PURPOSE:To lower the gate voltage being applied at writing-in and elimination of data are performed by a method wherein the 2nd gate region for which SiC is used is provided on the surface of the 1st gate region which constitutes a memory device and is formed of an SiO2 film. CONSTITUTION:A p type source region 2 and a drain region 3 are formed diffusively on an n type Si substrate 1 by using an SiO2 film and the like as a mask and a thick field SiO2 film is spread over the whole surface. Next, the part of the film 9 corresponding to the regions where the gate electrode 6 and source and drain electrodes 7 and 8 are to be formed is removed and there a thin SiO2 film 11 for the 1st gate is grown. After that, on the film 11 between the regions 2 and 3 the 2nd SiC film 10 is formed and, while the film 11 on the regions 2 and 3 is removed, the film 10 is packed by the film 11 formed monolithically, and on the surface thereof is formed the gate electrode 6. Then, the source electrode 7 and the drain electrode 8 are provided on the exposed regions 2 and 3 respectively, and thus even under a low voltage, the generation of a tunnel effect and the like becomes possible.

Semiconductor memory device

The voltage dependence of photoinjected currents in SiO2 films for electric fields less than about 106 V/cm exhibits anomalous behavior It is shown that the physical mechanism responsible for this behavior is the scattering of photoinjected electrons in the SiO2 image force potential well between the emitter and the potential maximum A previously published model attributing the effect to electron trapping in SiO2 is shown to be inconsistent with the experimental results A theoretical model is presented and the voltage dependence of photocurrents is derived including the effects of scattering and barrier lowering Experimental results from MIS structures using thermally grown SiO2 are found to be in excellent agreement with theoretical predictions when a 34 A mean free path for scattering in SiO2 is used in the model

Photoinjection into SiO2: Electron Scattering in the Image Force Potential Well

Two semiclassical ballistic transport models for thin films developed in 1971 treat the problem of "hot-electron" internal photoemission in Schottky-barrier diode IR detectors. Both formulations take into account multiple scattering from the surfaces as well as hot-electron-phonon and hot-electron-cold-electron collisions in the bulk. The models are compared for the case of uniform absorption and one of the models is then extended. The extensions incorporate the effect on internal quantum yield of small energy losses from electron-phonon collisions. Also, it is no longer assumed that the fraction removed by capture is small which insures that the yield cannot exceed the theoretical upper limit. The results are illustrated by Fowler plots over a range of scattering parameters and thicknesses germane to Schottky diodes of current interest, PtSi/Si and Pd 2 Si/Si. The main new features of the plots include curvature for photon energies close to the barrier energy due to phonon collision thermalization and roll-off at higher excitation energies whenever the yield is comparable in magnitude to the theoretical limit. The model is in good agreement with earlier Monte Carlo computations.

The theory of hot-electron photoemission in Schottky-barrier IR detectors

A floating gate type semiconductor non-volatile memory injects carriers from a carrier supply region to a floating gate by a phenomenon called "punch-through" injection in which a space charge region is formed in a semiconductor substrate between the carrier supply region and a carrier injection region so as to accelerate the carriers and inject them into the floating gate without forwardly biasing the carrier injection region or the substrate.

Semiconductor nonvolatile memory

Logarithmic conductivity of AlAl2O3Al tunneling junctions produced by plasma- and by thermal oxidation

Photomeasurements on Al–Al2O3–Au thin‐film sandwiches revealed a very asymmetric barrier shape, Φ1 and Φ2 being 1.8 and 4 eV, respectively. The image‐force lowering of the barrier can be explained by the high‐frequency dielectric constant. When photoemission measurements are performed only in the visible region, the Au electrode will not emit photoelectrons because of the large Φ2 value. The Al electrode, however, will emit photoelectrons if the Au electrode is sufficiently positively biased. The existence of only one source for photoelectrons facilitates the interpretation of photomeasurements. Monte Carlo calculations were performed to determine the scattering of hot electrons within these films. Electron‐optical phonon scattering was assumed and a mean free path of 10 A was found. The method to determine scattering by photoemission gives values on scattering within the image‐force region.

Monte Carlo Calculations of Internal Photoemission Yields in M‐I‐M Thin‐Film Structures

A nonvolatile memory cell is disclosed that has a buried n+ layer from which charge (electrons) is injected into the insulator of n-channel MNOS (Metal Nitride Oxide Semiconductor) type devices.

Nonvolatile punch through memory cell with buried n+ region in channel

A nonvolatile Charge Injection Device (NOVCID) of Metal-Nitride-Oxide-Semiconductor (MNOS) material is operated in a novel manner in combination with a flip-flop to provide a charge pumped volatile memory storage system that can be continuously nondestructively read and on command, by applying a high positive potential to the field plate of the NOVCID, the information stored in the volatile mode is transferred to the nonvolatile state. To recover the stored information an alternating current signal is applied to the field plate.

Quasi static, virtually nonvolatile random access memory cell

A dynamic, virtually nonvolatile random access memory (RAM) storage cell is provided by storing information in a Nonvolatile Charge Injection Device (NOVCID), first in volatile form, then by an electric signal transferring the stored intelligence into a nonvolatile form from which it may late be recovered. Since only on external command is the information transferred into the nonvolatile storage mode, the memory is described as a virtually nonvolatile RAM.

Virtually nonvolatile random access memory cell

The effect of write‐erase cycling on surface‐state generation and on retentivity in MNOS devices was studied. Annealing behavior of surface states and of threshold‐voltage‐decay rates was investigated. It is concluded that the threshold‐voltage‐decay rate is not controlled by surface states but by the nitride conductivity.

Charles R. Young

Papers

Monte Carlo Calculations of Internal Photoemission Yields in M‐I‐M Thin‐Film Structures

Nonvolatile punch through memory cell with buried n+ region in channel

Quasi static, virtually nonvolatile random access memory cell

Virtually nonvolatile random access memory cell

Endurance studies on MNOS devices