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26 March 2008 Diffraction based overlay metrology for α-carbon applications
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Applications that require overlay measurement between layers separated by absorbing interlayer films (such as α- carbon) pose significant challenges for sub-50nm processes. In this paper scatterometry methods are investigated as an alternative to meet these stringent overlay metrology requirements. In this article, a spectroscopic Diffraction Based Overlay (DBO) measurement technique is used where registration errors are extracted from specially designed diffraction targets. DBO measurements are performed on detailed set of wafers with varying α-carbon (ACL) thicknesses. The correlation in overlay values between wafers with varying ACL thicknesses will be discussed. The total measurement uncertainty (TMU) requirements for these layers are discussed and the DBO TMU results from sub-50nm samples are reviewed.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Chandra Saru Saravanan, Asher Tan, Prasad Dasari, Gary Goelzer, Nigel Smith, Seouk-Hoon Woo, Jang Ho Shin, Hyun Jae Kang, and Ho Chul Kim "Diffraction based overlay metrology for α-carbon applications", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69222W (26 March 2008);

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