Fast three-dimensional simulation of buried EUV mask defect interaction with absorber features - art. no. 67301S

To simulate the interaction of buried defects and absorber features in EUV masks, a full three-dimensional, fast, integrated, simulator based on ray tracing and a thin mask model is presented. This simulator allows rapid assessment of the effects of buried defects on EUV printing. This new simulator, RADICAL (Rapid Absorber Defect Interaction Computation for Advanced Lithography), gives a 450X speed increase compared to FDTD, and matches FDTD within 1.5nm for predicting CD change due to a buried defect. RADICAL consists of three sequential steps: the propagation of the mask illumination down through the absorber pattern, the reflection off the defective multilayer, and the propagation back up through the absorber. A propagated thin mask model is used to model the down/up propagation through the absorber pattern and a ray tracing simulator is used for the multilayer reflection. These simulators are linked together using a Fourier transform to convert the near field output of one simulator step into a set of plane wave inputs for the next.