20 October 2006 CD and profile metrology of EUV masks using scatterometry based optical digital profilometry
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Abstract
Research and development efforts on EUV technology for the 32 nm node and beyond are progressing rapidly. Although a big concern is defect control on EUV mask blanks, control of linewidth and profile will be an important factor in acceptance of EUV technology. In this paper, we discuss the issues and strategies surrounding CD and profile metrology of EUV masks. EUV mask blanks from Hoya and Asahi Glass Company were used in this study, and were measured on a Nanometrics Atlas-M measurement tool, generating CD and profile results using Timbre Technologies' ODP analysis software. The Atlas-M tool has dual optics, enabling use of either normal incidence Reflectometry or oblique incidence Ellipsometry, either of which may be used for Scatterometry. The relative merits of each of these technologies are discussed. The complex EUV stack presents numerous challenges for metrology; the critical task is to accurately measure the optical constants of the numerous layers in the stack. The multilayer MoSi stack is effectively modeled as a single layer for optical constants determination. Photoresist FEP171 was used for the patterning, and the CD and profile of the resist were measured, after which the absorber layer was etched. Parameters characterized in this study include photoresist CD and height, etched Absorber CD, and capping layer over etch. Correlation to top-down CD-SEM, cross-sectional SEM, and AFM is reported. No charging or other deformation was observed on the EUV masks. The data show that ODP Scatterometry provides a non-destructive method for monitoring resist CD and profile, as well as etched structure CD and over/underetch on EUV masks.
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Sung-yong Cho, Sung-yong Cho, Sanjay Yedur, Sanjay Yedur, Michael Kwon, Michael Kwon, Milad Tabet, Milad Tabet, } "CD and profile metrology of EUV masks using scatterometry based optical digital profilometry", Proc. SPIE 6349, Photomask Technology 2006, 63492I (20 October 2006); doi: 10.1117/12.686478; https://doi.org/10.1117/12.686478
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