Defect Characterization of an Extreme-Ultraviolet Mask Using a Coherent Extreme-Ultraviolet Scatterometry Microscope

On extreme-ultraviolet (EUV) masks, phase structures such as bumps or pits on the substrate or particles buried in the multilayers can form printable defects. Information on the properties of these defects is required for mask repair by defect hiding and compensation methods using the absorber pattern. We have developed a coherent EUV scatterometry microscope (CSM) to observe EUV masks, which uses a simple lensless system to record a diffraction image from mask patterns. We introduce preliminary observation results for programmed phase defects. We evaluated the defect width and height from the diffraction images, and the detection limit of the CSM system reached a width of 220 nm. To characterize small defects, we proposed a micro-CSM system that focused to the illumination onto the defect with a 100 nm diameter. The diffraction image recorded by the micro-CSM system provides raw defect data, which is essential for defect compensation. (C) 2012 The Japan Society of Applied Physics