Single-exposure general vortex phase-shift mask for contact hole

Yong Liu; Dun Liu; James Hu

doi:10.1117/12.567874

6 December 2004 Single-exposure general vortex phase-shift mask for contact hole

Yong Liu, Dun Liu, James Hu

Proceedings Volume 5567, 24th Annual BACUS Symposium on Photomask Technology; (2004) https://doi.org/10.1117/12.567874
Event: Photomask Technology, 2004, Monterey, California, United States

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].

Citation Download Citation

Yong Liu, Dun Liu, and James Hu "Single-exposure general vortex phase-shift mask for contact hole", Proc. SPIE 5567, 24th Annual BACUS Symposium on Photomask Technology, (6 December 2004); https://doi.org/10.1117/12.567874

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