Flare In Extreme Ultraviolet Lithography: Metrology, Out-Of-Band Radiation, Fractal Point-Spread Function, And Flare Map Calibration

The critical role of flare in extreme ultraviolet (EUV) lithography is well known. In this work, the implementation of a robust flare metrology is discussed, and the proposed approach is qualified both in terms of precision and accuracy. The flare measurements are compared to full-chip simulations using a simplified single fractal point-spread function (PSF), and the parameters of the analytical PSF are optimized by comparing the simulation output to the experimental results. After flare map calibration, the matching of simulation and experiment in the flare range from 4 to 12% is quite good, clearly indicating an offset of about 3%. The origin of this offset is attributed to the presence of DUV light. An experimental estimate of the DUV component is found in good agreement with the predicted value. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3238515]