• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.134-134
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• 2011

High-k dielectric materials such as $HfO_2$, $ZrO_2$ and $Al_2O_3$ increase gate capacitance and reduce gate leakage current in MOSFET structures. This behavior suggests that high-k materials will be promise candidates to substitute as a tunnel barrier. Furthermore, stack structure of low-k and high-k tunnel barrier named variable oxide thickness (VARIOT) is more efficient.[1] In this study, we fabricated the $WSi_2$ nanocrystals nonvolatile memory device with $SiO_2/HfO_2/Al_2O_3$ tunnel layer. The $WSi_2$ nano-floating gate capacitors were fabricated on p-type Si (100) wafers. After wafer cleaning, the phosphorus in-situ doped poly-Si layer with a thickness of 100 nm was deposited on isolated active region to confine source and drain. Then, on the gate region defined by using reactive ion etching, the barrier engineered multi-stack tunnel layers of $SiO_2/HfO_2/Al_2O_3$ (2 nm/1 nm/3 nm) were deposited the gate region on Si substrate by using atomic layer deposition. To fabricate $WSi_2$ nanocrystals, the ultrathin $WSi_2$ film with a thickness of 3-4 nm was deposited on the multi-stack tunnel layer by using direct current magnetron sputtering system [2]. Subsequently, the first post annealing process was carried out at $900^{\circ}C$ for 1 min by using rapid thermal annealing system in nitrogen gas ambient. The 15-nm-thick $SiO_2$ control layer was deposited by using ultra-high vacuum magnetron sputtering. For $SiO_2$ layer density, the second post annealing process was carried out at $900^{\circ}C$ for 30 seconds by using rapid thermal annealing system in nitrogen gas ambient. The aluminum gate electrodes of 200-nm thickness were formed by thermal evaporation. The electrical properties of devices were measured by using a HP 4156A precision semiconductor parameter analyzer with HP 41501A pulse generator, an Agillent 81104A 80MHz pulse/pattern generator and an Agillent E5250A low leakage switch mainframe. We will discuss the electrical properties for application next generation non-volatile memory device.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.156-157
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• 2012

단일 셀에서 비휘발성 및 고속의 휘발성 메모리를 모두 구동할 수 있는 다기능 메모리는 모바일 기기 및 embedded 장치의 폭발적인 성장에 있어 그 중요성이 커지고 있다. 따라서 최근 이러한 fusion기술을 응용한 unified RAM (URAM)과 같은 다기능 메모리의 연구가 주목 받고 있다. 이러한 다목적 메모리는 주로 silicon on insulator (SOI)기반의 1T-DRAM과 SONOS기술 기반의 비휘발성 메모리의 조합으로 이루어진다. 하지만 이런 다기능 메모리는 주로 단결정기반의 SOI wafer 위에서 구현되기 때문에 값이 비싸고 사용범위도 제한되어 있다. 따라서 이러한 다기능메모리를 다결정 실리콘을 이용하여 제작한다면 기판에 자유롭게 메모리 적용이 가능하고 추후 3차원 적층형 소자의 구현도 가능하기 때문에 다결정실리콘 기반의 메모리 구현은 필수적이라고 할 수 있겠다. 본 연구에서는 다결정실리콘을 이용한 channel recessed구조의 다기능메모리를 제작하였으며 각 1T-DRAM 및 NVM동작에 따른 memory 특성을 살펴보았다. 실험에 사용된 기판은 상부 비정질실리콘 100 nm, 매몰산화층 200 nm의 SOI구조의 기판을 이용하였으며 고상결정화 방법을 이용하여 $600^{\circ}C$ 24시간 열처리를 통해 결정화 시켰다. N+ poly Si을 이용하여 source/drain을 제작하였으며 RIE시스템을 이용하여 recessed channel을 형성하였다. 상부 ONO게이트 절연막은 rf sputter를 이용하여 각각 5/10/5 nm 증착하였다. $950^{\circ}C$ N2/O2 분위기에서 30초간 급속열처리를 진행하여 source/drain을 활성화 하였다. 계면상태 개선을 위해 $450^{\circ}C$ 2% H2/N2 분위기에서 30분간 열처리를 진행하였다. 제작된 Poly Si MFM에서 2.3V, 350mV/dec의 문턱전압과 subthreshold swing을 확인할 수 있었다. Nonvolatile memory mode는 FN tunneling, high-speed 1T-DRAM mode에서는 impact ionization을 이용하여 쓰기/소거 작업을 실시하였다. NVM 모드의 경우 약 2V의 memory window를 확보할 수 있었으며 $85^{\circ}C$에서의 retention 측정시에도 10년 후 약 0.9V의 memory window를 확보할 수 있었다. 1T-DRAM 모드의 경우에는 약 $30{\mu}s$의 retention과 $5{\mu}A$의 sensing margin을 확보할 수 있었다. 차후 engineered tunnel barrier기술이나 엑시머레이저를 이용한 결정화 방법을 적용한다면 device의 특성향상을 기대할 수 있을 것이다. 본 논문에서는 다결정실리콘을 이용한 다기능메모리를 제작 및 메모리 특성을 평가하였다. 제작된 소자의 단일 셀 내에서 NVM동작과 1T-DRAM동작이 모두 가능한 것을 확인할 수 있었다. 다결정실리콘의 특성상 단결정 SOI기반의 다기능 메모리에 비해 낮은 특성을 보여주었으나 이는 결정화방법, high-k절연막 적용 및 engineered tunnel barrier를 적용함으로써 해결 가능하다고 생각된다. 또한 sputter를 이용하여 저온증착된 O/N/O layer에서의 P/E특성을 확인함으로써 glass위에서의 MFM구현의 가능성도 확인할 수 있었으며, 차후 system on panel (SOP)적용도 가능할 것이라고 생각된다.

• Applied Biological Chemistry
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• v.34 no.4
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• pp.366-372
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• 1991

The volatile components, normal hydrocarbons, organic acids, and nonvolatile fatty acids in the various parts of Luffa cylindrica(L.) Roemer(sponge-gourd) were analyzed by GC and GC/MS. More than 150 volatile components were separated and thirty seven components were identified and quantified. The contents of essential oil were 0.05%, 0.05%, and 0.08% on a dried weight base in leaves, stem, and seeds respectively. Fruit juice and sap contained 0.06% and 0.03% oil on the fresh weight base. Twenty six components of normal hydrocarbons in leaves, stem, seed, and unripe fruit were separated, identified, and quantified. The total concentrations of the hydrocarbons were $75.5\;{\mu}g/g$ in leaf, $52.0\;{\mu}g/g$ in stem, $46.6\;{\mu}g/g$ in fruit juice, and $32.8\;{\mu}g/g$ in seed fractions. The major hydrocarbons in leaves, stem, and fruit juice were $nC_{25}$, $nC_{27}$, $nC_{29}$, and $nC_{31}$, $nC_{16}$, $nC_{17}$, $nC_{18}$, and $nC_{19}$ were abundant in seeds mainly. The concentration of malonic acid among the five organic acids was highest in leaves, stem, and flowers. Unripe fruit contained 24.5 mg/g of the five organic acids and malic and citric acids were higher. The concentrations of palmitic, linoleic, and linolenic acids were higher concentration in the various parts of sponge-gourd and palmitic acid was distributed in the most parts. The concentrations of organic and fatty acids in the sap were negligible.

• Korean Journal of Food Science and Technology
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• v.21 no.1
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• pp.68-74
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• 1989

The changes of the contents of chemical components and sensory evaluation of Kimchis which were prepared by addition of different amounts of garlic were investigated during fermentation at $21^{\circ}C$ for 8 days. The range of salinity of Kimchis was 1.8-2.0% The titratable acidity of Kimchis was rapidly increased with garlic contents during fermentation. Ascorbic acid was decreased with fermentation but increased with more addition of garlic. Total sugar content was decreased until third day and the free sugar content decreased to 0.8-1.1g/100g at the 8th day fermentation. It was found that lactic acid and succinic acid were relatively high among the nonvolatile organic acids. The lactic acid content increased with the addition of garlic while succinic acid was not certain. During the whole fermentation, the result of sensory evaluation suggested that Kimchis contained more than 2g garlic were more palatable and desirable than eliminated garlic.

• Korean Journal of Food Science and Technology
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• v.29 no.4
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• pp.663-670
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• 1997

Four kinds of commercial vinegars were investigated to compare physicochemical properties (pH, acidity, color, tannin and metal content), minor components (free sugar, free amino and organic acid), and their organoleptic tastes. The ratio of nonvolatile organic acid to the total organic acid was decreased in the order of brewed, cider, brown rice, and persimmon vinegar. Especially malic acid content was appeared to be highly remarkable in cider vinegar. Glucose and fructose were the predominant components among free sugars regardless of the kinds of vinegar. Free amino acid contents in cider, brown rice and persimmon vinegars have shown a little deviation among the same kind of vinegar samples, but were obviously more abundant than those in brewed vinegars. Color preference, sourness and sweetness of the vinegars were not statistically different (p>0.05) among four kinds of vinegars, whereas overall taste preference, background taste preference and intensity showed significant differences (p<0.05) with respect to the type of vinegar. Brewed and cider vinegars have revealed higher sensory scores in overall and background taste preference than the persimmon and brown rice vinegars. Even though there were no high relationships between minor components and organoleptic taste in commercial vinegars the ratio of acetic acid to the total organic acid was significantly correlated (p<0.01) with the overall taste preference.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.3
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• pp.1-10
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• 1987

For surveying of constituents concerning the flavor of the dried tomato fruits, nonvolatile components such as minerals, sugars, free amino acids, nucleotides and lipids were analyzed and determined. Potassium, calcium and phosphorus were the major conatituents of ashes, but trace amounts of cadmium and lead were determined. Glucose and fructose were the major constituents in sugars, and the latter slightly showed higher value than the former. The content of total free amino acids was 8322.5mg%, and that of the major components such as asparagine, aspartic acid, urea. glutamic acid, ${\beta}-alanine$ and ${\gamma}-aminobuthyric$acid showed 58.01% to the total amount. The nucleotides were composed of CMP, UMP, GMP and IMP, and CMP among them showed the highest value as about 58.07% to the total amount. On the other hand, IMP showed the lowest one. The major components of the total fatty acids from the saponifiable fraction in the lipids were $C_{18:2}$, $C_{18:1}$ and $C_{16:0}$ and those of the total sterols from unsaponifiable one were stigmasterol and ${\beta}-sitosterol$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.169-169
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• 2008

To keep pace with scaling trends of CMOS technologies, high-k metal oxides are to be introduced. Due to their high permittivity, high-k materials can achieve the required capacitance with stacks of higher physical thickness to reduce the leakage current through the scaled gate oxide, which make it become much more promising materials to instead of $SiO_2$. As further studying on high-k, an understanding of the relation between the etch characteristics of high-k dielectric materials and plasma properties is required for the low damaged removal process to match standard processing procedure. There are some reports on the dry etching of different high-k materials in ICP and ECR plasma with various plasma parameters, such as different gas combinations ($Cl_2$, $Cl_2/BCl_3$, $Cl_2$/Ar, $SF_6$/Ar, and $CH_4/H_2$/Ar etc). Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature and gas pressure. The choice of $BCl_3$ as the chemically active gas results from the fact that it is widely used for the etching o the materials covered by the native oxides due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. In this study, the surface reactions and the etch rate of $Al_2O_3$ films in $BCl_3/Cl_2$/Ar plasma were investigated in an inductively coupled plasma(ICP) reactor in terms of the gas mixing ratio, RF power, DC bias and chamber pressure. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by AFM and SEM. The chemical states of film was investigated using X-ray photoelectron spectroscopy (XPS), which confirmed the existence of nonvolatile etch byproducts.

• The KIPS Transactions:PartA
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• v.9A no.4
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• pp.399-404
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• 2002

Along the evolution of information and communication technologies, manufacturing embedded systems such as PDA (personal digital assistant), HPC (hand -held PC), settop box. and information appliance became realistic. And RTOS (real-time operating system) and filesystem have been played essential re]os within the embedded systems as well. For the filesystem of embedded systems, flash memory has been used extensively instead of traditional hard disk drives because of embedded system's requirements like portability, fast access time, and low power consumption. Other than these requirements, nonvolatile storage characteristic of flash memory is another reason for wide adoption in industry. However, there are some technical challenges to cope with to use the flash memory as an indispensable component of the embedded systems. These would be relatively slow cleaning time and the limited number of times to write-and-clean. In this paper, a new cleaning policy is proposed to overcome the problems mentioned above and relevant performance comparison results will be provided. Ranking cleaning policy(RCP) decides when and where to clean within the flash memory considering the cost of cleaning and the number of times of cleaning. This method will maximize not only the lifetime of flash memory but also the performance of access time and manageability. As a result of performance comparison, RCP has showed about 10 ~ 50% of performance evolution compared to traditional policies, Greedy and Cost-benefit methods, by write throughputs.

• Korean Journal of Food Science and Technology
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• v.23 no.3
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• pp.267-271
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• 1991

The chemical and organoleptic properties of dongchimi studied for their changes during fermentation at $4{\sim}35^{\circ}C$ in 7% NaCl solution with seasonings. It was found that pH decrease showed three variation points in its slope at about pH 5.2, 4.7 and 4.1 during fermentation. A negative linear relationship between total acidity and logarithmic value of pH was obtained. The slope of the relationship curve was increased as the fermentation temperature increased. The reducing sugar was increased until pH reached$4.0{\sim}4.2$ followed by a small decrease and its amount was lowered as the temperature increased from $4\;to\;25^{\circ}C$ The major nonvolatile organic acids were lactic and citric acids. The increase in lactic acid were more marked at $25^{\circ}C$ than at $4^{\circ}C$. As fermentation proceeded the fresh radish odor significantly decreased while sourness and yeast-moldy odor increased. The crispness of the radish decreased slightly during fermentation.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.2
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• pp.94-101
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• 2008

Non-volatile RAM (NVRAM) is a form of next-generation memory that has both characteristics of nonvolatility and byte addressability each of which can be found in nonvolatile storage and RAM, respectively. The advent of NVRAM may possibly bring about drastic changes to the system software landscape. When NVRAM is efficiently exploited in the system software layer, we expect that the system performance can be significantly improved. In this regards, we attempt to develop a new Flash file system, named MiNVFS (Metadata in NVram File System). MiNVFS maintains all the metadata in NVRAM, while storing all file data in Flash memory. In this paper, we present quantitative experimental results that show how much performance gains can be possible by exploiting NVRAM. Compared to YAFFS, a typical Flash file system, we show that MiNVFS requires only minimal time for mounting. MiNVFS outperforms YAFFS by an average of around 400% in terms of the total execution time for the realistic workloads that we considered.