Measurement sensitivity of DUV scatterfield microscopy parameterized with partial coherence for duty ratio-varied periodic nanofeatures

The deep ultraviolet (DUV) scatterfield imaging microscopy technique enables accurate dimensional measurements of periodic nanostructures with sub-nanometer sensitivity to support semiconductor device manufacturing. A parametric sensitivity analysis for targets with uneven duty ratios is essential as the duty ratios of many periodic nanostructures vary in practice. This paper presents an experimental implementation to optimize illumination conditions for nanoscale multi-line targets on a Molybdenum Silicide (MoSi) photomask with duty ratios of 0.43 to 0.68 using a scatterfield imaging microscope with 193 nm wavelength laser designed for angle-resolved illumination at the sample. Measurement sensitivities are analyzed using sensitivity coefficient maps parameterized by partial coherence factor, duty ratio of the target, and incident polarization.