Physical matching versus CD matching for CD SEM

Roman Kris; Galit Zuckerman; Elad Sommer; Zion Hadad; Shalev Dror; Aviram Tam; Naftali Shcolnik

doi:10.1117/12.711768

12 April 2007 Physical matching versus CD matching for CD SEM

Roman Kris, Galit Zuckerman, Elad Sommer, Zion Hadad, Shalev Dror, Aviram Tam, Naftali Shcolnik

Proceedings Volume 6518, Metrology, Inspection, and Process Control for Microlithography XXI; 65180O (2007) https://doi.org/10.1117/12.711768
Event: SPIE Advanced Lithography, 2007, San Jose, California, United States

Abstract

CD-SEMs fleet matching is a widely discussed subject and various approaches and procedures to determine it were described in the literature. The different approaches for matching are all based on statistical treatment of regular 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 (such as TMU) 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 this work the term "Physical Matching" is introduced and a new matching procedure based on physical parameters is described. This approach extends the conventional matching methods to enable significant improvement of the matching between CD-SEM tools in production environment. To study and demonstrate the physical matching, we focus on the limited parameters set - the image brightness and Signal/Noise ratio(SNR). We test the sensitivity of CD measurements to changes in these parameters both on different test layers - Etch and Litho. We show that sensitivity of CD based measurements is low and reasonable change of the image brightness or SNR has small effect. The advantage of the physical matching approach for case study is demonstrated. The improved matching procedures are based on new targets that are used to measure the above image parameters directly. This way it is possible to characterize correctly the physical state of the measurement tool and guarantee the same image characteristics which in turn guarantee improved matching on all layers. In the framework of the proposed matching approach a proper determination of the minimal set of physical parameters that is needed to guarantee CD-SEM tools stability and matching should be included.

Citation Download Citation

Roman Kris, Galit Zuckerman, Elad Sommer, Zion Hadad, Shalev Dror, Aviram Tam, and Naftali Shcolnik "Physical matching versus CD matching for CD SEM", Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 65180O (12 April 2007); https://doi.org/10.1117/12.711768

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KEYWORDS

Signal to noise ratio

Scanning electron microscopy

Sensors

Interference (communication)

Critical dimension metrology

Target detection

Image acquisition

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