In this research, we investigated the digital/analog-operation utilizing ferroelectric nondoped HfO2 (FeND-HfO2) as a blocking layer (BL) in the Hf-based metal/oxide/nitride/oxide/Si (MONOS) nonvolatile memory (NVM), so called FeNOS NVM. The Al/HfN0.5/HfN1.1/HfO2/p-Si(100) FeNOS diodes realized small equivalent oxide thickness (EOT) of 4.5 nm with the density of interface states (Dit) of 5.3 × 1010 eV-1cm-2 which were suitable for high-speed and low-voltage operation. The flat-band voltage (VFB) was well controlled as 80-100 mV with the input pulses of ±3 V/100 ms controlled by the partial polarization of FeND-HfO2 BL at each 2-bit state operated by the charge injection with the input pulses of +8 V/1-100 ms.

We demonstrate on the basis of ab initio calculations that metal-oxide-nitride-oxide-semiconductor (MONOS) memory is one of the most promising future high-density archive memories. We find that O related defects in a MONOS memory cause irreversible structural changes to the SiO2/Si3N4 interface at the atomistic level during program/erase (P/E) cycles. Carrier injection during the programming operation makes the structure energetically very stable, because all the O atoms in this structure take on three-fold-coordination. The estimated lifespan of the programmed state is of the order of a thousand years.

Resistive switching of metal-insulator-metal (MIM), consisting of a metal-organic chemical vapour deposition (MOCVD) TiO2 layer sandwiched between Pt electrodes, has been measured systematically before and after thermal annealing in different ambiences. With H2 annealing at 400, the current level in the high-resistive state (HRS) significantly decreased while little change in the low-resistive state (LRS) was observed. As a result, the switching ratio over 7 orders of magnitude at the current level was obtained. From the analysis of current-voltage (I-V) characteristics in HRS and LRS, we found that the LRS was characterized with an ohmic conduction, while in the HRS after H2 annealing, charge trapping became significant as a result of a significant decrease in the current level. In a separate experiment, a partial reduction in TiO2 was detected using high-resolution X-ray photoelectron spectroscopy (XPS) after resistant-state switching from HRS to LRS by using a Hg probe as a top electrode, which is associated with filament formation.

Due to the aggressive scaling of non-volatile memories, “charge-trap memories” such as MONOS-type memories become one of the most important targets. One of the merits of such MONOS-type memories is that they can trap charges inside atomic-scale defect sites in SiN layers. At the same time, however, charge traps with atomistic scale tend to induce additional large structural changes. Hydrogen has attracted a great attention as an important heteroatom in MONOS-type memories. We theoretically investigate the basic characteristics of hydrogen-defects in SiN layer in MONOS-type memories on the basis of the first-principles calculations. We find that SiN structures with a hydrogen impurity tend to reveal reversible structural change during program/erase operation.

This paper presents a detailed study of the retention characteristics in scaled multi-bit SONOS flash memories. By calculating the oxide field and tunneling currents, we evaluate the charge trapping mechanism. We calculate transient retention dynamics with the ONO fields, trapped charge, and tunneling currents. All the parameters were obtained by physics-based equations and without any fitting parameters or optimization steps. The results can be used with nanoscale nonvolatile memory. This modeling accounts for the VT shift as a function of trapped charge density, time, silicon fin thickness and type of trapped charge, and can be used for optimizing the ONO geometry and parameters for maximum performance.

In this paper, characteristics of the 2-bit recessed channel memory with lifted-charge trapping nodes are investigated. The length between the charge trapping nodes through channel, which is defined as the effective memory node length (Meff), is extended by lifting up them. The dependence of VTH window and short channel effect (SCE) on the recessed depth is analyzed. Improvement of short channel effect is achieved because the recessed channel structure increases the effective channel length (Leff). Moreover, this device shows highly scalable memory characteristics without suffering from the bottom-side effect (BSE).

We have studied the electrical and breakdown characteristics of 5 nm-thick HfSiOxNy (Hf/(Hf + Si)=0.43, nitrogen content=4.5-17.8 at.%) in Al-gate and NiSi-gate capacitors. For Al-gate capacitors, the flat-band shift due to positive fixed charges increases with the nitrogen content in the dielectric layer. In contrast, for NiSi-gate capacitors, the flat band is almost independent of the nitrogen content, which is presumably controlled by the quality of the interface between NiSi and the dielectric layer. The leakage current markedly increases with nitrogen content. Correspondingly, although the time-to-soft breakdown, tSBD, gradually decreases with increasing nitrogen content, the charge-to-soft breakdown, QSBD, increases with the nitrogen content. For Al-gate capacitors, the Weibull slope of time-dependent dielectric breakdown (TDDB) under constant voltage stress (CVS) remains constant at 2 for a nitrogen content of up to 12.5 at.% and then decreases to unity at 17.8 at.%. This must be a condition critical to the formation of the percolation path for breakdown. In contrast, for NiSi gate capacitors, a Weibull slope smaller than unity was obtained, suggesting that structural inhomogeneity, involving defect generation, is introduced during the NiSi gate fabrication, but this negative impact is reduced with nitrogen incorporation.