• 반도체디스플레이기술학회지
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• 제19권1호
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• pp.61-66
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• 2020

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.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.92-97
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• 2013

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.

• 한국전기전자재료학회논문지
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• 제28권3호
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• pp.154-159
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• 2015

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.

• 한국정보통신학회논문지
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• 제21권4호
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• pp.789-794
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• 2017

본 논문에서는 무접합 원통형 MOSFET의 해석학적 전위분포를 이용하여 문턱전압이하 전류모델을 제시하고 이를 이용하여 문턱전압이동을 해석하였다. 무접합 원통형 MOSFET는 채널을 게이트 단자가 감싸고 있기 때문에 캐리어 흐름을 제어하는 게이트 단자의 능력이 매우 우수하다. 본 연구에서는 쌍곡선 전위분포모델을 이용하여 포아송방정식을 풀고 이 때 얻어진 중심 전위분포를 이용하여 문턱전압이하 전류 모델을 제시하였다. 제시된 전류모델을 이용하여 $0.1{\mu}A$의 전류가 흐를 때 게이트 전압을 문턱전압으로 정의하고 2차원 시뮬레이션 값과 비교하였다. 비교결과 잘 일치하였으므로 이 전류모델을 이용하여 채널크기 및 도핑농도에 따라 문턱전압이동을 고찰하였다. 결과적으로 채널 반지름이 증가할수록 문턱전압이동은 매우 크게 나타났으며 산화막 두께가 증가할 경우도 문턱전압이동은 증가하였다. 채널 도핑농도에 따라 문턱전압을 관찰한 결과, 소스/드레인과 채널 간 도핑농도의 차이가 클수록 문턱전압은 크게 증가하는 것을 관찰하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.95-96
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• 2008

A new voltage-driven pixel circuit using soluble-processed organic thin film transistors (OTFTs) for an active matrix organic light emitting diode (AMOLED) is proposed. The proposed circuit is composed of four switching TFTs, one driving TFT and one storage capacitor. The proposed circuit can compensate for the degradation of OLED current caused by the threshold voltage shift of the OTFT. The simulation results show that the variation of OLED current corresponding to a 3V threshold voltage shift is decreased by 30% compared to the conventional 2TlC structure.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.517-520
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• 2008

A voltage-programming pixel circuit, which compensates the threshold voltage shift of TFTs and the degradation of OLED, is proposed for large sized a-Si:H active matrix organic light emitting diode (AMOLED) applications. Considering threshold voltage variation (or shift), OLED degradation and reverse bias annealing, HSPICE simulation results indicate that luminance error of every gray level is less than 0.4 LSB under the condition of +1V threshold voltage shift and from -0.2 LSB to 2.6 LSB within 30% degradation of OLED in the case of 40-inch full HDTV condition.

• ETRI Journal
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• 제36권2호
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• pp.321-324
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• 2014

This letter describes a two-phase clock oxide thin-film transistor shift register that executes a robust operation over a wide threshold voltage range and clock coupling noises. The proposed circuit employs an additional Q generation block to avoid the clock coupling noise effects. A SMART-SPICE simulation shows that the stable shift register operation is established for the clock coupling noises and the threshold voltage variation from -4 V to 5 V at a line time of $5{\mu}s$. The magnitude 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 at 100 kHz in the proposed circuit, compared to 6.8 dB and 10.9 dB in a conventional one. In addition, the estimated power consumption is 1.74 mW for the proposed 16-stage shift registers at $V_{TH}=-1.56V$, compared to 11.5 mW for the conventional circuits.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.141-145
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• 2021

The brightness of the Organic Light Emitting Diode (OLED) display is controlled by thin-film transistors (TFTs). Regardless of the materials and the structures of TFTs, an OLED suffers from the instable threshold voltage (V_th) of a TFT during operation. When designing an OLED pixel with circuit simulation tool such as SPICE, a designer needs to take V_th shift into account to improve the reliability of the circuit and various compensation methods have been proposed. In this paper, the effect of the compensation circuits from two typical OLED pixel circuits proposed in the literature are studied by the transient simulation with a SPICE tool in which the stretched-exponential time dependent V_th shift function is implemented. The simulation results show that the compensation circuits improve the reliability at the beginning of each frame, but V_th shifts from all TFTs in a pixel need to be considered to improve long-time reliability.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.981-984
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• 2005

본 논문에서는 전하트랩형 SONOS 메모리에서 프로그래밍 동작 후 변화되는 문턱전압을 시뮬레이션에 의하여 구현하고자 한다. SONOS 소자는 질화막내의 트랩 뿐 만아니라, 질화막-블로킹산화막 계면에 존재하는 트랩에 전하를 저장하는 전하트랩형 비휘발성기억소자로서, 기억상태에 따른 문턱전압을 시뮬레이션으로 구현하기위해서는 질화막내의 트랩을 정의할 수 있어야 된다. 그러나 기존의 시뮬레이터에서는 질화막내의 트랩모델이 개발되어 있지 않은 것이 현실이다. 따라서 본 연구에서는 SONOS 구조의 터널링산화막-질화막 계면과 질화막-블로킹산화막 계면에 두개의 전극을 정의하여 프로그램 전압과 시간에 따라서 전극에 유기되는 전하량으로부터 전하트랩형 기억소자의 문턱전압변화를 시뮬레이션 할 수 있는 새로운 방법을 제안한다.

• 한국전기전자재료학회논문지
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• 제26권5호
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• pp.341-346
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• 2013

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.