Mask defect inspection method by database comparison with 0.25-0.35 μm sensitivity

Photomasks used in the fabrication of ultra-LSI (ULSI) circuits must be inspected for defects. For 256 Mbit dynamic random access read write memory (DRAM), it is necessary to inspect defects as small as 0.15 µ m. Moreover, inspection of defects of phase-shift masks is becoming an important task of an inspection system. This paper describes an automated mask inspection system (MC-100) based on die-to-database comparison, and a defect inspection method with 0.15 µ m sensitivity for edge and pindot defects. System configuration and the defect inspection method are discussed in detail, including the difficulties of defect detection in an attenuated phase-shift mask.