Schematic of the MIRAI EUV mask inspection system which uses an annular Schwarzschild lens to project an image of the illuminated mask area onto an EUV CCD with magnification.
Schematic of the dual-mode Berkeley EUV mask inspection system. In imaging mode it records high magnification mask images projected by a Fresnel zone plate onto an EUV CCD camera. In scanning mode a beam traces a path across the mask surface while separate detectors record the bright field reflectivity and dark field scattered light.
EUV “actinic” inspections of the programed-defect region. (a) MIRAI tool data. (b) Berkeley tool dark field data. Square area corresponds to the measured SRN—figures are individually scaled for each tool. Open squares represent defects below detection threshold. Gray diamonds represent the relative size and location of surface contamination which occurred at some point after the MIRAI inspection shown here. Those dark regions were observed in the bright-field response measured with the Berkeley tool.
Column averages of the measured SNR in the two EUV tools. For each column, the AFM-measured surface width and height of the defects are given in nanometers, along with the spherical-equivalent-volume diameter , also in nanometers. The defect surface shape is indicated with G for Gaussian and TP for truncated pyramid.
Lasertec inspections of the programed-defect region: (a) M1350 and (b) MB266 . The square areas correspond to the “pixel” size of the above-threshold defects. The positions of several native defects are shown as gray diamonds; their pixel size was reported as two to ten times higher than the largest programed defects.
Column averages of the measured pixel size (dashed line) for the defects above detection threshold as detected by the M1350. The capture efficiency (CE) is shown (solid line) for each defect size. Defect dimensions are given in nanometers.
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