To support the successful implementation of extreme ultraviolet ͑EUV͒ lithography for high volume manufacturing, a spectrum of simulation tools is needed. For investigation of new materials and geometries, rigorous but computationally expensive simulations are required. For faster simulations, a new method, rapid absorber defect interaction computation for advanced lithography ͑RADICAL͒, is introduced. RADICAL is a modular program, that uses separate methods to simulate the absorber pattern and defective multilayer. Two different methods are used to simulate the multilayer within RADICAL: ray tracing and single surface approximation ͑SSA͒. Ray tracing can accurately simulate arbitrary multilayer geometries. SSA is only accurate for defects shorter than 4.5 nm on the multilayer surface. With ray tracing, RADICAL is nearly 1000 times faster than finite difference time domain ͑FDTD͒ for simulating line-space patterns over buried defects. RADICAL with SSA is nearly 25,000 times faster than FDTD. The accuracy of RADICAL is shown to be excellent for simulating defects in focus, and for simulating defects smaller than 2.5 nm through focus. The error can be as high as 4 nm in predicting CD change for larger defects out of focus due to the complexities of modeling the phase of buried defects. But this error is predictable and will likely be acceptable for most applications considering the huge speed advantages of RADICAL.A spectrum of simulation and modeling technology computer-aided design ͑CAD͒ tools is needed to successfully implement high volume extreme ultraviolet ͑EUV͒ lithography due to the interactions of buried nonplanar multilayer defects with patterned features. Buried defects in EUV masks are one of the main hurdles in the development of EUV lithography. 1 It is possible that defect-free mask blanks will never be available at a reasonable cost, so defect compensation may be necessary. 2 An example geometry that shows the complexity of a defective multilayer structure is shown in Fig. 1. The defect is on the substrate below the multilayer. The multilayer is grown on top of the defect, burying the defect, using the smoothing model described in Ref. 3. The absorber pattern sits on top of the multilayer. A defect buried in the multilayer affects the deposition of layers above it, which reduces the magnitude and disrupts the phase of reflected light.A detailed understanding of the quantitative scattering within a resonant nonplanar layer, mask diffraction of incident and reflected waves, and reduction of these phenomena by compensation of layouts will all be needed. This will require a spectrum of simulation methods ranging from rigorous detailed point-by-point analysis of electromagnetic simulation of scattering within and among structures, as well as more approximate aggregate methods with sufficient speed to support real-time quantitative design decisions. HistoryThe history of defective EUV mask simulation is extensive and has included several methods, like the ones presented in this work, to accelerate the sim...

A new fast-CAD imaging model for buried extreme ultra violet (EUV) mask defects is presented that exploits the smoothing process used to mitigate buried EUV multilayer defects. Since the characteristics of the smoothing process dictate nearly identical surface shapes for all defects a single parameter, the peak height of the final profile, is sufficient to predict the projection printed image for an arbitrary buried defect. Data is presented on the effect of smoothing on the reflected field and final wafer image. The degree of similarity among defects with different initial heights, widths and shapes is explored. A compact algebraic model to predict the aerial image dip strength is developed that depends only on the surface height of the EUV mask blank. This model is then integrated into a standard perturbation model for defect feature interaction, and the importance of accounting for absorber features shadowing of buried defects is demonstrated.

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