Validity of the thin mask approximation in extreme ultraviolet mask roughness simulations
In the case of extreme ultraviolet (EUV) lithography, modeling has shown that reflector phase roughness on the lithographic mask is a significant concern due to the image plan speckle it causes and the resulting line-edge roughness on imaged features. Modeling results have recently been used to determine the requirements for future production worthy masks yielding the extremely stringent specification of 50 pm rms roughness. Owing to the scale of the problem in terms of memory requirements, past modeling results have all been based on the thin mask approximation. EUV masks, however, are inherently three dimensional in nature and thus the question arises as to the validity of the thin mask approximation. Here we directly compare image plane speckle calculation results using the fast two dimensional thin mask model to rigorous finite-difference time-domain results and find the two methods to be comparable.
- Research Organization:
- Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
- Sponsoring Organization:
- Materials Sciences Division
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1011041
- Report Number(s):
- LBNL-4390E
- Journal Information:
- Applied Optics, Journal Name: Applied Optics; ISSN 0003-6935; ISSN APOPAI
- Country of Publication:
- United States
- Language:
- English
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