16 July 2002 Overlay excursion monitoring using SEM image
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More than decades the optical overlay metrology system is still using for the measurement. However, many results are reported on the subject of the mismatch between optical overlay measurement form overlay mark and real pattern registration that is caused by lens aberration, mask registration, dynamic distortion on chip level and wafer induced shift of overlay tool on wafer level. Therefore there are lots of report to investigate and resolve this gap. In this report, we study the measurement of overlay related value with slant measurement on real pattern. After etch a real pattern could be used for the overlay check at specific steps so that the registration excursion is checked using high resolution SEM image. Even though the slant value is not enough to obtain whole vector of overlay it is enough to check the overlay excursion along with critical direction. Also with specific structure the exact overlay can be measured and it is comparable with optical overlay value. Using this structure the Across Field Overlay Variation is successfully measured. The precision of the measurement is achieved same level of R and T on CD measurement. However there are still some limitations to be optimized on the algorithm because that is designed for the single contact-hole analysis to check the contact profile.
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Jeong-Ho Yeo, Jeong-Ho Yeo, Kyoung Mo Yang, Kyoung Mo Yang, Jung Soo Kim, Jung Soo Kim, Young S. Kang, Young S. Kang, } "Overlay excursion monitoring using SEM image", Proc. SPIE 4689, Metrology, Inspection, and Process Control for Microlithography XVI, (16 July 2002); doi: 10.1117/12.473413; https://doi.org/10.1117/12.473413

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