• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.454-459
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• 2020

In this study, a TiO₂/TiO_2-x-based resistance variable memory was fabricated using a DC/RF magnetron sputtering system and ALD. In order to analyze the effect of oxygen plasma treatment on the performance of resistance random access memory (ReRAM), the TiO₂/TiO_2-x-based ReRAM was evaluated by applying RF power to the TiO_2-x oxygen-holding layer at 30, 60, 90, 120, and 150 W, respectively. The ReRAM was fabricated, and the electrical and surface area performances were compared and analyzed. In the case of ReRAM without oxygen plasma treatment, the I-V curve had a hysteresis curve shape, but the width was very small, with a relatively high surface roughness of the oxygen-retaining layer. However, in the case of oxygen plasma treatment, the HRS/LRS ratio for the I-V curve improved as the applied RF power increased; stable improvement was also noted in the surface roughness of the oxygen-retaining layer. It was confirmed that the low voltage drive was not smooth due to charge trapping in the oxygen diffusion barrier layer owing to the high intensity ReRAM applied with an RF power of approximately 150 W.

• Journal of the Korean Magnetics Society
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• v.16 no.4
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• pp.197-200
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• 2006

Amorphous alloys of Co-rich magnetic amorphous films are well known as thpical soft magnetic alloys. They are used for many kinds of electric and electronic parts such as magnetic recording heads, transformers and inductors. CoFeHfO thin films were prepared by RF magnetron reactive sputtering. The films were deposited onto Si(100) substrates with a power of 300 W at room temperature. The reactive gas was introduced up to 10% ($O_2$/(Ar + $O_2$)) during deposition, and the $Co_{39}Fe_{34}Hf_{9.5}O_{17.5}$ thin film exhibit excellent soft magnetic properties : saturation magnetization ($4{\pi}M_s$) of 19kG, magnetic coercivity ($H_c$) of 0.37 Oe, anisotropy field ($H_k$) of 48.62 Oe, and an electrical property is also shown to be as high as 300 ${\mu}{\Omega}cm$. It is assumed that the good soft magnetic properties of $Co_{39}Fe_{34}Hf_{9.5}O_{17.5}$ thin film results from high electrical resistivity and large anisotropy field.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.30.1-30.1
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• 2009

정보화가 급속히 진전됨에 따라 보다 많은 양의 정보를 전송, 처리, 저장하게 되면서 이를 위해 대용량, 고속, 비휘발성의 특징을 갖는 차세대 메모리의 개발이 절실히 요구되고있다. 이 중 저항 변화 메모리(ReRAM)는 일반적으로 TiO2, Al2O3, NiO2, HfO2, ZrO2 등의 전이금속산화물을 이용한 MIM 구조로서 적당한 전기 신호를 가하면 저항이 높아서 전도되지 않는 상태(Offstate)에서 저항이 낮아져 전도가 가능한 상태(On state)로 바뀌는 메모리 특성을가진다. ReRAM은 비휘발성 메모리이며 종래의 비휘발성 기억소자인 Flash memory 보다 access time 이105 배 이상 빠르고, 5V 이하의 낮은 전압에서도 동작이 가능하다. 또한 구조가 간단하여 공정 단순화가 가능하고 소자의 집적화도 쉽다는 점 등 많은 장점들이 있어서 Flash memory를 대체할 수 있는 유력한 후보로 여겨지고 있다. 본연구에서는 DC-magnetron Sputtering 방법으로 전이금속 박막을 증착하고, Dry furnace로 산화시켜 전이금속산화물 박막을 제작한 후 저항변화 특성을 연구하였다. 두 개의 전이금속산화물 박막을 dual-layer로 형성시켜 저항변화특성을 관찰하였으며 또한, 전이금속산화물 박막의 조성을 달리 하여 저항변화를 관찰 하였다. 전이금속산화물 박막의 전기적 특성을 알아보기 위해 Si(100) wafer 위에 Pt를 이용 MIM 형태로 capacitor 시편을 제작 하여, probe station으로 I-V 측정을 하였고 조성 및 표면 분석을 위해서는 AES와 AFM을, 미세구조를 분석을 위해서는 TEM과 SEM 을 사용하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.307-307
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• 2012

In this study, we investigated that the resistance switching characteristics of Al-doped MgOx films with increasing Al doping concentration and increasing film thickness. The Al-doped MgOx based ReRAM devices with a TiN/Al-doped MgOx/Pt/Ti/SiO2 were fabricated on Si substrates. The 5 nm, 10 nm, and 15 nm thick Al-doped MgOx films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16 sccm, O2: 24 sccm). Micro-structure of Al-doped MgOx films and atomic concentration were investigated by XRD and XPS, respectively. The Al-doped MgOx films showed set/reset resistance switching behavior at various Al doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased with decreasing thickness of Al-doped MgOx films. Besides, the initial current of Al-doped MgOx films is increased with increasing Al doping concentration in MgOx films. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen of Al-doped MgOx.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.239-239
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• 2003

As a result of the recent miniaturization and enhancement in the performance of thin film inductors and thin film transformers, there are increased demands for the thin films with a high magnetic permeability in the high frequency range, a high saturation magnetization, a high electrical resistivity, and a low coercive force. In order to improve high frequency properties, we will investigate anisotropy field by shape and size of pattern. The Fe-Al-O thin films of 16mm diameter and 1$\mu\textrm{m}$ thickness were deposited on Si wafer, using RE magnetron reactive sputtering technique with the mixture of argon and oxygen gases. The fabricating conditions are obtained in the working partial pressure of 2m Torr, O$_2$ partial Pressure of 5%, Input power of 400w, and Al pellets on an Fe disk with purity of 99.9%. For continuous thin film is the 4Ms of 19.4kG, H$\sub$c/ of 0.6Oe, H$\sub$k/ of 6.0Oe and effective permeability of 2500 up to 100MHz. In this work, we expect to enhanced effect of magnetic anisotropy on patterned of Fe-Al-O thin films.

• Transactions on Electrical and Electronic Materials
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• v.8 no.2
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• pp.73-78
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• 2007

The crystallization temperature in GeTe solid electrolyte films was improved by in situ-nitrogen doping by rf magnetron co-sputtering technique at room temperature. The crystallization temperature of $250\;^{\circ}C$ in electrolyte films without nitrogen doping increased by approximately $300\;^{\circ}C$, $350\;^{\circ}C$, and above $400\;^{\circ}C$ in films deposited with nitrogen/argon flow ratios of 10, 20, and 30 %, respectively. A PMC memory device with $Ge_{45}Te_{55}$ solid electrolytes deposited with nitrogen/argon flow ratios of 20 % shows reproducible memory switching characteristics based on resistive switching at threshold voltage of 1.2 V with high $R_{off}/R_{on}$ ratios. Nitrogen doping into the silver saturated GeTe electrolyte films improves the crystallization temperature of electrolyte films and does not appear to have a negative impact on the switching characteristics of PMC memory devices.

• Journal of the Korean institute of surface engineering
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• v.26 no.6
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• pp.316-326
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• 1993

Adhesion and hardeness are the most important properties of a hard coated layer which is applied to wear-resistant devices. Zr/ZrN layer was deposited on tool steel(SKH9) and stainless steel(SUS304) by a re-active D.C. magnetron sputtering technique and their microhardness and adhesion strength were measured for the films processed by changing the partial pressures of $N_2$ gas (4~10$\times$$10^{-4}$mbar) and the substrate bias voltage(0~250V). The adhesion strength was evaluated by acoustic signals through the scratch-test with the incremental applied load. As the partial pressure of $N_2$ gas and the substrate bias voltage were increased, the adhesion strength of tool steel was observed to be stronger than that of the stainless steel. The adhesion strength was generally, observed to decrease with the same tendency regardless of the kinds of substrates. The adhesion strength of tool steel was increased more and more strongly than that of stainless steel as heat-treated temperature was increased. The strength of tool steel was appeared to be high adhesion strength at $400^{\circ}C$. From the failure mode of the film during the scratch adhesion test, the cohesive failure was observed to be obvious and the adhesive failure in a minor portion in the Zr/ZrN doublelayer regardless of the kinds of substrates.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.335-340
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• 2001

$Ga_2O_3$(1 wt%)-doped ZnO(GZO) thin films were grown on ${\alpha}-Al_2O_3$ (0001) by rf magnetron sputtering at $510^{\circ}C$, whose crystal structure was polycrystalline. As-grown GZO thin film shows poor electrical properties and photoluminescence (PL) spectra. To improve these properties, GZO thin films were annealed at 800-$900^{\circ}C$ in $N_2$atmosphere for 3 min. After the rapid thermal annealing(RTA), deep defect-level emission disappears and near-band emission is greatly enhanced. Annealed GZO thin films show very low resisitivity of $2.6\times10^{-4}\Omega$/cm with $3.9\times10^{20}/\textrm{cm}^3$ carrier concentration and exceptionally high mobility of 60 $\textrm{cm}^2$/V.s. These improved physical properties are explained in terms of translation of doped-Ga atoms from interstitial to substitutional site.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.410-410
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• 2013

Next-generation nonvolatile memory (NVM) has attracted increasing attention about emerging NVMs such as ferroelectric random access memory, phase-change random access memory, magnetic random access memory and resistance random access memory (RRAM). Previous studies have demonstrated that RRAM is promising because of its excellent properties, including simple structure, high speed and high density integration. Many research groups have reported a lot of metal oxides as resistive materials like TiO2, NiO, SrTiO3 and ZnO [1]. Among them, the ZnO-based film is one of the most promising materials for RRAM because of its good switching characteristics, reliability and high transparency [2]. However, in many studies about ZnO-based RRAMs, there was a problem to get lower current level for reducing the operating power dissipation and improving the device reliability such an endurance and an retention time of memory devices. Thus in this paper, we investigated that highly reproducible bipolar resistive switching characteristics of W doped ZnO RRAM device and it showed low resistive switching current level and large ON/OFF ratio. This may be caused by the interdiffusion of the W atoms in the ZnO film, whch serves as dopants, and leakage current would rise resulting in the lowering of current level [3]. In this work, a ZnO film and W doped ZnO film were fabricated on a Si substrate using RF magnetron sputtering from ZnO and W targets at room temperature with Ar gas ambient, and compared their current levels. Compared with the conventional ZnO-based RRAM, the W doped ZnO ReRAM device shows the reduction of reset current from ~$10^{-6}$ A to ~$10^{-9}$ A and large ON/OFF ratio of ~$10^3$ along with self-rectifying characteristic as shown in Fig. 1. In addition, we observed good endurance of $10^3$ times and retention time of $10^4$ s in the W doped ZnO ReRAM device. With this advantageous characteristics, W doped ZnO thin film device is a promising candidates for CMOS compatible and high-density RRAM devices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.27-36
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• 2019

The demand for a low dispersion lens with a small refractive index and a high refractive index is increasing, and accordingly, there is an increasing need for a releasable protective film with high heat resistance and abrasion resistance. On the other hand, the optical industry has not yet established a clear standard for the manufacturing process and quality standards for mold-releasing protective films used in aspheric glass lens molding. Optical lens manufacturers treat this technology as proprietary information. In this study, an experiment was conducted regarding the optimization of ion etching, magnetron, and arc current at each source and filter part, and bias voltage in FCVA (filtered cathode vacuum arc)-based Ta-C thin film coatings. This study found that compared to iridium-rhenium alloy thin film sputtering products, the coating conditions were improved by approximately 50%, 20%, and 40% in terms of thickness, hardness, and adhesive strength of the film, respectively. The thin-film coating process proposed in this study is expected to contribute significantly to the development and utilization of glass lenses, which will help enhance the minimum mechanical properties and quality of the mold-release thin film layer required for glass mold surface forming technology.