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The Mechanistic Determination of Doping Contrast from Fermi Level Pinned Surfaces in the Scanning Electron Microscope Using Energy-Filtered Imaging and Calculated Potential Distributions

Published online by Cambridge University Press:  22 September 2022

Augustus K.W. Chee
Augustus K.W. Chee*
Affiliation:
Oatley Laboratory, Department of Engineering, Trumpington Street, Cambridge CB2 1PZ, United Kingdom Center for High Resolution Electron Microscopy, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB3 0FS, UK Wolfson Lab, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom BK21 FOUR, Kyungpook National University, Daegu 41566, Republic of Korea
*
*Email: augustus-chee@ieee.org
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Abstract

Secondary electron (SE) doping contrast in the scanning electron microscope is correlated with Fermi level pinned surfaces of Si samples prepared using HF-based wet-chemical treatment or focused ion beam (FIB) micromachining en route to quantitative dopant profiling. Using energy-resolved SE imaging techniques and finite-element analyses of surface states and surface junction potentials, we clarified the surface band-bending effects post-NH4F-treatment, consistent with brighter p-contrast from degenerately doped (>1019 cm−3) regions. In general, SE spectromicroscopy scan measurements unambiguously indicated heavy suppression of patch fields, while the empirical discovery of scan frequency-modulated contrast inversion due to Chee et al. [Springer Proceedings in Physics, 120, pp. 407–410 (2008)] is ascribable to competing fixed oxide charge and dynamic charge injection phenomena (particularly at dwell times >29 μs). Leveraging numerical simulations of electric potentials and variable-voltage experimental data, the theoretical model based on amorphization damage-mediated Fermi level pinning is elucidated for Ga+ FIB-processed site-specific doping contrast on patch field-free surfaces. This work successfully argues against the notion that doping contrast ultimately or exclusively entails patch fields or adventitious metal–semiconductor contacts.

Keywords

focused ion beampatch fieldsp–n junctionssecondary electronssurface band-bending
Type
Software and Instrumentation
Information
Microscopy and Microanalysis , Volume 28 , Issue 5 , October 2022 , pp. 1538 - 1549
Copyright
Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of the Microscopy Society of America

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