Transient charging current measurements and modelling in silicon nanocrystal floating gate devices

Nanocrystals-based memories are promising candidates for the scaling of Flash memories in the next decade. However, tools to specify where the carriers are actually stored are still needed in order to optimize the elaboration processes of the nanocrystals. This article presents a model which may be used to extract the physical parameters of the objects in which the carriers are charged. These parameters are extracted from transient current measurements which may be performed by most conventional static ammeters. The model is based on the study of an equivalent circuit followed by a finite elements analysis of the memory device. This technique has been used to study MOS capacitors containing silicon nanocrystals obtained by annealing LPCVD silicon rich oxide layers. Our model was found to predict all the transient features observed in the current. It quantitatively determined that in average, one electron is charged into 3–5 nm diameter nanocrystals having a density of 0.84–1.5 × 1012 cm−2. These parameters are very close to the size and the density which have been targeted during the elaboration process.