Comparison of fast three-dimensional simulation and actinic inspection for extreme ultraviolet masks with buried defects and absorber features

The printability of buried extreme ultraviolet (EUV) defects near absorber features is studied using aerial images from the actinic inspection tool (AIT) and the fast EUV mask simulation program RADICAL. This work begins by comparing the printability of isolated defects through focus predicted by RADICAL and measured by the AIT. Then, images of defects near features from both simulation and experiment are investigated for different defect sizes and positions through focus. Finally, RADICAL is used to assess the expected defect printability levels in the less in coherent conditions which are expected to be used for production. Defect printability will be investigated as a function of defect size, position, and focus for the small absorber lines critical to 22 nm imaging using a top-hat illumination condition of sigma=0.75. Here, defects as small as 0.8 nm surface height cause a critical dimension (CD) change greater than 10% at best focus when located in the worst case position. Defects as small as 2.2 nm cause a CD change greater than 10% even when located under the center of the absorber.