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19 October 2017 Evaluating the effects of modeling errors for isolated finite three-dimensional targets
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Optical three-dimensional (3-D) nanostructure metrology utilizes a model-based metrology approach to determine critical dimensions (CDs) that are well below the inspection wavelength. Our project at the National Institute of Standards and Technology is evaluating how to attain key CD and shape parameters from engineered in-die capable metrology targets. More specifically, the quantities of interest are determined by varying the input parameters for a physical model until the simulations agree with the actual measurements within acceptable error bounds. As in most applications, establishing a reasonable balance between model accuracy and time efficiency is a complicated task. A well-established simplification is to model the intrinsically finite 3-D nanostructures as either periodic or infinite in one direction, reducing the computationally expensive 3-D simulations to usually less complex two-dimensional (2-D) problems. Systematic errors caused by this simplified model can directly influence the fitting of the model to the measurement data and are expected to become more apparent with decreasing lengths of the structures. We identify these effects using selected simulation results and present experimental setups, e.g., illumination numerical apertures and focal ranges, that can increase the validity of the 2-D approach.
Mark-Alexander Henn, Bryan M. Barnes, and Hui Zhou "Evaluating the effects of modeling errors for isolated finite three-dimensional targets," Journal of Micro/Nanolithography, MEMS, and MOEMS 16(4), 044001 (19 October 2017).
Received: 25 April 2017; Accepted: 29 September 2017; Published: 19 October 2017

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