• JSTS:Journal of Semiconductor Technology and Science
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• 제16권2호
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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.

• 한국표면공학회지
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• 제47권5호
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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 $14.2cm^2/V{\cdot}s$.

• 한국표면공학회지
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• 제48권6호
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• pp.292-296
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• 2015

Indium tin zinc oxide (ITZO) thin films were deposited on glass and quartz substrates by RF magnetron sputtering. The substrate temperature varied from $100^{\circ}C$ to $400^{\circ}C$. The structural and optical properties of thin films were investigated by X-ray diffraction (XRD), Field Emission Scanning electron microscopy (FESEM) and UV-Visible transmission spectra. It has been found from X-ray diffraction patterns that increasing the substrate temperature, the amorphous structure changes into polycrystalline structure. The FESEM results showed that all ITZO thin films have a smooth surface. The average optical transmittance (400 - 800 nm) was 82% and 80% at all films deposited at $200^{\circ}C$. The band gap energy ranges 3.41 to 3.57eV and 2.81 to 3.44eV with a maximum value at $200^{\circ}C$ all substrates temperature.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.159-159
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• 2008

투명전도체 (transparent conducting oxides: TCOs) 는 일반적으로 $10^3\Omega^{-1}Cm^{-1}$의 전도도, 가시광 영역에서 80%이상의 투명성을 가지는 재료로서, 액정 박막 표시 장치(TFT-LCD), 광기전성 소자, 유기 발광 소자, 에너지 절약 창문, 태양전지(sollar cell) 등 전극으로 사용되고 있다. 최근에는 TCO의 전도도특성을 조절하여 반도성특성을 가진 투명 산화물 반도체(transparent oxide semiconductor: TOS) 을 이용한 박막 트랜지스터 연구가 활발히 진행 중이다. 기존의 실리콘을 기반으로 하는 박막 트랜지스터의 낮은 이동도, 불투명성의 특성을 가지고 있지만, 산화물 박막트랜지스터는 높은 이동도를 발현 할 수 있을 뿐만 아니라, 넓은 밴드갭 에너지를 갖는 산화물을 이용하므로 투명한 특성도 발현 할 수 있어 차세대 디스플레이의 구동소자로서 응용연구가 되고 있다. 이에 본 연구에서는 박막트랜지스터 channel layer로서의 Indium-Tin-Zinc oxide 적용특성을 조사하였다. Indium, Tin, Zinc 의 혼합비율을 다양하게 조절하여 타겟을 제작하였다. 이를 RF magnetron sputtering 를 이용하여 박막으로 성장시켰으며, 기판으로는 glass 기판을 사용하였다. 박막 성장시 아르곤과 산소의 비율을 다양하게 조절하였다. 성장시킨 박막은 Hall effect, Transmittance, Work function, XRD등을 이용하여 전기적, 광학적, 구조특성을 평가하였다. Indium-Tin-Zinc Oxide(ITZO) 을 channel layer로 사용하여 Thin-film transistor 을 제작하여, TFT의 I-V 및 stability특성을 평가하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.170-170
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• 2010

Thin-film transistors (TFT) have become the key components of electronic and optoelectronic devices. Most conventional thin-film field-effect transistors in display applications use an amorphous or polycrystal Si:H layer as the channel. This silicon layers are opaque in the visible range and severely restrict the amount of light detected by the observer due to its bandgap energy smaller than the visible light. Therefore, Si:H TFT devices reduce the efficiency of light transmittance and brightness. One method to increase the efficiency is to use the transparent oxides for the channel, electrode, and gate insulator. The development of transparent oxides for the components of thin-film field-effect transistors and the room-temperature fabrication with low voltage operations of the devices can offer the flexibility in designing the devices and contribute to the progress of next generation display technologies based on transparent displays and flexible displays. In this thesis, I report on the dc performance of transparent thin-film transistors using amorphous indium tin zinc oxides for an active layer. $SiO_2$ was employed as the gate dielectric oxide. The amorphous indium tin zinc oxides were deposited by RF magnetron sputtering. The carrier concentration of amorphous indium tin zinc oxides was controlled by oxygen pressure in the sputtering ambient. Devices are realized that display a threshold voltage of 4.17V and an on/off ration of ${\sim}10^9$ operated as an n-type enhancement mode with saturation mobility with $15.8\;cm^2/Vs$. In conclusion, the fabrication and characterization of thin-film transistors using amorphous indium tin zinc oxides for an active layer were reported. The devices were fabricated at room temperature by RF magnetron sputtering. The operation of the devices was an n-type enhancement mode with good saturation characteristics.