HRTEM image simulations for gate oxide metrology

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High resolution transmission electron microscopy (HRTEM) has found extensive use in the semiconductor industry for performing device metrology and characterization. However, shrinking device dimensions (gate oxides are rapidly approaching 10{angstrom}) present challenges to the use of HRTEM for many applications, including gate oxide metrology. In this study, we performed HRTEM image simulations of a MOSFET device to examine the accuracy of HRTEM in measuring gate oxide thickness. Length measurements extracted from simulated images were compared to actual dimensions in the model structure to assess TEM accuracy. The effects of specimen tilt, specimen thickness, objective lens defocus and coefficient of spherical ... continued below

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3 pages; OS: WNT

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Taylor, Seth; Mardinly, John; O'Keefe, Michael A. & Gronsky, R. February 10, 2000.

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Description

High resolution transmission electron microscopy (HRTEM) has found extensive use in the semiconductor industry for performing device metrology and characterization. However, shrinking device dimensions (gate oxides are rapidly approaching 10{angstrom}) present challenges to the use of HRTEM for many applications, including gate oxide metrology. In this study, we performed HRTEM image simulations of a MOSFET device to examine the accuracy of HRTEM in measuring gate oxide thickness. Length measurements extracted from simulated images were compared to actual dimensions in the model structure to assess TEM accuracy. The effects of specimen tilt, specimen thickness, objective lens defocus and coefficient of spherical aberration (C{sub s}) on measurement accuracy were explored for nominal 10{angstrom} and 16{angstrom} gate oxide thicknesses. The gate oxide was modeled as an amorphous silicon oxide situated between a gate electrode and substrate, both modeled as single crystal Si(100). Image simulations of the sandwich structure were performed in cross-section (with Si[110] parallel to beam direction) using the multislice approximation for a 200 kV microscope with C{sub s}=0.5mm. Amorphous slices were added to the top and bottom of the specimen to simulate the amorphization that occurs during typical specimen preparation. The actual gate oxide thickness, T, is defined as the distance between the bounding Si atoms in the model structure. The gate oxide thickness was also measured directly in pixels from the simulated image. We use a statistical routine to calculate the standard deviation in pixel intensity for each horizontal row (or y-coordinate) in the simulated image. Local minima in the standard deviation, which correspond to low-intensity regions between Si[110] dumbbells, were used to calibrate the image length scale. The measured gate oxide thickness was then compared to the actual (model) thickness to assess accuracy for a variety of microscope and specimen conditions. Results reveal no consistent trends in measurement accuracy as a function of specimen thickness, specimen tilt, or objective lens defocus.

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3 pages; OS: WNT

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OSTI as DE00775172

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  • Microscopy and Microanalysis 2000, Philadelphia, PA (US), 08/13/2000--08/17/2000

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  • Report No.: LBNL--47220
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 775172
  • Archival Resource Key: ark:/67531/metadc718021

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  • February 10, 2000

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  • Sept. 29, 2015, 5:31 a.m.

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  • April 5, 2016, 5:11 p.m.

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Taylor, Seth; Mardinly, John; O'Keefe, Michael A. & Gronsky, R. HRTEM image simulations for gate oxide metrology, article, February 10, 2000; California. (digital.library.unt.edu/ark:/67531/metadc718021/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.