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Proceedings Paper

Effects of reticle birefringence on 193-nm lithography
Author(s): Scott Light; Irina Tsyba; Christopher Petz; Pary Baluswamy; Brett Rolfson
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Paper Abstract

Unpolarized light has traditionally been used for photolithography. However, polarized light can improve contrast and exposure latitudes at high numerical aperture (NA), especially for immersion lithography with an NA > 1.0. As polarized light passes through a reticle, any birefringence (BR) in the reticle material can cause a change in the orientation or degree of polarization, reducing the contrast in the final resist image. This paper shows the effects of reticle BR on dry and immersion imaging for 193nm lithography. The BR magnitude and orientation of the fast axis were mapped across several unpatterned mask blanks, covering a range of BR from 0 to 10 nm/cm. These reticles were printed with a series of open areas surrounded by test structures. The BR was measured again on the patterned reticles, and several locations were selected to cover a range of magnitudes at different orientations of the fast axis. Dry and immersion imaging were evaluated, looking at BR effects on dense lines and contact structures. Mask error enhancement factor (MEEF), line edge roughness (LER), and dose and focus latitudes were studied on line/space patterns. Dose and focus latitudes and 2-D effects were studied on contact patterns. Based upon these results, the effect of reticle BR on CD is minimal, even for BR values up to 10 nm/cm.

Paper Details

Date Published: 26 March 2007
PDF: 12 pages
Proc. SPIE 6520, Optical Microlithography XX, 65201K (26 March 2007); doi: 10.1117/12.712251
Show Author Affiliations
Scott Light, Micron Technology, Inc. (United States)
Irina Tsyba, Micron Technology, Inc. (United States)
Christopher Petz, Univ. of Washington (United States)
Pary Baluswamy, Micron Technology, Inc. (United States)
Brett Rolfson, Micron Technology, Inc. (United States)

Published in SPIE Proceedings Vol. 6520:
Optical Microlithography XX
Donis G. Flagello, Editor(s)

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