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Proceedings Paper

Single-exposure general vortex phase-shift mask for contact hole
Author(s): Yong Liu; Dun Liu; James Hu
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Paper Abstract

Vortex phase-shift mask had been shown to have excellent image quality by Marc Levenson et al. [1, 2]. However, its application has been restricted to uniform contact-hole arrays and non-uniform contact holes on uniform grid requiring double exposure technique. In this paper, we show that random contact holes in a real layout can be imaged using vortex phase shift mask, with a single exposure. We use a DRAM contact-hole layout as an example. At minimum half-pitch size of 80nm (k1=0.28) and pitch of 160nm, using 193nm stepper with 0.68 numerical aperture and 0.3 degrees of partial coherence, we are able to achieve 0.4um DOF with 10% exposure latitude. The possibility of using a single exposure and low NA stepper should far outweigh the increased cost of vortex mask for high volume products. In comparison, the corresponding alternating phase-shift mask, however, can only achieve 0.2um DOF at 10% exposure latitude, even with the aid of higher numerical aperture of 0.90 and high degrees of partial coherence of 0.15. For non-uniform contact holes, image asymmetry is an issue. We show OPC-corrected images that are substantially symmetrical. Phase error is always a concern for any phase-shift mask. We show that substantial process windows remain even in the presence of phase errors. Furthermore, we demonstrate that random contact-hole layout can be successfully phase-shifted using vortex phase-shift method. Finally, we shall that the same phase-shift mask design technology for vortex mask can be applied to double line-space phase-shift mask method [3].

Paper Details

Date Published: 6 December 2004
PDF: 9 pages
Proc. SPIE 5567, 24th Annual BACUS Symposium on Photomask Technology, (6 December 2004); doi: 10.1117/12.567874
Show Author Affiliations
Yong Liu, Third Dimension Design, Inc. (United States)
Dun Liu, Third Dimension Design, Inc. (United States)
James Hu, Third Dimension Design, Inc. (United States)


Published in SPIE Proceedings Vol. 5567:
24th Annual BACUS Symposium on Photomask Technology
Wolfgang Staud; J. Tracy Weed, Editor(s)

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