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10 April 2013 Characterization of a 'first measurement effect' in CD-SEM measurement
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As semiconductor industry moves towards advanced technology node, requirement for tighter Critical Dimension (CD) control constantly raises the bar for CD metrology. Yet despite various intrinsic bias origins, CD-SEM is still serving as the workhorse and ‘go to’ metrology mean for inline CD control in modern IC fabrication day in and day out. Such confidence comes from extensive studies around the underlying physics of SEM as major bias types are all marked as 'accountable' and some even 'predictable' nowadays. Still there are times when unexpected metrology results slip through with no obvious trace leading to any well established theories. And it is none the less necessary and challenging to single out the root cause from the complex physics models. Such a case is presented in this work. A reproducible CD diving behavior on the scale of 0.4~0.8nm during the very first one or two measurements by SEM on Poly-Si sample is described and verified. Various experiments are conducted to identify the physical origin. We propose that this ‘first measurement effect (FME)’ is related to SEM proximity shadowing and e-beam seasoning on pattern sidewall material.
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Boxiu Cai, Yi-Shih Lin, Qiang Wu, Yi Huang, Siyuan Yang, Wen-Hui Li, and Michael Hao "Characterization of a 'first measurement effect' in CD-SEM measurement", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 868131 (10 April 2013);


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