A comprehensive trapped charge profiling technique for SONOS flash EEPROMs

Nair, Pradeep R.; Kumar, Brijesh; Sharma, Ravinder; Mahapatra, S.; Kamohara, S.

doi:10.1109/iedm.2004.1419170

Cited by 7 publications

(12 citation statements)

References 5 publications

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“…These observations rule out vertical or lateral charge redistribution in ONO to be the major cause behind disturb, as explained below. In these programmed cells, the lateral spread of trapped electrons was found to be 40-50 nm, of which about 30-40 nm is above channel region and the rest in gate-drain overlap region [16]. The peak of this distribution is near the gate edge and the magnitude gradually decreases toward center of the channel.…”

Section: A Identification Of Disturb Mechanismmentioning

confidence: 95%

“…A programmed cell with charge (equivalent to the ONO trapped charge) placed at the Si/SiO 2 interface was used for these simulations [16]. Fig.…”

Section: A Identification Of Disturb Mechanismmentioning

confidence: 99%

“…CP [16]- [18] is used to verify hole injection and any resultant generation of interface traps (N IT ) after disturb and erase. Fig.…”

Section: A Identification Of Disturb Mechanismmentioning

confidence: 99%

“…It is more likely that more hot holes are being injected in compensated cells having lower L. One possible source of this additional component could be the channel leakage current. Localized charge trapping in SONOS cells degrades the subthreshold slope of programmed cells [16], [22], which can lead to channel leakage current even under disturb conditions, especially at scaled L. The channel electrons can undergo impact ionization due to large lateral fields and the generated holes can also get heated and injected into ONO stack. Compensated cells have a lower V TH , resulting in higher channel leakage current under similar disturb bias, which could lead to larger disturb in these cells.…”

Section: B Impact Of Device Structure and Dopingmentioning

confidence: 99%

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Investigation of Drain Disturb in SONOS Flash EEPROMs

Kumar

Sharma

Nair

et al. 2007

IEEE Trans. Electron Devices

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Abstract-The mechanism of drain disturb is studied in siliconoxide-nitride-oxide-silicon Flash electrically erasable programmable read-only memory cells. It is shown that disturb is a serious problem in programmed cells and is caused by injection of hot holes from substrate into the oxide/nitride/oxide stack. The origin of these holes is identified by analyzing the influence of halo doping, channel doping, and channel length scaling on drain disturb. Band-to-band tunneling at the drain junction is normally the dominant source of these holes. It is also shown that holes generated out of impact ionization of channel electrons become dominant in cells with high channel leakage (especially at lower channel lengths). Finally, the effect of repeated program/ erase cycling on drain disturb is studied. Drain disturb becomes less severe with cycling, the reasons for which are determined using gate-induced drain leakage measurements and device simulations.Index Terms-Band-to-band tunneling (BTBT), charge pumping (CP), drain disturb, Flash electrically erasable programmable read-only memories (EEPROMs), gate-induced drain leakage (GIDL), hot holes, silicon-oxide-nitride-oxide-silicon (SONOS).

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Section: A Identification Of Disturb Mechanismmentioning

confidence: 95%

“…A programmed cell with charge (equivalent to the ONO trapped charge) placed at the Si/SiO 2 interface was used for these simulations [16]. Fig.…”

Section: A Identification Of Disturb Mechanismmentioning

confidence: 99%

“…CP [16]- [18] is used to verify hole injection and any resultant generation of interface traps (N IT ) after disturb and erase. Fig.…”

Section: A Identification Of Disturb Mechanismmentioning

confidence: 99%

Section: B Impact Of Device Structure and Dopingmentioning

confidence: 99%

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Investigation of Drain Disturb in SONOS Flash EEPROMs

Kumar

Sharma

Nair

et al. 2007

IEEE Trans. Electron Devices

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“…In this paper, we use all the above methods (I-V , GIDL, and CP) to comprehensively establish the lateral profile of trapped electrons in a programmed SONOS cell and remove the ambiguity [1]. We also use Monte Carlo simulations to determine the lateral CHE distribution.…”

Section: Lateral Profiling Of Trapped Charge In Sonos Flashmentioning

confidence: 99%

Lateral profiling of trapped charge in SONOS flash EEPROMs programmed using CHE injection

Kumar

Nair

Sharma

et al. 2006

IEEE Trans. Electron Devices

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The lateral profile of trapped charge in a siliconoxide-nitride-oxide-silicon (SONOS) electrically erasable programmable read-only memory programmed using channel-hotelectron injection is determined using current-voltage (I D-V G) measurements along with two-dimensional device simulations and is verified using gate-induced-drain-leakage measurements, charge-pumping (CP) measurements, and Monte Carlo simulations. An iterative procedure is used to match simulated I D-V G characteristics with experimental I D-V G characteristics at different stages of programming, by sequentially increasing the trapped electron charge in simulations. Fresh cells are found to contain a high laterally nonuniform trapped charge, which (along with large electron injection during the program) make the conventional CP techniques inadequate for extracting the charge profile. This charge results in a nonmonotonous variation of threshold and flat-band voltages along the channel and makes it impossible to simultaneously determine interface and trapped charge profiles using CP alone. The CP technique is modified for application to SONOS cells and is used to verify the charge profile obtained using I D-V G and to estimate the interface degradation. This paper enhances the study presented in our earlier work. Index Terms-Channel-hot-electron (CHE) injection, charge pumping (CP), gate-induced drain leakage (GIDL), nonuniform charge trapping, silicon-oxide-nitride-oxide-silicon (SONOS) electrically erasable programmable read-only memories (EEPROMs), trapped charge profiling. I. INTRODUCTION T HERE IS A renewed interest in silicon-oxide-nitrideoxide-silicon (SONOS) (including NROM type) electrically erasable programmable read-only memories (EEPROMs) as floating-gate (FG) EEPROMs are approaching their scaling limits [2]-[6]. In addition to their better scalability compared to FG EEPROMs, SONOS EEPROMs are also easier to fabricate making them suitable for embedded applications [4], [5]. They also provide a 2-bit/cell operation, when the charge storage is laterally localized in the nitride by using localized injection mechanisms like channel-hot-electron (CHE) injection Manuscript received

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Directly resolving particles in an electric field: local charge, force, torque, and applications

Liu

2011

Numerical Meth Engineering

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SUMMARYProsperetti's seminal Physalis method for fluid flows with suspended particles is extended to electric fields to directly resolve finite-sized particles and to investigate accurately the mutual fluid-particle, particleparticle, and particle-boundary interactions. The present paper shows the straightforward extension of the two dimensions [Liu, Q., 2011, J. Comput. Phys. 230:8256-8274] to three dimensions as one of the important advantages. The method can be used for uncharged/charged dielectrics, uncharged/charged conductors, conductors with specified voltage, and general weak and strong discontinuous interface conditions. These general interface conditions can be in terms of field variable, its gradients, and surface integration, which has not been addressed by other numerical methods. In addition, for the first time, we rigourously derive the force and torque on the finite-sized particles resulting from the interactions between harmonics. The method, for the first time, directly resolves the particles with accurate local charge distribution, force, and torque on the particles, making many applications in engineering, mechanics, physics, chemistry, and biology possible, such as heterogeneous materials, microfluidics, electrophotography, electric double-layer capacitors, and microstructures of nanodispersions. In the present paper, the accuracy of the coefficients in the general analytical solutions is extensively investigated. The method is numerically verified to be accurate even for very strong jump in the weak and strong discontinuous interface conditions, which have not yet been investigated in any other numerical methods. The efficiency of the method is demonstrated with up to 100,000 3D particles, which suggests that the method can be used for many important engineering applications of broad interest.

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A comprehensive trapped charge profiling technique for SONOS flash EEPROMs

Cited by 7 publications

References 5 publications

Investigation of Drain Disturb in SONOS Flash EEPROMs

Investigation of Drain Disturb in SONOS Flash EEPROMs

Lateral profiling of trapped charge in SONOS flash EEPROMs programmed using CHE injection

Directly resolving particles in an electric field: local charge, force, torque, and applications

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