14 June 1999 Resist-profile-dependent photobias and in-line DICD control strategy
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In-line DICD control is universally used in wafer fabs to ensure on-target FICD and to monitor process fluctuation. However, how to set up an optimal DICD target sometimes becomes ambiguous as the device dimension shrinks and various photo- and etch-bias begin to emerge. In this paper, we have investigated the root cause of photo-bias and found that for i-line resist with pattern dimension smaller than 0.45 micrometers , the so-called photo bias is largely caused by resist profile change. From resist cross section pictures we verify that the in-line DICD measurement usually deviates from the resist bottom CD and the deviation is resist profile dependent. Based on this understanding, we present an in-line DICD control strategy that is more efficient in terms of resist process characterization and requires no CD- SEM measurement algorithm change.
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Chung Yih Lee, Thian Teck Ong, Ma Wei Wen, Alex Tsun-Lung Cheng, Lin Yih Shung, "Resist-profile-dependent photobias and in-line DICD control strategy", Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); doi: 10.1117/12.350785; https://doi.org/10.1117/12.350785

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