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Low-Energy STEM of Multilayers and Dopant Profiles

Published online by Cambridge University Press:  28 January 2005

P.G. Merli  and
V. Morandi
P.G. Merli
Affiliation:
Consiglio Nazionale delle Ricerche-Istituto per la Microeletironica e i Microsistemi, Sezione di Bologna, Via Gobetti 101, 40129 Bologna, Italy
V. Morandi
Affiliation:
Consiglio Nazionale delle Ricerche-Istituto per la Microeletironica e i Microsistemi, Sezione di Bologna, Via Gobetti 101, 40129 Bologna, Italy
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Abstract

A conventional scanning electron microscope equipped with a LaB6 source has been modified to operate in a scanning transmission mode. Two detection strategies have been considered, one based on the direct collection of transmitted electrons, the other on the collection of secondary electrons resulting from the conversion of the transmitted ones. Two types of specimens have been mainly investigated: semiconductor multilayers and dopant profiles in As-implanted Si. The results show that the contrast obeys the rules of mass–thickness contrast whereas the resolution is always defined by the probe size independently of specimen thickness and beam broadening. The detection strategy may affect the bright field (light regions look brighter) or dark field (heavy regions look brighter) appearance of the image. Using a direct collection of the transmitted electrons, the contrast can be deduced from the angular distribution of transmitted electrons and their collection angles. When collecting the secondary electrons to explain the image contrast, it is also necessary to take into account the secondary yield dependence on the incidence angle of the transmitted electrons.

Keywords

STEMlow-energy STEMdopant profilessemiconductor multilayersSE yieldMonte Carlo simulationmass–thickness contrastelectron device investigation
Type
INSTRUMENTATION AND TECHNIQUES
Information
Microscopy and Microanalysis , Volume 11 , Issue 1 , February 2005 , pp. 97 - 104
Copyright
© 2005 Microscopy Society of America

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