• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.462-462
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• 2009

$CeO_2$는 고체 산화물 연료전지 (SOFC, soild oxide fuel cell)의 전해질 재료와 CMP(Chemical Mechanical Polishing) 슬러리 재료, 자동차의 3원 촉매, gas sensor, UV absorbent등 여러 분야에서 사용되고 있다. 본 연구에서는 위의 활용범위 외에 $CeO_2$의 구조적 안정성과 빠른 $Ce^{3+}/Ce^{4+}$의 전환 특성을 이용하여 lithium ion battery의 anode 재료로서 전기화학적 특성을 알아보고자 실험을 실시하였다. $CeO_2$ 합성에 사용되는 전구체인 cerium carbonate의 형상 및 크기, 비표면적과 같은 물리화학적 특성이 $CeO_2$ 분말의 특성에 직접적인 영향을 주기 때문에 전구체의 합성 단계에서 입자의 특성을 조절하였다. 전구체 합성의 출발원료로 cerium nitrate hexahydrate 와 ammonium carbonate를 사용하였고 반응온도 및 농도 등을 변화시켜 입자의 형상 및 결정상을 fiber형태의 orthorombic $Ce_2O(CO_3)_2{\cdot}H_2O$와 구형의 hexagonal $CeCO_3OH$의 세리아 전구체를 합성하였다. 이를 $300^{\circ}C$에서 30분 동안 하소하여 전구체의 입자형상을 유지하는 cubic $CeO_2$를 합성하고 X-ray diffraction, FE-SEM, micropore physisorption analyzer 분석을 통하여 입자의 결정상과 형상, 비표면적 등을 비교 분석하고 $Li/CeO_2$ couple의 충,방전 용량과 수명특성을 비교 분석하여 $CeO_2$의 전기화학적 특성을 알아보았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.192-192
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• 2009

We have successfully demonstrated the inkjet printing process to fabricate $Al_2O_3$ thick films without a high temperature sintering process. A single solvent system had a coffee ring pattern after printing of $Al_2O_3$ dot, line and area. In order to fabricate the smooth surface of $Al_2O_3$ thick film, we have introduced a co-solvent system which has nano-sized $Al_2O_3$ powders in the mixture of Ethylene glycol monomethyl ester and Di propylene glycol methyl ether. This co-solvent system approached a uniform and dense deposition of $Al_2O_3$ powders on the substrate. The packing density of inkjet-printed $Al_2O_3$ films is more than 70% which is very high compared to the value obtained from the films synthesized by other conventional methods such as casting processes. The characterization of the inkjet-printed $Al_2O_3$ films has been implemented to investigate its thickness and roughness. Also the dielectric loss of the films has been measured to understand the feasibility of its application to 3D integration package substrate.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.59-59
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• 2009

현재 CMP분야는 광역 평탄화 반도체 소자의 집적화 및 소형화가 진행됨에 따라서 CMP 공정의 중요성은 날로 성장하고 있다. 하지만 이러한 CMP공정은 불가피하게도 scratch, pit, CMP residue와 같은 defect들을 발생시키고 있으며, 점점 선폭이 작아짐에 따라, 이러한 defect들이 반도체 수율에 미치는 영향은 심각해지고 있다. Defect들 중에 특히 scratch는 반도체에 치명적인 circuit failure를 일으키게 된다. 또한 반도체 내구성과 신뢰성을 감소시키게 되고, 누전전류를 증가시키는 등 바람직하지 못한 현상들이 생기게 된다. 본 연구에서는 scratch 와 같은 deflect들을 효율적으로 검출, 분석하고, scratch를 감소시키는데 그 목적이 있다. 본 실험을 위해 8" TEOS wafer와 commercial oxide slurry 및 friction polisher (Poli-500, G&P tech., Korea)를 사용하여 CMP 공정을 진행하였으며, CMP 공정조건은 각각 80rpm/80rpm/1psi(Platen speed/Head speed/Pressure)에서 1분 동안 연마를 한 후 scratch 발생 경향을 살펴보았다. CMP 후 wafer위에 오염되어 있는 slurry residue들을 제거하기 위해 SC-1, HF 세정을 이용하여 최적화된 post-CMP 공정기술을 제안하였다. Scratch 검출 및 분석을 위해 wafer surface analyzer (Surfscan 6200, Tencor, USA)와 optical microscope (LV100D, Nicon, Japan)를 사용하였다. CMP 공정 변수들에 따른 scratch 발생정도를 비교하였으며, scratch 발생 요인들에 따른 scratch 형태 및 발생정도를 살펴보았다. 최적화된 post-CMP 세정 조건은 메가소닉과 함께 SC-1 세정을 실시하여 slurry residue들을 제거한 후, HF 세정을 실시하여 잔여 오염물들을 제거하고 검출이 용이하도록 scratch를 확장시킬 수 있도록 제안하였으며, 100%의 particle removal efficiency (PRE)를 얻을 수 있었다. 실제 CMP 공정후 post-CMP 세정 단계별 scratch 개수를 측정한 결과, SC-1 세정 후 약 220개의 scratch가 검출되었으며, 검출되지 않았던 scratch가 HF 세정 후 확장되어 드러남에 따라 약 500개의 scratch 가 검출되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.52-52
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• 2009

To date, chalcogenide alloy such as $Ge_2Sb_2Te_5$(GST) have not only been rigorously studied for use in Phase Change Random Access Memory(PRAM) applications, but also temperature gap to make different states is not enough to apply to device between amorphous and crystalline state. In this study, we have investigated a new system of phase change media based on the In-Sb-Te(IST) ternary alloys for PRAM. IST chalcogenide thin films were prepared in trench structure (aspect ratio 5:1 of length=500nm, width=100nm) using Tri methyl Indium $(In(CH_3)_4$), $Sb(iPr)_3$ $(Sb(C_3H_7)_3)$ and $Te(iPr)_2(Te(C_3H_7)_2)$ precursors. MOCVD process is very powerful system to deposit in ultra integrated device like 100nm scaled trench structure. And IST materials for PRAM can be grown at low deposition temperature below $200^{\circ}C$ in comparison with GST materials. Although Melting temperature of 1ST materials was $\sim 630^{\circ}C$ like GST, Crystalline temperature of them was ~$290^{\circ}C$; one of GST were $130^{\circ}C$. In-Sb-Te materials will be good candidate materials for PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.21-21
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• 2009

후막 광식각 기술을 이용하여 형성된 Ag 전극과 LTCC 기판 사이의 접착력을 향상시키기 위하여 무기 바인더로서 anorthite, diopside 및 MLS-62 glass frit을 첨가하여 감광성 Ag paste를 제조하였다. 소성 후의 glass pool effect를 감소시키기 위해 attrition mill을 통하여 미세 glass 분말을 준비하였다. Glass frit은 Ag powder의 5vol%~25vol%의 함량으로 첨가하여 감광성 Ag paste를 제조하였고 패턴 형성 후 $850^{\circ}C$에서 1시간 소결하였다. 전극과 기판 사이의 접착력은 micro-ball shear test 법으로 측정하였으며, Ag 전극 부착력은 glass frit의 함량 증가에 따라 증가하다가 감소하는 경향을 보이는데, 이는 과량의 glass frit 첨가로 인한 전극 내부에 액상 풀의 형성에 기인한 것으로 보여진다. Ag 전극의 면저항은 glass frit의 함량이 증가함에 따라 $0.13m{\Omega}{/\square}$에서 $2.06m{\Omega}{/\square}$까지 증가하는 경향을 나타내었다. 소성 전후의 전극 패턴의-수축율은 $100{\mu}m$의 선폭을 기준으로 glass frit의 첨가랑이 증가할수록 43.3%에서 35.0%로 감소하였으며, 그 결과 최소 선폭 $25{\mu}m$의 미세 전극 패턴의 형성이 가능하였다.

• 한국재료학회지
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• 제22권3호
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• pp.140-144
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• 2012

Compared with bulk material, quantum dots have received increasing attention due to their fascinating physical properties, including optical and electronic properties, which are due to the quantum confinement effect. Especially, Luminescent CdSe quantum dots have been highly investigated due to their tunable size-dependent photoluminescence across the visible spectrum. They are of great interest for technical applications such as light-emitting devices, lasers, and fluorescent labels. In particular, quantum dot-based light-emitting diodes emit high luminance. Quantum dots have very high luminescence properties because of their absorption coefficient and quantum efficiency, which are higher than those of typical dyes. CdSe quantum dots were synthesized as a function of the synthesis time and synthesis temperature. The photoluminescence properties were found strongly to depend on the reaction time and the temperature due to the core size changing. It was also observed that the photoluminescence intensity is decreased with the synthesis time due to the temperature dependence of the band gap. The wavelength of the synthesized quantum dots was about 550-700 nm and the intensity of the photoluminescence increased about 22~70%. After the CdSe quantum dots were synthesized, the particles were found to have grown until reaching a saturated concentration as time increased. Red shift occurred because of the particle growth. The microstructure and phase developments were measured by transmission electron microscopy (TEM) and X-ray diffractometry (XRD), respectively.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.956-960
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• 2010

CuO doped $WO_3-SnO_2$ thick film gas sensors were fabricated by screen printing method on alumina substrates and heat-treated at $350^{\circ}C$ in air. The effects of mixing ratio of $WO_3$ with $SnO_2$ on the structural and morphological properties of $WO_3-SnO_2$ were investigated X-ray diffraction and Scanning Electron Microscope. The structural properties of the $WO_3-SnO_2$:CuO thick film by XRD showed that the monoclinic of $WO_3$ and the tetragonal of $SnO_2$ phase were mixed. Nano CuO was coated on the $WO_3-SnO_2$ surface and then the surface of $WO_3$ was coated with $SnO_2$ particles with $1\sim1.5{\mu}m$ in diameters, as confirmed form the SEM image. The sensitivity of the $WO_3-SnO_2$:CuO sensor to 2000 ppm $CO_2$ gas and 50 ppm $H_2S$ gas for the various ratio of $WO_3$ and $SnO_2$ was investigated. The 4 wt% CuO doped $WO_3-SnO_2$(75:25) tkick films showed the highest sensitivity to $CO_2$ gas and $H_2S$ gas.

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.449-453
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• 2010

In this paper, the electrical characteristics of Fin-type SONOS(silicon-oxide-nitride-oxide-silicon) flash memory device with different trapping layers are analyzed in depth. Two kinds of trapping layers i.e., silicon nitride($Si_3N_4$) and hafnium oxide($HfO_2$) are applied. Compared to the conventional Fin-type SONOS device using the $Si_3N_4$ trapping layer, the Fin-type SOHOS(silicon-oxide-high-k-oxide-silicon) device using the $HfO_2$ trapping layer shows superior program/erase speed. However, the data retention properties in SOHOS device are worse than the SONOS flash memory device. Degraded data retention in the SOHOS device may be attributed to the tunneling leakage current induced by interface trap states, which are supported by the subthreshold slope and low frequency noise characteristics.

• 한국전기전자재료학회논문지
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• 제23권9호
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• pp.676-680
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• 2010

In this paper, Fin-type silicon-oxide-nitride-oxide-silicon (SONOS) flash memory are fabricated and the electrical characteristics are analyzed. Compared to the planar-type SONOS devices, Fin-type SONOS devices show good short channel effect (SCE) immunity due to the enhanced gate controllability. In memory characteristics such as program/erase speed, endurance and data retention, Fin-type SONOS flash memory are also superior to those of conventional planar-type. In addition, Fin-type SONOS device shows improved SCE immunity in accordance with the decrease of Fin width. This is known to be due to the fully depleted mode operation as the Fin width decreases. In Fin-type, however, the memory characteristic improvement is not shown in narrower Fin width. This is thought to be caused by the Fin structure where the electric field of Fin top can interference with the Fin side electric field and be lowered.

• 한국전기전자재료학회논문지
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• 제27권4호
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• pp.257-261
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• 2014

Carbon nanotubes (CNT) has the excellent physical characteristics in the sensor, medicine, manufacturing and energy fields, and it has been studied in those fields for the several years. We fabricated the NOx gas sensors of MOS-FET type using the MWCNT. The fabricated sensor was used to detect the NOx gas for the variation of $V_{gs}$ (gate-source voltage) with the ambient temperature. The gas sensor absorbed the NOx gas molecules showed the decrease of resistance, and the sensitivity of sensor was reduced by the NOx gas molecules accumulated on the MWCNT surface. Furthermore, when the voltage ($V_{gs}$) was applied to the gas sensor, the term of the decrease in resistance was increased. On the other hand, the sensor sensitivity for the injection of NOx gas was the highest value at the ambient temperature of $40^{\circ}C$. We also obtained the adsorption energy ($40^{\circ}C$) using the Arrhenius plots by the reduction of resistance due to the $V_{gs}$ voltage variations. As a result, we obtained that the adsorption energy also was increased with the increasement of the applied $V_{gs}$ voltages.