Mask 3D effects on contact layouts of 1Xnm NAND flash devices

Jongwon Jang; Hyungjeong Jeong; Hyungsoon Yune; Seyoung Oh; Hyunjo Yang; Donggyu Yim

doi:10.1117/12.2011659

12 April 2013 Mask 3D effects on contact layouts of 1Xnm NAND flash devices

Jongwon Jang, Hyungjeong Jeong, Hyungsoon Yune, Seyoung Oh, Hyunjo Yang, Donggyu Yim

Author Affiliations +

Proceedings Volume 8683, Optical Microlithography XXVI; 86831V (2013) https://doi.org/10.1117/12.2011659
Event: SPIE Advanced Lithography, 2013, San Jose, California, United States

Abstract

It is a distinctive feature of the metal contact layout in NAND flash memory devices that there are small-pitch contact patterns and random-pitch contact patterns in one layout. This kind of pitch difference between cell array patterns and isolated single patterns hadn’t had a decisive effect on wafers when the illumination condition is not aggressive. However, the pattern pitch difference has caused various problems including the best focus shift due to extreme illuminations. The common DOF margin of a contact layout is degraded when the best focus depth for each pattern is variable. Mask topography effect is well known for the major cause of best focus shift between contact patterns which have different pitches. The demand for device technology node shrink for production cost reduction has required adoption of hyper NA illumination conditions, and this aggressive illumination made it hard to secure an enough common DOF margin due to the best focus shift. In this work, the best focus shift phenomenon among different-pitch patterns caused by mask 3D effects is studied according to the various illumination conditions. It is found that the more aggressive illumination condition is and the bigger the pitch difference among patterns in one layout is, the bigger the best focus shift become. Also, we suggest the solution for avoiding this DOF margin degradation, which is SRAF optimization.

Citation Download Citation

Jongwon Jang, Hyungjeong Jeong, Hyungsoon Yune, Seyoung Oh, Hyunjo Yang, and Donggyu Yim "Mask 3D effects on contact layouts of 1Xnm NAND flash devices", Proc. SPIE 8683, Optical Microlithography XXVI, 86831V (12 April 2013); https://doi.org/10.1117/12.2011659

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KEYWORDS

SRAF

Optical proximity correction

Photomasks

Metals

Modulation

Scanning electron microscopy

Cadmium sulfide

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