16 April 2008 Further study on the verification of CD-SEM based monitoring for hyper NA lithography
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In our previous paper*[1], next generation lithography offering improved resolution by use of Hyper-NA and Low-k1, changes in exposure tool focus were seen to influence pattern shape and it was verified that pattern profile variation occurs even when measured CD values are similar. This shows the necessity for process control to include pattern shape information, conventional methods using the CD value alone will be insufficient as process latitudes continue to shrink. In such a situation, to be able to precisely measure the physical dimensions of design features becomes more and more important. In this study, we have investigated improved precision of Process Window (PW) determination by using the MPPC function that allows the pattern profile shape to be quantified. We have also evaluated pattern shape variation by means of Litho-simulation. As a result, it was confirmed that resist loss is the main change in shape that occurs. Therefore, we have focused our attention on resist loss and optimized the MPPC parameters by SEM simulation*[2]. As a consequence, it was possible to precisely detect the resist loss. Using this technique, it was possible to show the possibility for highly precise 3D measurement determination, for use in exposure tool monitoring, by using the MPPC measurement technique.
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T. Ishimoto, T. Ishimoto, M. Osaki, M. Osaki, K. Sekiguchi, K. Sekiguchi, N. Hasegawa, N. Hasegawa, K. Watanabe, K. Watanabe, D. Laidler, D. Laidler, S. Cheng, S. Cheng, } "Further study on the verification of CD-SEM based monitoring for hyper NA lithography", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69222O (16 April 2008); doi: 10.1117/12.771894; https://doi.org/10.1117/12.771894

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