Observation of Residual-Type Thin Absorber Defect on Extreme Ultraviolet Lithography Mask Using an Extreme Ultraviolet Microscope

A local etching technique using electron beams has been proposed to repair defects on an absorber pattern. In this paper, the effect of pattern contrast over a thin absorber film left on a multilayer was examined. Various residual absorber films on the multilayer were fabricated and examined using an extreme ultraviolet (EUV) microscope employed as an at-wavelength mask pattern inspection tool. As a result, the contrast decreased by 30% in the remaining thickness of 2.9 nm for half-pitch 225 nm features. The EUV microscope proved to be an effective tool for examining the post repair effects.

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