Profile reconstruction of a local defect in a groove structure and the theoretical limit under the vector diffraction theory.

Abstract

The profile of a fine local defect in a periodic surface relief structure is reconstructed from a scattered wave. This defect cannot be imaged with an optical imaging system owing to the diffraction limit, and complicated multiscattering among the high-aspect-ratio grooves and the defect makes it difficult to reconstruct the profile using the scalar diffraction theory. We propose and numerically demonstrate a reconstruction algorithm by applying an efficient vector analysis method-the difference-field boundary element method. We also classify the profile according to the difficulty of reconstruction, which depends on the observation system and the noise level. Finally, this analysis provides the accuracy and limit of reconstruction under the vector diffraction theory.