Aerial Image Inspection is a mask inspection technique that evaluates the mask based on the image it will actually produce in the lithographic exposure system — rather than inspecting the physical mask features directly, it examines the aerial image (the optical image projected onto the wafer), capturing how mask features and defects will actually print.

Aerial Image Inspection Methods

• AIMS (Aerial Image Measurement System): A dedicated tool that reproduces the scanner's imaging conditions — same NA, wavelength, illumination.
• Simulation: Computational aerial image simulation from mask inspection data — virtual AIMS.
• Through-Focus: Evaluate the aerial image at multiple focus positions — assess printability across the process window.
• Defect Disposition: Determine if a detected mask defect will actually print on the wafer — avoid unnecessary repairs.

Why It Matters

• Printability: Not all mask defects print — aerial image inspection determines which defects matter.
• Cost Savings: Avoiding unnecessary repairs saves time and reduces mask damage risk from over-repair.
• EUV: Critical for EUV masks where physical inspection alone cannot predict printability through the complex multilayer reflector.

Aerial Image Inspection is seeing what the wafer sees — evaluating mask quality from the perspective of the actual lithographic image.