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Proceedings Paper

Patterning of 90nm node flash contact hole with assist feature using KrF
Author(s): Yeonah Shim; Sungho Jun; Jaeyoung Choi; Kwangseon Choi; Jae-won Han; Kechang Wang; John McCarthy; Guangming Xiao; Grace Dai; DongHwan Son; Xin Zhou; Thomas Cecil; David Kim; KiHo Baik
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Paper Abstract

Patterning of contact holes using KrF lithography system is one of the most challenging tasks for the sub-90nm technology node,. Contact hole patterns can be printed with a KrF lithography system using Off-Axis Illumination (OAI) such as Quasar or Quadrupole. However, such a source usually offers poor image contrast and poor depth of focus (DOF), especially for isolated contact holes. In addition to image contrast and DOF, circularity of hole shape is also an important parameter for device performance. Sub-resolution assist features (SRAF) can be used to improve the image contrast, DOF and circularity for isolated contact holes. Application of SRAFs, modifies the intensity profile of isolated features to be more like dense ones, improving the focal response of the isolated feature. The insertion of SRAFs in a contact design is most commonly done using rule-based scripting, where the initial rules for configuring the SRAFs are derived using a simulation tool to determining the distance of assist features to main feature, and the size and number of assist features to be used.. However in the case of random contact holes, rule-based SRAF placement is a nearly impossible task. To address this problem, an inverse lithography technique was successfully used to treat random contact holes. The impact of SRAF configuration on pattern profile, especially circularity and process margin, is demonstrated. It is also shown that the experimental data are easily predicted by calibrating aerial image simulation results. Finally, a methodology for optimizing SRAF rules using inverse lithography technology is described.

Paper Details

Date Published: 23 September 2009
PDF: 8 pages
Proc. SPIE 7488, Photomask Technology 2009, 748837 (23 September 2009); doi: 10.1117/12.833499
Show Author Affiliations
Yeonah Shim, Dongbu HiTek Co., Ltd. (Korea, Republic of)
Sungho Jun, Dongbu HiTek Co., Ltd. (Korea, Republic of)
Jaeyoung Choi, Dongbu HiTek Co., Ltd. (Korea, Republic of)
Kwangseon Choi, Dongbu HiTek Co., Ltd. (Korea, Republic of)
Jae-won Han, Dongbu HiTek Co., Ltd. (Korea, Republic of)
Kechang Wang, Luminescent Technologies, Inc. (United States)
John McCarthy, Luminescent Technologies, Inc. (United States)
Guangming Xiao, Luminescent Technologies, Inc. (United States)
Grace Dai, Luminescent Technologies, Inc. (United States)
DongHwan Son, Luminescent Technologies, Inc. (United States)
Xin Zhou, Luminescent Technologies, Inc. (United States)
Thomas Cecil, Luminescent Technologies, Inc. (United States)
David Kim, Luminescent Technologies, Inc. (United States)
KiHo Baik, Luminescent Technologies, Inc. (United States)


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

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