Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences


UC Berkeley


2010 Research Summary

Fast 3D Simulation and Compensation for Buried Defects in Extreme Ultraviolet Masks with Absorber Features (RADICAL)

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Chris H. Clifford and Andrew R. Neureuther


Extreme Ultraviolet (EUV) lithography is a leading candidate for next generation integrated circuit manufacturing. EUV lithography represents a major change from current methods and significant development is still needed for it to be implemented successfully.

A new simulator, RADICAL (Rapid Absorber Defect Interaction Computation for Advanced Lithography) has been created that can simulate a 3D EUV mask with a buried defect 400 times faster than rigorous electromagnetic methods while still maintaining comparable accuracy. RADICAL simulates the multilayer stack and absorber pattern separately, using methods optimal for each. It links the results of the two simulators using Fourier optics. RADICAL allows multiple simulations to be done very quickly, which opens up new research opportunities.

One new area of research is to leverage RADICAL to develop compensation methods for EUV defects. Once compensation techniques are developed and tested using RADICAL, masks with a large buried defects will made useful by modifying only the absorber pattern to compensate for the defect. This will be a very inexpensive solution to the problem of buried defects in EUV lithography.

Figure 1
Figure 1: Example cross-section geometry of an EUV mask with a buried multilayer defect

Figure 2
Figure 2: Block diagram representing the operation of RADICAL

C. H. Clifford, et al. “Comparison of fast three-dimensional simulation and actinic inspection for extreme ultraviolet masks with buried defects and absorber features,” J. Vac. Sci. Technol. B Volume 27, Issue 6, (2009)
C. H. Clifford, A. R. Neureuther, “Fast simulation methods and modeling for extreme ultraviolet masks with buried defects”, J. Micro/Nanolith. MEMS MOEMS 8, 031402 (2009)