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Proceedings Paper

SRAF enhancement using inverse lithography for 32nm hole patterning and beyond
Author(s): V. Farys; F. Chaoui; J. Entradas; F. Robert; O. Toublan; Y. Trouiller
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Paper Abstract

At 32 nm node and beyond, one of the most critical processes is the holes patterning due to the Depth of Focus (DOF) that becomes rapidly limited. Thus the use of Sub Resolution Assist Features (SRAF) becomes mandatory to keep DOF at a sufficient level through pitch. SRAF are generally generated using Rule Based OPC with a different cleaning step to avoid risk of SRAF printing or conflict with main feature. One of the key challenges of using such a technique is the ability of placing SRAF in random holes features. The rule based approach cannot treat all the configurations resulting in non-optimal SRAF placement for certain main feature. On the other hand, Inverse Lithography has shown the ability of generating SRAF at the ideal size and position (theoretically) 1 and interest of this technique has been proven experimentally 2,3. Nevertheless, this kind of technique is not yet ready for maskshop due to MRC limitation caused by the pixelated SRAF output, and the important mask writing time due to the shotcount 4. In this paper we propose to make a comparison of the two approaches on random 2D features. We will see that Inverse Lithography permits to keep a sufficient DOF on 2D features configurations where Rule based appears to be limited. Simulated and experimental results will be presented comparing Rule based, Ideal and MRC constraint SRAF in terms of DOF and Runtime performance for hole patterning

Paper Details

Date Published: 30 September 2009
PDF: 8 pages
Proc. SPIE 7488, Photomask Technology 2009, 748813 (30 September 2009); doi: 10.1117/12.829894
Show Author Affiliations
V. Farys, STMicroelectronics (France)
F. Chaoui, Mentor Graphics (France)
J. Entradas, Mentor Graphics (France)
F. Robert, STMicroelectronics (France)
O. Toublan, Mentor Graphics (France)
Y. Trouiller, CEA-Leti (France)

Published in SPIE Proceedings Vol. 7488:
Photomask Technology 2009
Larry S. Zurbrick; M. Warren Montgomery, Editor(s)

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