• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.84-84
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• 2012

소자가 고집적화 됨에 따라, 비저항이 낮고 electro migration (EM), Stress Migration (SM) 특성이 우수한 구리(Cu)를 배선재료로서 사용하고 있다. 그러나, 구리는 Si과 $SiO_2$의 내부로 확산이 빠르게 일어나, Si 소자 내부에 deep donor level을 형성하고, 누설 전류를 증가시키는 등 소자의 성능을 저하시킬 수 있는 문제점을 가지고 있다. 그러나, electroplating 을 이용하여 증착한 Cu 박막은 일반적으로 확산 방지막으로 쓰이는 TiN, TaN, 등의 물질과의 접착 (adhesion) 특성이 나쁘다. 따라서, Cu CMP 에서 증착된 Cu 박막의 벗겨지거나(peeling), EM or SM 저항성 저하 등의 배선에서의 reliability 문제를 야기하게된다. 따라서 Cu 와 접착 특성이 좋은 새로운 확산방지막 또는 adhesion layer의 필요성이 대두되고 있다. 본 연구에서는 이러한 Cu 배선에서의 접착성 문제를 해결하고자 Metal organic chemical vapor deposition (MOCVD)을 이용하여 제조한 코발트(Co) 박막을 $Cu/TaN_x$ 사이의 접착력 개선을 위한 adhesion layer로 적용하려는 시도를 하였다. Co는 비저항이 낮고, Cu 와 adhesion이 좋으며, Cu direct electroplating 이 가능하다는 장점을 가지고 있다. 하지만, 수소 분위기에서 $C_{12}H_{10}O_6(Co)_2$ (dicobalt hexacarbonyl tert-butylacetylene, CCTBA) 전구체에 의한 MOCVD Co 박막의 경우 탄소, 산소와 같은 불순물이 다량 함유되어 있어, 비저항, surface roughness 가 높아지게 된다. 따라서 구리 전착 초기에 구리의 핵 생성(nucleation)을 저해하고 핵 생성 후에도 응집(agglomeration)이 발생하여 연속적이고 얇은 구리막 형성을 방해한다. 이를 해결하기 위해, MOCVD Co 박막 증착 시 수소 반응 가스에 암모니아를 추가로 주입하여, 수소/암모니아의 분압을 1:1, 1:6, 1:10으로 변화시켜 $Co/TaN_x$ 박막의 특성을 비교 분석하였다. 각각의 수소/암모니아 분압에 따른 $Co/TaN_x$ 박막을 TEM (Transmission electron microscopy), XRD (X-ray diffraction), AES (Auger electron spectroscopy)를 통해 물성 및 조성을 분석하였고, AFM (Atomic force microscopy)를 이용하여, surface roughness를 측정하였다. 실험 결과, $Co/TaN_x$ 박막은 수소/암모니아 분압 1:6에서 90 ${\mu}{\Omega}-cm$의 낮은 비저항과 0.97 nm 의 낮은 surface roughness 를 가졌다. 뿐만 아니라, MOCVD 에 의해 증착된 Co 박막이4-6 % concentration 의 탄소 및 산소 함량을 가지는 것으로 나타났고, 24nm 크기의 trench 기판 위에 약 6nm의 $Co/TaN_x$ 박막이 매우 균일하게 형성된 것을 확인 할 수 있었다. 이러한 결과들은, 향후 $Co/TaN_x$ 박막이 Cu direct electroplating 공정이 가능한 diffusion barrier로서 성공적으로 사용될 수 있음을 보여준다.

• 콘크리트학회논문집
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• 제16권4호
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• pp.549-555
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• 2004

Cement of three alkalinities (equivalent alkalinities of 0.36,0.52 and 0.97) was employed in fabricating a set of classical G109 type specimens. To-date, these have been subjected to a one week wet-one week dry cyclic pending using 15 w/o NaCl solution. At the end of the dry period, potential and macro-cell current were measured to indicate whether the top reinforcing steel was in the passive or active state. Once this bar became active, the specimen was autopsied and the extent of corrosion was documented. Subsequent to visual inspection, concrete powder samples were collected from the upper region of the top rebar trace; and at a certain times concrete cores were taken from non-reinforced specimens. Using these, determinations were made of (1) critical chloride concentration for corrosion initiation ($Cl_{th}^-$), (2) effective chloride diffusion coefficient ($D_e$), and (3) pore water alkalinity ($[OH^-]$). The pore water alkalinity was strongly related to the alkali content of cement that was used in the mix. The chloride concentration, ($Cl^-$), was greater at active than at passive sites, presumably as a consequence of electro migration and accumulation of these species at active site subsequent to corrosion initiation. Accordingly, ($Cl^-$) at passive sites was considered indicative of the threshold concentration fur corrosion initiation. The $Cl_{th}^-$ was increased with increasing Time-to-corrosion ($T_i$). Consequently, the HA(High Alkalinity) specimens exhibited the highest $Cl_{th}^-$ and the NA(Normal Alkalinity) was the least. This range exceeds what has previously been reported in North America. In addition, the effective diffusion coefficient, $D_e$, was about 40 percent lower for concrete prepared with the HA cement compared to the NA and LA(Low Alkalinity) ones.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.542-545
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• 2002

High performance organic electroluminescnet(EL) devices which are composed of organic thin multilayer films are fabricated. The basic structure is ITO/Emitting layer/LiF/Al in which have a blended emitting layer. The emitting layer is consisted of a host material(N,N' diphenyl-N,N' (3-methyl phenyl)-l,l'-biphenyl-4,4'diamine)(TPD)) and a guest emitting material(poly(3-hexylthiophehe)(P3HT)). We think that the energy transfer in blending layer occurred from TPD to P3HT. Red emitting multilayer EL devices were fabricated using tris(8-hydroxyqunolinate) aluminum$(Alq_3)$ as electron transport material. The device structure of ITO/blending layer(TPD+P3HT)$/Alq_3$/LiF/Al was employed. In the Voltage-current-luminance characteristics of multilayer device, the device tum on at the 2V and the luminance of $10{\mu}W/cm^2$ obtain at l0V. Red emission peak at 640nm was observed with this device structure. We have presented evidence that the excitation energy migration between a polymeric host and guest has to be explained. And by using multilayer, the red light emitting EL device enhances not only Voltage-current-luminance characteristic but also stability of device.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.217-220
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• 2009

Conductive adhesives have been investigated for use in microelectronics packaging as a lead-free solder substitute due to their advantages, such as low bonding temperature. However, high resistivity and poor mechanical behavior may be the limiting factors for the development of conductive adhesives. The metal fillers and the polymer resins provide electrical and mechanical interconnections between surface mount device components and a substrate. As metal fillers used in conductive adhesives, silver is the most commonly used due to its high conductivity and the stability. However the cost of conductive adhesives with silver fillers is much higher than usual lead-free solders and silver has poor electro-migration performance. So, copper can be a promising candidate for conductive filler metal due to its low resistivity and low cost, but oxidation causes this metal to lose its conductivity. In this study, electrically conductive adhesives (ECAs) using surface modified copper fillers were developed. Especially, in order to overcome the problem associated with the oxidation of copper, copper particles were coated with silver, and the silver-coated copper was tested as a filler metal. Especially the effect of silver coating on the electrical resistance just after curing and after aging was investigated. As a result, it was found that the electrical resistance of ECA with silver-coated copper filler was clearly lower and more stable than that of ECA with pure copper filler after curing process. And, during high temperature storage test, the degradation rate of electrical resistance for ECA with silver coated copper filler was quite slower than that for ECA with pure copper filler.

• 한국진공학회지
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• 제18권3호
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• pp.203-207
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• 2009

반도체 공정에서 기존 금속배선으로 사용되던 Al을 대체하여 사용되는 금속배선으로는 Cu가 그 대안으로 인식되고 있다. 이는 비저항값이 Al ($2.66{\mu}{\Omega}$-cm)보다 Cu ($1.67{\mu}{\Omega}$-cm)가 더 작아 RC 지연 시간 (RC delay time)을 극복하기 때문이다. 그러나 Cu의 녹는점은 $1085^{\circ}C$로 높지만 저온에서 쉽게 Si기판과 반응하는 특성을 가지고 있고, 또한 Si과의 접착력이 좋이 않는 것으로 알려져 있다. 이러한 이유로 Cu와 Si과의 반응을 방지하고 접착력을 높이기 위하여 확산방지막의 연구가 꾸준히 진행되고 있다. 본 연구그룹에서는 Cu의 확산을 방지하기 위하여 W-C-N의 확산방지막에 대하여 연구하여 왔다. 지금까지 보고된 연구 결과에 의하면 W-C-N (tungsten-carbon-nitrogen) 확산방지막은 고온에서도 Cu와 Si과의 확산을 효과적으로 방지하는 것으로 보고되었다. 이 논문에서는 W-C-N 확산방지막에 질소(N) 비율을 다르게 증착하여 지금까지 진행한 연구 결과를 기반으로 새로이 Cu의 전자거동현상(Electromigration)에 대하여 연구하였고, 고온 열처리 과정에서 박막의 표면강도 (Surface hardness)를 Nano-Indenter system을 이용하여 연구하였다. 이러한 연구를 통하여 박막내 질소가 포함된 W-C-N 확산방지막이 Cu의 전자거동에 더 안정적이며, 고온 열처리 과정에서도 표면 강도가 더 안정한 연구 결과를 획득하였다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 춘계 학술대회
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• pp.101-109
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• 2005

본 논문에서는 불필요한 용액의 발생이 없이 전해 반응계로 주입되는 용액을 오직 pH 만을 조절시켜 배출시키기 위한 연속식 이온 교환막 전해 시스템을 개발하였다. 여기서는 전해 반응기 앞에 한 pH-조정조를 두고 대상 용액을 pH-조정조로 주입하면서 pH-조정조의 용액의 일부를 이온 교환막에 따라 음극방 또는 양극방으로 거처 다시 pH-조정조로 순환하게 하고. 또한 pH-조정조의 용액의 일부는 상대극방을 통과시킴으로써 pH가 산성 또는 알카리로 조절되어 배출되게 하였다. 이러한 전해반응기에서 pH 조절 과정은 음극과 양극 사이에 전압 차가 형성될 시, 이온 교환막을 통한 용액에 존재하는 이온의 전기이동 현상에 의해 유발되는 음극방과 양극방에서 용액의 전하 비 평형 현상과 이에 따른 물의 전해 분해 과정에 의해 설명되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.546-546
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• 2008

Copper (Cu) Chemical mechanical polishing (CMP) has been an essential process for Cu wifing of DRAM and NAND flash memory beyond 45nm. Copper has been employed as ideal material for interconnect and metal line due to the low resistivity and high resistant to electro-migration. Damascene process is currently used in conjunction with CMP in the fabrication of multi-level copper interconnects for advanced logic and memory devices. Cu CMP involves removal of material by the combination of chemical and mechanical action. Chemicals in slurry aid in material removal by modifying the surface film while abrasion between the particles, pad, and the modified film facilitates mechanical removal. In our research, we emphasized on the role of chemical effect of slurry on Cu CMP, especially on the effect of amine functional group on removal rate selectivity between Cu and Tantalum-nitride (TaN) film. We investigated the two different kinds of complexing agent both with amine functional group. On the one hand, Polyacrylamide as a polymer affected the stability of abrasive, viscosity of slurry and the corrosion current of copper film especially at high concentration. At higher concentration, the aggregation of abrasive particles was suppressed by the steric effect of PAM, thus showed higher fraction of small particle distribution. It also showed a fluctuation behavior of the viscosity of slurry at high shear rate due to transformation of polymer chain. Also, because of forming thick passivation layer on the surface of Cu film, the diffusion of oxidant to the Cu surface was inhibited; therefore, the corrosion current with 0.7wt% PAM was smaller than that without PAM. the polishing rate of Cu film slightly increased up to 0.3wt%, then decreased with increasing of PAM concentration. On the contrary, the polishing rate of TaN film was strongly suppressed and saturated with increasing of PAM concentration at 0.3wt%. We also studied the electrostatic interaction between abrasive particle and Cu/TaN film with different PAM concentration. On the other hand, amino-methyl-propanol (AMP) as a single molecule does not affect the stability, rheological and corrosion behavior of the slurry as the polymer PAM. The polishing behavior of TaN film and selectivity with AMP appeared the similar trend to the slurry with PAM. The polishing behavior of Cu film with AMP, however, was quite different with that of PAM. We assume this difference was originated from different compactness of surface passivation layer on the Cu film under the same concentration due to the different molecular weight of PAM and AMP.