aerial image inspection

**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.