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23 March 2009 Through-focus scanning and scatterfield optical methods for advanced overlay target analysis
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In this paper we present overlay measurement techniques that use small overlay targets for advanced semiconductor applications. We employ two different optical methods to measure overlay using modified conventional optical microscope platforms. They are scatterfield and through-focus scanning optical microscope (TSOM) imaging methods. In the TSOM method a target is scanned through the focus of an optical microscope, simultaneously acquiring optical images at different focal positions. The TSOM images are constructed using the through-focus optical images. Overlay analysis is then performed using the TSOM images. In the scatterfield method, a small aperture is scanned at the conjugate back focal plane of an optical microscope. This enables angle-resolved scatterometry on a high-magnification optical platform. We also present evaluation of optical constants using the scatterfield method.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ravikiran Attota, Michael Stocker, Richard Silver, Alan Heckert, Hui Zhou, Richard Kasica, Lei Chen, Ronald Dixson, George Orji, Bryan Barnes, and Peter Lipscomb "Through-focus scanning and scatterfield optical methods for advanced overlay target analysis", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 727214 (23 March 2009);

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