Berlin 2005 – wissenschaftliches Programm
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SYFS: Nichtflüchtige Festkörperspeicher
SYFS 4: Poster
SYFS 4.5: Poster
Samstag, 5. März 2005, 08:30–16:30, Poster TU C
Ion irradiation through SiO2-Si interfaces: TEM study of self-organized Si nanocrystals applicable in nonvolatile memories — •Lars Röntzsch, Karl-Heinz Heinig, and Bernd Schmidt — Research Center Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden
In recent years, immense effort has been devoted to the synthesis of Si nanocrystals (NCs) for multi-dot floating-gate MOSFETs. To assure optimum memory device characteristics, the Si NCs should be equal in size and equally distant from the transistor channel. This desired Si NCs structure can be fabricated in a two-step process of ion irradiation through a SiO2-Si interface and subsequent annealing [1,2]. Previously, the Si NCs could not directly been studied with XTEM because of the low mass contrast of Si NCs to SiO2 and their very small size of less than 3nm.
In this XTEM study we prove the validity of the Si NC formation process. For a mass contrast enhancement of the Si NCs we used Ge to decorate them: A thin Ge layer was embedded into the oxide. During annealing, diffusing Ge is captured by the Si NCs due to the favourable Si-Ge bond. Thereby, the Si NCs are alloyed resulting in Si1−xGex NCs which are equally aligned with the SiO2-Si interface in a tunnel distance of about 3nm. These structural results are in line with the eletronic device characteristics which are dicussed in the contributions of Heinig and Schmidt in this symposium.
[1] Heinig et al., Appl. Phys. A77, 17 (2003)
[2] Röntzsch et al., submitted to Appl. Phys. Lett.