K. A. Nasyrov

A new low voltage fast SONOS memory with high-k dielectric

Abstract The comparison of simulated write/erase characteristics of silicon–oxide–nitride–oxide–silicon (SONOS) nonvolatile memory with different oxides SiO 2 , Al 2 O 3 and ZrO 2 as a top dielectric was made. We demonstrate, that an application of high- k dielectrics allows to decrease the write/erase programming voltage amplitude or programming time from 1 ms to 10 μs. The ZrO 2 suppresses parasitic electron injection from polysilicon gate. Also the design of SONOS memory based on high- k dielectrics is promising for terabit scale using hot carriers injection EEPROM and DRAM memory.

Two-bands charge transport in silicon nitride due to phonon-assisted trap ionization

The charge transport in the amorphous Si3N4 is studied experimentally and theoretically. We have found, that widely accepted Frenkel model of the trap ionization gives the unphysical low value of the attempt to escape factor, and the enormously high value of the electron tunnel mass. Experimental data are well described by theory of the two-bands conduction and the phonon-assisted trap ionization in Si3N4.

Charge transport mechanism in amorphous alumina

The charge transport mechanism in amorphous Al2O3 was examined both experimentally and theoretically. We have found that electrons are dominant charge carriers in Al2O3. A satisfactory agreement between the experimental and calculated data was obtained assuming the multiphonon ionization mechanism for deep traps in Al2O3. For the thermal and optical trap ionization energies in Al2O3, the values WT=1.5 eV and Wopt=3.0 eV were obtained.

Multiphonon mechanism of the ionization of traps in Al2O3: Experiment and numerical simulation

Charge transfer in Al2O3 has been investigated experimentally and theoretically. The experimental results are in qualitative agreement with the theory of the multiphonon ionization of deep centers. The thermal (WT = 1.5 eV) and optical (Wopt = 3.0 eV) energies of the deep centers have been determined. It has been found that the experimental data are unsatisfactorily described by the Pool-Frenkel mechanism, which provides a non-physically small frequency factor and anomalously large effective tunneling mass.

Multiphonon ionization of deep centers in amorphous silicon nitride: Experiment and numerical simulations

The conductivity of amorphous silicon nitride has been studied experimentally in a wide range of electric fields and temperatures. The experimental results are in a quantitative agreement with the theory of multiphonon ionization of deep centers for the bipolar model of conductivity. The best agreement between experiment and the calculation has been obtained for the same parameters of deep electron and hole centers.

A new memory element based on silicon nanoclusters in a ZrO2 insulator with a high permittivity for electrically erasable read-only memory

The write and erase function and the data retention characteristics of a memory element designed to be used in electrically erasable read-only memory and based on a silicon-oxide-(silicon dot)-oxide-polysilicon structure, in which either a SiO2 insulator or a ZrO2 high-permittivity insulator are used as blocking oxides, are simulated. It is established that the use of the high-permittivity insulator gives rise to a number of effects: spurious injection from poly-Si is reduced; the electric field in the tunneling oxide increases; it becomes possible to increase the thickness of the tunneling insulator and, consequently, to increase the data retention time; and lower voltages for the write and erase functions can be used. Programming with a pulse of ±11 V possessing a width of 10 ms makes it possible to retain a memory window of ∼3 V for 10 years.

High-Permittivity-Insulator EEPROM Cell Using Al2O3 or ZrO2

A theoretical investigation is carried out into memory cells based on a polysilicon–oxide–nitride–oxide–silicon structure in which a high-permittivity dielectric is used instead of SiO2 as the gate insulator. The dielectric is taken to be Al2O3 or ZrO2. Write/erase (W/E) cycles are simulated numerically. It is shown for the first time that changing to a high-permittivity insulator reduces the unwanted carrier injection from the gate region and allows one to employ lower and/or shorter W/E pulses; specifically, the W/E time can be decreased from 1 ms to 10 μs. It is concluded that high-permittivity insulators might be useful in carrier-trapping EEPROMs and RAMs.