Fabrication and characterization of hybrid nanodots for floating gate application

We have designed and fabricated hybrid nanodots (NDs) structures, in which Si quantum dots (QDs) as charge counting nodes and either Ni- or Pt-silicide NDs as charge storage nodes are stacked with an ultrathin SiO₂ interlayer, to realize novel functional floating gate (FG) leading to both large memory windows and multi-valued capability. In the fabrication process, self-assembling of high-density Si-QDs on ultrathin SiO₂ in the early stages of chemical vapor deposition (CVD) using SiH₄ and the full-silicidation of pre-grown Si-QDs promoted with remote H₂-plasma exposure after metal evaporation were controlled precisely. From characteristics of MOS capacitors and nMOSFETs with a hybrid FG, stable storage of many charges in the deep potential well of each silicide ND and stepwise charge injection to and emission from silicide NDs through discrete energy states in Si-QDs were confirmed. In addition, by 1310nm (~0.95eV) light irradiation, a distinct optical response in C-V characteristics was detected, which can be interpreted in terms of the shift of charge centroid in the hybrid FG stack due to transfer of photoexcited electrons from silicide NDs to the Si-QDs.