• Transactions on Electrical and Electronic Materials
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• v.12 no.3
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• pp.127-130
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• 2011

We investigated the effects of $O_2$ annealing (i.e., temperature and time) on the characteristics of hafnium silicate ($HfSi_xO_y$) films deposited on a Si substrate by atomic layer deposition process (ALD). We found that the post deposition annealing under oxidizing ambient causes the oxidation of residual Hf metal components, resulting in the improvement of electrical characteristics (e.g., hysteresis window and leakage current are decreased). In addition, we observed the annealing temperature is more important than the annealing time for post deposition annealing. Based on these observations, we suggest that post deposition annealing under oxidizing ambient is necessary to improve the electrical characteristics of $HfSi_xO_y$ films deposited by ALD. However, the annealing temperature has to be carefully controlled to minimize the regrowth of interfacial oxide, which degrades the value of equivalent oxide thickness.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.38-42
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• 2007

The crystallographic and magnetic properties of $KFeO_2$ powder prepared by ball-mill method, have been studied by x-ray diffraction(XRD), $M\"{o}ssbauer$ spectroscopy, and vibrating sample magnetometer(VSM) measurements. The crystal structure of $KFeO_2$ powder at room temperature is determined to be an orthorhombic structure of Pbca with its lattice constants $a_0=5.557{\AA},\;b_0=11.227{\AA},\;c_0=15.890{\AA}$ by Rietveld refinement. $M\"{o}ssbauer$ spectra of $KFeO_2$ were taken at various temperatures ranging from 4.2 to 818 K. The magnetic hyperfine field and isomer shift value at 4.2 K and RT were 519 kOe, 489 kOe and 0.19 mm/s, 0.05 mm/s respectively. The average hyperfine field $H_{hf}(T)$ of the $KFeO_2$ shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.36(T/T_N)^{5/2}$ for $T/T_N$<0.7, indicative of spin-wave excitation.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.42-43
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• 2002

반도체 디바이스의 발전은 높은 직접화 및 동작 속도를 추구하고 있으며, 이를 위해서 MOSFET의 scale down시 발생되는 문제를 해결해야만 한다. 특히, Channel이 짧아짐으로써 발생하는 device의 열화현상으로 동작전압의 조절이 어려워 짐을 해결해야만 하며, gate oxide 두께를 줄임으로써 억제할 수 있다고 알려져 왔다. 현재, gate oxide으로 사용되고 있는 SiO2박막은 비정질로써 ～8.7 eV의 높은 band gap과 Si기판 위에서 성장이 용이하며 안정하다는 장점이 있으나, 두께가 1.6 nm 이하로 얇아질 경우 전자의 direct Tunneling에 의한 leakage current 증가와 gate impurity인 Boron의 channel로의 확산, 그리고 poly Si gate의 depletion effect[1,2] 등의 문제점으로 더 이상 사용할 수 없게 된다. 2001년 ITRS에 의하면 ASIC제품의 경우 2004년부터 0.9～l.4 nm 이하의 EOT가 요구된다고 발표하였다. 따라서, gate oxide의 물리적인 두께를 증가시켜 전자의 Tunneling을 억제하는 동시에 유전막에 걸리는 capacitance를 크게 할 수 있다는 측면에서 high-k 재료를 적용하기 위한 연구가 진행되고 있다[3]. High-k 재료로 가능성 있는 절연체들로는 A1₂O₃, Y₂O₃, CeO₂, Ta₂O, TiO₂, HfO₂, ZrO₂,STO 그리고 BST등이 있으며, 이들 재료 중 gate oxide에 적용하기 위해 크게 두 가지 측면에서 고려해야 하는데, 첫째, Si과 열역학적으로 안정하여 후속 열처리 공정에서 계면층 형성을 배제하여야 하며 둘째, 일반적으로 high-k 재료들은 유전상수에 반비례하는 band gap을 갖는 것으로 알려줘 있는데 이 Barrier Height에 지수적으로 의존하는 leakage current때문에 절연체의 band gap이 낮아서는 안 된다는 점이다. 최근 20이상의 유전상수와 ～5 eV 이상의 Band Gap을 가지며 Si기판과 열역학적으로 안정한 ZrO₂[4], HfiO₂[5]가 관심을 끌고 있다. HfO₂은 ～30의 고유전상수, ～5.7 eV의 높은 band gap, 실리콘 기판과의 열역학적 안전성 그리고 poly-Si와 호환성등의 장점으로 최근 많이 연구가 진행되고 있다. 또한, Hf은 SiO₂를 환원시켜 HfO₂가 될 수 있으며, 다른 silicide와 다르게 Hf silicide는 쉽게 산화될 수 있는 점이 보고되고 있다.

• Journal of the Korean Magnetics Society
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• v.3 no.1
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• pp.23-28
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• 1993

Thin films of soft magnetic Fe-Hf-C alloys with nanoscale crystallites were investigated in this study. The films were fabricated by an RF diode magnetron sputtering apparatus and subsequently annealed in vacuum. The soft magnetic properties of the films were observed to differ depending on the different substrates such as Corning 7059, $CaTiO_3$ and $Al_2O_3-TiC$ with various underlayer(Cr, $SiO_2$) thickness. This results may be due to the interdiffusion between the substrate and the magnetic layer and/or between the underlayer and the magnetic layer, rather than the microstructural change such as grain size. The Fe-Hf-C films with high permeability up to 4000(at 1 MHz) and saturation magnetization up to 16 kG were obtained in the vicinity of phase boundary between the crystalline and amorphous state when the size of ${\alpha}-Fe$ grains is about 5 nm. And also the films were found to have thermal stability up to $600^{\circ}C$.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.792-799
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• 2019

The present study aims to investigate the fluorination of thorium oxide ($ThO_2$) by ammonium hydrogen difluoride ($NH_4HF_2$). Fluorination was performed at room temperature by mixing $ThO_2$ and $NH_4HF_2$ at different molar ratios, which was then left to react for 20 days. Next, the mixtures were analyzed using X-ray diffraction (XRD) at the intervals of 5, 10, 15, and 20 days, followed by the heating of the mixtures at $450-750^{\circ}C$ with argon gas flow. The characterization of $ThF_4$ was established using X-ray diffraction (XRD) and scanning electron microscopy-dispersion X-ray spectroscopy (SEM-EDX). In this study, ammonium thorium fluoride was synthesized through the fluorination of $ThO_2$ at room temperature. The optimum molar ratio in synthesizing ammonium thorium fluoride was 1.0:5.5 ($ThO_2:NH_4HF_2$) with 5 days reaction time. In addition, the heating of ammonium thorium fluoride at $450^{\circ}C$ was sufficient to produce $ThF_4$. Overall, this study proved that $NH_4HF_2$ is one of the fluorination agents that is capable of synthesizing $ThF_4$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.1
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• pp.218-221
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• 2004

This study was performed to investigate the effect of rosiglitazone, a new antidiabetic agent, on in vivo synthesis of bone collagen. The mice were divided into low-fat diet group (LF), high-fat diet group (HF), and high-fat diet with rosiglitazone (6.3 $\mu\textrm{g}$/kcal diet) group (HF-Rosi), The synthesis of bone collagen was measured by stable isotope-mass spectrometric technique using $^2$$H_2O$ as a tracer. The $^2$$H_2O$ labeling protocol consisted of an initial intraperitoneal injection of 99.9% $^2$$H_2O$, to achieve approximately 2.5% body water enrichment followed by administration of 4％ $^2$$H_2O$ in drinking water for 3 weeks. Although body weight gain and daily diet intake were not significantly different between groups, HF-Rosi had slightly higher body weight gain and daily diet intake than LF and HF. In addition, HF-Rosi showed significantly higher body fat content than LF and HF. Bone collagen synthesis was reduced in HF than LF and further decreased by the treatment of rosiglitazone. These results suggest rosiglitazone affect body fat content and bone turnover in mice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.158-158
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• 2009

This paper focuses on improving organic thin film transistor (OTFT) characteristics by controlling the self-organization of pentacene molecules with an alignable high-dielectric-constant film. The process, based on the growth of pentacene film through high-vacuum sublimation, is a method of self-organization using ion-beam (IB) bombardment of the $HfO_2/Al_2O_3$ surface used as the gate dielectric layer. X-ray photoelectron spectroscopy indicates that the IB raises the rate of the structural anisotropy of the $HfO_2/Al_2O_3$film, and X-ray diffraction patterns show the possibility of increasing the anisotropy to create the self-organization of pentacene molecules in the first polarized monolayer. An effective mobility of $2.3{\times}10^{-3}cm^2V^{-1}s^{-1}$ was achieved, which is significantly different from that of pentacene films that are not aligned. The proposed OTFT devices with an ultrathin $HfO_2$ structure as the gate dielectric layer were operated at a gate voltage lower than 5 V.

• Weed & Turfgrass Science
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• v.7 no.1
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• pp.62-71
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• 2018

This study was conducted to evaluate the effect of liquid fertilizer containing humate (LFH) on changes of turfgrass quality and growth by investigating visual quality, chlorophyll content, dry weight of clipping, and nutrient content in leaves tissue. Treatments were designed as follows; control fertilizer (CF), HF-1 ($CF+1.0mL\;m^{-2}\;LFH$), HF-2 ($CF+2.0mL\;m^{-2}\;LFH$), and HF-3 ($CF+4.0mL\;m^{-2}\;LFH$). As compared with CF, soil chemical properties of LFH treatments were not significantly. Visual quality and root dry weight of LFH treatments were higher than that of CF. Chlorophyll content, clipping yield and nitrogen uptake of HF-2 and HF-3 were increased 11.2-11.8%, 15.3-30.0%, 22-42% by application of LFH. The LFH level was positively correlated with visual quality, chlorophyll content, clipping yield or nutrient uptake amount. These results indicated that the application of LFH improved the growth and quality of creeping bentgrass by increasing nutrient uptake and by prompting root growth.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.39-45
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• 2012

Three-dimensional integrated circuit(3D IC) technology has become increasingly important due to the demand for high system performance and functionality. In this work, BOE and HF wet etching of Cu line surfaces after CMP were conducted for Cu-Cu pattern direct bonding. Step height of Cu and $SiO_2$ as well as Cu dishing after Cu CMP were analyzed by the 3D-Profiler. Step height increased and Cu dishing decreased with increasing BOE and HF wet etching times. XPS analysis of Cu surface revealed that Cu surface oxide layer was partially removed by BOE and HF wet etching treatment. BOE treatment showed not only the effective $SiO_2$ etching but also reduced dishing and Cu surface oxide rather than HF treatment, which can be used as an meaningful process data for reliable Cu-Cu pattern bonding characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.218-218
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• 2010

기존의 비휘발성 메모리 소자는 터널 절연막으로 $SiO_2$ 단일 절연막을 이용하였다. 그러나 소자의 축소화와 함께 비휘발성 메모리 소자의 동작 전압을 낮추기 위해서 $SiO_2$ 단일 절연막의 두께도 감소 시켜야만 하였다. 하지만 $SiO_2$ 단일 절연막의 두께 감소에 따라, 메모리의 동작 횟수와 데이터 보존 시간의 감소등의 문제점들로 인해 기술적인 한계점에 이르렀다. 이러한 문제점들을 해결하기 위한 연구가 활발히 진행되고 있는 가운데, 최근 high-k 물질을 기반으로 하는 Tunnel Barrier Engineered (TEB) 기술이 주목 받고 있다. TBE 기술이란, 터널 절연막을 위해 서로 다른 유전율을 갖는 유전체를 적층함으로써 쓰기/지우기 속도의 향상과 함께, 물리적인 두께 증가로 인한 데이터 보존 시간을 향상 시킬 수 있는 기술이다. 따라서, 본 연구에서는 적층된 터널 절연막에 이용되는 $HfO_2$를 FGA (Forming Gas Annealing)와 RTA (Rapid Thermal Annealing) 공정에 의한 열처리 효과를 알아보기 위해, 온도에 따른 전기적인 특성을 MIS-Capacitor 제작을 통하여 분석하였다. 이를 위해 먼저 Si 기판 위에 $SiO_2$를 약 3 nm 성장시킨 후, $HfO_2$를 Atomic Layer Deposition (ALD) 방법으로 약 8 nm를 증착 하였고, Aluminum을 약 150 nm 증착 하여 게이트 전극으로 이용하였다. 이를 C-V와 I-V 특성을 이용하여 분석함으로 써, 열처리 공정을 통한 $HfO_2$의 터널 절연막 특성이 향상됨을 확인 하였다. 특히, $450^{\circ}C$ $H_2/N_2$(98%/2%) 분위기에서 진행한 FGA 공정은 $HfO_2$의 전하 트랩핑 현상을 줄일 뿐 만 아니라, 낮은 전계에서는 낮은 누설 전류를, 높은 전계에서는 높은 터널링 전류가 흐르는 것을 확인 하였다. 이와 같은 전압에 대한 터널링 전류의 민감도의 향상은 비휘발성 메모리 소자의 쓰기/지우기 특성을 개선할 수 있음을 의미한다. 반면 $N_2$ 분위기에서 실시한 RTA 공정에서는, 전하 트랩핑 현상은 감소 하였지만 FGA 공정 후 보다는 전하 트랩핑 현상이 더 크게 나타났다. 따라서, 적층된 터널 절연막은 적절한 열처리 공정을 통하여 비휘발성 메모리 소자의 성능을 향상 시킬 수 있음이 기대된다.