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23 March 2011 Overcome the process limitation by using inverse lithography technology with assist feature
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Patterning of contact hole using KrF lithography system for the sub 90nm technology node is one of the most challenging tasks. Contact hole pattern can be printed using Off-Axis Illumination(OAI) such as dipole or Quasar or Quadrupole at KrF lithography system. However this condition usually offer poor image contrast and poor Depth Of Focus(DOF), especially isolated contact hole. Sub-resolution assist features (SRAF) have been shown to provide significant process window enhancement and across chip CD variation reduction. The insertion of SRAF in a contact design is mostly done using rule based scripting. However the rule based SRAF strategy that has been followed historically is not always able to increase the process window of these 'forbidden pitches' sufficiently to allow sustainable manufacturing. Especially in case of random contact hole, rule-based SRAF placement is almost impossible task. We have used an inverse lithography technique to treat random contact hole. In this paper we proved the impact of SRAF configuration. Inverse lithography technique was successfully used to treat random contact holes. 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. As a conclusion, we suggest methodology to set up optimum SRAF configuration with rule and inverse lithography technology.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yeon-Ah Shim, Sungho Jun, Jaeyoung Choi, Kwangseon Choi, Jae-won Han, Kechang Wang, John McCarthy, Guangming Xiao, Grace Dai, DongHwan Son, Xin Zhou, Tom Cecil, David Kim, and Ki-Ho Baik "Overcome the process limitation by using inverse lithography technology with assist feature", Proc. SPIE 7973, Optical Microlithography XXIV, 79732S (23 March 2011);

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