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Toward Site-Specific Dopant Contrast in Scanning Electron Microscopy

Published online by Cambridge University Press:  20 May 2014

Zdena Druckmüllerová ,
Miroslav Kolíbal ,
Tomáš Vystavěl  and
Tomáš Šikola
Zdena Druckmüllerová
Affiliation:
Institute of Physical Engineering, Brno University of Technology, Technická 2, 61669 Brno, Czech Republic CEITEC BUT, Brno University of Technology, Technická 10, 61669 Brno, Czech Republic
Miroslav Kolíbal*
Affiliation:
Institute of Physical Engineering, Brno University of Technology, Technická 2, 61669 Brno, Czech Republic CEITEC BUT, Brno University of Technology, Technická 10, 61669 Brno, Czech Republic
Tomáš Vystavěl
Affiliation:
FEI Company, Podnikatelská 6, 61200 Brno, Czech Republic
Tomáš Šikola
Affiliation:
Institute of Physical Engineering, Brno University of Technology, Technická 2, 61669 Brno, Czech Republic CEITEC BUT, Brno University of Technology, Technická 10, 61669 Brno, Czech Republic
*
*Corresponding author. [email protected]
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Abstract

Since semiconductor devices are being scaled down to dimensions of several nanometers there is a growing need for techniques capable of quantitative analysis of dopant concentrations at the nanometer scale in all three dimensions. Imaging dopant contrast by scanning electron microscopy (SEM) is a very promising method, but many unresolved issues hinder its routine application for device analysis, especially in cases of buried layers where site-specific sample preparation is challenging. Here, we report on optimization of site-specific sample preparation by the focused Ga ion beam (FIB) technique that provides improved dopant contrast in SEM. Similar to FIB lamella preparation for transmission electron microscopy, a polishing sequence with decreasing ion energy is necessary to minimize the thickness of the electronically dead layer. We have achieved contrast values comparable to the cleaved sample, being able to detect dopant concentrations down to 1×1016 cm−3. A theoretical model shows that the electronically dead layer corresponds to an amorphized Si layer formed during ion beam polishing. Our results also demonstrate that contamination issues are significantly suppressed for FIB-treated samples compared with cleaved ones.

Keywords

dopant mappingscanning electron microscopy (SEM)focused ion beam (FIB)amorphizationsemiconductors and semiconductor devices
Type
Techniques and Instrumentation Development
Information
Microscopy and Microanalysis , Volume 20 , Issue 4 , August 2014 , pp. 1312 - 1317
Copyright
© Microscopy Society of America 2014 

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