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TEM Imaging of Amorphous Silicon Oxide - Silicon Nitride - Silicon Oxide Dielectric Films

Published online by Cambridge University Press:  02 July 2020

Lew Rabenberg ,
J. P. Zhou ,
Kil-Soo Ko  and
Rita Johnson
Lew Rabenberg
Affiliation:
Texas Materials Institute, University of Texas at Austin, Austin, TX78712 , USA
J. P. Zhou
Affiliation:
Texas Materials Institute, University of Texas at Austin, Austin, TX78712 , USA
Kil-Soo Ko
Affiliation:
Texas Materials Institute, University of Texas at Austin, Austin, TX78712 , USA
Rita Johnson
Affiliation:
Samsung Austin Semiconductor, Austin, TX, Now at Motorola, Austin, TX
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Abstract

Thin films of amorphous silicon oxide and silicon nitride are routinely used as gate dielectrics in silicon-based microelectronic devices. It is valuable to be able to image them and measure their thicknesses quickly and accurately. This brief note describes conditions that can be used to obtain accurate and reproducible TEM images of oxide-nitride-oxide (ONO) thin films.

Obtaining adequate contrast differences between oxide and nitride is not trivial because they have the same average atomic number, and both phases are amorphous. As stoichiometric compounds, both SiO2 and Si3N4 would have average atomic numbers equal to 10. For SiO2, (14+2(8))/3=10, and for Si3N4, (3(14)+4(7))/7=10. Thus, the atomic number contrast between these two is weak or nonexistent. Similarly, the amorphous character prevents the use of conventional diffraction contrast techniques.

However, the density of Si3N4 (3.2 g/cm3) is considerably greater than the density of SiO2 (2.6 g/cm3), reflecting the higher average coordination of N compared with O.

Type
Thin Films & Coatings
Information
Microscopy and Microanalysis , Volume 7 , Issue S2: Proceedings: Microscopy & Microanalysis 2001, Microscopy Society of America 59th Annual Meeting, Microbeam Analysis Society 35th Annual Meeting, Long Beach, California August 5-9, 2001 , August 2001 , pp. 1228 - 1229
Copyright
Copyright © Microscopy Society of America 2001

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