• Title, Summary, Keyword: Threshold voltage roll-off

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Bottom Gate Voltage Dependent Threshold Voltage Roll-off of Asymmetric Double Gate MOSFET (하단게이트 전압에 따른 비대칭 이중게이트 MOSFET의 문턱전압이동 의존성)

  • Jung, Hakkee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.6
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    • pp.1422-1428
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    • 2014
  • This paper has analyzed threshold voltage roll-off for bottom gate voltages of asymmetric double gate(DG) MOSFET. Since the asymmetric DGMOSFET is four terminal device to be able to separately bias for top and bottom gates, the bottom gate voltage influences on threshold voltage. It is, therefore, investigated how the threshold voltage roll-off known as short channel effects is reduced with bottom gate voltage. In the pursuit of this purpose, off-current model is presented in the subthreshold region, and the threshold voltage roll-off is observed for channel length and thickness with a parameter of bottom gate voltage as threshold voltage is defined by top gate voltage that off-currnt is $10^{-7}A/{\mu}m$ per channel width. As a result to observe the threshold voltage roll-off for bottom gate voltage using this model, we know the bottom gate voltage greatly influences on threshold voltage roll-off voltages, especially in the region of short channel length and thickness.

Threshold Voltage Roll-off for Bottom Gate Voltage of Asymmetric Double Gate MOSFET (비대칭 이중게이트 MOSFET의 하단게이트 전압에 따른 문턱전압이동현상)

  • Jung, Hakkee
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.741-744
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    • 2014
  • This paper has analyzed threshold voltage roll-off for bottom gate voltages of asymmetric double gate(DG) MOSFET. Since the asymmetric DGMOSFET is four terminal device to be able to separately bias for top and bottom gates, the bottom gate voltage influences on threshold voltage. It is, therefore, investigated how the threshold voltage roll-off known as short channel effects is reduced with bottom gate voltage. In the pursuit of this purpose, off-current model is presented in the subthreshold region, and the threshold voltage roll-off is observed for channel length and thickness with a parameter of bottom gate voltage as threshold voltage is defined by top gate voltage that off-currnt is $10^{-7}A/{\mu}m$ per channel width. As a result to observe the threshold voltage roll-off for bottom gate voltage using this model, we know the bottom gate voltage greatly influences on threshold voltage roll-off voltages, especially in the region of short channel length and thickness.

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Analysis of Doping Profile Dependent Threshold Voltage for DGMOSFET Using Gaussian Function

  • Jung, Hak-Kee
    • Journal of information and communication convergence engineering
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    • v.9 no.3
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    • pp.310-314
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    • 2011
  • This paper has presented doping profile dependent threshold voltage for DGMOSFET using analytical transport model based on Gaussian function. Two dimensional analytical transport model has been derived from Poisson's equation for symmetrical Double Gate MOSFETs(DGMOSFETs). Threshold voltage roll-off is very important short channel effects(SCEs) for nano structures since it determines turn on/off of MOSFETs. Threshold voltage has to be constant with decrease of channel length, but it shows roll-off due to SCEs. This analytical transport model is used to obtain the dependence of threshold voltage on channel doping profile for DGMOSFET profiles. Also we have analyzed threshold voltage for structure of channel such as channel length and gate oxide thickness.

Analysis of Threshold Voltage Roll-Off and Drain Induced Barrier Lowering in Junction-Based and Junctionless Double Gate MOSFET (접합 및 무접합 이중게이트 MOSFET에 대한 문턱전압 이동 및 드레인 유도 장벽 감소 분석)

  • Jung, Hak Kee
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.2
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    • pp.104-109
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    • 2019
  • An analytical threshold voltage model is proposed to analyze the threshold voltage roll-off and drain-induced barrier lowering (DIBL) for a junction-based double-gate (JBDG) MOSFET and a junction-less double-gate (JLDG) MOSFET. We used the series-type potential distribution function derived from the Poisson equation, and observed that it is sufficient to use n=1 due to the drastic decrease in eigenvalues when increasing the n of the series-type potential function. The threshold voltage derived from this threshold voltage model was in good agreement with the result of TCAD simulation. The threshold voltage roll-off of the JBDG MOSFET was about 57% better than that of the JLDG MOSFET for a channel length of 25 nm, channel thickness of 10 nm, and oxide thickness of 2 nm. The DIBL of the JBDG MOSFET was about 12% better than that of the JLDG MOSFET, at a gate metal work-function of 5 eV. It was also found that decreasing the work-function of the gate metal significantly reduces the DIBL.

Relationship of Threshold Voltage Roll-off and Gate Oxide Thickness in Asymmetric Junctionless Double Gate MOSFET (비대칭형 무접합 이중게이트 MOSFET에서 산화막 두께와 문턱전압이동 관계)

  • Jung, Hakkee
    • Journal of IKEEE
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    • v.24 no.1
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    • pp.194-199
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    • 2020
  • The threshold voltage roll-off for an asymmetric junctionless double gate MOSFET is analyzed according to the top and bottom gate oxide thicknesses. In the asymmetric structure, the top and bottom gate oxide thicknesses can be made differently, so that the top and bottom oxide thicknesses can be adjusted to reduce the leakage current that may occur in the top gate while keeping the threshold voltage roll-off constant. An analytical threshold voltage model is presented, and this model is in good agreement with the 2D simulation value. As a result, if the thickness of the bottom gate oxide film is decreased while maintaining a constant threshold voltage roll-off, the top gate oxide film thickness can be increased, and the leakage current that may occur in the top gate can be reduced. Especially, it is observed that the increase of the bottom gate oxide thickness does not affect the threshold voltage roll-off.

Analysis of Dimension Dependent Threshold Voltage Roll-off for Nano Structure Double Gate FinFET (나노구조 이중게이트 FinFET의 크기변화에 따른 문턱전압이동 분석)

  • Jeong Hak-Gi;Lee Jae-Hyung;Joung Dong-Su
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.869-872
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    • 2006
  • In this paper, the threshold voltage roll-off been analyzed for nano structure double gate FinFET. The analytical current model has been developed , including thermionic current and tunneling current models. The potential distribution by Poisson equation and carrier distribution by Maxwell-Boltzman statistics are used to calculate thermionic emission current, and WKB(Wentzel- framers-Brillouin) approximation to tunneling current. The threshold voltage roll-offs are obtained by simple adding two currents since two current is independent. The threshold voltage roll-off by this model are compared with those by two dimensional simulation and two values are good agreement. Since the tunneling current increases especially under channel length of 10nm, the threshold voltage roll-off Is very large. The channel and gate oxide thickness have to be fabricated as thin as possible to decrease this short channel effects and this process has to be developed.

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Analysis of Dimension-Dependent Threshold Voltage Roll-off and DIBL for Nano Structure Double Gate FinFET (나노구조 이중게이트 FinFET의 크기변화에 따른 문턱전압이동 및 DIBL 분석)

  • Jung, Hak-Kee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.4
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    • pp.760-765
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    • 2007
  • In this paper, the threshold voltage roll-off and drain induced barrier lowering(DIBL) have been analyzed for nano structure double gate FinFET. The analytical current model has been developed, including thermionic current and tunneling current models. The potential distribution by Poisson equation and carrier distribution by Maxwell-Boltzman statistics were used to calculate thermionic omission current, and WKB(Wentzel- Kramers-Brillouin) approximation to tunneling current. The threshold voltage roll-offs are obtained by simple adding two currents since two current is independent. The threshold voltage roll-off by this model are compared with those by two dimensional simulation and two values are good agreement. Since the tunneling current increases especially under channel length of 10nm, the threshold voltage roll-off and DIBL are very large. The channel and gate oxide thickness have to be fabricated as thin as possible to decrease this short channel effects, and this process has to be developed.

Analysis of Threshold Voltage Roll-off for Ratio of Channel Length and Thickness in DGMOSFET (DGMOSFET에서 채널길이와 두께 비에 따른 문턱전압변화분석)

  • Jung, Hak-Kee
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.765-767
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    • 2010
  • In this paper, the variations of threshold voltage characteristics for ratio of channel length and thickness have been alanyzed for DG(Double Gate)MOSFET having top gate and bottom gate. Since the DGMOSFET has two gates, it has advantages that contollability of gate for current is nearly twice and SCE(Short Channel Effects) shrinks in nano devices. The channel length and thickness in MOSFET determines device size and extensively influences on SCEs. The threshold voltage roll-off, one of the SCEs, is large with decreasing channel length. The threshold voltage roll-off has been analyzed with various ratio of channel length and thickness for DGMOSFET in this study.

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Analysis of Threshold Voltage Roll-off for Ratio of Channel Length and Thickness in DGMOSFET (DGMOSFET에서 채널길이와 두께 비에 따른 문턱전압변화분석)

  • Jung, Hak-Kee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.14 no.10
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    • pp.2305-2309
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    • 2010
  • In this paper, the variations of threshold voltage characteristics for ratio of channel length and thickness have been alanyzed for DG(Double Gate)MOSFET having top gate and bottom gate. Since the DGMOSFET has two gates, it has advantages that contollability of gate for current is nearly twice and SCE(Short Channel Effects) shrinks in nano devices. The channel length and thickness in MOSFET determines device size and extensively influences on SCEs. The threshold voltage roll-off, one of the SCEs, is large with decreasing channel length. The threshold voltage roll-off and drain induced barrier lowing have been analyzed with various ratio of channel length and thickness for DGMOSFET in this study.

Two-Dimensional Analytical Model for Deriving the Threshold Voltage of a Short Channel Fully Depleted Cylindrical/Surrounding Gate MOSFET

  • Suh, Chung-Ha
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.11 no.2
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    • pp.111-120
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    • 2011
  • A two-dimensional analytical model for deriving the threshold voltage of a short channel fully depleted (FD) cylindrical/surrounding gate MOSFET (CGT/SGT) is suggested. By taking into account the lateral variation of the surface potential, introducing the natural length expression, and using the Bessel functions of the first and the second kinds of order zero, we can derive potentials in the gate oxide layer and the silicon core fully two-dimensionally. Making use of these potentials, the minimum surface potential can be obtained to derive the threshold voltage as a closed-form expression in terms of various device parameters and applied voltages. Obtained results can be used to explain the drain-induced threshold voltage roll-off of a CGT/SGT in a unified manner.