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Propagation of surface topography of EUV blank substrate through multilayer and impact of phase defect structure on wafer image

Our recent study reveals that the propagation of a phase defect (PD) from an EUV mask substrate surface through a multilayer does not always propagate in a vertical direction. In this study, to fully understand the propagation model of PDs, two types of defects on a Qz substrate are prepared. One is space patterns fabricated by a mask patterning process followed by an etching giving a cross-sectional angle of 90 degrees. The others are AFM scratched space patterns with their cross-sectional angles as 30 and 60 degrees. After coating, a patterned Qz substrate with a multilayer, propagation of PDs through the multilayer was observed by a TEM. As a result, the TEM images clearly exhibited a tendency that originating from the Qz substrate while the PDs propagated through the multilayer their propagation path was inclined toward the center of the mask. A maximum inclination of this path was found to be 5.9 degrees at a distance of 93 mm away from the mask’s center. The impacts of the inclination angles on the printed images on wafer calculated using a simulator. A phase defect with an inclination angle of one degree corresponded to a positional shift of one nanometer on printed wafer image.