• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.347-350
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• 2013

By inserting a very thin metal layer of Ag between two outer oxide layers of amorphous silicon indium zinc oxide (SIZO), we fabricated a highly transparent SIZO/Ag/SIZO multilayer on a glass substrate. In order to find the optimized thickness of Ag layers, we investigated the variation of optical properties depending on Ag thickness. It was found that the transition of Ag layer from island formation to a continuous film occurred at a critical thickness. Continuity of the Ag film is very important for optical properties in SIZO/Ag/SIZO multilayer. With about 15 nm thick Ag layer, the multilayer showed a high optical transmittance of 80% at 550 nm and low emissivity in IR.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.211-216
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• 2020

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors, because of their relatively low mobility, have limits in attempts to fulfill high-end specifications for display backplanes. In-Zn-O (IZO) is a promising semiconductor material for high mobility device applications with excellent transparency to visible light region and low temperature process capability. In this paper, the effects of working pressure on the physical and electrical properties of IZO films and thin film transistors are investigated. The working pressure is modulated from 2 mTorr to 5 mTorr, whereas the other process conditions are fixed. As the working pressure increases, the extracted optical band gap of IZO films gradually decreases. Absorption coefficient spectra indicate that subgap states increase at high working pressure. Furthermore, IZO film fabricated at low working pressure shows smoother surface morphology. As a result, IZO thin film transistors with optimum conditions exhibit excellent switching characteristics with high mobility (≥ 30㎠/Vs) and large on/off ratio.

• Journal of the Semiconductor & Display Technology
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• v.15 no.4
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• pp.46-50
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• 2016

In this study, we have investigated the effect of the substrate temperature and hydrogen flow rate on the characteristics of IGZO thin films for the TCO(transparent conducting oxide). For this purpose, IGZO thin films were deposited by RF magnetron sputtering at room temperature and $300^{\circ}C$ with various $H_2$ flow rate. In order to investigate the influences of the hydrogen, the flow rate of hydrogen in argon mixing gas has been changed from 0.1sccm to 1.0sccm. IGZO thin films deposited at room temperature show amorphous structure, whereas IGZO thin films deposited at $300^{\circ}C$ show crystalline structure having an (222) preferential orientation. The electrical resistivity of the amorphous-IGZO films deposited at R.T. was lower than that of the crystalline-IGZO thin films deposited at $300^{\circ}C$. The increase of electrical resistivity with increasing substrate temperature was interpreted in terms of the decrease of the charge carrier mobility. The transmittance of the IGZO films deposited at $300^{\circ}C$ was decreased deposited with hydrogen gas.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.1-5
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• 2016

In this study, we have investigated the effect of the substrate temperature on the characteristics of IGZO thin films for the TCO(transparent conducting oxide). For this purpose, IGZO thin films were deposited by RF magnetron sputtering at various substrate temperature (room temperature ${\sim}400^{\circ}C$). IGZO thin films deposited at room temperature show amorphous structure, whereas IGZO thin films deposited at $250^{\circ}C$ or more show crystalline structure having an (222) preferential orientation. The electrical resistivity of IGZO film increased with increasing temperature. The change of electrical resistivity with increasing temperature was mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. The electrical resistivity of the amorphous-IGZO films deposited at R.T. was lower than that of the crystalline-IGZO thin films deposited at $300^{\circ}C$. The transmittance of the IGZO films deposited at $300^{\circ}C$ was decreased deposited with hydrogen gas.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.44-50
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• 2001

Metal oxide semiconductor (MOS) structures containing nanocrystals are fabricated by using rapid thermal oxidations of amorphous silicon films. The amorphous films are deposited either by electron beam deposition method or by electron beam deposition assisted by Ar ion beam during deposition. Post oxidation of e-beam deposited film results in relatively small hysteresis of capacitance-voltage (C-V) and the flat band voltage shift, $\DeltaV_{FB}$ is less than 1V indicative of the formation of low density nanocrystals in $SiO_2$ near $SiO_2$/Si interface. By contrast, we observe very large hysteresis in C-V characteristics for oxidized ion-beam assisted e-beam deposited sample. The flat band voltage shift is larger than 22V and the hysteresis becomes even broader as increasing injection times of holes at accumulation condition and electrons at inversion condition. The result indicates the formation of slow traps in $SiO_2$ near $SiO_2$/Si interface which might be related to large density nanocrystals. Roughly estimated trap density is $1{\times}10^{13}cm^{-2}$. Such a large hysteresis may be explained in terms of the activation of adatom migration by Ar ion during deposition. The activated migration may increase nucleation rate of Si nuclei in amorphous Si matrix. During post oxidation process, nuclei grow into nanocrystals. Therefore, ion beam assistance during deposition may be very feasible for MOS structure containing nanocrystals with large density which is a basic building block for single electron memory device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.3
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• pp.185-190
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• 2015

In this study, we fabricated the indium gallium zinc oxide (IGZO), zinc oxide (ZnO), aluminum zinc oxide (AZO). oxide and silver are deposited by magnetron sputtering and thermal evaporator, respectively transparency and energy bandgap were changed by the thickness of silver layer. To fabricate metal oxide metal (OMO) structure, IGZO sputtered on a corning 1,737 glass substrate was used as bottom oxide material and then silver was evaporated on the IGZO layer, finally IGZO was sputtered on the silver layer we get the final OMO structure. The radio-frequency power of the target was fixed at 30 W. The chamber pressure was set to $6.0{\times}10^{-3}$ Torr, and the gas ratio of Ar was fixed at 25 sccm. The silver thickness are varied from 3 to 15 nm. The OMO thin films was analyzed using XRD. XRD shows broad peak which clearly indicates amorphous phase. ZnO, AZO, OMO show the peak [002] direction at $34^{\circ}$. This indicate that ZnO, AZO OMO structure show the crystalline peak. Average transmittance of visible region was over 75%, while that of infrared region was under 20%. Energy band gap of OMO layer was increased with increasing thickness of Ag layer. As a result total transmittance was decreased.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.338.1-338.1
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• 2014

비정질 산화물 반도체(Amorphous Oxide Smeiconcuctor)를 이용하여 투명 박막 트랜지스터의 채널층으로 많은 연구가 진행되고 있다. 투명 박막 트랜지스터의 채널층으로 사용되고 있는 IGZO박막은 비정질임에도 불구하고 높은 이동도와 넓은 밴드갭을 갖고 있는 것으로 알려져 있다. 본 연구는 RF magnetron sputtering법으로 유리기판 위에 IGZO박막을 증착시켰으며 소결된 타겟으로는 In:Ga:ZnO를 각각 1:1:2mol%의 조성비로 혼합하여 이용하였으며, $30{\times}30mm$의 XG Glass 유리기판에 sputtering 방식으로 증착하였다. 박막 증착 조건은 초기압력 $3.0{\times}10^{-6}Torr$, 증착 압력 20mTorr, 반응가스 Ar 25sccm, 공정 변수로는 RF Power 25W, 50W, 75W, 100W 각각 변화를 주어 실험을 진행 하였으며, 증착온도는 실온으로 고정 하였다. 분석 결과로 RF Power 25W 일 때 XRD 분석결과 Bragg's 법칙을 만족하는 피크가 나타나지 않는 비정질 구조임을 확인하였으며, AFM 분석결과 0.5 mm 이하의 Roughness를 가졌다. UV-Visible-NIR 측정 결과 가시광선 영역에서 87%이상의 투과도를 나타냈으며, Hall 측정 결과 Carrier concentration $3.31{\times}10^{19}$, Mobility $10.9cm^2/V.s$, Resistivity $1.8{\times}10^{-2}$, 투명 박막 트랜지스터의 채널층으로 사용 가능함을 확인 할 수 있었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.8
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• pp.674-677
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• 2011

The dependency of sputtering power on the electrical performances in amorphous HIZO-TFT (hafnium-indium-zinc-oxide thin film transistors) has been investigated. The HIZO channel layers were prepared by using radio frequency (RF) magnetron sputtering method with different sputtering power at room temperature. TOF-SIMS (time of flight secondary ion mass spectrometry) was performed to confirm doping of hafnium atom in IZO film. The field effect mobility (${\mu}FE$) increased and threshold voltage ($V_{th}$) shifted to negative direction with increasing sputtering power. This result can be attributed to the high energy particles knocking-out oxygen atoms. As a result, oxygen vacancies generated in HIZO channel layer with increasing sputtering power resulted in negative shift in Vth and increase in on-current.

• Transactions on Electrical and Electronic Materials
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• v.16 no.5
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• pp.234-240
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• 2015

Amorphous oxide-based thin-film transistors (TFTs) have drawn a lot of attention recently for the next-generation high-resolution display industry. The required field-effect mobility of oxide-based TFTs has been increasing rapidly to meet the demands of the high-resolution, large panel size and 3D displays in the market. In this regard, the current status and major trends in the high mobility oxide-based TFTs are briefly reviewed. The various approaches, including the use of semiconductor, dielectric, electrode materials and the corresponding device structures for realizing high mobility oxide-based TFT devices are discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.106-110
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• 2014

The passivation property of $Al_2O_3$ thin film formed using atomic layer deposition (ALD) for the application of crystalline Si solar cells was investigated using microwave photoconductance decay (${\mu}$-PCD). After post-annealing at $400^{\circ}C$ for 5 min, $Al_2O_3$ thin film exhibited the structural stability having amorphous nature without the interfacial reaction between $Al_2O_3$ and Si. The post-annealing at $400^{\circ}C$ for 5 min led to an increase in the relative effective lifetime of $Al_2O_3$ thin film. This could be associated with the field effective passivation combined with surface passivation of textured Si. The capacitance-voltage (C-V) characteristics of the metal-oxide-semiconductor (MOS) with $Al_2O_3$ thin film post-annealed at $400^{\circ}C$ for 5 min was carried out to evaluate the negative fixed charge of $Al_2O_3$ thin film. From the relationship between flatband voltage ($V_{FB}$) and equivalent oxide thickness (EOT), which were extracted from C-V characteristics, the negative fixed charge of $Al_2O_3$ thin film was calculated to be $2.5{\times}10^{12}cm^{-2}$, of which value was applicable to the passivation layer of n-type crystalline Si solar cells.