RADICAL has been applied to many important issues in EUV lithography. But, RADICAL’s modular design allows the re-use of multilayer simulation results so subsequent simulations of different patterns over the same defect geometry take a small fraction of the time of the first simulation. RADICAL is typically about 1,000 times faster than FDTD for a single simulation of a two-dimensional absorber pattern. This accuracy is acceptable because the EUV defects expected in production lithography are expected be 2nm tall or less. It matches actinic inspection results, within the error of the experiment, for defects up to 6.5nm tall on the surface. RADICAL matches the critical dimension (CD) predicted by FDTD within 1nm for defects up to 2.5nm tall on the multilayer surface. The accuracy and speed of RADICAL has been verified by comparisons with rigorous finite difference time domain (FDTD) simulations, rigorous waveguide method simulations, and actinic inspection experiments provided by Lawrence Berkeley National Laboratory (LBNL) and Intel. The multilayer and absorber simulation results are linked by a Fourier transform which converts the electric field output by one simulator into a set of plane waves for the next. RADICAL achieves this performance by using simulation and modeling methods designed specifically for the individual EUV mask components, the absorber and multilayer, simulated.
This dissertation describes the development and application of a new simulator, RADICAL, which can accurately simulate the electromagnetic interaction in extreme ultraviolet (EUV) lithography at a wavelength of 13.5nm between the mask absorber features and a buried multilayer defect three orders of magnitude faster than rigorous methods.
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