Programmable Read Research Articles

Bi-dimensional ballistic model of a trap capture cross-section

Electron traps are usually induced by defects and create levels in the forbidden gap, from which they can capture or reemit carriers into the nearest band. In the case of a thin insulating layer (<10 nm) used in electrical erasable programmable read only memory (EEPROM), traps are generated by stresses created by an electrical field, which could 10 6–10 7 V/cm yet. These stresses induce a leakage current call stress induced leakage current. Traps are generally defined by their density, energy, constant trapping time, and capture cross section. When the electrical field ⩾5 × 10 8 Vm −1, we take into account the influence of such electrical fields on the trap parameters and in particular the capture cross-section. By using a numerical ballistic model, we have plotted the free electron motion submitted to a constant electrical field and an attractive coulombian potential. With this model we show that the capture cross-section radius, varies inversely with the square root of the electrical field, and is dependent on the temperature. By the introduction of a potential well screening, it is possible to have a description of the trapping time.

Flash memory: towards single-electronics

Since their invention in 1984, flash memories have evolved from single device components to megabit nonvolatile memory (NVM) arrays. Flash memories were born from the need to find easily scalable replacements for EPROMs (erasable programmable read only memory) and EEPROMs (electrically erasable programmable read only memory). Unlike EPROMs and EEPROMs, flash memory cells provide single-cell electrical program and fast simultaneous block electrical erase. Thus, a small cell size is combined with a fast in-system erase capability.

Thin Oxides Grown on Disilane-Based Polysilicon

This report describes the thin oxide (<10 nm) thermally grown on polysilicon film, which was prepared by disilane (Si2H6) chemical vapor deposition. In comparison with the thin oxide grown on conventional silane (SiH4) polysilicon film, the prepared oxides have lower leakage currents, a lower electron trapping rate and a larger charge to breakdown distribution. These good properties are attributed to the smooth surface of the disilane poly-I film. This film is suitable for use as the interpoly oxide of electrically-erasable programmable read only memory.

A novel nonvolatile memory cell suitable for both flash and byte-writable applications

The structure, operation, and fabrication of a novel EEPROM/flash cell and array architecture are described. The cell is about half the size of the traditional floating gate tunnel oxide (FLOTOX) electrically erasable programmable read only memory (EEPROM) cell when laid out with the same design rules. This approach has a simple fabrication sequence and requires minimum overhead circuitry rendering it especially suitable for embedded applications. Characterization shows this approach has good retention and has million cycle endurance. Both read and write disturbs are characterized. There are large margins for both types of disturbs. In fact, the data on write disturbs show the disturb margins to be so large that disturb margin can be safely traded off for reduced stress on select transistors.

Design and Implementation of Discrete Event Control Systems: A Petri Net Based Hardware Approach

This paper presents a methodology for modeling and hardware implementation of discrete event control systems based on the formalism of Petri nets (PN). The control algorithm is initially specified as an executable PN specification which is subsequently compiled directly into a compact machine code and stored in commercially available programmable read only memory (PROM). As an implementation platform, a programmable Petri net based dedicated discrete event controller is proposed. The scalable architecture of the controller is optimized to process PN constructs of all possible classes. A remarkable feature of the proposed architecture is its ability to handle explicit concurrency. The controller exploits hardware-level parallelism to track multiple tokens (control threads) through the net. The performance of the architecture has been verified and benchmarked on the fabricated integrated circuit (IC) prototype of the controller.

High reliability polyoxide fabricated by using TEOS oxide deposited on disilane polysilicon film

This paper reports the TEOS oxide deposited on the polysilicon film which was prepared by using the disilane chemical vapor deposition. Compared to the thermally grown oxide or TEOS (tetra-ethyl-ortho-silicate) oxide deposited on the conventional silane polysilicon film, it had symmetrical J-E characteristics that had lower leakage currents but much higher breakdown field, a lower electron trapping rate, and a much larger charge to breakdown. These good properties are attributed to the smoother surface of the deposited disilane poly-I film and the more incorporation of nitrogen during the rapid thermal annealing (RTA) in N/sub 2/O ambient. It is suitable to be as the inter-polyoxide of the electrically-erasable programmable read only memory (EEPROM).

Use of a reluctance stepper motor for solar tracking based on a programmable logic array (PLA) controller

The tracking of solar cell panels in solar-generation systems has improved their overall efficiency to a great extent. The methods used previously were either active or passive. In order to ensure a relatively small position resolution for the panel axis, the DC motors ordinarily used for active solar tracking need a complicated gear system. In this work, a 8/6 four-phase, reluctance stepper motor (RSM) controlled by a programmable logic array (PLA) is used. The angular position resolution for the RSM is 7.5°. This resolution is guaranteed due to locking of the RSM at each step through a power converter fed from a 220 V DC supply. The control circuit for the power converter consists of an Erasable Electronic Programmable Read Only Memory (EEPROM) and a PLA chip. The control circuit is fed from two separate sensing cells which determine the movement to the next angular position. The application of this tracker is essential for stand-alone systems in remote areas. Its use may result in improving the solar energy generation by a considerable factor. The control system is a completely closed loop system without any human interference.

Effect of some technological parameters on Fowler–Nordheim injection through tunnel oxides for non-volatile memories

In this work the effects of various technological parameters on Fowler–Nordheim injection through thin (around 7.2 nm) silicon dioxide films in metal-oxide-semiconductor capacitors have been studied. Attention has been paid to the effect of gate geometry (round or strip gate) and area, substrate doping type (boron or phosphorus one), polycrystalline silicon gate structure (simple polysilicon or polysilicon-oxide-nitride-oxide-polysilicon structure) and tunnel oxide type (standard or nitrided silicon dioxide). The effect of all these parameters on Fowler–Nordheim tunneling injection and on the potential barrier height at both oxide injecting interfaces are usually neglected in literature and moreover the tunnel coefficients obtained from a simple capacitor are used in the simulation of programmable operations of electrically erasable programmable read only memories. Quasi-static capacitance (voltage) and current (voltage) measurements have been performed and the latter have been simulated by using a constant effective barrier height at the injecting interface. We have found that Fowler–Nordheim tunneling parameters and potential barrier height at both oxide injecting interfaces are affected by the substrate doping type, oxide type, gate geometry and gate structure but they are not affected by the gate area. Moreover in all structures, a difference between the barrier heights at the two injecting interfaces has been observed. The variation induced by the studied technological parameters on the potential barrier height are comparable to the variation induced by considering a constant (classical theory) or electrical field dependent (quantum theory) barrier height as reported in literature.

Radioactive Reliability of Programmable Memories

In this study, we examine the reliability of erasable programmable read only memory (EPROM) and electrically erasable programmable read only memory (EEPROM) components under the influence of gamma radiation. This problem has significance in military industry and space technology. Total dose results are presented for the JL 27C512D EPROM and 28C64C EEPROM components. There is evidence that EPROM components have better radioactive reliability than EEPROM components. Also, the changes to the EPROM are reversible, and after erasing and reprogramming all EPROM components are functional. On the other hand, changes to the EEPROM are irreversible, and under the influence of gamma radiation, all EEPROM components became permanently nonfunctional. The obtained results are analyzed and explained via the interaction of gamma radiation with oxide layers.

A Novel High-Density and High-Speed NAND-Type Electrical Erasable Programmable Read Only Memory

A new NAND-type electrical erasable programmable read only memory (EEPROM), which employs (1) the novel in-cell temporary storage (ICTS) technique and (2) the novel multiple-wordline parallel programming (MWPP) method, is proposed to reduce the unit cell size and decrease the overall programming time. The ICTS approach latches input data directly to the selected EEPROM cells by an inverted channel with different input bitline voltages. After all the selected cells are latched to individual data, the MWPP method simultaneously raises all selected wordlines to high voltage to perform FN tunneling for parallel programming. The equivalent byte programming time is considerably reduced by employing parallel programming. The high-speed and high-density features further reduce the EEPROM testing cost for manufacturers and save programming time and cost for system providers.

Measurements of dose with individual FAMOS transistors

A new method is described for measuring the doses absorbed by microstructures from an exposure to ionizing radiation. The decrease in the duration of ultraviolet light (UV) exposure required to erase each cell of a commercial UltraViolet erasable Programmable Read Only Memory (UVPROM) correlates with the dose absorbed by the floating gate of that transistor. This technique facilitates analysis of the microdose distribution across the array and the occurrence of Single Event Upsets (SEU) like anomalous shifts due to rare large energy-deposition events.

Directional Breakdown of Metal/a-Si:H/c-Si Heterostructures and its Application to PROMs

AbstractThis paper gives the first report of a directional breakdown phenomenon present in specially constructed amorphous silicon / crystalline silicon heterojunction structures. After breakdown, the forward current can be greatly increased, but the reverse leakage current remains unchanged or even lowered. We use the Analysis of Microelectronic and Photonic Structures (AMPS) [1] device simulation tool to study this phenomenon and show that the structures can provide a new approach to producing Programmable Read Only Memory (PROM).

Dosimetry based on the erasure of floating gates in the natural radiation environments in space

A new method is described for measuring ionizing radiation on spacecraft using an array of floating gate avalanche injected metal oxide silicon (FAMOS) transistors. A commercial ultraviolet erasable programmable read only memory (UVPROM) is used to demonstrate the technique for both ground and space dosimetry applications. An indirect measurement of the charge remaining on the floating gate is used to determine the absorbed dose. This method of determining dose leaves the data and the detector intact and capable of further measurements. The device requires power only during readout. Measurements of different ionizing radiation types are presented. Results from an experiment using this technique aboard the Microelectronics and Photonics Test Bed (MPTB) satellite are discussed.

Thermal Stress Analysis of Floating-Gate Tunneling Oxide Electrically Erasable Programmable Read Only Memory During Manufacturing Process

In this study, finite element modeling was used to evaluate the residual thermal stress in floating-gate tunneling oxide electrically erasable programmable read only memory (FLOTOX E2 PROMs) manufacturing process. Special attention is paid to the tunnel oxide region, in which high field electron injection is the basis to E2 PROMs operation. Calculated results show the presence of large stresses and stress gradients at the fringe. This may contribute to the invalidation of E2 PROMs. A possible failure mechanism of E2 PROM related to residual thermal stress-induced leakage is proposed.

Improving radiation hardness of EEPROM/flash cell by N2O annealing

The effects of an N/sub 2/O anneal on the radiation effects of a split-gate electrical erasable programmable read only memory (EEPROM)/flash cell with a recently-proposed horn-shaped floating gate were studied. We have found that although the cells appear to survive 1 Mrad(Si) Co/sup 60/ irradiation without data retention failure, the write/erase cycling endurance was severely impeded after irradiation. Specifically, the write/erase cycling endurance was degraded to 20 K from the pre-irradiation value of 50 K. However, by adding an N/sub 2/O annealing step after the interpoly oxidation, the after-irradiation write/erase cycling endurance of the resultant cell can be significantly improved to over 45 K. N/sub 2/O annealing also improves the after-irradiation program and erase efficiencies. The N/sub 2/O annealing step therefore presents a potential method for enhancing the robustness of the horn-shaped floating-gate EEPROM/flash cells for radiation-hard applications.

Reliability of nitrided wet silicon dioxide thin films in WSi2 or TaSi2 polycide process : influence of the nitridation temperature

In this paper it is investigated the influence of two polycide processes using WSi2 chemical vapor deposition (CVD) or TaSi2 deposition by sputtering on the integrity of wet and nitrided tunnel oxides (t ox= 6.6 nm) used in Electrical Erasable Programmable Read Only Memory (EEPROM) under negative Fowler Nordheim electron injection (FNEI). It was confirmed that the nitridation reduces the generation rates of defects created by FNEI (interface states, neutral traps, positive and negative charges) and the stress induced leakage current (SILC).This reduction is more pronounced when TaSi2 is used rather than WSi 2. In sputtering TaSi 2 process compared to the CVD WSi2 one, it was observed : ( i) - the generation of positive charges and the SILC are higher while the generation rates of interface states and negative charges are smaller ; ( ii) - the generation rate of neutral traps is higher in wet oxide while it is smaller in nitrided oxides. Whatever the polycide process, the generation of the different types of defects created by FNEI is reduced by increasing the nitridation temperature while the SILC is increased.

A Study on the Radiation Hardness of Flash Cell with Horn-Shaped Floating-Gate

The effects of radiation on the characteristics of split-gate electrical erasable programmable read only memory (EEPROM)/flash cells with recently-proposed horn-shaped floating gates are studied in terms of cell read current, data retention, cycling endurance, program/erase efficiency, threshold voltage and junction leakage. Our results show that the cells appear to survive after 1 Mrad (Si) Co60 irradiation. Moreover, the after-irradiation cell read current actually increases in the “erase” (i.e., low-threshold voltage, high-conducting) state (i.e., improves), albeit the cell read current also increases in the “program” (i.e., high-threshold voltage, low-conducting) state (i.e., a degradation). Our results also show that, despite an improvement in the initial read current in the “erase” state immediately after radiation, the write/erase cycling endurance of the flash cells is significantly impeded after irradiation, due to a much faster “window closure” rate in the “erase” state, although the cell read current is found to remain relatively stable in the “program” state after cycling.

Limitation of the TiN/Ti layer formed by the rapid thermal heat treatment of pure Ti films in an NH/sub 3/ ambient in fabrication of submicrometer CMOS flash EPROM IC's

In this study, the technical feasibility and limitation of the TiN film formed by the rapid thermal heat treatment (RTHT) in an ammonia ambient for the fabrication of 0.85-/spl mu/m CMOS flash electrically programmable read only memory (EPROM) integrated circuits having a contact aspect ratio of approximately 1.5, were investigated. When the as-deposited thickness of the Ti film was less than 130 /spl Aring/, all memory contacts exhibited an "electrically open" contact signature (>4750 /spl Omega//contact). Transmission electron microscopy (TEM) cross section examination of a failed contact chain structure indicated that the failure mechanism could be a physical separation at the W-plug/silicon interface. For the Ti films with thickness between 130 and 240 /spl Aring/, the contact resistance dropped to a value between 59 and 68 /spl Omega//contact. Furthermore, the contact failure rate (contacts exhibiting "electrically open" signature) decreased as the thickness of the Ti film increased. In this case, the failure mechanism appeared to be the direct contact between the TiN layer and the silicon at the contact interface. This condition was created during the multistep nitridation process where approximately 240 to 250 /spl Aring/ of the Ti film was converted to TiN. For the memory devices having Ti films thicker than 240 /spl Aring/, all memory contacts were electrically and mechanically stable, and exhibited equivalent or higher circuit yields compared to devices having a sputter deposited TiN/Ti bilayer film (control group).

Trade policy and learning by doing: the case of semiconductors

The study examines the role of learning by doing for production of different types of semiconductors and how this affects the dynamics of market structure. For erasable programmable read only memories (EPROMs) the learning curve determines aggregate market dynamics, whereas for dynamic random access memories (DRAMs) economies of scale seem to be more important. These results are compared with some stylised facts. For EPROMs, persistence of leadership in product innovation could be observed, whereas for DRAMs, there was leap-frogging in product innovation. Moreover, scope for vertical product differentiation is more enhanced for EPROMs and price competition is less intense. These findings are then related to the problem of identifying the appropriate trade policies in oligopolistic industries. The analysis concerns the antidumping actions undertaken by the European Commission. It is shown how markets enjoying similar patterns of protection have a completely different evolution of market shares for European producers. The conclusion for strategic trade policy is that industry specific features matter crucially.

A Novel High-Density EEPROM Cell Using a Polysilicon-Gate Hole (POLE) Structure Suitable for Low-Power Applications

A novel-high density electrically erasable and programmable read only memory (EEPROM) cell technology is proposed. The new cell utilizing a polysilicon-gate hole (POLE) structure can be used to reduce the channel length and the substrate current I sub by 2 orders of magnitude in comparison with a conventional stacked-gate flash cell by isolating the charge transfer region and thus strongly reducing band-to-band tunneling current. A 36 µm2 cell, which is 20% smaller than that of a floating gate tunnel oxide (FLOTOX) type EEPROM, with a 0.6 µm design rule can be realized. Furthermore, stable write and erase (W/E) operations are confirmed, and the characteristics of 1 million W/E cycles and 10-year data retention have been achieved.