• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.45-51
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• 2001

The effects of wettability and surface oxidation on the low temperature and ultra-fine solder bump formation have been studied. Difference sequences of near eutectic In-Ag and eutectic Bi-Sn solders were evaporated on Au/Cu/Cr or Au/Ni/Ti Under Bump Metallurgy (UBM) pads. Solder bumps were formed using lift-off method and were reflowed in Rapid Thermal Annealing (RTA) system. The solder bumps in which In was in contact with UBM in In-Ag solder and the solder bumps in which Sn was in contact with UBM in Bi-Sn solder showed better bump formability during reflow than other solder bumps. The ability to form spherical solder bumps was affected mainly by the wettability of solders to UBM pads.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1501-1506
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• 1994

The precipitate of FeCl2.4H2O and NaOH, Fe(OH)2 was rapidly made to oxidize by H2O2 to prepare $\delta$-FeOOH. The particle size, surface and morphology of $\delta$-FeOOH, and the shape and structure of thermally decomposed $\delta$-FeOOH were investigated by the use of high resolution STEM. $\delta$-FeOOH prepared under the condition of reaction temperature of Fe(OH)2 at 4$0^{\circ}C$, [OH-][Fe2+]=5 and aging time of 2 hr Fe(OH)2, had 630$\AA$ mean particle size, 4~5 aspect ratio, 20.8 emu/g saturation magnetization and 210 Oe coercivity. The edges of $\delta$-FeOOH were inclined to (001) about 41$^{\circ}$, 60$^{\circ}$ and coincident with (102), (101) respectively. When $\delta$-FeOOH was thermally decomposed at 25$0^{\circ}C$ for 2 hr in vacuo, which had micropores of 0.9 nm thickness and crystallites of 2.4 nm thickness. (001)hex, [10]hex. of $\delta$-FeOOH parallel with (001)hex, [100]hex. of $\alpha$-Fe2O3 respectively. This showed three dimensional topotaxial structure transition, which was investigated by SADP (Selected Area Diffraction Pattern) of STEM.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.234-239
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• 2007

This paper describes the TiW ohmic contact characteristics under the surface treatment of the polycrystalline 3C-SiC thin film grown on $SiO_2/Si(100)$ wafers by APCVD. The poly 3C-SiC surface was polished by using CMP(chemical mechanical polishing) process and then oxidized by wet-oxidation process, and finally removed SiC oxide layers. A TiW thin film as a metalization process was deposited on the surface treated poly 3C-SiC layer and was annealed through a RTA(rapid thermal annealing) process. TiW/poly 3C-SiC was investigated to get mechanical, physical, and electrical characteristics using SEM, XRD, XPS, AFM, optical microscope, I-V characteristic, and four-point probe, respectively. Contact resistivity of the surface treated 3C-SiC was measured as the lowest $1.2{\times}10^{-5}{\Omega}cm^2$ at $900^{\circ}C$ for 45 sec. Therefore, the surface treatments of poly 3C-SiC are necessary to get better contact resistance for extreme environment MEMS applications.

• Korean Journal of Materials Research
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• v.9 no.9
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• pp.932-936
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• 1999

4NH(sub)3+$3O_2$$\longrightarrow$$2N_2$+$6H_2$O 의 화학반응식을 가지며$ O_2$ 및 $H_2$O를 산화제로 하는 $NH_3$/$O_2$산화의 성장모델을 세웠으며, 그 결과 Fick의 제 1 법칙을 기초로 하는 건식 및 습식 산화메카니즘으로 이해되는 Deal-Grove의 산화막 성장모델과 유사한 결과가 도출되었다. 이 성장모델에 의하면 산화제$ O_2$ 및 $H_2$O가 상호보완적으로 산화에 영향을 미치므로 산화온도 뿐 아니라 $NH_3$/O$_2$의 유량비도 산화율을 결정한다. rapid thermal processing(RTP)에 의한 산화막 성장실험으로 본 연구에서 제안하는 성장모델을 확인하였으며, NH$_3$분자의 분해에 의해 발생하는 N 원자의 산화막 내부확산을 secondary ion mass spectroscopy(SIMS)로 확인하였으며, Auger electron spectroscopy (AES) 측정결과 N 원자의 존재는 무시할만한 수준이었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.564-570
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• 1996

We have observed the red and blue luminescence from porous silicon (PS) without any rapid thermal oxidation. Aged porous silicon specimens prepared in dilute HF concentration, especially for the short duration of etching, display the increase of the blue band. The measured luminescence decay time at room temperature exhibits a decay time of about 100 ps and shows appreciably faster decay time than that of 20 K. No photoluminescence (PL) peak maximum shift is observed for the blue PL band at 77 K. However, the red PL band shows the blue shift and displays yellow luminescence at 77 K. The origin of red luminescence has some properties related to Si crystallites, whereas blue luminescence seems to be associated other than Si crystallites.

• Electrical & Electronic Materials
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• v.16 no.9
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• pp.64.2-65
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• 2003

A 4 nm layer of ZrOx (targeted x-2) was deposited on an interfacial layer(IL) of native oxide (SiO, t∼1.2 nm) surface on 200 mm Si wafers by a manufacturable atomic layer chemical vapor deposition technique at 30$0^{\circ}C$. Some as-deposited layers were subjected to a post-deposition, rapid thermal annealing at $700^{\circ}C$ for 5 min in flowing oxygen at atmospheric pressure. The experimental x-ray diffraction, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and high-resolution parallel electron energy loss spectroscopy results showed that a multiphase and heterogeneous structure evolved, which we call the Zr-O/IL/Si stack. The as-deposited Zr-O layer was amorphous $ZrO_2$-rich Zr silicate containing about 15% by volume of embedded $ZrO_2$ nanocrystals, which transformed to a glass nanoceramic (with over 90% by volume of predominantly tetragonal-$ZrO_2$(t-$ZrO_2$) and monoclinic-$ZrO_2$(m-$ZrO_2$) nanocrystals) upon annealing. The formation of disordered amorphous regions within some of the nanocrystals, as well as crystalline regions with defects, probably gave rise to lattice strains and deformations. The interfacial layer (IL) was partitioned into an upper Si $o_2$-rich Zr silicate and the lower $SiO_{x}$. The latter was sub-toichiometric and the average oxidation state increased from Si0.86$^{＋}$ in $SiO_{0.43}$ (as-deposited) to Si1.32$^{＋}$ in $SiO_{0.66}$ (annealed). This high oxygen deficiency in $SiO_{x}$ indicative of the low mobility of oxidizing specie in the Zr-O layer. The stacks were characterized for their dielectric properties in the Pt/{Zr-O/IL}/Si metal oxide-semiconductor capacitor(MOSCAP) configuration. The measured equivalent oxide thickness (EOT) was not consistent with the calculated EOT using a bilayer model of $ZrO_2$ and $SiO_2$, and the capacitance in accumulation (and therefore, EOT and kZr-O) was frequency dispersive, trends well documented in literature. This behavior is qualitatively explained in terms of the multi-layer nanostructure and nanochemistry that evolves.ves.ves.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.438-439
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• 2013

Microelectronic devices의 접촉저항의 향상을 위해 Metal silicides의 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 지난 수십년에 걸쳐, Ti silicide, Co silicide, Ni silicide 등에 대한 개발이 이루어져 왔으나, 계속적인 저저항 접촉 소재에 대한 요구에 의해 최근에는 Rare earth silicide에 관한 연구가 시작되고 있다. Rare-earth silicide는 저온에서 silicides를 형성하고, n-type Si과 낮은 schottky barrier contact (~0.3 eV)를 이룬다. 또한, 비교적 낮은 resistivity와 hexagonal AlB2 crystal structure에 의해 Si과 좋은 lattice match를 가져 Si wafer에서 high quality silicide thin film을 성장시킬 수 있다. Rare earth silicides 중에서 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 낮은 schottky barrier 응용에서 쓰이고 있다. 이로 인해, n-channel schottky barrier MOSFETs의 source/drain으로써 주목받고 있다. 특히 ytterbium과 molybdenum co-deposition을 하여 증착할 경우 thin film 형성에 있어 안정적인 morphology를 나타낸다. 또한, ytterbium silicide와 마찬가지로 낮은 면저항과 electric work function을 갖는다. 그러나 ytterbium silicide에 molybdenum을 화합물로써 높은 농도로 포함할 경우 높은 schottky barrier를 형성하고 epitaxial growth를 방해하여 silicide film의 quality 저하를 야기할 수 있다. 본 연구에서는 ytterbium과 molybdenum의 co-deposition에 따른 silicide 형성과 전기적 특성 변화에 대한 자세한 분석을 TEM, 4-probe point 등의 다양한 분석 도구를 이용하여 진행하였다. Ytterbium과 molybdenum을 co-deposition하기 위하여 기판으로 $1{\sim}0{\Omega}{\cdot}cm$의 비저항을 갖는 low doped n-type Si (100) bulk wafer를 사용하였다. Native oxide layer를 제거하기 위해 1%의 hydrofluoric (HF) acid solution에 wafer를 세정하였다. 그리고 고진공에서 RF sputtering 법을 이용하여 Ytterbium과 molybdenum을 동시에 증착하였다. RE metal의 경우 oxygen과 높은 반응성을 가지므로 oxidation을 막기 위해 그 위에 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, 진공 분위기에서 rapid thermal anneal(RTA)을 이용하여 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium silicides를 형성하였다. 전기적 특성 평가를 위한 sheet resistance 측정은 4-point probe를 사용하였고, Mo doped ytterbium silicide와 Si interface의 atomic scale의 미세 구조를 통한 Mo doped ytterbium silicide의 형성 mechanism 분석을 위하여 trasmission electron microscopy (JEM-2100F)를 이용하였다.

• Journal of Nutrition and Health
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• v.11 no.3
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• pp.25-30
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• 1978

A study was planned to evaluate the influence of continual heating at $150{\pm}5^{\circ}C$ and $170{\pm}5^{\circ}C$ respectively upon edible oils for frying the several food. Two kinds of domestic edible oils (Sample A and B) were collected by random sampling from market and in order to estimate deterioration degrees at both temperatures previously mentioned, thiobarbituric acid (TBA) value, acid value (AV), peroxide value (POV) and carbonyl value (CV) were measured at intervals due to its optical density. Those values were examined and compared according to the temperatures and times, and it was concluded as follows: 1) TBA value was rapidly increased until 24 hours in both temperatures and after 1 day its value have shown a slower increase as compared with initial rapid reaction. 2) Acid value and peroxide value of both oils (A & B) used for frying were increased continuously during heating and the changes in these values were dependent on the thermal oxidation, and moreover at low temperature $(150{\pm}5^{\circ}C)$ these values were found to be increased more readily than at high temperature $(170{\pm}5^{\circ}C)$. 3) Carbonyl value of both sample A and B show almost the same increasing rate at either $150{\pm}5^{\circ}C$ or $170{\pm}5^{\circ}C$ in proportion to the heating time. 4) It was found that there were differences between the chemical changes caused by heating sample A and B at high and low temperature.

• Journal of Powder Materials
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• v.11 no.4
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.358-361
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• 2002

Self-aligned MOSFETS using a polysilicon gate are widely fabricated in silicon technology. The polysilicon layer acts as a mask for the source and drain implants and does as gate electrode in the final product. However, the usage of polysilicon gate as a self-aligned mask is restricted in fabricating SiC MOSFETS since the following processes such as dopant activation, ohmic contacts are done at the very high temperature to attack the stability of the polysilicon layer. A metal instead of polysilicon can be used as a gate material and even can be used for ohmic contact to source region of SiC MOSFETS, which may reduce the number of the fabrication processes. Co-formation process of metal-source/drain ohmic contact and gate has been examined in the 4H-SiC based vertical power MOSFET At low bias region (<20V), increment of leakage current after RTA was detected. However, the amount of leakage current increment was less than a few tens of ph. The interface trap densities calculated from high-low frequency C-V curves do not show any difference between w/ RTA and w/o RTA. From the C-V characteristic curves, equivalent oxide thickness was calculated. The calculated thickness was 55 and 62nm for w/o RTA and w/ RTA, respectively. During the annealing, oxidation and silicidation of Ni can be occurred. Even though refractory nature of Ni, 950$^{\circ}C$ is high enough to oxidize it. Ni reacts with silicon and oxygen from SiO$_2$ 1ayer and form Ni-silicide and Ni-oxide, respectively. These extra layers result in the change of capacitance of whole oxide layer and the leakage current