Ion-beam Synthesis of Nanocrystals for Multidot Memory Structures

Conclusion

Three different approaches for the IBS of nanocrystals in the gate oxide of MOS structures were discussed. In all cases clear memory behaviour was observed. A variance of multidot devices from DRAM-like to non-volatile-semiconductormemory-like applications was shown. For high-dose IBS swelling, sputtering and IF-mixing have to be taken into account, which have a strong influence on the memory capabilities. It has been found that for Si-IBS or Ge-IBS, annealing influences the elemental depth profiles and the corresponding NC-distribution in a very different way. As a consequence, samples prepared by Si-IBS tend more to NVRAM-like behaviour, whereas the redistribution of Ge observed in Ge-LE-IBS provides DRAM-like properties. The latter combines the formation of NCs in a short distance to the Si substrate caused by IF-irradiation with a high density of small, well-separated NCs, which are fundamental requirements of common and future memory devices. Thus, IBS has the potential for use in cost-effective multidot memory applications, for example, in a multidot DRAM with prolonged retention time.