Fowler-Nordheim Injection Research Articles

Analysis of damage curing in a MOSFET with joule heat generated by forward junction current at the source and drain

This study demonstrates a method for curing the gate dielectric of a MOSFET using Joule heat (JH) generated by forward bias current in the PN-junction in the drain-to-body (D-B) and source-to-body (SB). To accurately quantify the curing effect by the D-B JH and the SB JH, the interface trap density (Nit) of the gate dielectric was laterally profiled using a charge pumping characterization method. The curing method was applied to repair damage in the gate dielectric caused by Fowler-Nordheim (FN) and hot-carrier injection (HCI) stress. When FN stress was applied to the device, there is no difference in curing the damage by the D-B JH and the SB JH. However, when HCI stress, which asymmetrically causes more damage to the drain, was applied, the D-B JH showed better recovery than the SB JH.

High-$\kappa~{\rm Eu}_{2}{\rm O}_{3}$ and ${\rm Y}_{2}{\rm O}_{3}$ Poly-Si Thin-Film Transistor Nonvolatile Memory Devices

In this paper, we have successfully fabricated low-temperature polycrystalline silicon thin-film transistor (LTPS-TFT) nonvolatile memory devices employing high-κ Eu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> films as the charge trapping layer. The LTPS-TFT memory device uses band-to-band tunneling-induced hot hole injection and gate Fowler-Nordheim injection as the program and erase methods, respectively. Compared with the Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film, the LTPS-TFT memory device using an Eu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> charge-trapping layer exhibited a lower subthreshold swing and a larger memory window, a smaller charge loss, and a better endurance performance, presumably because of the higher charge-trapping efficiency of the Eu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film.

Erbium emission in MOS light emitting devices: from energy transfer to direct impact excitation

The electroluminescence (EL) at 1.54 µm of metal–oxide–semiconductor (MOS) devices with Er3+ ions embedded in the silicon-rich silicon oxide (SRSO) layer has been investigated under different polarization conditions and compared with that of erbium doped SiO2 layers. EL time-resolved measurements allowed us to distinguish between two different excitation mechanisms responsible for the Er3+ emission under an alternate pulsed voltage signal (APV). Energy transfer from silicon nanoclusters (Si-ncs) to Er3+ is clearly observed at low-field APV excitation. We demonstrate that sequential electron and hole injection at the edges of the pulses creates excited states in Si-ncs which upon recombination transfer their energy to Er3+ ions. On the contrary, direct impact excitation of Er3+ by hot injected carriers starts at the Fowler–Nordheim injection threshold (above 5 MV cm−1) and dominates for high-field APV excitation.

Effect of high temperature annealing on the performance of MANOS charge trapping memory

We have investigated the effect of post deposition annealing (PDA) temperature of Al2O3 blocking layer on the performance of charge trapping memory capacitors. Two splits of PDA were performed in N2 ambient at 850°C/60 s and 1050°C/60 s, respectively. The 1050°C annealed capacitor could be programmed and erased normally by using Fowler-Nordheim (FN) injection. In contrast, the 850°C annealed device could not be erased, even though it could be programmed properly. By measuring the gate leakage current and the flatband voltage shift, we found the erase failure in the 850°C annealed device was due to a larger gate back-injection leakage current at V g<0. The trend of gate leakage current was further verified in two Al/Al2O3/SiO2/p-Si control capacitors with the same PDA splits. In addition, constant voltage stress measurements on control capacitors in the FN regime showed that the change of gate leakage current followed an empirical Curie-von Schweidler law at V g<0. The data pointed out the importance to further study the relation between PDA conditions and the defect generation properties in Al2O3 blocking layer.

Dynamics of the Charge Centroid in Metal–Oxide–Nitride–Oxide–Silicon Memory Cells during Avalanche Injection and Fowler–Nordheim Injection Based on Incremental-Step-Pulse Programming

Dynamics of the Charge Centroid in Metal–Oxide–Nitride–Oxide–Silicon Memory Cells during Avalanche Injection and Fowler–Nordheim Injection Based on Incremental-Step-Pulse Programming

Dynamics of the Charge Centroid in Metal–Oxide–Nitride–Oxide–Silicon Memory Cells during Avalanche Injection and Fowler–Nordheim Injection Based on Incremental-Step-Pulse Programming

In this study we have carried out a precise analysis on transient charge centroid dynamics during the programming of metal–oxide–nitride–oxide–silicon (MONOS) memory cells. Using the incremental-step-pulse programming (ISPP) scheme, the charge centroid is exactly extracted during the programming. Furthermore, avalanche injection enables low-field carrier injection, making it easy to identify the accessible trap sites in the charge trap layer. Avalanche injection is also used to study the field dependence of available traps. From this analysis, the charge centroid of MONOS memory is found to move from the tunnel layer/charge layer interface to the charge layer/block layer interface during low-field programming. In contrast, the location of the charge centroid is limited to the charge layer/block layer interface when the Fowler–Nordheim (FN) injection is used for programming at a high electric field. Furthermore, the low-electric-field programming achieves a high capture efficiency owing to a larger flatband shift in this programming than in high-electric-field programming. Therefore, low-electric-field programming is desired to increase the trap site availability and carrier capture efficiency.

Nonvolatile Memory With Ge/Si Heteronanocrystals as Floating Gate

A p-channel memory with Ge/Si heteronanocrystals (HNCs) as the floating gate was fabricated and tested. The nanocrystals (NCs) were synthesized by low-pressure chemical vapor deposition of Si NCs followed by selective growth of Ge on top of Si. Both hole and electron storages were characterized in Ge/Si HNC memory. Fowler-Nordheim and hot carrier injection programming operations were studied. Compared to Si NC memory, enhanced memory performances were demonstrated in Ge/Si HNC memory in terms of longer retention, larger storage capability, and faster programming.

Repeating of positive and negative high electric field stress and corresponding thermal post-stress annealing of the n-channel power VDMOSFETs

We have subjected n-channel power VDMOSFETs to a positive and negative high electric field stress (HEFS) followed by biased annealing at 150°C. Stress-induced defects have been monitored using midgap-subthreshold and charge-pumping techniques, the use of which in tandem has enabled an insight into behaviours of fixed and switching traps in the gate oxide and oxide/silicon interface. The repetition of the stress/annealing sequence has resulted in some quantitative but no qualitative differences in response compared to the original sequence. We have observed complex kinetics of different types the stress-induced defects during post-HEFS annealing, including an intriguing latent buildup of “true” interface traps. Comparison of post-HEFS and post-irradiation annealing data has indicated differences of the nature of defects induced by Fowler-Nordheim injection and irradiation in our samples.

Microwatt MOSLED Using ${\hbox {SiO}}_{\rm x}$ With Buried Si Nanocrystals on Si Nano-Pillar Array

Microwatt light emission from a metal-oxide-semiconductor light-emitting diode (MOSLED) made by using SiOx film with buried Si nanocrystals on Si nano-pillar array is demonstrated. The Si nano-pillar array obtained by drying the rapidly self-aggregated Ni nano-dot-masked Si substrate exhibit size, aspect ratio, and density of 30 nm, 10, and 2.8times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , respectively. These high-aspect-ratio Si nano-pillar array helps to enhance the Fowler-Nordheim tunneling-based carrier injection and to facilitate the complete relaxation on total internal reflection, thus increasing the quantum efficiency by one order of magnitude and improving the light extraction from the nano-roughened device surface by three times at least. The light-emission intensity, turn-on current and power-current slope of the MOSLED are 0.2 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 20-30 muA, and 3plusmn0.5 mW/A, respectively. At a biased current of 400 muA, the highest external quantum efficiency is over 0.2% to obtain the maximum EL power of > 1 muW. Compared with the same device made on smooth Si substrate under a power conversion ratio of 1 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , such an output power performance is enhanced by at least one order of magnitude.

Negative bias temperature instability and Fowler-Nordheim injection in silicon oxynitride insulators

Negative bias temperature instability and Fowler-Nordheim injection measurements have been performed on p-channel field effect transistors. For Fowler-Nordheim injection a comparison of the threshold voltage shift and the reduced channel transconductance shows similar linear behavior to that observed for hot electron stressing of n-channel devices. Comparison for bias temperature instability shows dramatically different behaviors. Simultaneous negative bias temperature instability and Fowler-Nordheim injection lead to potentially significant errors in the estimation of the reliability lifetime.

Finite-Element Analysis of Corona Discharge Onset in Air With Artificial Diffusion Scheme and Under Fowler–Nordheim Electron Emission

A complete finite-element analysis method for corona discharge process, which is governed and coupled by charge transport equation and electric field equation, was presented. The charge transport equation of first order was transformed into second order by utilizing the artificial diffusion scheme. The two second-order equations were analyzed by the finite-element formulation which is well-developed for second-order equations. The Fowler-Nordheim injection boundary condition was adopted for charge transport equation. After verifying the numerical results by comparing to the analytic solutions using parallel plane electrodes with one carrier system, we extended the result to blade-plane electrodes in 2-D xy geometry with three carriers system. Radius of the sharp tip was taken to be 50 mum. When this sharp geometry was solved by utilizing the space discretizing methods, the very sharp tip was found to cause a singularity in electric field and space charge distribution around the tip. To avoid these numerical difficulties in the finite-element method, finer meshes, a higher-order shape function, and artificial diffusion scheme were employed

Charge transport along luminescent oxide layers containing Si and SiC nanoparticles

The electrical conductivity of silicon oxides containing silicon and silicon–carbon nanoparticles has been investigated. By use of sequential Si + and C + ion implantations in silicon oxide followed by an annealing at 1100 °C, luminescent Si nanocrystals and SiC nanoparticles were precipitated. The characterization of the electrical transport has been carried out on two kinds of structures, allowing parallel or perpendicular transport, with respect to the substrate. The first type of samples were elaborated by means of a focus-ion-beam technique: electrical contacts to embedded nanoparticles were made by milling two nanotrenches on the sample surface until reaching the buried layer, then filling them with tungsten. The distance between the electrodes is about 100 nm. The second type of samples correspond to 40 nm thick typical MOS capacitors. The electron transport along the buried layer has shown a dramatic lowering of the electrical current, up to five orders of magnitude, when applying a sequence of voltages. It has been related to a progressive charge retention inside the nanoparticles, which, on its turn, suppresses the electrical conduction along the layer. On the other hand, the MOS capacitors show a reversible carrier charge and discharge effect that limits the current at low voltage, mostly due to the presence of C in the layers. A typical Fowler–Nordheim injection takes place at higher applied voltages, with a threshold voltage equal to 23 V.

On the generation and recovery of interface traps in MOSFETs subjected to NBTI, FN, and HCI stress

A common framework for interface-trap (NIT) generation involving broken equivSi-H and equivSi-O bonds is developed for negative bias temperature instability (NBTI), Fowler-Nordheim (FN), and hot-carrier injection (HCI) stress. Holes (from inversion layer for pMOSFET NBTI, from channel due to impact ionization, and from gate poly due to anode-hole injection or valence-band hole tunneling for nMOSFET HCI) break equivSi-H bonds, whose time evolution is governed by either one-dimensional (NBTI or FN) or two-dimensional (HCI) reaction-diffusion models. Hot holes break equivSi-O bonds during both FN and HCI stress. Power-law time exponent of NIT during stress and recovery of NIT after stress are governed by relative contribution of broken equivSi-H and equivSi-O bonds (determined by cold- and hot-hole densities) and have important implications for lifetime prediction under NBTI, FN, and HCI stress conditions

Single molecule electrical transport using self-assembled-monolayers

The understanding of current flow through molecular conductors requires an interdisciplinary approach to molecular electronics. New reproducible experiments with better assembling, including more sophisticated fabrication processes and structural control as a feedback for assembling of molecular devices, and designing molecular electronic devices with pre-defined properties are essential for this goal. Any interpretation of molecular transport experimental data requires information on the number of molecular wires per device, device structure and geometry, and the nature of the molecular-electrode bonding. The lack of this knowledge is the pivotal problem in molecular electronics. We have thus embarked in developing approaches to fabricate molecular electronic devices through self-assembled-monolayer (SAM) of molecular wires and insulating molecules in solid-state solutions that enable fine structural control, along with development of spectroscopic and electrical transport tools to study these structures. We used ellipsometry and reflectance spectroscopy to verify that the SAM films can be tuned by changing the ratio, r of molecular conductors (wires, such as Me-BDT) to insulating molecules (spacers, such as PT). We used surface titration for estimating the number of molecular wires per device. The single molecule electrical transport process in the vertical sandwich configuration SAM diodes with small r-value (r < 10 −3) that is based on isolated molecular wires, reveals a Fowler-Nordheim type tunneling injection mechanism. However this behavior is not observed in devices fabricated with large r-values.

Hole energy dependent interface trap generation in MOSFET Si/SiO/sub 2/ interface

The nature and composition of generated interface-trap (/spl Delta/N/sub IT/) in p-MOSFETs is studied as a function of hole energy. By observing the time dependence of generation during stress and the amount of recovery after stress, it is shown that /spl Delta/N/sub IT/ is due to both broken /spl equiv/Si--H and /spl equiv/Si--O-- bonds, their ratio governed by hole energy. In the absence of hot holes /spl Delta/N/sub IT/ is primarily composed of broken /spl equiv/Si--H, which show a lower power-law time exponent and a fraction of which anneal after stress. Additional /spl Delta/N/sub IT/ is created in the presence of hot holes, which is due to broken /spl equiv/Si--O-- bonds. These traps show a much larger power-law time exponent, and they do not anneal after stress. These observations have important implications for lifetime prediction under negative bias temperature instability, Fowler-Nordheim, and hot carrier injection stress conditions.

EEPROM programming window changes with operating temperature

This paper is devoted to the understanding of Electrically Erasable Programmable Read Only Memory (EEPROM) programming window (PW) changes with operating temperature. First a theoretical analysis is carried out, and two main contributions to the PW change are identified: change of the sense transistor characteristics and variation of the FN (Fowler–Nordheim) injection mechanism. An experimental study is then conducted on samples with various size (0.8 and 19 360 μm 2) and coupling coefficients (0.45, 0.62 and 0.71), for temperatures in the range 25–200 °C. Whereas the results concerning the erased mode are reproducible and quantitatively explained by the model, data relative to the written state of real size cells features an irreproducible behavior which was not elucidated.

A Novel PHINES Flash Memory Cell with Low Power Program/Erase, Small Pitch, Two-Bits-Per-Cell for Data Storage Applications

A novel programming by hot-hole injection nitride electron storage (PHINES) Flash memory technology is developed. The memory bit size of 0.046 /spl mu/m/sup 2/ is fabricated based on 0.13-/spl mu/m technology. PHINES cell uses a nitride trapping storage cell structure. Fowler-Nordheim (FN) injection is performed to raise V/sub t/ in erase while programming is done by lowering a local V/sub t/ through band-to-band tunneling-induced hot hole (BTBT HH) injection. Two-bits-per-cell feasibility, low-power and high-speed program/erase, good endurance and data retentivity make it a promising candidate for Flash EEPROM technology in gigabit era applications.

Master equation approach to charge injection and transport in organic insulators

We develop a master equation model of a disordered organic insulator sandwiched between metallic electrodes by treating as rate processes both the injection and the internal transport. We show how the master equation model allows for the inclusion of crucial correlation effects in the charge transport, particularly of the Pauli exclusion principle and of space-charge effects, besides, being dependent on just the microscopic form of the transfer rate between the localized electronic states, it allows for the investigation of different microscopic scenarios in the organic, such as polaronic hopping, correlated energy levels, interaction with image charge, etc. The model allows for a separate analysis of the injection and the recombination currents. We find that the disorder, besides increasing the injection current, eliminates the possibility of observation of a Fowler-Nordheim injection current at zero temperature, and that it does not alter the Schottky barrier size of the zero-field thermionic injection current from the value based on the energy difference between the electrode Fermi level and the highest occupied molecular orbital/lowest unoccupied molecular orbital levels in the organic, but it makes the Arrhenius temperature dependence appear at larger temperatures. We investigate how the I(V) characteristics of a device is affected by the presence of correlations in the site energy distribution and by the form of the internal hopping rate, specifically the Miller-Abrahams rate and the Marcus or small-polaron rate. We show that the disorder does not modify significantly the ebeta square root E field dependence of the net current due to the Schottky barrier lowering caused by the attraction between the charge and its image in the electrode.

Dynamic Fowler–Nordheim injection in EEPROM tunnel oxides at realistic time scales

The purpose of this work is to investigate the dynamic behaviour of Fowler–Nordeim injection through EEPROM tunnel oxides, in conditions representative of the standard device operation. An experimental procedure based on the acquisition of current transients induced by trapezoidal-shape short voltage pulses is presented. It is then used to evidence a rapid positive charging and to determine some of its properties. Implications regarding the device behaviour and modelling are finally discussed.

Hole-Traps in Silicon Dioxides—Part II: Generation Mechanism

After studying the properties of hole traps in Part I, attention is turned to the physical processes responsible for generating hole traps in Part II of this work. The applicability of four models to hole-trap creation will be examined. These are the trapped hole-electron recombination model, the electrical field energy model, the hole injection model, and the hydrogen model. To testify these models, stresses have to be carried out not only under substrate hole injection (SHI), but also under Fowler-Nordheim injection (FNI). By combining FNI with SHI, we will be able to control hole fluency independent of the electron-induced hydrogen release. This allows us to determine how important hydrogen is for hole-trap generation. Although it was reported that hydrogen could play a major role in positive charge generation for devices with an Al gate or without a gate, we will show that hydrogen does not dominate hole-trap generation, when poly-si gated devices are stressed under our test conditions. Unambiguous results will also be given to show that key predictions of the recombination model and the electrical field energy model are not observed here. In this paper, the most important process for hole-trap generation is found to be the direct interaction of injected holes with the oxide.