A nanoscale approach to the electrical properties of MOS memory devices with Si-nanocrystals

Memory devices based on MOS structures with Silicon nanocrystals (Si-nc) embedded in the gate oxide have been investigated at the nanoscale with a Conductive Atomic Force Microscope (C-AFM). The high lateral resolution of this technique allows to study extremely small areas (∼300 nm2) and, therefore, the electrical properties of a reduced number of Si-nc. C-AFM experiments have demonstrated that Si-nc enhance the gate oxide electrical conduction due to assisted tunneling. On the other hand, Si-nc can act as trapping centers. The amount of charge stored in Si-nc has been estimated through the change induced in the barrier height measured from the I-V characteristics. The results show that only ∼20% of the Si-nc are charged (in agreement with the macroscopic characterization), demonstrating that C-AFM is a powerful tool to investigate the performance of Si-nc memory devices.