Advanced mask metrology system for up to 4-Gb DRAM

Abstract

Photolithography using photomasks will be used for at least up to the 4 Gbit DRAM generation. For these advanced photomasks, higher performance will be demanded from the mask metrology system. The metrology system must satisfy performance criteria such as higher measurement accuracy, handling capability for larger reticles (9' by 9') and so forth, because the pattern rule for reticles will be tighter and the exposure field area will grow in the next generation. Nikon Corporation has been providing a mask metrology system, the XY-5i which can be used for up to the 1 Gbit DRAM generation. In order to meet the above mentioned required performance for the next generation system, Nikon has developed a new metrology system, the XY-6i. The XY-6i has higher measurement accuracy and resolution for pattern coordinates and critical dimensions on reticles and can also measure wafers and next generation reticles (9' by 9') automatically.