• Bulletin of the Korean Chemical Society
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• v.22 no.9
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• pp.1015-1018
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• 2001

Vanadium oxide thin films with thickness of about 2000 $\AA$ have been prepared by radio frequency sputter deposition using a V2O5 target in a mixed argon and oxygen atmosphere with different Ar/O2 ratio ranging from 99/1 to 90/10. X-ray diffraction and X-ray absorption near edge structure spectroscopic studies show that the oxygen content higher than 5% crystallizes a stoichiometric V2O5 phase, while oxygen deficient phase is formed in the lower oxygen content. The oxygen content in the mixed Ar + O2 has a significant influence on electrochemical lithium insertion/deinsertion property. The discharge-charge capacity of vanadium oxide film increases with increasing the reactive oxygen content. The V2O5 film deposited at the Ar/O2 ratio of 90/10 exhibits high discharge capacity of 100 ${\mu}Ah/cm2-{\mu}m$ along with good cycle performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.36-41
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• 2023

We investigated the properties of vanadium oxide (VOx) buffer layers deposited by a dual RF magnetron sputtering method under various target powers for inverted organic solar cells (IOSCs). Sputter fabricatged VOx thin films exhibited higher crystallinity with the increase of target power, resulting in a uniform and large grain size. The electrical properties of VOx films are improved with the increase of target power because of the increase of V content. In the results, the performance of IOSCs critically depended on the target power during the film growth because the crystalllinity of the VOx film affects the carrier mobility of the VOx film.

• 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.

• Journal of the Korean institute of surface engineering
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• v.40 no.3
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• pp.117-124
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• 2007

The ITO films were deposited on glass substrates by RF-superimposed dc reactive magnetron sputtering and were annealed in $N_2$ vacuum furnace with temperatures in the range of $403K{\sim}573K$ for 30 minutes. Electrical, optical and structural properties of ITO films were examined with varying annealing temperatures from 403 K to 573 K. The resistivity of as-deposited ITO films was $5.4{\times}10^{-4}{\Omega}cm$ at the sputter conditions of applied RF/DC power of 200/200 W, $O_{2}$ flow of 0.2 seem and Ar flow of 0.2 seem. As a result of annealing in the temperature range of $403K{\sim}573K$, the crystallization occurred at 423 K that is lower than the crystallization temperature caused by a conventional sputtering method. And the resistivity decreased from $5.4{\times}10^{-4}{\Omega}cm\;to\;2.3{\times}10^{-4}{\Omega}cm$, the carrier concentration and mobility of ITO films increased from $4.9{\times}10^{20}/cm^3\;to\;6.4{\times}10^{20}/cm^3$, from $20.4cm^2/Vsec\;to\;41.0cm^2/Vsec$, respectively. The transmittance of ITO films in visible became higher than 90% when annealed in the temperature range of $423K{\sim}573K$. High quality ITO thin films made by RF-superimposed dc reactive magnetron sputtering and annealing in $N_2$ vacuum furnace will be applied to transparent conductive oxides of the advanced flat panel display.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.310-310
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• 2016

최근 NAND flash memory는 높은 집적성과 데이터의 비휘발성, 낮은 소비전력, 간단한 입, 출력 등의 장점들로 인해 핸드폰, MP3, USB 등의 휴대용 저장 장치 및 노트북 시장에서 많이 이용되어 왔다. 특히, 최근에는 smart watch, wearable device등과 같은 차세대 디스플레이 소자에 대한 관심이 증가함에 따라 유연하고 투명한 메모리 소자에 대한 연구가 다양하게 진행되고 있다. 대표적인 플래시 메모리 소자의 구조로 charge trapping type flash memory (CTF)가 있다. CTF 메모리 소자는 trap layer의 trap site를 이용하여 메모리 동작을 하는 소자이다. 하지만 작은 window의 크기, trap site의 열화로 인해 메모리 특성이 나빠지는 문제점 등이 있다. 따라서 최근, trap layer에 다양한 물질을 적용하여 CTF 소자의 문제점을 해결하고자 하는 연구들이 진행되고 있다. 특히, 산화물 반도체인 zinc oxide (ZnO)를 trap layer로 하는 CTF 메모리 소자가 최근 몇몇 보고 되었다. 산화물 반도체인 ZnO는 n-type 반도체이며, shallow와 deep trap site를 동시에 가지고 있는 독특한 물질이다. 이 특성으로 인해 메모리 소자의 programming 시에는 deep trap site에 charging이 일어나고, erasing 시에는 shallow trap site에 캐리어들이 쉽게 공급되면서 deep trap site에 갇혀있던 charge가 쉽게 de-trapped 된다는 장점을 가지고 있다. 따라서, 본 실험에서는 산화물 반도체인 ZnO를 trap layer로 하는 CTF 소자의 메모리 특성을 확인하기 위해 간단한 구조인 metal-oxide capacitor (MOSCAP)구조로 제작하여 메모리 특성을 평가하였다. 먼저, RCA cleaning 처리된 n-Si bulk 기판 위에 tunnel layer인 SiO2 5 nm를 rf sputter로 증착한 후 furnace 장비를 이용하여 forming gas annealing을 $450^{\circ}C$에서 실시하였다. 그 후 ZnO를 20 nm, SiO2를 30 nm rf sputter로 증착한 후, 상부전극을 E-beam evaporator 장비를 사용하여 Al 150 nm를 증착하였다. 제작된 소자의 신뢰성 및 내구성 평가를 위해 상온에서 retention과 endurance 측정을 진행하였다. 상온에서의 endurance 측정결과 1000 cycles에서 약 19.08%의 charge loss를 보였으며, Retention 측정결과, 10년 후 약 33.57%의 charge loss를 보여 좋은 메모리 특성을 가지는 것을 확인하였다. 본 실험 결과를 바탕으로, 차세대 메모리 시장에서 trap layer 물질로 산화물 반도체를 사용하는 CTF의 연구 및 계발, 활용가치가 높을 것으로 기대된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.208.1-208.1
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• 2015

최근, 차세대 투명 디스플레이 구동소자로서 산화물 반도체를 이용한 Transparent Amorphous Oxide Semiconductor (TAOS) 기술이 큰 주목을 받고 있다. 산화물 반도체는 기존의 a-Si에 비해 우수한 전기적인 특성과 낮은 구동전압 그리고 넓은 밴드 갭으로 인한 투명성의 장점들이 있다. 그리고 낮은 공정 온도에서도 제작이 가능하기 때문에 유리나 플라스틱과 같은 다양한 기판에서도 박막 증착이 가능하다. 하지만 기존의 furnace를 이용한 열처리 방식은 낮은 온도에서 우수한 전기적인 특성을 내기 어려우며, 공정 시간이 길어지는 단점들이 있다. 따라서 본 연구에서는 산화물 반도체중 In-Ga-Zn-O (IGZO)와 In-Sn-O(ITO)를 각각 채널 층과 게이트 전극으로 이용하였다. 또한 마이크로웨이브 열처리 기술을 이용하여 기존의 열처리 방식에 비해 에너지 전달 효율이 높고 짧은 시간동안 저온 공정이 가능하며 우수한 전기적인 특성을 가지는 투명 박막 트랜지스터를 구현 하였다. 본 실험은 glass 기판위에서 진행되었으며, RF sputter를 이용하여 ITO를 150 nm 증착한 후, photo-lithography 공정을 통하여 하부 게이트 전극을 형성하였다. 이후에 RF sputter를 이용하여 SiO2 와 IGZO 를 각각 300, 50 nm 증착하였고, patterning 과정을 통하여 채널 영역을 형성하였다. 또한 소자의 전기적인 특성 향상을 위해 마이크로웨이브 열처리를 1000 Watt로 2 분간 진행 하였고, 비교를 위하여 기존 방식인 furnace 를 이용하여 N2 분위기에서 $400^{\circ}C$로 30분간 진행한 소자도 병행하였다. 그 결과 마이크로웨이브를 통해 열처리한 소자는 공정 온도가 $100^{\circ}C$ 이하로 낮기 때문에 glass 기판에 영향을 주지 않고 기존 furnace 열처리 한 소자보다 전체적으로 전기적인 특성이 우수한 것을 확인 하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.41.2-41.2
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• 2011

Recently, scaling down of ULSI (Ultra Large Scale Integration) circuit of CMOS (Complementary Metal Oxide Semiconductor) based electronic devices become much faster speed and smaller size than ever before. However, very narrow interconnect line width causes some drawbacks. For example, deposition of conformal and thin barrier is not easy moreover metallization process needs deposition of diffusion barrier and glue layer. Therefore, there is not enough space for copper filling process. In order to overcome these negative effects, simple process of copper metallization is required. In this research, Cu-V thin alloy film was formed by using RF magnetron sputter deposition system. Cu-V alloy film was deposited on the plane $SiO_2$/Si bi-layer substrate with smooth and uniform surface. Cu-V film thickness was about 50 nm. Cu-V layer was deposited at RT, 100, 150, 200, and $250^{\circ}C$. XRD, AFM, Hall measurement system, and XPS were used to analyze Cu-V thin film. For the barrier formation, Cu-V film was annealed at 200, 300, 400, 500, and $600^{\circ}C$ (1 hour). As a result, V-based thin interlayer between Cu-V film and $SiO_2$ dielectric layer was formed by itself with annealing. Thin interlayer was confirmed by TEM (Transmission Electron Microscope) analysis. Barrier thermal stability was tested with I-V (for measuring leakage current) and XRD analysis after 300, 400, 500, 600, and $700^{\circ}C$ (12 hour) annealing. With this research, over $500^{\circ}C$ annealed barrier has large leakage current. However V-based diffusion barrier annealed at $400^{\circ}C$ has good thermal stability. Thus, thermal stability of vanadium-based thin interlayer as diffusion barrier is good for copper interconnection.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.231-231
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• 2010

Thermoelectric properties of a multi-layered thin film, which was composed with indium selenide and bismuth telluride, were investigated. The structure of the layered thin film is Bi-Te /In-Se/Bi-Te and it was prepared on sapphire substrate by RF magnetron sputter using stoichiometric $Bi_2Te_3$ (99.9%) and $In_2Se_3$(99.99%) target at room temperature. Then, it was annealed at temperature range of 150 - $500^{\circ}C$ in Ar ambient. Structural characterizations were done using X-ray diffraction(XRD, BRUKER, D8, 60kW) and transmission electron microscopy (TEM, FEI, Tecnai, F30 S-Twin), respectively. Cross-section of multi-layer structure was observed by Scanning electron microscopy (SEM). The resistivity and Seebeck coefficient of these samples were also measured by conventional equipment at room temperature. The maximum value of power factor was $1.16\;{\mu}W/k^2m$ at annealing temperature of $400^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.49-53
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• 2011

Diamond-like carbon (DLC) films is a metastable form of amorphous carbon containing a significant fraction of Sp3 bond. DLC films have been characterized by a range of attractive mechanical, chemical, tribological, as well as optical and electrical properties. In this study DLC films were prepared by the RF magnetron sputter system on $SiO_2$ substrates using graphite target. The effects of the post annealing temperature on the Property variation of the DLC films were examined. The DLC films were annealed at temperatures ranging from 300 to $500^{\circ}C$ using rapid thermal process equipment in vacuum. The variation of electrical property and surface morphology as a function of annealing treatment was investigated by using a Hall Effect measurement and atomic force microscopy. Raman and X-ray photoelectron spectroscopy analyses revealed a structural change in the DLC films.