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Dopant profiling based on scanning electron and helium ion microscopy

Dopant profiling based on scanning electron and helium ion microscopy
Dopant profiling based on scanning electron and helium ion microscopy
In this paper, we evaluate and compare doping contrast generated inside the scanning electron microscope (SEM) and scanning helium ion microscope (SHIM). Specialised energy-filtering techniques are often required to produce strong doping contrast to map donor distributions using the secondary electron (SE) signal in the SEM. However, strong doping contrast can be obtained from n-type regions in the SHIM, even without energy-filtering. This SHIM technique is more sensitive than the SEM to donor density changes above its sensitivity threshold, i.e. 1016 or 1017 donors cm-3 respectively on specimens with or without a p-n junction; its sensitivity limit is well above 2×1017 acceptors cm-3 on specimens with or without a p-n junction. Good correlation is found between the widths and slopes of experimentally measured doping contrast profiles of thin p-layers and the calculated widths and slopes of the potential energy distributions across these layers, at a depth of 1–3 nm and 5–10 nm below the surface in the SHIM and the SEM respectively. This is consistent with the mean escape depth of SEs in Si being about 1.8 nm and 7 nm in the SHIM and SEM respectively, and we conclude that short escape depth, low energy SE signals are most suitable for donor profiling.
doping contrast, secondary electron energy filtering, sensitivity limit, electric potentials, escape depth, p-n junction
0304-3991
1-18
Chee, Augustus K.W.
58d02d5b-9a0b-4c2c-aa4c-d17037f350d1
Boden, Stuart A.
83976b65-e90f-42d1-9a01-fe9cfc571bf8
Chee, Augustus K.W.
58d02d5b-9a0b-4c2c-aa4c-d17037f350d1
Boden, Stuart A.
83976b65-e90f-42d1-9a01-fe9cfc571bf8

Chee, Augustus K.W. and Boden, Stuart A. (2015) Dopant profiling based on scanning electron and helium ion microscopy. Ultramicroscopy, 1-18. (doi:10.1016/j.ultramic.2015.10.003).

Record type: Article

Abstract

In this paper, we evaluate and compare doping contrast generated inside the scanning electron microscope (SEM) and scanning helium ion microscope (SHIM). Specialised energy-filtering techniques are often required to produce strong doping contrast to map donor distributions using the secondary electron (SE) signal in the SEM. However, strong doping contrast can be obtained from n-type regions in the SHIM, even without energy-filtering. This SHIM technique is more sensitive than the SEM to donor density changes above its sensitivity threshold, i.e. 1016 or 1017 donors cm-3 respectively on specimens with or without a p-n junction; its sensitivity limit is well above 2×1017 acceptors cm-3 on specimens with or without a p-n junction. Good correlation is found between the widths and slopes of experimentally measured doping contrast profiles of thin p-layers and the calculated widths and slopes of the potential energy distributions across these layers, at a depth of 1–3 nm and 5–10 nm below the surface in the SHIM and the SEM respectively. This is consistent with the mean escape depth of SEs in Si being about 1.8 nm and 7 nm in the SHIM and SEM respectively, and we conclude that short escape depth, low energy SE signals are most suitable for donor profiling.

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Accepted/In Press date: 6 October 2015
Published date: 19 October 2015
Keywords: doping contrast, secondary electron energy filtering, sensitivity limit, electric potentials, escape depth, p-n junction
Organisations: Electronics & Computer Science

Identifiers

Local EPrints ID: 383688
URI: https://eprints.soton.ac.uk/id/eprint/383688
ISSN: 0304-3991
PURE UUID: cbd9a202-432b-405f-b93f-f1b70b9c0236
ORCID for Stuart A. Boden: ORCID iD orcid.org/0000-0002-4232-1828

Catalogue record

Date deposited: 09 Nov 2015 12:04
Last modified: 01 Mar 2019 05:01

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