Nanocrystals by ion beams - from fundamentals to application in non-volatile memories

Ion beams are widely used in research and development as well as in different fields of industrial applications, for example for doping of semiconductors in microelectronics. Furthermore, among other techniques ion beams exhibit a great potential for synthesis of new materials. One of the goals of materials research using ion beams is the ion beam synthesis (IBS) of nanocrystals (NC´s) in a solid matrix, for example the synthesis of semiconducting or metallic NC´s in insulating films.
NC´s embedded in the gate oxide of a MOS field effect transistor can be charged/decharged by tunnelling of electrons from/to the Si substrate, caused by an appropriate voltage pulse applied to the gate. There is a difference in the source/drain current for charged and neutral NCs which can be used for the storage of information. The basis of this memory concept is quite simple. However, the fabrication of tiny NCs (~2 nm) placed at the right position within the very thin (< 20 nm) gate oxide is a strong challenge. Different processes are being developed for realization. Among these, only ion implantation of impurity atoms into the gate oxide followed by their precipitation during subsequent annealing is completely compatible with CMOS technology.
The lecture will first address the fundamentals governing ion beam synthesis NC´s in extremely thin SiO2 layers, with well-controlled size and position tailoring. The results of the fundamental investigations form the base for technology transfer to the production of non-volatile memories. In the frame of national and international R&D projects and in strong collaboration with local microelectronics industries, the viability of a new technology route to memory device fabrication is demonstrated.