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Proceedings Paper

Evaluation of extendibility for Fourier diffraction theory for topographical mask structure under hyper NA lithography
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Paper Abstract

Recent progress of immersion lithography technique could realize to apply hyper NA condition for real IC device manufacturing. Under the hyper NA lithography, we have to face the paradigm shift from scalar treatment to vector consideration in the region of modeling everywhere. In the historical view points, vector lithographic imaging model was introduced in 19861, and the beginning of 90’s, various evaluation works were reported in the field. And the research or evaluation of topographical mask effects were also focused and concentrated the same era using rigorous electromagnetic simulations2-4. But as for the “oblique illumination effects” at a reticle side, much concerns had not been paid about them. It was because the relaxation of incident angle due to magnification factor (4X or 5X), using small σ for alternating phase-shifting mask, and higher NA seemed to work worse as for decreasing DOF. Since the immersion lithography technique would be considered as “effective reduction of exposure wavelength by factor of the refraction index of immersion material” and superior DOF characteristics to the dry case, development of increasing exposure tool’s NA beyond 1.0 have been accelerated. In such a hyper NA region, we have to consider about the “oblique illumination effects” once again for various fields, such as combining to the model-based OPC application and so on. In this paper, 1st order approximation model is suggested and evaluated how much degree of influence of the oblique illumination effects should be taken care of, and how large area could be covered using this model. The former results denoted that around 10% of target CD might be varied in the case of hyper NA condition. But from the latter results, we did not sufficient validity for this model, so some additional approximation should be considered to improve the prediction accuracy.

Paper Details

Date Published: 12 May 2005
PDF: 11 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.600447
Show Author Affiliations
Satoshi Tanaka, Toshiba Corp. (Japan)
Akiko Mimotogi, Toshiba Corp. (Japan)
Soichi Inoue, Toshiba Corp. (Japan)

Published in SPIE Proceedings Vol. 5754:
Optical Microlithography XVIII
Bruce W. Smith, Editor(s)

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