Real-time aerial-images-based mask inspection, die-to-wafer image inspection

The concept of defect printability, i.e., mask error enhancement factor (MEEF), should be integrated into mask defect inspection procedures, and thus avoid the huge burden of defect detection algorithm development. It is necessary to simplify the difficult task of defining defect size which is caused by nonlinear transfer of killer defects, and which is strongly dependent on defect types. One solution to the problem is to incorporate defect printability study using aerial image based inspection into the existing mask inspection system. This paper shows how the measured mask pattern images obtained from mask inspection system are transformed into wafer-like images by simulation-based software. It is important that wafer-like images (WI) from measured mask images are created within a reasonable calculation time and the result has sufficient accuracy. The paper also introduces calculation of aerial images using perturbation approach and demonstrates the possibility of D-to-WI inspection. The paper points out that the technique of generating wafer-like image from measured mask pattern is well established for attenuated PSMs and Cr binary masks.