• Title/Summary/Keyword: Zinc-tin oxide TFT

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Pressure Dependency of Electrical Properties of In-free SiZnSnO Thin Film Transistors (공정 압력에 따라 제작되어진 비인듐계 SiZnSnO 박막을 이용한 박막트랜지스터의 성능 연구)

  • Lee, Sang-Yeol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.8
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    • pp.580-583
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    • 2012
  • The dependency of processing pressure on the electrical performances in amorphous silicon-zinc-tin-oxide thin film transistors (SZTO-TFT) has been investigated. The SZTO channel layers were deposited by using radio frequency (RF) magnetron sputtering method with different partial pressure. The field effect mobility (${\mu}_{FE}$) increased and threshold voltage ($V_{th}$) shifted to negative direction with increasing pressure during deposition processing. As a result, oxygen vacancies generated in SZTO channel layer with increasing partial pressure resulted in negative shift in $V_{th}$ and increase in on-current.

Al 도핑 및 열처리 온도에 따른 용액 공정 기반 AlZnSnO TFT의 특성 향상 연구

  • Kim, Hyeon-U;Choe, Byeong-Deok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2015.08a
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    • pp.216.1-216.1
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    • 2015
  • 본 연구에서는 용액 공정 기반 AZTO (Aluminum-Zinc-Tin Oxide, AlZnSnO) 박막 트랜지스터를 제작하여 Al (Aluminum) 도핑과 열처리 온도의 가변을 통한 특성 향상을 확인하였다. ZTO 용액의 Zn:Sn 비율(4:7)을 고정하고 Al 도핑(0~8.3%)과 열처리 온도($350{\sim}550^{\circ}C$)를 가변하였다. 실험 결과 Al 도핑이 증가할수록 드레인 전류는 감소하고 문턱 전압이 양의 방향으로 이동하면서 포화 이동도와 아문턱 기울기가 감소하였다. 열처리 온도가 증가할 때는 드레인 전류가 증가하고 문턱 전압은 음의 방향으로 이동하며 이동도와 아문턱 기울기가 증가하였다. Al 도핑은 강한 금속-산소 결합에 의해 oxygen vacancy와 전자 농도가 감소하게 하여 드레인 전류, 이동도, 아문턱 기울기의 감소와 양의 방향 문턱 전압 이동을 야기한다. 열처리 온도가 높아지면 반도체 층의 분자 구조가 더 밀집되고 oxygen vacancy 가 증가하며, 이는 전자 농도의 증가로 이어져 Al 도핑의 효과와 반대의 경향을 보인다. 실험 결과를 통해 Al:Zn:Sn=0.5:4:7의 비율과 $350^{\circ}C$ 열처리 조건에서 문턱 전압과 이동도, 아문턱 기울기, 전류 온오프 비($I_{on}/I_{off}$)가 각각 3.54V, $0.16cm^2/Vs$, 0.43 V/dec, $8.1{\times}10^5$으로 우수한 특성을 확인하였다.

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Effects of Mg Suppressor Layer on the InZnSnO Thin-Film Transistors

  • Song, Chang-Woo;Kim, Kyung-Hyun;Yang, Ji-Woong;Kim, Dae-Hwan;Choi, Yong-Jin;Hong, Chan-Hwa;Shin, Jae-Heon;Kwon, Hyuck-In;Song, Sang-Hun;Cheong, Woo-Seok
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.16 no.2
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    • pp.198-203
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    • 2016
  • We investigate the effects of magnesium (Mg) suppressor layer on the electrical performances and stabilities of amorphous indium-zinc-tin-oxide (a-ITZO) thin-film transistors (TFTs). Compared to the ITZO TFT without a Mg suppressor layer, the ITZO:Mg TFT exhibits slightly smaller field-effect mobility and much reduced subthreshold slope. The ITZO:Mg TFT shows improved electrical stabilities compared to the ITZO TFT under both positive-bias and negative-bias-illumination stresses. From the X-ray photoelectron spectroscopy O1s spectra with fitted curves for ITZO and ITZO:Mg films, we observe that Mg doping contributes to an enhancement of the oxygen bond without oxygen vacancy and a reduction of the oxygen bonds with oxygen vacancies. This result shows that the Mg can be an effective suppressor in a-ITZO TFTs.

Characteristics of amorphous IZTO-based transparent thin film transistors (비정질 IZTO기반의 투명 박막 트렌지스터 특성)

  • Shin, Han-Jae;Lee, Keun-Young;Han, Dong-Cheul;Lee, Do-Kyung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.151-151
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    • 2009
  • Recently, there has been increasing interest in amorphous oxide semiconductors to find alternative materials for an amorphous silicon or organic semiconductor layer as a channel in thin film transistors(TFTs) for transparent electronic devices owing to their high mobility and low photo-sensitivity. The fabriction of amorphous oxide-based TFTs at room temperature on plastic substrates is a key technology to realize transparent flexible electronics. Amorphous oxides allows for controllable conductivity, which permits it to be used both as a transparent semiconductor or conductor, and so to be used both as active and source/drain layers in TFTs. One of the materials that is being responsible for this revolution in the electronics is indium-zinc-tin oxide(IZTO). Since this is relatively new material, it is important to study the properties of room-temperature deposited IZTO thin films and exploration in a possible integration of the material in flexible TFT devices. In this research, we deposited IZTO thin films on polyethylene naphthalate substrate at room temperature by using magnetron sputtering system and investigated their properties. Furthermore, we revealed the fabrication and characteristics of top-gate-type transparent TFTs with IZTO layers, seen in Fig. 1. The experimental results show that by varying the oxygen flow rate during deposition, it can be prepared the IZTO thin films of two-types; One a conductive film that exhibits a resistivity of $2\times10^{-4}$ ohm${\cdot}$cm; the other, semiconductor film with a resistivity of 9 ohm${\cdot}$cm. The TFT devices with IZTO layers are optically transparent in visible region and operate in enhancement mode. The threshold voltage, field effect mobility, on-off current ratio, and sub-threshold slope of the TFT are -0.5 V, $7.2\;cm^2/Vs$, $\sim10^7$ and 0.2 V/decade, respectively. These results will contribute to applications of select TFT to transparent flexible electronics.

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A Protective Layer on the Active Layer of Al-Zn-Sn-O Thin-Film Transistors for Transparent AMOLEDs

  • Cho, Doo-Hee;KoPark, Sang-Hee;Yang, Shin-Hyuk;Byun, Chun-Won;Cho, Kyoung-Ik;Ryu, Min-Ki;Chung, Sung-Mook;Cheong, Woo-Seok;Yoon, Sung-Min;Hwang, Chi-Sun
    • Journal of Information Display
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    • v.10 no.4
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    • pp.137-142
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    • 2009
  • Transparent top-gate Al-Zn-Sn-O (AZTO) thin-film transistors (TFTs) with an $Al_2O_3$ protective layer (PL) on an active layer were studied, and a transparent 2.5-inch QCIF+AMOLED (active-matrix organic light-emitting diode) display panel was fabricated using an AZTO TFT backplane. The AZTO active layers were deposited via RF magnetron sputtering at room temperature, and the PL was deposited via two different atomic-layer deposition (ALD) processes. The mobility and subthreshold slope were superior in the TFTs annealed in vacuum and with oxygen plasma PLs compared to the TFTs annealed in $O_2$ and with water vapor PLs, but the bias stability of the TFTs annealed in $O_2$ and with water vapor PLs was excellent.

Electrical and Optical Properties of Amorphous ITZO Deposited at Room Temperature by RF Magnetron Sputtering (RF 마그네트론 스퍼터링법으로 상온 증착된 비정질 ITZO 산화물의 전기적 및 광학적 특성)

  • Lee, Ki Chang;Jo, Kwang-Min;Lee, Joon-Hyung;Kim, Jeong-Joo;Heo, Young-Woo
    • Journal of the Korean institute of surface engineering
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    • v.47 no.5
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    • pp.239-243
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    • 2014
  • The electrical and optical properties of amorphous In-Tin-Zinc-Oxide(ITZO) deposited at room temperature using rf-magnetron sputtering were investigated. The amorphous ITZO thin films were obtained at the composition of In:Sn:Zn = 6:2:2, 4:3:3, and 2:4:4, but the ITZO (8:1:1) showed a crystalline phase of bixbyite structure of In2O3. The resistivity of ITZO could be controlled by oxygen pressure in the sputtering ambient. The resistivity of post-annealed ITZO thin films exhibited the dependence on the amount of Indium. Optical energy band gap and transmittance increased as the amount of indium in ITZO increased. For the device application with ITZO, the bottom-gated thin-film transistor using ITZO as a active channel layer was fabricated. It showed a threshold voltage of 1.42V and an on/off ratio of $5.63{\times}10^7$ operated with saturation field-effect mobility of $14.2cm^2/V{\cdot}s$.