• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.109-109
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• 2011

1T-1C로 구성되는 기존의 DRAM(Dynamic Random Access Memory)은 데이터를 저장하기 위한 적절한 capacitance를 확보해야 한다. 따라서 캐패시터 면적으로 인한 집적도에 한계에 직면해있다. 따라서 이를 대체하기 위한 새로운 DRAM인 1T (Transistor) DRAM이 각광받고 있다. 기존의 DRAM과 달리 SOI (Silicon On Insulator)기술을 이용한 1T-DRAM은 데이터 저장을 위한 캐패시터가 필요없다. Impact Ionization 또는 GIDL을 이용해 발생한 정공을 채널영역에 가둠으로 서 발생하는 포텐셜 변화를 이용한다. 이로서 드레인 전류가 변화하며, 이를 이용해 '0'과 '1'을 구분한다. 기존의 1T-DRAM은 단결정 실리콘을 이용하여 개발되었으나 좀더 광범위한 디바이스로의 적용을 위해서는 다결정 실리콘 박막의 형태로 제작이 필수적이다. 단결정 실리콘을 이용할 경우 3차원 집적이나 기판재료선택에 제한적이지만 다결정 실리콘을 이용할 경우, 기판결정이 자유로우며 실리콘 박막이나 매몰 산화층의 형성 및 두께 조절이 용이하다. 때문에 3차원 적층에 유리하여 다결정 실리콘 박막 형태의 1T-DRAM 제작이 요구되고 있다. 따라서 이번연구에서는 엑시머 레이저 어닐링 및 고상결정화 방법을 이용하여 결정화 시킨 다결정 실리콘을 이용하여 1T-DRAM을 제작하였으며 메모리 특성을 확인하였다. 기판은 상부실리콘 100 nm, buried oxide 200 nm로 구성된 SOI구조의 기판을 사용하였다. 엑시머 레이저 어닐링의 경우 400 mJ/cm2의 에너지를 가지는 KrF 248 nm 엑시머 레이저 이용하여 결정화시켰으며, 고상결정화 방법은 $400^{\circ}C$ 질소 분위기에서 24시간 열처리하여 결정화 시켰다. 두가지 결정화 방법을 사용하여 제작되어진 박막트랜지스터 1T-DRAM 모두 kink 현상을 확인할 수 있었으며 메모리 특성 역시 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.446-446
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• 2012

최근 반도체 칩의 트랜지스터 집적화 기술이 발달됨에 따라 dynamic random access memory(DRAM)의 memory cell 영역을 작게 만들어야 하는 문제가 제기되고 있다. 이러한 문제점을 해결하기 위해서 대체 기술이 끊임없이 연구되고 있는 가운데 하나의 트랜지스터와 하나의 캐패시터로 구성된 기존의 DRAM에서 캐패시터가 없이 하나의 트랜지스터만으로 이루어진 1T-DRAM 소자의 연구가 활발히 진행되고 있다. 이는 기존 DRAM의 구조에 비해 캐패시터가 필요하지 않아 복잡한 공정이 줄어들어 소자 제작이 용이하며, 더 높은 집적도를 구현할 수 있는 장점이 있다. 일반적인 planar 타입의 1T-DRAM의 경우 소스 및 드레인과 기판과의 접합면에서 누설 전류가 큰 특징을 가지며 소자의 집적화에 따른 단 채널 효과가 발생하게 되는데, 본 연구에서는 이러한 문제점을 해결하기 위해서 유효 채널 길이를 늘려 단 채널 효과에 의한 영향을 감소시키고, 소스 및 드레인과 기판과의 접합면을 줄여 누설 전류를 줄일 수 있는 recessed 채널 타입의 1T-DRAM을 제작하였다. 1T-DRAM의 메모리 구동방법에는 여러 가지가 있는데 본 연구에서는 impact ionization (II)을 이용한 방법과 gate induced drain leakage (GIDL)을 이용한 방법을 사용하여 1T-DRAM의 채널구조에 따라 어떠한 구동방법이 더 적합한지 평가하였고, 그 결과 recessed 채널 1T-DRAM의 동작은 II 에 의한 측정 방법이 더 적합한 것으로 보여졌다.

• Archives of Pharmacal Research
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• v.23 no.4
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• pp.374-380
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• 2000

Propentofylline (PPF, 3-methyl-1-(5-oxohexyl)-7-propylxanthine) has been reported to be a compound for treatment of both vascular dementia and dementia of the Alzheimer type. The short half-life (about 15 min) of PPF at the terminal elimination phase and poor bioavailability after oral administration of PPF to rabbits (Kim et al., 1992) suggest in part that this drug takes the extensive first-pass metabolism in the liver. In addition, the metabolic pathway for PPF remains unclear. The objective of this experiment is to identify urinary metabolites of PPF in rats. For the identification of the metabolites, rat urine was collected after oral administration of 100${m}g/kg$ PPF. PPF metabolite, 3-methyl-1-(5-hydroxyhexyl)-7-propylxanthine, was synthesized and confirmed by gas chromatography/mass spectroscopy (GC/MS) and $^1H$ nuclear magnetic resonance spectroscopy. The urinary metabolites of PPF were extracted with diethyl ether and identified by electron impact and chemical ionization GC/MS. One urinary metabolite was confirmed to be 3-methyl-1-(5-hydroxyhexyl)-7-propylxanthine by synthesized authentic compound. Several metabolites of monohydroxy- and dihydroxy-PPF were identified based on mass fragmentation of both intact and trimethylsilylated derivatives of PPF metabolites and the novel structure of these metabolites is suggested based on mass spectra.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.665-668
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• 2001

As reducing the physical size of devices, we can integrate more devices per the unit chip area and make its speed better. We have investigated MOSFET built on an epitaxial layer(EPI) of a heavily-doped ground plane. We compared and analyzed the characteristics of such device structure, i.e., impact ionization, electric field and I-V characteristics curve with lightly-doped drain(LDD) MOSFET. We simulated MOSFET with gate lengths from 0.10 to 0.06${\mu}{\textrm}{m}$ step 0.01${\mu}{\textrm}{m}$ in according to constant voltage scaling theory.

• KSBB Journal
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• v.18 no.1
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• pp.74-77
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• 2003

A simple, reproducible, and rapid gas chromatographic method for putrefactive metabolite determination in feces was developed. The method involves the direct injection of fecal supernatants into the gas chromatograph, without pretreatment. The mass spectra of these metabolites were obtained using an HP 5971 mass selective detector operated in electron impact (EI) ionization mode. This method produced sharp peaks and allowed the simultaneous determination of fecal putrefactive metabolites.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.351-352
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• 2007

Polymers submitted to thermo/electrical stress suffer from ageing that can drastically affect their functional behaviour. Understanding the physico/chemical processes at play during ageing and defining transport regimes in which these mechanisms start to be critical is therefore a prime goal to prevent degradation and to develop new formulation or new materials with improved properties. It is thought that a way to define these critical regimes is to investigate under which conditions (in terms of stress parameters) light is generated in the material by electroluminescence (EL). This can happen through impact excitation/ionization involving hot carriers or upon bi-polar charge recombination (a definition that excludes light from partial discharges, which would sign an advanced stage in the degradation process). After a brief review of the EL phenomenology under DC, we introduce a numerical model of charge transport postulating a recombination controlled electroluminescence. The model output is critically evaluated with special emphasize on the comparison between simulated and experimental light emission. Finally, we comment some open questions and perspectives.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.228-230
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• 1994

A Spotter ion Plating(SIP) system with a r. f. coil electrode and the Facing Target Sputter(FTS) source was designed for high-quality thin film formation. The rf discharge was combined with DC facing target sputtering in order to enhance ionization degree of a sputtered atoms. The discharge voltage-discharge characteristics curves of a FTS source could be characterized by the fern of $I{\propto}V^n$ with n in the range of $8{\sim}12$. The energy of ions incident on the substrate depended on the sheath potential of DC biased substrate. The mean impact ion energy increased with negative bias voltage and rf power. The adhesive force of the TiN film formed was in the range of $30{\sim}50N$, and markedly influenced by substrate bias voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.199-200
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• 2005

In this paper, the electrical characteristics and hot-carrier induced electrical performance degradations of high-voltage LDMOSFET fabricated by the existing CMOS technology were investigated. Different from the low voltage CMOS device, the only specific on-resistance was degraded due to hot-carrier stressing in LDMOS transistor. However, other electrical parameters such as threshold voltage, transconductance, and saturated drain current were not degraded after stressing. The amount of on-resistance degradation of LDMOS transistor that was implanted n-well with $1.0\times10^{13}/cm^2$ was approximately 1.6 times more than that of LDMOS transistor implanted n-well with $1.0\times10^{12}/cm^2$. Similar to low voltage CMOS device, the peak on-resistance degradation in LDMOS device was observed at gate voltage of 2.2V while the drain applied voltage was 50V. It means that the maximum impact ionization at the drain junction occurs at the gate voltage of 2.2V applying the drain voltage of 50V.

• YAKHAK HOEJI
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• v.44 no.5
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• pp.384-390
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• 2000

Metabolism study of the dye, benzidine, was performed by gas chromatography-mass selective detector (GC/MSD) in the urine of rats orally administered 100 mg/kg benzidine. Urine samples were collected in metabolic cages for 0-24, 24-48, and 48-72 hrs. Ten ml of the urine was extracted with XAD-2 resin and the XAD-2 column was eluted with methanol. After evaporation, benzidine and its metabolites were extracted with diethyl ether (for non-conjugated fraction). For conjugated metabolites, $\beta$-glucu-ronidase was added to the aqueous layer that was incubated for 1 hr at 5$0^{\circ}C$ and the aqueous layer was extracted as in non-conjugated fraction. Aliquot of trimethylsilylated derivatives was applied to the GC/MSD. The mutagenicity of benzidine and its acetylated metabolites was tested by histidine/reversion assay. Five metabolites observed and confirmed either by electron impact and chemical ionization modes of the GC/MSD, or authentic compounds were monoacetyl-, diacetyl-, hydroxyacetyl-, hydroxydiacetyl-, and hydroxy-benzidine. Monoacetyl-benzidine was more potent than benzidine in histidine/reversion assay. This data indicates that monoacetylation of benzidine may be one of the metabolites produced in metabolic activation process.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.44-48
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• 2017

We explain optical and electrical properties of top and bottom-emission structured alternating-current powder electroluminescent devices (ACPELDs) with Ga-doped ZnO(GZO) transparent electrode. The top-emission ACPELDs were layered as the metal electrode/dielectric layer/emission layer/top transparent electrode and the bottom-emission ACPELDs were structured as the bottom transparent electrode/emission layer/dielectric layer/metal electrode. The yellow-emitting ZnS:Mn, Cu phosphor and the barium titanate dielectric layers were layered through the screen printing method. The GZO transparent electrode was deposited by the sputtering, its sheet resistivity is $275{\Omega}/{\Box}$. The transparency at the yellow EL peak was 98 % for GZO. Regardless of EL structures, EL spectra of ACPELDs were exponentially increased with increasing voltages and they were linearly increased with increasing frequencies. It suggests that the EL mechanism was attributed to the impact ionization by charges injected from the interface between emitting phosphor layer and the transparent electrode. The top-emission structure obtained higher EL intensity than the bottom-structure. In addition, charge densities for sinusoidal applied voltages were measured through Sawyer-Tower method.