Formation and Characterization of Silicon-Quantum-Dots/Metal-Silicide-Nanodots Hybrid Stack and Its Application to Floating Gate Functional Devices

摘要

Hybrid nanodots (NDs) structures have been designed and fabricated as a noble functional floating gate, 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 satisfy both large memory windows and multi-valued capability. In the sample preparation, spontaneous formation 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. MOS capacitors and nMOSFETs with a hybrid FG show clear characteristics caused by stable storage of many charges in the deep potential well of each silicide ND and stepwise charge injection to and emission from NDs through discrete energy states in Si-QDs. In addition, a distinct optical response to 1310nm light irradiation was detected in the C-V characteristics, being 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.