Resistive switching devices were used as technological synapses to learn about the spatial- and temporal-correlated neuron spikes.

This paper presents a comprehensive investigation of random telegraph noise (RTN) in deca-nanometer Flash memories, considering both the nor and the nand architecture. The statistical distribution of the threshold voltage instability is analyzed in detail, evidencing that the slope of its exponential tails is the critical parameter determining the scaling trend for RTN. By means of 3-D TCAD simulations, the slope is shown to be the result of cell geometry, atomistic substrate doping, and random placement of traps over the cell active area. Finally, the slope dependence on cell geometry (width, length, and oxide thickness), doping, and bias conditions is summarized in a powerful formula that is able to predict the RTN instabilities in deca-nanometer Flash memories.

We present results of the numerical simulation of the transient behavior of shallow junction single photon avalanche diodes (SPAD's). We developed a bidimensional model for above breakdown simulations and show that the initially photogenerated charge density builds up locally by an avalanche multiplication process and then spreads over the entire detector area by a diffusion-assisted process. To model real geometries, we developed a simplified model based on the obtained results. The importance of the photon-assisted spreading mechanism is evaluated and compared with the diffusive one. The contribution of the photon-assisted mechanism is minor in these geometries. The model is compared with the experimental data on the avalanche leading edge and the timing resolution; the agreement is good. We conclude that the model can be considered to be a useful tool for the design of improved structures.

This paper presents a new physics-based statistical model for random telegraph noise in Flash memories. From the probabilistic superposition of elementary Markov processes describing the trapping/detrapping events taking place in the cell tunnel oxide, the model can explain the main features of the random telegraph noise threshold-voltage instability. The results on the statistical distribution of the threshold-voltage difference between two subsequent read accesses show good agreement between measurements and model predictions, even considering the time drift of the distribution tails. Moreover, the model gives a detailed spectroscopic analysis of the oxide defects responsible for the random telegraph noise, allowing a spatial and energetic localization of the traps involved in the threshold-voltage instability process.

This paper reviews what changed in the reliability of NAND Flash memory arrays after the paradigm shift in technology evolution determined by the transition from 2-D to 3-D integration schemes. Starting from a quick glance at the fundamentals of raw array reliability, the reasons for its worsening with the evolution of 2-D technologies will be discussed, focusing on the physical phenomena which contributed more to that outcome. By exploring the dependence of the magnitude of these phenomena on cell and array parameters, the abrupt improvements achieved from the 3-D transition in terms of raw array reliability will then be explained, highlighting also that these improvements were turned into new opportunities for the technology. Finally, the physical issues specific to 3-D arrays will be addressed, providing a glimpse of the challenges that the NAND Flash technology will have to face from the standpoint of array reliability in the near future.

This letter presents a detailed investigation of the random telegraph noise (RTN) effects on the threshold-voltage distribution of flash memory arrays programmed by the staircase algorithm. RTN is shown to introduce an exponential tail above the program verify level when considering the cell threshold voltage that ends the program operation. In addition, when a subsequent read operation is considered, a clear exponential tail is shown to appear even below the program verify level. We present a simple analysis that is able to predict the threshold-voltage distribution width accounting for both these enlargement contributions, defining practical formulas for the programming accuracy as a function of the staircase step amplitude and the RTN distribution.