Substrate Hot Hole Injection Research Articles

Stress induced leakage current generated by hot-hole injection

Graphical abstractDisplay Omitted SILC caused by hot-hole injection depends only on the number of injected holes.SILC is independent of the filed, and carrier density and energy at the stress.SILC increases exponentially at an early stress and linearly at a large stress. Stress induced leakage current (SILC) of the gate dielectrics is one of the most critical problems in a scaling down of flash memories, and it is important to clarify the mechanism of SILC generation. In this paper SILC caused by substrate hot-hole injection is investigated. The SILC caused by hot-hole injection depends only on the number of injected holes and is independent of the oxide field, hole energy, and injected hole density. SILC is defined by the current at largest leakage path, and the largest leakage path increases with the increase of the stress at the early stress region and SILC is defined by average value of the large number of leakage spots, then the SILC increases linearly with the stress.

Comparison of hot-hole injections in ultrashort channel LDD nMOSFETs with ultrathin oxide under an alternating stress

The behaviours of three types of hot-hole injections in ultrashort channel lightly doped drain (LDD) nMOSFETs with ultrathin oxide under an alternating stress have been compared. The three types of hot-hole injections, i.e. low gate voltage hot hole injection (LGVHHI), gate-induced drain leakage induced hot-hole injection (GIDLIHHI) and substrate hot-hole injection (SHHI), have different influences on the devices damaged already by the previous hot electron injection (HEI) because of the different locations of trapping holes and interface states induced by the three types of injections, i.e. three types of stresses. Experimental results show that GIDLIHHI and LGVHHI cannot recover the degradation of electron trapping, but SHHI can. Although SHHI can recover the device's performance, the recovery is slight and reaches saturation quickly, which is suggested here to be attributed to the fact that trapped holes are too few and the equilibrium is reached between the trapping and releasing of holes which can be set up quickly in the ultrathin oxide.

Evidence of Deep Energy States from Low Temperature Measurements and Its Role in Charge Trapping in Metal Gate/Hf-Silicate Gate Stacks

Pre-existing electron and hole trap energy levels, lying deep within the bulk high-k bandgap, are experimentally observed from low temperature measurements for the first time in metal organic chemical vapor deposited (MOCVD) TiN/HfSixOy based gate stacks. Their role in trapping under constant voltage and substrate hot hole stress conditions is investigated. Mixed degradation due to both electron and hole trapping in the deep pre-existing bulk traps, which induces a turn-around effect in flatband voltage shift (DVFB), is observed for n-channel MOS capacitors under gate injection. Bulk hole trap generation, which causes DVFB to follow tn power law dependence, is observed for p+-ringed p-channel MOS capacitors under substrate hot hole injection. Activation energies of the stress induced traps and pre-existing deep defects are experimentally found to be different.

A novel SONOS nonvolatile flash memory device using substrate hot-hole injection for write and gate tunneling for erase

In this work, we describe a novel SONOS device suitable for future nonvolatile flash memories. Substrate hot-hole injection (HHI) through a bottom oxide is used for write and gate tunneling through a thin top oxide is employed for erase. We present device DC and dynamic characteristics at low voltages (<10 V) for SONOS devices with a gate dielectric stack consisting of a 3.8 nm bottom oxide, 1.5 nm nitride and 3.0 nm top oxide. We obtain a reduction in power consumption by 4 orders of magnitude, an improvement in retention by 90%, and an improvement in subthreshold swing by 40% with a novel write/erase technique compared with Substrate HHI for erase and channel hot electron (CHE) injection for write.

Analysis of the kinetics for interface state generation following hole injection

Interface state generation is a major reliability issue for metal–oxide–semiconductor based devices. The generation can take place not only during stresses, but also after terminating the stress. Our attention is focused on analyzing the dynamic behavior of the generation after substrate hot hole injection. Despite previous efforts in this area, the generation kinetics is not fully understood, and there is insufficient information on the process limiting the generation rate. We start by showing that the normalized generation kinetics is insensitive to either the defect density or the processing condition. We then investigate the effect of various stressing parameters on the kinetics, including the oxide field strength during and posthole injection, the stress time, the energy and current of hot holes. This is followed by examining why the available models are inapplicable in our cases, including hydrogen transportation, trapped hole conversion, and coupling models. Finally, we propose both hydrogen emission and detrapping of a certain type of hole traps as the rate limiting processes, and the relative importance of these two is addressed.

Interaction between low-energy electrons and defects created by hot holes in ultrathin silicon dioxide

The interaction of injected electrons with defects created by hot holes in 2.0-nm-thick silicon dioxide is studied using substrate hot hole injection and concomitant electron tunneling. The ratio of injected hot holes to electrons is varied from approximately 10−3 to 100 by changing the forward biased substrate hot hole injector voltage. Increased bulk and interfacial degradation caused by the interaction of concomitantly injected electrons with defects created by hole injection is not observed for the experimental conditions studied. The ability of defects to produce catastrophic breakdown is also not affected. The results suggest that the interaction of tunneling electrons with defects created by hot holes is not a viable mechanism for explaining the catastrophic breakdown of the oxide layer in field-effect transistors.

Reliability of ultra-thin silicon dioxide under substrate hot-electron, substrate hot-hole and tunneling stress

Substrate hot-electron and substrate hot-hole injection experiments are used to provide insight into defect generation and breakdown of ultra-thin silicon dioxide under constant voltage tunneling stress. Results from substrate hot-electron injection confirm that energetic electrons are responsible for degradation and breakdown of ultra-thin silicon dioxide under tunneling stress conditions. Substrate hot-hole injection experiments suggest that mechanisms other than trapping of hot holes may be responsible for the breakdown of ultra-thin silicon dioxide.

Defect generation and breakdown of ultrathin silicon dioxide induced by substrate hot-hole injection

Hole-induced bulk and interface defect generation and breakdown in ultrathin silicon dioxide (2.0 and 3.0 nm) are studied using substrate hot-hole injection. The results show that although these substrate hot holes are effective in creating electrically active damage in the dielectrics, these defects are very ineffective in causing breakdown as compared to those defects created by constant voltage tunneling stress. Identical to hole trapping in thicker oxides, substrate hot-hole defect generation was independent of electric field, decreased with decreasing thickness, and increased with decreasing temperature. The defect generation and breakdown of ultrathin oxides by substrate hot-hole stress is significantly different from that observed for constant voltage tunneling stress. The results suggest that the degradation and breakdown of ultrathin silicon dioxide cannot be explained by the trapping of hot holes alone.

Excess currents induced by hot hole injection and FN electron injection in thin SiO/sub 2/ films

The behavior of excess currents induced by Fowler-Nordheim electron injection stress (FN electron injection) has been investigated for 6.0-nm oxides. Excess currents are induced by FN electron injection in 6.0-nm oxides together with positive charges being induced in it. To clarify the role of hole injection in FN electron injection, the behavior of excess currents induced by substrate hot hole injection has also been investigated in 6.0-nm oxides. The leakage behavior after hot hole injection is the same as FN electron injection. The excess currents induced both by the FN electron injection and by the substrate hot hole injection are due to trap-assisted tunneling and field enhancement at the cathode due to the positive trapped charge. The charge centroid of the positive charges induced by both stresses are located 3.0 nm from the Si/SiO/sub 2/ interface which is at the center of 6.0-nm oxide. The excess currents induced by hot hole injection and FN electron injection are caused by traps in SiO/sub 2/ films produced by injected holes from the anode.

Degradation of oxides and oxynitrides under hot hole stress

The impact of nitridation on hot hole injection and the induced degradation is quantitatively studied by comparing the behavior of a control oxide and oxynitrides. The oxynitride is prepared by either annealing the oxide in N/sub 2/O or growing directly in N/sub 2/O. The pMOSFET's are uniformly stressed by using the substrate hot hole injection technique. The physical quantities analyzed include the hole injection current, the density of created interface states and the density of trapped holes. It is found that a 30 min annealing in N/sub 2/O at 950/spl deg/C can enhance the effective barrier for hole injection by 0.6 eV. However, the interface state generation during the injection is insensitive to nitridation. The continuing degradation post the hole injection is also investigated. This includes a poststress interface state build-up and the generation of new precursors for interface states. The nitridation reduces the poststress degradation considerably. Where it is necessary, the hole induced degradation is compared with that induced by electrons. The applicability of the models proposed for oxynitrides to the present results is examined.

Increased hole trapping in gate oxides as latent damage from plasma charging

With aggressive device scaling and the wide use of plasma-assisted processes, the device damage caused by process-induced charging is receiving growing attention, from both basic understanding and technological points of view. The paper presents results of hole-trapping studies in the thin gate oxide of plasma-damaged NMOS and PMOS transistors. In addition to neutral electron traps and passivated interface damage, which are commonly observed in plasma charging latent damage, we observed and identified hole traps, generated by plasma stress. Enhanced hole trapping in the gate oxide of plasma-damaged devices was studied using Fowler - Nordheim stress and substrate hot-hole injection applied to antenna test structures sensitive to process-induced charging. The number of hole traps increases with increasing antenna ratio, indicating that the mechanism of hole-trap generation is based on electrical stress and current flow, forced through the oxide due to charging under plasma etching or ion implantation conditions.

Dielectric breakdown caused by hole-induced-defect in thin SiO 2 films

The dielectric breakdown induced by substrate hot-hole injection has been investigated using p-channel MOSFETs with the gate oxide of the thickness ranging from 60 to 120 Å and it has been revealed that the breakdown is induced by hole injection from the Si substrate even at low oxide fields. The positive charge to breakdown ( Q PBD) calculated from integrating the hole current is independent of the oxide field, but decreases rapidly with decreasing the oxide thickness. Also, it has been shown that the positive charges in SiO 2 film induced by hole injection are removed by the annealing at 250°C, while the hole trap centers are not disappeared. This suggests that the dielectric breakdown occurs at a weak oxide spot, which can capture the positive charges.

Oxide thickness dependence of hole trap generation in MOS structures under high-field electron injection

Hole trapping in the gate oxide of MOS devices causes instabilities of device parameters and serious reliability problems in MOS transistors and memories. In this work, hole traps, generated by high-field electron injection, are studied in thermal oxides in the thickness range below 10 nm. PMOS transistors, after various doses of positive and negative FN injection and post-stress annealing are subjected to substrate hot hole injection to investigate hole trapping kinetics. Parameters of hole traps, generated under the stress, are studied as a function of gate oxide thickness and stress dose.

Characterization of Hole Traps Generated by Electron Injection in Thin SiO2 Films

ABSTRACTMOS device stability can be significantly affected by charge trapping in the gate oxide, which changes device parameters and causes serious reliability problems in transistors and memory cells. Hole traps, generated by high-field electron injection, are studied in this work in devices with thermal oxides less than 10 nm thick. PMOS transistors, after various doses of positive and negative Fowler-Nordheim injection and post-stress annealing, are subjected to substrate hot hole injection to investigate hole trapping kinetics. Parameters of hole traps, generated under the stress, are studied as a function of gate oxide thickness and electron injection dose.

Generation of hole traps in thin silicon oxide layers under high-field electron injection

The letter reports an observation of a new degradation mechanism in thermal silicon dioxide layers on silicon, namely generation of hole traps under high-field stressing of metal-oxide-semiconductor (MOS) structure. Excess hole trapping due to newly generated hole traps is observed by substrate hot-hole injection in 9 nm oxide of p-channel MOS transistors after high-field Fowler-Nordheim stress followed by standard post-metallization annealing in nitrogen. The concentration of generated traps has a weak stress-polarity dependence and increases with electron fluence during degrading stress. Relaxation behavior under switching oxide fields indicates that the nature of hole trapping sites is different from anomalous positive charge centers.

Generation of Hole Traps in Silicon Dioxide Under Fowler-Nordheim Stress

AbstractHigh field electron injection in silicon oxide layers in metal-oxide-semiconductor system is widely known to degrade thin silicon oxide layers and the silicon-oxide interface, eventually leading to catastrophic oxide breakdown. In this work we report generation of hole traps under high-field stressing of thermal silicon dioxide layers on silicon. Excess hole trapping on newly generated hole traps is observed by substrate hot-hole injection in 9 nm oxide PMOS transistors after high-field Fowler-Nordheim stress followed by standard post-metallization annealing in nitrogen. The concentration of generated traps is stress-polarity dependent and increases with electron fluence during degrading stress. Relaxation behavior under switching oxide fields indicates that the nature of hole trapping sites is different from anomalous positive charge centers. A correlation of density of generated hole traps with the amount of generated electron traps shows that both types of traps are effectively generated in the oxide layer under Fowler-Nordheim tunneling electron injection.

Non-local effects in p-MOSFET substrate hot-hole injection experiments

Extensive measurements of hot-hole injection probability from silicon into silicon dioxide covering a wide range of oxide fields and substrate biases are presented and compared with results previously published in the literature. It is found that, in the highly inhomogeneous electric fields typically needed to induce substrate hole injection, nonlocal effects take place that limit the possibility to accurately describe injection probability data by means of a unique set of lucky carrier model parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Generation and relaxation phenomena of positive charge and interface trap in a metal-oxide-semiconductor structure

Positive charge and interface trap generation during substrate hot-hole injection into the insulating layer of a metal-oxide-semiconductor (MOS) structure is investigated using p-channel MOS transistors with very thin oxide thicknesses in the range from 4.6 to 15 nm. Positive charge fluence in the oxide due to hole trapping is found to saturate for an injected hole density over 1016 cm−2. A model based on first-order trapping kinetics is presented to describe hole trapping phenomena including the dispersive nature of capture cross-section. A universal relationship between hole trapping and interface trap generation is observed experimentally, which implies direct involvement of holes in the formation of interface traps at the Si/SiO2 interface. A generation mechanism related with hole trapping in the oxide is discussed. Postinjection relaxation of the trapped holes showed strong dependence on both oxide field magnitude and polarity. Detrapping under positive gate voltage is consistent with the concept of direct tunneling discharge, while negative gate voltage relaxation occurs due to electron injection by Fowler–Nordheim mechanism. A new phenomena of time dependent annealing of interface traps has been observed after the end of hole injection, which contradicts the reports of time delayed interface trap generation.

Spatial distribution of trapped holes in SiO2

Spatial distribution of trapped holes and the position of charge centroid in the insulating layer of a metal-oxide-semiconductor (MOS) structure are determined after substrate hot-hole injection experiments using MOS transistors with very thin oxides. Considerable hole trapping is observed even in samples with extremely thin (∼4.6 nm) oxide film. Most of the trapped holes exist between 2–6 nm from the Si/SiO2 interface. Trapped holes are found to be distributed in the form of an exponentially decaying function of distance from the same interface. Charge centroid is determined to be located at 3.2 nm from the Si/SiO2 interface for the oxide thickness range used in this study.

Critical analysis of the substrate hot-hole injection technique

To explore its potentials and limitations as a technique for the controlled injection of holes in the study of degradation phenomena in MOSFETs, the substrate hot-hole injection technique has been analyzed in detail. The minority carrier flow and the corresponding potential drop in the channel during operation has been analytically modeled. The nature of the measured gate current has been examined. The gate current is, at moderate oxide fields and trapped charge levels, uniquely consisting of holes injected uniformly from the silicon substrate into the gate oxide, while under very high oxide field and/or trapping conditions, simultaneous injection of electrons from the gate may occur. The hot-hole injection probability at 295 K has been modeled with a “lucky-hole” model, that takes into account over-the-barrier injection as well as through-the-barrier tunneling. Due to backtunneling of injected holes, the effective injection probability at 77 K is smaller than at 295 K. It is concluded that under proper operating conditions, substrate hot-hole injection is a powerful and reliable technique.