Electrical characterization using Scanning Capacitance Microscopy of the local electronics properties of Ge semiconducto
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O10.12.1
Electrical characterization using Scanning Capacitance Microscopy of the local electronics properties of Ge semiconductor nanostructures. G. Brémond1, J.J. Marchand1, A. Descamps1, P. Budau1*, F. Bassani2,A. Ronda2, I. Berbezier2, T. Stoïca3, L. Vescan3 1 Laboratoire de la Physique de la Matière (UMR 5511) INSA-Lyon, Bat. Blaise Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne, France 2 Laboratoire Matériaux et Microélectronique de Provence (UMR CNRS 6117)- Université d’Aix-Marseille, Technopôle de Château – Gombert, 13451 Marseille Cedex 20 3 Ungszentrum Juelich GmbH, Institut für Schichten und Grenzflächen, ISG-1, D-52425 Juelich, Germany
ABSTRACT Ge nanocrystals embedded in SiO2 via a low temperature thermal oxidation of a Si/Ge/Si stack structure grown by low pressure chemical vapour deposition or by molecular beam epitaxy in localized focalized ion beam nanopatterns are characterized by scanning capacitance microscopy. Local electrical spectroscopy on the Ge structure shows hole or electron charging by the Ge nanocrystal, thanks to the complete electrical isolation induced by the oxidation process. The scanning capacitance microscope allows measuring the discharging kinetics of the electron, giving an order of the retention time value of several hours.
INTRODUCTION The development of the nanotechnology field including the use of single semi-conductor nanostructure and nanocrystal needs of novel experimental methods of probing techniques in order to permit the measurement of the local electronic properties of devices integrating such materials [1]. The use of nanocrystals (ncs) to form floating gate memories has been demonstrated as an important route to reduce the problem of charge loss encountered in conventional flash memories. The principle of the work of such non volatile memory (NVM) concerned by ncs is based on the charge exchange between the ncs and the inversion layer of the MOS device. The key challenges are the control of the charge transfer from the MOS channel to ncs (writing process) and the retention time in the ncs [2-4]. In order to improve the data retention in such NVM, Ge ncs has been suggested instead of Si ncs thanks to the smaller band gap. In such NVM, the charging process is still not well understood since it has been evidenced that interface traps may play a major role in the trapping/de-trapping mechanism [5]. This paper reports on the characterization study of single Ge nanocrystals in SiO2 using electrical spectroscopy obtained by scanning capacitance microscopy via the use of an atomic force microscope. Results have been obtained on charge capture mechanism and on retention time data, pointing out the good electrical isolation of such Ge ncs.
O10.12.2
EXPERIMENTAL DETAILS Standard p-type (1-2 Ωcm) Si substrates with a thin SiO2 sacrificial oxide layer have been structured using focalized ion beam (FIB). The FIB nanopatterns have diameter between 40 nm to 100 nm and depth between 1nm to 10 nm depending of the Ga beam parameters used. The Ga contamination has been remo
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