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Proceedings Paper

244-nm imaging interferometric lithography test bed
Author(s): Svjatoslav Smolev; A. Biswas; A. Frauenglass; Steven R. J. Brueck
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Paper Abstract

The minimum half-pitch feature accessible by optical lithography is CD = λ/(4NA). For an imaging system, the ultimate resolution does not reach this level as a result of the need to capture the information in the pattern-dependent sidebands around the fundamental frequency; roughly a system with these capabilities should be able to print ~ λ/(3NA) to λ/(3.5NA) half-pitch patterns. Imaging interferometric lithography (IIL), combining low-σ, off-axis illumination (OAI) at the limits of the pupil with pupil-plane filters (PPF), to ensure a uniform frequency-space coverage, and multiple exposures covering different regions of spatial frequency-space, provides an approach to accessing these fundamental, linear-systemsresolution limits with simple binary chrome-on-glass masks without any requirement for either optical proximity correction (OPC) or phase shift masks (PSM). Polarization control is an advantage of IIL, as with other off-axis approaches, that is becoming more important as hyper-NA tools are introduced. Additionally, the PPFs allow for intensity adjustment in the pupil plane, which can further improve the image contrast. A test bed has been assembled at a 244-nm wavelength using a 0.9 NA optical system. For this system, the minimum half-pitch is 68 nm, and the limiting half-pitch for arbitrary features is ~ 70- to 60- nm. Demonstrations of printing arbitrary 113-, 100-, 90- and 86-nm half-pitch patterns are reported. Good imaging was achieved with simple binary chrome-on-glass masks without the use of any additional OPC or PSM. The image improvement by adjusting the contrast of the image with a simple intensity PPF mask is demonstrated. These results scale to the 45-nm half-pitch node for a 193 nm source and a 1.3 NA. The essential point is that robust imaging for a 45-nm half-pitch is available using IIL without any mask-based resolution enhancement techniques.

Paper Details

Date Published: 15 March 2006
PDF: 10 pages
Proc. SPIE 6154, Optical Microlithography XIX, 61542K (15 March 2006); doi: 10.1117/12.656584
Show Author Affiliations
Svjatoslav Smolev, Univ. of New Mexico (United States)
A. Biswas, Univ. of New Mexico (United States)
A. Frauenglass, Univ. of New Mexico (United States)
Steven R. J. Brueck, Univ. of New Mexico (United States)


Published in SPIE Proceedings Vol. 6154:
Optical Microlithography XIX
Donis G. Flagello, Editor(s)

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