Recipe optimization of fab mask inspection for 180～90nm reticles to save inspection time and improve productivity

摘要

IC manufacturing fabs are experiencing mask reliability issues caused by progressive mask defects, such as crystal growth, haze and etc. with the increase of the usage of DUV, especially 193nm lithography on 90nm technology node and beyond. 193nm lithography has triggered an increasing demand for mask re-qualification in those manufacturing fabs which process 90nm technology node wafers in mass production. Due to dramatic increase in re-qualification demand, the capacity of mask inspection becomes constrain of the manufacturing output. In this paper authors employed widely used KLA SLF inspection systems and investigated inspection scan modes (Fastscan mode and Normal scan mode) and algorithms to optimize recipes on STARlight. Economically and practically, it is important for wafer fabs to optimize mask inspection recipes and improve throughput in order to extend the capacity of mask inspections without additional equipment investment. The Fastscan mode has the capability to move reticle stage as fast as twice of the Normal scan mode in x-direction resulting in a substantial saving of inspection time. Even faster stage move causes slightly reduction on the sampling of contamination defects, the overall defect inspection maintains the same quality as the Normal scan mode in terms of early warning of mask re-qualification. During the study we collect and analyze inspection data on two production masks and a standard test mask Orion5B. Based on empirical data collected in the study, the Fastscan inspection mode is able to reduce inspection time approximately 28% to 38% at P150.