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Multi-Dot Floating-Gates in MOSFETs for Nonvolatile Memories – Their Ion Beam Synthesis and Morphology

Published online by Cambridge University Press:  01 February 2011

T. Müller ,
K.-H. Heinig ,
C. Bonafos ,
H. Coffin ,
N. Cherkashin ,
G. Ben Assayag ,
S. Schamm ,
G. Zanchi ,
A. Claverie  and
M. Tencé
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T. Müller
Affiliation:
Research Center Rossendorf, Institute of Ion Beam Physics and Materials Research, PO Box 51 01 19, 01314 Dresden, Germany
K.-H. Heinig
Affiliation:
Research Center Rossendorf, Institute of Ion Beam Physics and Materials Research, PO Box 51 01 19, 01314 Dresden, Germany
C. Bonafos
Affiliation:
CNRS/CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse, France
H. Coffin
Affiliation:
CNRS/CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse, France
N. Cherkashin
Affiliation:
Research Center Rossendorf, Institute of Ion Beam Physics and Materials Research, PO Box 51 01 19, 01314 Dresden, Germany
G. Ben Assayag
Affiliation:
CNRS/CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse, France
S. Schamm
Affiliation:
CNRS/CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse, France
G. Zanchi
Affiliation:
CNRS/CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse, France
A. Claverie
Affiliation:
CNRS/CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse, France
M. Tencé
Affiliation:
Laboratoire de Physique des Solides, Université Paris-Sud - UMR 8502, 91405 Orsay, France
C. Colliex
Affiliation:
Laboratoire de Physique des Solides, Université Paris-Sud - UMR 8502, 91405 Orsay, France
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Abstract

Scalability and performance of current flash memories can be improved substantially by novel devices based on Multi-Dot Floating Gate MOSFETs. The multi-dot layer in the very thin gate oxide can be fabricated CMOS-compatibly by ion beam synthesis (IBS). Here, we present both experimental and theoretical studies on IBS of multi-dot layers consisting of Si nanocrystals (NCs). The NCs are produced by ultra low energy Si+ ion implantation, which causes a high Si supersaturation in the shallow implantation region. During post-implantation annealing, this supersaturation leads to phase separation of the excess Si from the SiO2. Till now, the study of this phase separation suffered from the weak z contrast between Si and SiO2 phases in Transmission Electron Microscopy (TEM). Here, this imaging problem is solved by Energy Filtered Scanning Transmission Electron Microscopy (EFSTEM). Additionally, kinetic lattice Monte Carlo simulations of Si phase separation have been performed and compared with EFSTEM images. It has been predicted theoretically that the morphology of the multi-dot Si floating gate changes with increasing ion fluence from isolated, spherical NCs to percolated spinodal Si pattern. These patterns agree remarkably with EFSTEM images. However, the predicted fluence for spinodal pattern is lower than the experimental one. Because oxidants of the ambient atmosphere penetrate into the as-implanted SiO2, a substantial fraction of the implanted Si is lost due to oxidation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 792: Symposium R – Radiation Effects and Ion Beam Processing of Materials , 2003 , R8.7
Copyright
Copyright © Materials Research Society 2004

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References

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