We present an investigation of the program and erase speed characteristics of three-dimensional (3D) gate-all-around (GAA) metal–oxide–SiN X –oxide–silicon (MONOS) cells. The effect of the tunneling oxide layer thickness in 3D GAA MONOS cells has been experimentally investigated and studied by 3D technology computer-aided design (TCAD) simulation. In particular, we considered physical parameters such as trap density, capture cross section, and trap level in order to analyze the physical properties of the silicon nitride layer. Simulation results indicated that the trap density significantly affects the program efficiency compared with other physical parameters, and the trap level mainly affects the erase efficiency. From these simulation results, we confirmed from the experimental results that the modeling accuracy is about 80%. Moreover, the simulation results for the program and erase speeds of the GAA MONOS cells were in reasonable agreement with experimental results.

We investigate the electrical characteristics according to changing temperature on trap distribution in the energy gap of grain boundary (GB) and interface trap density (D(it)) between polycrystalline-silicon (poly-Si) channel and tunnel oxide in Vertical NAND (VNAND) flash cell with poly-Si channel. We confirmed that there are two factors changing GB potential barrier height such as trap distribution in GB and D(it) using technology computer-aided design (TCAD) simulation. Also, we found that the electrical characteristics according to changing temperature are significantly dependent on height and position of GB potential barrier in VNAND flash cell with poly-Si channel. We expect that it is required to develop more accurate extraction method for trap distribution in each GB and D(it) for better understanding temperature dependence of electrical characteristics in VNAND Flash cell.

A multiple alloy metal nano-dots memory using FN tunneling was investigated in order to confirm its structural possibility for future flash memory. In this work, a multiple FePt nano-dots device with a high work function (∼5.2 eV) and extremely high dot density (∼1.2 × 10 13 cm −2 ) was fabricated. Its structural effect for multiple layers was evaluated and compared to the one with a single layer in terms of the cell characteristics and reliability. We confirm that MOS capacitor structures with two to four multiple FePt nano-dot layers provide a larger threshold voltage window and better retention characteristics. Furthermore, it was also revealed that several process parameters for block oxide and inter-tunnel oxide between the nano-dot layers are very important to improve the efficiency of electron injection into multiple nano-dots. From these results, it is expected that a multiple FePt nano-dots memory using Fowler-Nordheim (FN) tunneling could be a candidate structure for future flash memory.

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The initial susceptibility and the average free-energy singularities for a disordered Ising spin system on a Cayley tree have been studied. A set of recursion relations for the probability distribution functions of the effective fields at each generation of the tree is formulated. It is shown that the susceptibility is Curie-like at any temperature, for an equal number of ferromagnetic and antiferromagnetic bonds. The average free energy behaves as hZ"(Tl where his an applied field and 1 C K < CO for 0 C T C T,; the latter is a finite limiting temperature.