18 April 2013 DCM: device correlated metrology for overlay measurements
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One of the main issues with overlay error metrology accuracy is the bias between results based on overlay (OVL) targets and actual device overlay error. In this study, we introduce the concept of Device Correlated Metrology (DCM), which is a systematic approach to quantifying and overcoming the bias between target-based overlay results and device overlay issues. For systematically quantifying the bias components between target and device, we introduce a new hybrid target integrating an optical OVL target with a device mimicking CD-SEM (Critical Dimension – Scanning Electron Microscope) target. The hybrid OVL target is designed to accurately represent the process influence found on the real device. In the general case, the CD-SEM can measure the bias between target and device on the same layer at AEI (After Etch Inspection) for all layers, the OVL between layers at AEI for most cases and at ADI (After Develop Inspection) for limited cases such as DPL (Double Patterning Lithography). The results shown demonstrate that for the new process compatible hybrid targets the bias between target and device is small, of the order of CD-SEM measurement uncertainty. Direct OVL measurements by CD-SEM show excellent correlation with optical OVL measurements in certain conditions. This correlation helps verify the accuracy of the optical measurement results and is applicable for imaging based OVL metrology methods using AIM or AIMid OVL targets, and scatterometry-based overlay methods such as SCOL (Scatterometry OVL). Future plans include broadening the hybrid target design to better mimic each layer’s process conditions such as pattern density. We are also designing hybrid targets for memory devices.
© (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Charlie Chen, Charlie Chen, George K. C. Huang, George K. C. Huang, Yuan Chi Pai, Yuan Chi Pai, Jimmy C. H. Wu, Jimmy C. H. Wu, Yu Wei Cheng, Yu Wei Cheng, Simon C. C. Hsu, Simon C. C. Hsu, Chun Chi Yu, Chun Chi Yu, Nuriel Amir, Nuriel Amir, Dongsub Choi, Dongsub Choi, Tal Itzkovich, Tal Itzkovich, Inna Tarshish-Shapir, Inna Tarshish-Shapir, David C. Tien, David C. Tien, Eros Huang, Eros Huang, Kelly T. L. Kuo, Kelly T. L. Kuo, Takeshi Kato, Takeshi Kato, Osamu Inoue, Osamu Inoue, Hiroki Kawada, Hiroki Kawada, Yutaka Okagawa, Yutaka Okagawa, Luis Huang, Luis Huang, Matthew Hsu, Matthew Hsu, Amei Su, Amei Su, } "DCM: device correlated metrology for overlay measurements", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86812R (18 April 2013); doi: 10.1117/12.2011363; https://doi.org/10.1117/12.2011363

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