mask inspection

**Mask Inspection** is the **process of detecting defects on photomasks using high-resolution imaging and comparison algorithms** — scanning the entire mask pattern at high resolution and comparing it to the design database (die-to-database) or to adjacent identical dies (die-to-die) to find any deviations. **Inspection Modes** - **Die-to-Database**: Compare the mask image to the design layout — detects any deviation from the intended pattern. - **Die-to-Die**: Compare identical dies on the mask — defects appear as differences between dies. - **Reflected/Transmitted**: Inspect using reflected light (for EUV masks) or transmitted light (for DUV transmissive masks). - **Wavelength**: DUV inspection wavelengths (193nm, 248nm) for highest resolution — actinic (EUV) inspection for EUV masks. **Why It Matters** - **Zero Tolerance**: A single undetected mask defect prints on every wafer — mask inspection must have near-perfect sensitivity. - **Sensitivity**: Must detect defects small enough to print — sensitivity requirements tighten with each technology node. - **Cost**: Inspection is a significant fraction of the total mask manufacturing time and cost. **Mask Inspection** is **finding the needle in the mask** — high-resolution scanning and comparison to detect every printable defect on the photomask.