A high-resolution contamination-mode inspection method providing a complete solution to the inspection challenges for advanced photomasks

High-resolution contamination inspection for advanced reticles remains crucial in light of the increasing trend of progressive defects such as crystal growth, etc., introduced with DUV lithography, especially for low k1 processes. In most fab environments, routine incoming and re-qualification inspections for photomasks have been implemented. Although this high-resolution inspection provides required high-sensitivity, it often introduces inspection challenges on advanced photomasks. Aggressive OPCs and dense primary and secondary geometries are some of the many factors that can result in false-defect problems for the inspection systems, and results in inspection desensitization. As an effort to identify a methodology that provides inspectability while maintaining the necessary high-sensitivity, we characterized a new combination-mode inspection method. This technical paper will list the details of this special contamination inspection technique that will allow users to maintain the same high inspection throughput while providing similar or higher resolution inspection for these advanced reticles with superior inspectability.