4 April 2008 Physical matching of CD-SEM: noise analysis and verification in FAB environment
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Abstract
CD-SEMs fleet matching is a widely discussed subject and various approaches and procedures to determine it were described in the literature [1,2,4-6]. The different approaches for matching are all based on statistical treatment of CD measurements that are performed on dedicated test structures. The test structures are a limited finite set of features, thus the matching results should be treated as valid only for the specific defined set of test features. The credibility of the matching should be in question for different layers and specifically production layers. Since matching is crucial for reliable process monitoring by a fleet of CD-SEMs, the current matching approaches must be extended so that the matching will be only tool dependent and reproducible on all layers regardless their specific material or topographic characteristics. In our previous work [1] the new approach named "Physical Matching" was introduced and a new matching procedure based on the direct estimation of tool physical parameters was described. This approach extends the conventional matching methods to enable significant improvement of the matching between CD-SEM tools in production environment. In this work we present results of applying the physical matching method in FAB environment by using the physical parameters of the brightness and SNR, extend it to noise frequency domain characteristics monitoring, and enhanced collection uniformity. Improving the collection uniformity is also demonstrated and proved to be a significant factor. The advantage of the physical matching with noise spectra analysis approach for a case study is demonstrated. This method will enable detection of specific reasons for mismatching between the tools, based on analysis of specific frequencies that are resulted from known mechanical/electrical noise. The proposed procedure allows tool problems fixing before CD measurements are affected. In order to get a reliable visualization of the difference between two systems, new automatic and manual tool finger print methods were developed. The application of the proposed approach to vendor to vendor matching problem is considered.
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Uwe Kramer, Uwe Kramer, Alessandra Navarra, Alessandra Navarra, Goeran Fleischer, Goeran Fleischer, Jan Kaiser, Jan Kaiser, Frank Voss, Frank Voss, Galit Zuckerman, Galit Zuckerman, Roman Kris, Roman Kris, Igal Ben-Dayan, Igal Ben-Dayan, Elad Sommer, Elad Sommer, Amir Len, Amir Len, Shalev Dror, Shalev Dror, Dirk Schöne, Dirk Schöne, Stefano Ventola, Stefano Ventola, } "Physical matching of CD-SEM: noise analysis and verification in FAB environment", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69221R (4 April 2008); doi: 10.1117/12.776865; https://doi.org/10.1117/12.776865
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