Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2005-05-03
2005-05-03
Huff, Mark (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S030000, C430S311000, C430S396000, C716S030000
Reexamination Certificate
active
06887625
ABSTRACT:
In a mask pattern for a device such as a DRAM including a nearly regular array of isolated features, assist features are positioned so as to make the array more symmetric. Where the isolated features are positioned at most but not all of the points of a regular unit cell, the assist features may be positioned at the points of the unit cell not occupied by the isolated features. The isolated features may represent contact holes.
REFERENCES:
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patent: 6001512 (1999-12-01), Tzu et al.
patent: 6074787 (2000-06-01), Takeuchi
Kroyan et al., “Effects of Sub-Resolution Assist Features on Depth of Focus and Uniformity of Contact Windows for 193 nm Lithography, ”Part of the SPIE Conference on Optical Microlithography XII, Santa Clara, CA, Mar. 1999, vol. 3679, pt. 1-2, pp. 630-638.
Peter D. Buck et al., “Phase Shift Mask Applications,” Proceedings of SPIE—The International Society for Optical Engineering, Optical/Laser Microlithography IV, Mar. 6-8, 1991, Coversheet + 9 pages.
Tsuneo Terasawa et al., “Improved resolution of ani-line stepper using a phase-shifting mask,”J. Vac. Sci. Technol B., vol. 8 No. 6 Nov/Dec 1990, pp. 1300-1308.
Yong Liu et al., “Computer Aided Phase Shift Mask Design with Reduced Complexity,” Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, CA 94720, SPIE vol. 1927 Optical/Laser Microlithography VI (1993) pp. 477-493.
Baselmans Johannes Jacobus Matheus
Flagello Donis George
Schluter Markus
Socha Robert John
ASML Netherlands B.V.
Huff Mark
Mohamedulla Saleha
Pillsbury & Winthrop LLP
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