• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.160-160
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• 2015

InGaZnO (IGZO) thin-film transistors (TFTs) are very promising due to their potential use in high performance display backplane [1]. However, the stability of IGZO TFTs under the various stresses has been issued for the practical IGZO applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of IGZO thin film. In this study, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of IGZO TFTs by this new deposition method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.466-468
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• 2012

Amorphous InGaZnO (${\alpha}$-IGZO) thin-film transistors (TFTs) are are very promising due to their potential use in thin film electronics and display drivers [1]. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the ${\alpha}$-IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of ${\alpha}$-IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of ${\alpha}$-IGZO thin film. In this paper, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in ${\alpha}$-IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of ${\alpha}$-IGZO TFTs by this new deposition method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.446-447
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• 2007

The rapid thermal annealing effect of transparent IZTO(indium zinc oxide) and IAZO(indium alminium zinc oxide) films grown on glass substrate for solar cell or flat panel displays(FPDs) was studied. We prepared IZTO using RF magnetron sputtering and IAZO using DC co-sputtering method. Subsequently, using rapid thermal annealing(RTA) system, prepared IZTO and IAZO films were annealed at 300, 400, 500, $600^{\circ}C$ for 90sec. In addition, Electrical and optical characteristics were measured by Hall effect measurement and UV/Vis spectrometer examinations, respectively. To analyze structural properties and surface smoothness of the IZTO and IAZO films, XRD and SEM examinations were performed, respectively. It was shown that IZTO and IAZO films exhibited microcrystalline structure over $400^{\circ}C$ and amorphous structural regardless of RTA temperature, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.451-452
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• 2006

We studied the electro-optical characteristic of vertical alignment liquid crystal display(VA-LCD) on the $SiO_x$ thin film deposited $45^{\circ}$ oblique by rf magnetic sputtering system. LC alignment characteristic showed homeotropic alignment, and pretilt angle was about $90^{\circ}$. A uniform liquid crystal alignment effect on the $SiO_x$ thin film was achieved and the electro-optical characteristic of the $SiO_x$ thin film deposited $45^{\circ}$ oblique by rf magnetic sputtering system was excellent.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.120-121
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• 2006

To investigate the ZnO thin films which are interested in the next generation of short wavelength LEDs and Lasers, the ZnO thin films were deposited by RF magnetron sputtering system. Al sputtering process of ZnO thin films substrate temperature, work pressure respectively is $100^{\circ}C$ and 15 mTorr, and the purity of target is ZnO 5N. The ZnO thin films were in-situ annealed at $600^{\circ}C$, $800^{\circ}C$ in $O_2$ atmosphere. Phosphorus (P) and arsenic (As) were diffused into ZnO thin films sputtered by RF magnetron sputtering system in ampoule tube which was below $5{\times}10^{-7}$ Torr. The dopant sources of phosphorus and arsenic were $Zn_3P_2$ and $ZnAS_2$. Those diffusion was perform at $650^{\circ}C$ during 3hr. We confirmed that p-type properties of ZnO thin films were concerned with dopant sources rather than diffusion temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.969-973
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• 2009

In this study, the electrical and optical properties of $(SiO_2)_x(ZnO)_{100-x}$ (SZO) films prepared on the coming 7059 glass substrates by using rf-magnetron sputtering method are investigated. The deposition rate becomes maximum near 3 wt.% and gradually decreases when the $SiO_2$ content further increases. The growth rates of the SZO film with $SiO_2$ content of 3 wt.% is $4\;{\AA}/s$. We found that the average transmittance of all films is over 80% in the wavelength range above 500 nm. The optical band gap were decreased from 3.52 to 3.33 eV as an increase the deposition thickness. X-ray diffraction patterns showed that the film with a relatively low $SiO_2$ content (< 4 wt.%) is amorphous. SZO film with the $SiO_2$ contents of 2 wt.% showed the resistivity of about $3.8{\times}10^{-3}\;{\Omega}{\cdot}cm$. The sheet resistance decreases with increasing the heat treatment temperature.

• Journal of the Semiconductor & Display Technology
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• v.15 no.4
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• pp.41-45
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• 2016

ITO/GZO double layered thin films were prepared on transparent glass substrates. Ga-doped ZnO(GZO) films were deposited by RF magnetron sputtering using an ZnO:Ga (98: 2 wt%) target. The post deposition annealing process was conducted for 30 minutes at different temperature of 100, 200, 300 and $400^{\circ}C$, respectively. As increase annealing temperature, ITO/GZO double layered thin films show the increment of the prefer orientation of ZnO diffraction peak (002) in the XRD patterns. We obtained Ga-doped ZnO thin films with a lowest resistivity of $1.84{\times}10^{-4}{\Omega}-cm$ at $400^{\circ}C$ and transparency above 80% in visible ranges. The figure of merit obtained in this study means that ITO/GZO double layered thin films which annealed at $400^{\circ}C$ have the highest optoelectrical performance in this study.

• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.77-81
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• 2010

The AZO thin films were deposited on the corning 1737 glass plate by the RF magnetron sputtering and effects of working pressure and oxygen contents on the electrical properties were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM for the 70mTorr. From the surface analysis (AFM), the number of crystal grain of AZO thin film increased as working pressure increased. The film deposited with 70mTorr of working pressure showed n-type semiconductor characteristic having suitable resistivity $-1.59{\times}10^{-2}{\Omega}cm$, carrier concentration $-10.1{\times}10^{19}cm^{-3}$, and mobility $-4.35cm^2V^{-1}s^{-1}$ while other films by 7 mTorr, 20 mTorr of working pressure closed to metallic films. The films including the oxygen represent stoichiometric composition similar to the oxide. The transmittance of the film was over 85% in the visible light range regardless of the changes in working pressure and oxygen contents.

• Journal of the Semiconductor & Display Technology
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• v.9 no.3
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• pp.41-45
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• 2010

The ZnO thin films doped with Ga(GZO) and both Ga and Ge(GZO:Ge) were deposited on glass substrate by using RF sputtering system respectively. Structural, morphological and optical properties of the films deposited in the same condition were investigated. Structural properties of the films were investigated by Field Emission Scanning Electron Microscopy, FE-SEM images and X-ray diffraction, XRD analysis. These studies showed shape of films' surface and direction of film growth respectively. It's showed that all films were deposited by vertical orientation strongly. It can be confirmed that all dopants of targets were included in deposited films by results of EDX analysis. UV-Vis spectrometer results showed that all samples had highly transparent characteristics in visible region and have similar 3.28~3.31 eV band gap. It was found that existence of all dopants by EDX analysis. Morphology and roughness of surface of each film were clearly shown by Atomic Force Microscopy, AFM images. It was found in this research that film doped with Ge more dense and stable with hardly any difference in gap energy compared to ZnO films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.32-36
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• 2022

AGZO thin films were deposited on glass substrates using RF magnetron sputtering system under Ar flow rates, and their structural, electrical, and optical properties were analyzed systematically. As a result of the XRD pattern, the peak of the (002) (2θ≈33.7˚) orientation was observed, and it was found to have a hexagonal wurtzite structure. The sheet resistance of Ar 5 sccm was 3.073×10² Ω/sq and showed the best electrical properties because of the improvement of mobility due to the increase of the grain size and the variation of RMS roughness. In addition, the average transmittance was more than 90% for all samples, which demonstrated good optical properties. It is expected that the TCO characteristics can be improved by controlling Ar flow rates, and this will increase the efficiency of photoelectronic devices such as OLED and solar cells.