Stretched-Exponential 형태의 문턱전압 이동 모델의 SPICE구현

정태호,Jung, Taeho 한국반도체디스플레이기술학회 2020 반도체디스플레이기술학회지 Vol.19 No.1

Threshold voltage shift occurring during operation is implemented in a SPICE simulation tool. Among the shift models the stretched-exponential function model, which is frequently observed from both single-crystal silicon and thin-film transistors regardless of the nature of causes, is selected, adapted to transient simulation, and added to BSIM4 developed by BSIM Research Group at the University of California, Berkeley. The adaptation method used in this research is to select degradation and recovery models based on the comparison between the gate and threshold voltages. The threshold voltage shift is extracted from SPICE transient simulation and shows the stretched-exponential time dependence for both degradation and recovery situations. The implementation method developed in this research is not limited to the stretched-exponential function model and BSIM model. The proposed method enables to perform transient simulation with threshold voltage shift in situ and will help to verify the reliability of a circuit.

유기박막 트랜지스터에서 문턱전압 이동의 모델링 및 시뮬레이션

정태호,Jung, Taeho 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.2

In this paper the author proposes a method of implementing a numerical model for threshold voltage ($V_{th}$) shift in organic thin-film transistors (OTFTs) into SPICE tools. $V_{th}$ shift is first numerically modeled by dividing the shift into sequentially ordered groups. The model is then used to derive a simulations model which takes into simulation parameters and calculation complexity. Finally, the numerical and simulation models are implemented in AIM-SPICE. The SPICE simulation results agree well with the $V_{th}$ shift obtained from an OTFT fabricated without any optimization. The proposed method is also used to implement the stretched-exponential time dependent $V_{th}$ shift in AIM-SPICE and the results show the proposed method is applicable to various types of $V_{th}$ shifts.

High performance p-type chlorinated-benzothiadiazole-based polymer electrolyte gated organic field-effect transistors

Tabi, Grace Dansoa,Nketia-Yawson, Benjamin,Kang, So-Huei,Yang, Changduk,Noh, Yong-Young Elsevier 2018 ORGANIC ELECTRONICS Vol.54 No.-

<P><B>Abstract</B></P> <P>We report the evaluation of charge transport parameters of four p-type dichlorinated-2,1,3-benzothiadiazole (2ClBT) based conjugated polymers end-capped with different electron-donor units (thiophene (T), thieno[3,2-<I>b</I>]thiophene (TT), 2,2′-bithiophene (DT), and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT)) in electrolyte gated organic field-effect transistors operating at a driving voltage of −2 V. Remarkable hole mobility improvement of 0.13–0.56 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> were achieved in 2ClBTs based polymers, with P2ClBT-DT recording the highest mobility of 0.56 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> and current on/off ratio ∼10<SUP>7</SUP>. Interestingly, a positive threshold voltage shift (Δ<I>V</I> <SUB>Th</SUB>) was observed in the transfer characteristics from the linear to saturation regime of all the 2ClBTs based polymer electrolyte gated OFET devices of <I>L</I> = 10 μm, contrary to devices with conventional poly(methyl methacrylate) gate dielectric, which showed a negative Δ<I>V</I> <SUB>Th</SUB> shift. Among the 2ClBTs based polymers, P2ClBT-TVT devices showed the lowest mobility and Δ<I>V</I> <SUB>Th</SUB> shift, which is attributed to severe ion diffusion in the polymer semiconducting layer owing to the vinyl group backbone susceptible to electrochemical doping. Our results emphasize essential selection consideration of the monomeric moieties, molecular ordering, π-π stacking and backbone planarity of conjugated polymers for electrolyte based organic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report high performance benzothiadiazole based OFETs with solid state ion dielectrics. </LI> <LI> Remarkable hole mobility improvement of 0.13–0.56 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> were achieved. </LI> <LI> Structure-property relationship mainly is discussed by using different electron-donor units. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

강유전체를 이용한 음의 정전용량 무접합 이중 게이트 MOSFET의 문턱전압 모델

정학기 ( Hakkee Jung ) 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.2

An analytical threshold voltage model is presented to observe the change in threshold voltage shift ΔV_th of a junctionless double gate MOSFET using ferroelectric-metal-SiO₂ as a gate oxide film. The negative capacitance transistors using ferroelectric have the characteristics of increasing on-current and lowering off-current. The change in the threshold voltage of the transistor affects the power dissipation. Therefore, the change in the threshold voltage as a function of theferroelectric thickness is analyzed. The presented threshold voltage model is in a good agreement with the results of TCAD. As a results of our analysis using this analytical threshold voltage model, the change in the threshold voltage with respect to the change in the ferroelectric thickness showed that the threshold voltage increased with the increase of the absolute value of charges in the employed ferroelectric. This suggests that it is possible to obtain an optimum ferroelectric thickness at which the threshold voltage shift becomes 0 V by the voltage across the ferroelectric even when the channel length is reduced. It was also found that the ferroelectric thickness increased as the silicon thickness increased when the channel length was less than 30 nm, but the ferroelectric thickness decreased as the silicon thickness increased when the channel length was 30 nm or more in order to satisfy ΔV_th=0.

박막트랜지스터의 병렬형 가역과 비가역 문턱전압 이동에 대한 모델링

정태호,Jung, Taeho 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.7

Threshold voltage shift has been observed from many thin-film transistors (TFTs) and the time evolution of the shift can be modeled as the stretched-exponential and -hyperbola function. These analytic models are derived from the kinetic equation for defect-creation or charge-trapping and the equation consists of only reversible reactions. In reality TFT's a shift is permanent due to an irreversible reaction and, as a result, it is reasonable to consider that both reversible and irreversible reactions exist in a TFT. In this paper the case when both reactions exist in parallel and make a combined threshold voltage shift is modeled and simulated. The results show that a combined threshold voltage shift observed from a TFT may agrees with the analytic models and, thus, the analytic models don't guarantee whether the cause of the shift is defection-creation or charge-trapping.

Robust low power DC-type shift register circuit capable of compensating threshold voltage shift of oxide TFTs

Seo, J.,Song, S.J.,Kim, D.,Nam, H. IPC Science and Technology Press ; Elsevier Scienc 2017 Displays Vol.49 No.-

This paper proposes an oxide TFT DC-type shift register that consists of eleven TFTs and one bootstrapping capacitor. The proposed circuit connects drain nodes of large size pull-up TFTs of output drivers to positive supply voltage instead of alternating clock signals for low power consumption. In addition, a robust internal inverter capable of maintaining the high voltage level of the output over the large positive threshold voltage shift by bootstrapping is implemented. For a 120Hz Full-HD display, the SPICE simulation estimates the clock power consumption of the proposed DC-type circuit as 0.56mW at 32 shift registers and ensures the robust operation over the wide range of threshold voltage shift from -4V to 10V.

온도에 의한 산화물 박막트랜지스터의 문턱전압 이동 시뮬레이션 방안

권세용,정태호,Kwon, Seyong,Jung, Taeho 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.3

In this paper, we propose a numerical method to model temperature dependent threshold voltage shift observed in metal oxide thin-film transistors (TFTs). The proposed model is then implemented in AIM-SPICE circuit simulation tool. The proposed method consists of modeling the well-known stretched-exponential time dependent threshold voltage shift and their temperature dependent coefficients. The outputs from AIM-SPICE tool and the stretched-exponential model at different temperatures in the literature are compared and they show a good agreement. Since metal oxide TFTs are the promising candidate for flat panel displays, the proposed method will be a good stepping stone to help enhance reliability of fast-evolving display circuits.

Control of Current Saturation and Threshold Voltage Shift in Indium Oxide Nanowire Transistors with Femtosecond Laser Annealing

Lee, Chunghun,Srisungsitthisunti, Pornsak,Park, Sangphill,Kim, Seongmin,Xu, Xianfan,Roy, Kaushik,Janes, David B.,Zhou, Chongwu,Ju, Sanghyun,Qi, Minghao American Chemical Society 2011 ACS NANO Vol.5 No.2

<P>Transistors based on various types of nonsilicon nanowires have shown great potential for a variety of applications, especially for those that require transparency and low-temperature substrates. However, critical requirements for circuit functionality, such as saturated source-drain current and matched threshold voltages of individual nanowire transistors in a way that is compatible with low temperature substrates, have not been achieved. Here we show that femtosecond laser pulses can anneal individual transistors based on In<SUB>2</SUB>O<SUB>3</SUB> nanowires, improve the saturation of the source-drain current, and permanently shift the threshold voltage to the positive direction. We applied this technique and successfully shifted the switching threshold voltages of NMOS-based inverters and improved their noise margin, in both depletion and enhancement modes. Our demonstration provides a method to trim the parameters of individual nanowire transistors, and suggests potential for large-scale integration of nanowire-based circuit blocks and systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-2/nn102723w/production/images/medium/nn-2010-02723w_0005.gif'></P>

Robust Two-Phase Clock Oxide TFT Shift Register over Threshold Voltage Variation and Clock Coupling Noises

남형식,송은지 한국전자통신연구원 2014 ETRI Journal Vol.36 No.2

This letter describes a two-phase clock oxide thin-filmtransistor shift register that executes a robust operation over awide threshold voltage range and clock coupling noises. Theproposed circuit employs an additional Q generation block toavoid the clock coupling noise effects. A SMART-SPICEsimulation shows that the stable shift register operation isestablished for the clock coupling noises and the thresholdvoltage variation from –4 V to 5 V at a line time of 5 μs. Themagnitude of coupling noises on the Q(15) node and Qb(15)node of the 15th stage is respectively –12.6 dB and –26.1 dB at100 kHz in the proposed circuit, compared to 6.8 dB and10.9 dB in a conventional one. In addition, the estimated powerconsumption is 1.74 mW for the proposed 16-stage shiftregisters at VTH = –1.56 V, compared to 11.5 mW for theconventional circuits.

박막트랜지스터의 문턱전압 이동 시뮬레이션 방안

정태호,Jung, Taeho 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.5

Threshold voltage shift caused by trapping and release of charge carriers in a thin-film transistor (TFT) is implemented in AIM-SPICE tool. Turning on and off voltages are alternatively applied to a TFT to extract charge trapping and releasing process. Each process is divided into sequentially ordered processes, which are numerically modeled and implemented in a computer language. The results show a good agreement with the experimental data, which are modeled. Since the proposed method is independent of TFT's behavior models implemented in SPICE tools, it can be easily added to them.