• Resources Recycling
• /
• v.12 no.4
• /
• pp.20-29
• /
• 2003

In order to efficiently recycle the waste solution resulting from shadow mask processing, nano-sized Ni-ferrite powder was fab-ricated through spray pyrolysis process. The average particle size of the powder was below 100nm. In this study, the effects of the reaction temperature. the concentration of raw material solution and the injection speed of solution on the properties of powder were respectively investigated. As the reaction temperature increased from $800^{\circ}C$ to $1100^{\circ}C$, average particle size of the powder significantly Increased and power structure became more solid, whereat its specific surface area was greatly reduced. Formation rate and crystallization of($NiFe_2$$O_4$) phale increased along with the temperature rise. As the concentrations of iron and nickel components in wastere solution increased, particle size of the powder became larger, particle size distribution became more irregular, and specific surface area was reduced. Formation rate and crystallization of $NiFe_2$$O_4$ phase increased significantly along with the increase of the concentration of solution. As the inlet speed of solution increased, particle size of the powder became larger, particle size distribution became wider, specific surface area was reduced and powder structure became less solid. As the inlet speed of solution decreased, formation rate and crystallization of $NiFe_2$$O_4$ phase significantly increased.

• Journal of Surface Science and Engineering
• /
• v.55 no.1
• /
• pp.24-31
• /
• 2022

This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C₂H₂O₄) solution containing various ammonium fluoride (NH₄F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm² of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na₂SiO₃ solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH₄F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH₄F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH₄F more than 0.3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.222-222
• /
• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• Corrosion Science and Technology
• /
• v.7 no.3
• /
• pp.179-181
• /
• 2008

With nano-$SiO_2$ and sulphate acid, a kind of colloid electrolyte is synthesized by sol-gel method. It is placed outside the reference electrode as a layer of gel electrolyte so as to decrease the leaching of $Cu^{2+}$ and increase the life of the reference electrode. The performance of the gel electrode in simulating soil solution is measured as follows: the potential of the electrodes ranging from 60 mV to 80 mV (vs. SCE) with potential variation no more than $\pm10mV$, enough resistance to polarization. The $Cu^{2+}$ effusion rate of the reference electrode without gel electrolyte is 3 times that with colloid electrolyte, which means that gel electrolyte can extend the life of the reference electrode significantly.

• Journal of the Korean Vacuum Society
• /
• v.17 no.6
• /
• pp.528-537
• /
• 2008

60 nm and 20 nm thick hydrogenated amorphous silicon(a-Si:H) layers were deposited on 200 nm $SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by an e-beam evaporator. Finally, 30 nm-Ni/(60 nm and 20 nm) a-Si:H/200 nm-$SiO_2$/single-Si structures were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 40 sec. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide from the 60 nm a-Si:H substrate showed low sheet resistance from $400^{\circ}C$ which is compatible for low temperature processing. The nickel silicide from 20 nm a-Si:H substrate showed low resistance from $300^{\circ}C$. Through HRXRD analysis, the phase transformation occurred with silicidation temperature without a-Si:H layer thickness dependence. With the result of FE-SEM and TEM, the nickel silicides from 60 nm a-Si:H substrate showed the microstructure of 60 nm-thick silicide layers with the residual silicon regime, while the ones from 20 nm a-Si:H formed 20 nm-thick uniform silicide layers. In case of SPM, the RMS value of nickel silicide layers increased as the silicidation temperature increased. Especially, the nickel silicide from 20 nm a-Si:H substrate showed the lowest RMS value of 0.75 at $300^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.5
• /
• pp.353-357
• /
• 2010

Recently, silicon etching have received much attention for display industry, nano imprint technology, silicon photonics, and MEMS application. After the etching process, removing of etch mask and residue of sidewall is very important. The investigation of the etched mask removing was carried out by using the ashing, HF dipping and acid cleaning process. Experiment shows that oxygen component of reactive gas and photoresist react with silicon and converting them into the mask fence. It is very difficult to remove by using ashing or acid cleaning process because mask fence consisted of Si and O compounds. However, dilute HF dipping is very effective process for SiOx layer removing. Finally, we found optimized condition for etched mask removing.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.136.2-136.2
• /
• 2015

반도체 제조는 chip의 성능 향상 및 단가 하락을 위해 지속적으로 pattern size가 nano size로 감소해 왔고, capacitor 용량은 증가해 왔다. 이러한 현상은 contact hole의 aspect ratio를 지속적으로 증가시킨바, 그에 따라 최적의 HARC (high aspect ratio contact)을 확보하는 적합한 dry etch process가 필수적이다. 그러나 HARC dry etch process는 많은 critical plasma properties 에 의존하는 매우 복잡한 공정이다. 따라서, critical plasma properties를 적절히 조절하여 higher aspect ratio, higher etch selectivity, tighter critical dimension control, lower P2ID과 같은 plasma characteristics을 확보하는 것이 요구된다. 현재 critical plasma properties를 제어하기 위해 다양한 plasma etching 방법이 연구 되어왔다. 이 중 plasma를 낮은 kHz의 frequency에서 on/off 하는 pulsed plasma etching technique은 nanoscale semiconductor material의 etch 특성을 효과적으로 향상 시킬 수 있다. 따라서 본 실험에서는 dual-frequency capacitive coupled plasma (DF-CCP)을 사용하여 plasma operation 동안 duty ratio와 pulse frequency와 같은 pulse parameters를 적용하여 plasma의 특성을 각각 제어함으로써 etch selectivity와 uniformity를 향상 시키고자 하였다. Selective SiO2 contact etching을 위해 top electrode에는 60 MHz pulsed RF source power를, bottom electrode에는 2MHz pulse plasma를 인가하여 synchronously pulsed dual-frequency capacitive coupled plasma (DF-CCP)에서의 plasma 특성과 dual pulsed plasma의 sync. pulsing duty ratio의 영향에 따른 etching 특성 등을 연구 진행하였다. 또한 emissive probe를 통해 전자온도, OES를 통한 radical 분석으로 critical Plasma properties를 분석하였고 SEM을 통한 etch 특성분석과 XPS를 통한 표면분석도 함께 진행하였다. 그 결과 60%의 source duty percentage와 50%의 bias duty percentage에서 가장 향상된 etch 특성을 얻을 수 있었다.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.6
• /
• pp.2425-2433
• /
• 2018

This study investigates a new organic based material and its dielectric and mechanical properties. It is a comprehensive nanocomposite comprising a combination of various types of nanofillers with hydrophobic silica nanoparticles (AEROSIL R 974) as a matrix modifier and a polyamide nano nonwoven textile, Ultramid-Polyamide 6, pulped in the electrostatic field as a dielectric barrier. The polymer matrix is an epoxy network based on diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamine (Laromine C260). The designed nanocomposite material is an alternative to the conventional three-component composites containing fiberglass and mica with properties that exceed current electroinsulating systems (volume resistivity on the order of $10^{16}{\Omega}{\cdot}m$, dissipation factor tan ${\delta}=4.7{\cdot}10^{-3}$, dielectric strength 39 kV/mm).

• Journal of the Korea Organic Resources Recycling Association
• /
• v.32 no.3
• /
• pp.57-66
• /
• 2024

In this study, silicon sludge from a semiconductor packaging process is recycled to fabricate silica coated silicon-sludge and applied as a filler for an epoxy molding compound(EMC). Silicon-sludge powder(S-sludge) is treated with acid to remove metallic impurities and then coated using the sol-gel method to synthesize silica coated silicon-sludge powder(SS-sludge). The as-synthesized SS-sludge is subsequently mixed with epoxy resin, a curing agent, and carbon black to create an EMC(SS-sludge EMC). The heat dissipation properties of the EMC were examined using an IR camera. IR camera analysis confirmed that the SS-sludge EMC exhibited the highest surface temperature of 58.5℃ compared to SiO₂-based EMC. This enhancement in heat dissipation using SS-sludge EMC is attributed to the excellent thermal conductivity(150W/mK) of the silicon substrate and the presence of the silica layer on the SS-sludge surface which effectively enhances the thermal property of the EMC. Therefore, this study successfully demonstrates the recycling of silicon sludge from a semiconductor packaging process by synthesizing silica coated silicon-sludge and suggests a novel application of this material in semiconductor packaging.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1297-1298
• /
• 2006

Omega-shaped-gate (OSG) nanowire-based field effect transistors (FETs) have been attracted recently attention due to their highdevice performance expected from theoretical simulations among nanowire-based FETs with other gate geometries. OSG FETs with the channels of ZnO nanowires were successfully fabricated in this study with photolithographic processes. In the OSG FETs fabricated on oxidized Si substrates, the channels of ZnO nanowires with diameters of about 60 nm are coated surroundingly by $Al_{2}O_{3}$ as gate dielectrics with atomic layer deposition. About 80 % of the surfaces of the nanowires coated with $Al_{2}O_{3}$ is covered with gate metal to form OSG FETs. A representative OSG FET fabricated in this study exhibits a mobility of 98.9 $cm^{2}/Vs$, a peak transconductance of 0.4 ${\mu}S$, and an Ion/Ioff ratio of $10^6$ the value of the Ion/Ioff ratio obtained from this OSG FET is the highest among nanowire-based FETs, to our knowledge. Its mobility, peak transconductance, and Ion/Ioff ratio arc remarkably enhanced by 11.5, 32, and $10^6$ times, respectively, compared with a back-gate FET with the same ZnO nanowire channel as utilized in the OSG FET.