Application of the transport of intensity equation to EUV multilayer defect analysis

This paper proposes a new method for the characterization of multilayer defects of EUV masks. The method uses measured or simulated EUV projection images at different focus positions. The Transport of Intensity Equation (TIE) is applied to retrieve the phase distribution of the reected light in the vicinity of the defect. An Artificial Neural Network (ANN) is applied to correlate the optical properties of the intensity and recovered phase of the defect with the defect geometry parameters and to reconstruct the defect geometry parameters from though-focus-images of unknown defects.