Direct probing of trapped charge dynamics in SiN by Kelvin Force Microscopy

Abstract

In this work, we explore the potential of Kelvin Force Microscopy (KFM) measurements to investigate the lateral charge transport in SiN layers with two different compositions (standard, std, and Silicon rich, Si-rich). The dynamics of the lateral spread of the trapped charge is analyzed with the help of three dimensional numerical device simulations.

Explanation of the Charge Trapping Properties of Silicon Nitride Storage Layers for NVMs—Part II: Atomistic and Electrical Modeling

“…These conclusions are not inconsistent with the findings in [7] and [8], where very similar energy distributions have been proposed for traps in nearly stoichiometric and Si-rich SiN samples. The similar trap energy depth is also in qualitative agreement with KFM measurements of the lateral charge spread in SiN layers [9], [43] and the retention experiments on thick tunnel oxide devices [10]. However, the very small energy difference (≈0.1-0.2 eV) reported for the traps in std and Si-rich SiN films is insufficient to explain the large difference in the retention experiments of the two SiN compositions [see Fig.…”

“…Although possible corrections to the trap energy depth will be discussed in the following, at this stage, it is worth to note that, since the two defects have similar energy level (within approximately 0.2 eV), they are difficult to discriminate by means of activation energy experiments, as already pointed out in [43]. This evidence is also in qualitative agreement with the results of the KFM measurements in [9] that do not show differences in the detrapping rates of SiN films with different stoichiometries.…”

“…However, the very slight difference in energy depths reported in the literature for Si-rich SiN traps compared to std SiN traps [7], [8] cannot exhaustively explain all the experimental findings on SiN-based memory cells. Furthermore, the Kelvin force microscopy (KFM) measurements on charge diffusion reported in [9] and the retention characteristics of thick tunnel oxide test structures (type-A device) presented in the accompanying paper seem to suggest a similar energy depth for the traps of the std and the Si-rich SiN films, thus demanding a clarification on the effective microscopic nature of the traps in SiN layers with different compositions.…”

Charge diffusion in silicon nitrides: Scalability assessment of nitride based flash memory

“…Vianello, et al, recently reported a work on charge dynamics in silicon nitride based on similar experimental setup, where they focused on electron diffusion dynamics and additional quantification was performed based on numerical simulation [23]. In this work, we provide a more complete description of charge dynamics attainable by EFM, and present analyses on both carriers (electrons and holes) at various temperatures, which was supported by quantification of temperature dependent diffusion coefficients based on a simple analytic model.…”

Self-consistent simulation on multiple activation energy of retention characteristics in charge trapping flash memory

“…This may be problematic because, until recently, it has been continually reported that the lateral charge transport gives a significant effect to the charge retention [13,14]. The lateral migration was proved in many different ways, for example, the direct probing method (AFM) [15,16], electrical measurement [13,17] and theoretical simulation [13]. This lateral leakage cannot be eliminated by separating the nitride region for each cells because of the reliability degradation due to the cutting of the nitride layer [17].…”