatures.

The collected scatter signals are converted into electrical signals and processed by the system's image-analysis software. Defects are classified by size, type, and location using algorithms trained on reference die or golden images. The tool can operate in both brightfield and darkfield modes depending on configuration, but the Altair series is dedicated to darkfield detection.

The tools sit between front-end-of-line and back-end-of-line processing, often as part of a defect-review workflow. Wafers rejected by darkfield inspection may be sent to review scanning electron microscopes or atomic-force microscopes for further analysis.

Common applications include incoming substrate qualification, post-chemical-mechanical planarization residue checks, defect-density monitoring after dielectric deposition, and post-etch inspection. The high throughput of automated darkfield systems makes them suitable for volume production environments.