mask repair

**Mask Repair** is the **process of correcting defects found on photomasks during inspection** — adding missing material (additive repair) or removing unwanted material (subtractive repair) to fix isolated defects that would otherwise cause yield loss on wafers. **Repair Technologies** - **FIB (Focused Ion Beam)**: Gallium ion beam for subtractive repair (milling) and gas-assisted deposition for additive repair. - **E-Beam Repair**: Electron beam-induced deposition/etching — higher resolution than FIB, no Ga implantation. - **Laser Repair**: Pulsed laser ablation — fast but lower resolution, suitable for clear defects. - **Nanomachining**: AFM-based mechanical removal of defects — for specific defect types. **Why It Matters** - **Yield Recovery**: Repairing a mask defect is far cheaper than remaking the mask ($100K-$500K). - **EUV**: EUV mask repair is extremely challenging — absorber defects AND multilayer defects both need repair capability. - **Verification**: Post-repair inspection and AIMS review are essential to confirm successful repair. **Mask Repair** is **fixing flaws in the master pattern** — using precision tools to correct defects and restore mask quality to specification.