Cu/CeO₂ 촉매의 구조적 특성이 일산화탄소 저온 산화반응에 미치는 영향 연구

김민수(Min Su Kim),최경륜(Gyeong Ryun Choi),김세원(Se Won Kim),홍성창(Chang Hong) 한국청정기술학회 2020 청정기술 Vol.26 No.4

본 연구는 Cu/CeO₂-X 촉매의 저온 CO 산화 활성에 미치는 영향을 촉매의 구조적 특성, 반응 특성을 통해 확인하였다. 사용된 촉매는 습윤 함침법으로 제조되었으며, 각기 다른 소성온도(300~600 ℃)에서 형성된 CeO₂ (지지체)를 이용하여 Cu (활성금속)를 담지함으로써 Cu/CeO₂-X 촉매를 제조하였다. 제조된 Cu/CeO₂-X 촉매는 저온 CO 산화 활성을 평가하였다. 125 ℃에서 Cu/CeO₂_300 촉매는 90% 이상의 활성을 나타냈으며, CeO₂의 소성온도가 증가됨에 따라 활성이 점차 감소하여, Cu/CeO₂_600 촉매는 65%를 나타냈다. 다음으로 촉매의 물리/화학적 특성을 Raman, BET, XRD, H₂-TPR, XPS 분석으로 확인하였다. XPS 분석 결과, CeO₂-X의 소성온도가 낮을 수록 불안정한 Ce<SUP>3+</SUP> 종(비 화학양론 종) 비율이 증가하였다. 증가된 Ce<SUP>3+</SUP>종은 Cu와 결합함으로 써 치환결합을 형성하였으며 Raman 분석의 CeO₂ peak 변화와 H₂-TPR 분석의 치환결합 구조의 환원 peak를 통해 확인하였다. 결과적으로 Cu와 CeO₂의 치환 결합 형성은 촉매의 redox 특성 및 저온 CO 산화 활성을 증진시켰다고 판단된다. This study confirmed the effect of the Cu/CeO₂-X catalyst on the CO oxidation activity at low temperature through the catalyst’s structure and reaction characteristics. The catalyst was prepared by the wet impregnation method. Cu/CeO₂_X catalysts were manufactured by loading Cu (active metal) using CeO₂ (support) formed at different calcination temperatures (300-600 ℃). Manufactured Cu/CeO₂_X catalysts were evaluated for the low-temperature activity of carbon monoxide. The Cu/CeO₂_300 catalyst showed an activity of 90% at 125 ℃, but the activity gradually decreased as the calcination temperature of the CeO₂-X and Cu/CeO₂_600 catalysts showed an activity of 65% at 125 ℃. Raman, XRD, H₂-TPR, and XPS analysis confirmed the physicochemical properties of the catalysts. Based on the XPS analysis, the lower the calcination temperature of the CeO₂ was, the higher the unstable Ce<SUP>3+</SUP> species (non-stoichiometric species) ratio became. The increased Ce<SUP>3+</SUP> species formed a solid solution bond between Cu and CeO₂-X, and it was confirmed by the change of the CeO₂ peak in Raman analysis and the reduction peak of the solid solution structure in H₂-TPR analysis. According to the result, the formation of the solid solution bond between Cu and Ce has been enhanced by the redox properties of the catalysts and by CO oxidation activity at low temperatures.

The Effects of Alloying and Pressing Routes in Equal Channel Angular Pressing of Cu-Fe-Cr and Cu-Fe-Cr-Ag Composites

최영철,김형섭,홍순익 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5

Equal channel angular pressing (ECAP) was carried out on Cu-Fe-Cr and Cu-Fe-Cr-Ag composites at room temperature. ECAPed Cu-Fe-Cr and Cu-Fe-Cr-Ag exhibited ultrafine-grained microstructures with the shape and distribution of Fe-Cr phase were dependent on the processing routes. In route A, the initial dendrites of Fe-Cr phase were elongated along the shear direction and developed into filaments, whereas in route Bc the initial dendrites became finer by fragmentation with no pronounced change of the shape. The hardness of ECAPed Cu-Fe-Cr-Ag is greater than that of ECAPed Cu-Fe-Cr. The higher hardness in Cu-Fe-Cr-Ag is ascribed to the more effective matrix strengthening due to the dislocation storage and the precipitation hardening. The hardness of ECAPed Cu-Fe-Cr was lower than that of the drawn Cu-Fe-Cr at the same deformation strain because of the less effective refinement and elongation of the two-phase filamentary microstructure. The addition of silver was found to increase the hardness of the ECAPed composite above the strength level of heavily drawn Cu-Fe-Cr, rendering the processing method of applying alloying and ECAP to Cu-Fe-Cr composite an attractive approach to producing bulky high strength Cu base composites. Equal channel angular pressing (ECAP) was carried out on Cu-Fe-Cr and Cu-Fe-Cr-Ag composites at room temperature. ECAPed Cu-Fe-Cr and Cu-Fe-Cr-Ag exhibited ultrafine-grained microstructures with the shape and distribution of Fe-Cr phase were dependent on the processing routes. In route A, the initial dendrites of Fe-Cr phase were elongated along the shear direction and developed into filaments, whereas in route Bc the initial dendrites became finer by fragmentation with no pronounced change of the shape. The hardness of ECAPed Cu-Fe-Cr-Ag is greater than that of ECAPed Cu-Fe-Cr. The higher hardness in Cu-Fe-Cr-Ag is ascribed to the more effective matrix strengthening due to the dislocation storage and the precipitation hardening. The hardness of ECAPed Cu-Fe-Cr was lower than that of the drawn Cu-Fe-Cr at the same deformation strain because of the less effective refinement and elongation of the two-phase filamentary microstructure. The addition of silver was found to increase the hardness of the ECAPed composite above the strength level of heavily drawn Cu-Fe-Cr, rendering the processing method of applying alloying and ECAP to Cu-Fe-Cr composite an attractive approach to producing bulky high strength Cu base composites.

Microstructure Evolution in Cu Pillar/Eutectic SnPb Solder System during Isothermal Annealing

김병준,이기욱,박영배,이호영,주영창,김재동,임기태 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5

The reaction between Cu pillar and eutectic SnPb solder during isothermal annealing was studied systematically. Intermetallic compounds (IMCs), such as Cu6Sn5 and Cu3Sn, were formed in between Cu and SnThe parabolic rate law was observed on IMC formation, which indicated that the growth of IMCs was controlled by atomic diffusion (a diffusion-limited process). Annealing at 165 °C for 160 h decreased the growth rate of Cu6Sn5, and at the same time increased the growth rate of Cu3Sn. This was when Sn in solder was exhausted completely. The activation energies for the growth of Cu3Sn and Cu6Sn5 were measured to be 1.77 eV and 0.72 eV, respectively. The Kirkendall void that formed at the interface between Cu pillar and solder obeyed the parabolic rate law. The growth rate of the Kirkendall void increased when the Sn in solder was consumed in its entirety. The reaction between Cu pillar and eutectic SnPb solder during isothermal annealing was studied systematically. Intermetallic compounds (IMCs), such as Cu6Sn5 and Cu3Sn, were formed in between Cu and SnThe parabolic rate law was observed on IMC formation, which indicated that the growth of IMCs was controlled by atomic diffusion (a diffusion-limited process). Annealing at 165 °C for 160 h decreased the growth rate of Cu6Sn5, and at the same time increased the growth rate of Cu3Sn. This was when Sn in solder was exhausted completely. The activation energies for the growth of Cu3Sn and Cu6Sn5 were measured to be 1.77 eV and 0.72 eV, respectively. The Kirkendall void that formed at the interface between Cu pillar and solder obeyed the parabolic rate law. The growth rate of the Kirkendall void increased when the Sn in solder was consumed in its entirety.

Electrical contact properties of Cu2S nanowires grown vertically on Cu foil by gas–solid reaction

Youngseok Lim,Young-Woo Ok,Sung-Ju Tark,Yoonmook Kang,김동환 한국물리학회 2009 Current Applied Physics Vol.9 No.5

We grew Cu2S nanowires vertically on Cu foil by gas–solid reaction with a gas mixture of O2 and H2S. The electrical contact properties between the Cu2S nanowires and Cu foil were investigated using a modified current–voltage–temperature plot. The Cu/Cu2S layer exhibited the characteristics of a Schottky barrier with a barrier height of ~0.72 eV, which was closer to the value for Cu/Cu2O than to Cu/Cu2S. Energy dispersive spectroscopy results showed the presence of Cu-oxide between the Cu2S nanowires and Cu foil. The overall structure was Cu/Cu-oxide/Cu2S and the electrical properties were controlled by the Cu/Cuoxide.

Cu-Cu 패턴 직접접합을 위한 습식 용액에 따른 Cu 표면 식각 특성 평가

박종명,김영래,김성동,김재원,박영배,Park, Jong-Myeong,Kim, Yeong-Rae,Kim, Sung-Dong,Kim, Jae-Won,Park, Young-Bae 한국마이크로전자및패키징학회 2012 마이크로전자 및 패키징학회지 Vol.19 No.1

Cu-Cu 패턴의 직접접합 공정을 위하여 Buffered Oxide Etch(BOE) 및 Hydrofluoric acid(HF)의 습식 조건에 따른 Cu와 $SiO_2$의 식각 특성에 대한 평가를 수행하였다. 접촉식 3차원측정기(3D-Profiler)를 이용하여 Cu와 $SiO_2$의 단차 및 Chemical Mechanical Polishing(CMP)에 의한 Cu의 dishing된 정도를 분석 하였다. 실험 결과 BOE 및 HF 습식 식각 시간이 증가함에 따라 단차가 증가 하였고, BOE가 HF보다 더 식각 속도가 빠른 것을 확인하였다. BOE 및 HF 습식 식각 후 Cu의 dishing도 식각시간 증가에 따라 감소하였다. 식각 후 산화막 유무를 알아보기 위해 Cu표면을 X-선 광전자 분광법(X-ray Photoelectron Spectroscopy, XPS)를 이용하여 분석 한 결과 HF습식 식각 후 BOE습식 식각보다 Cu표면산화막이 상대적으로 더 얇아 진 것을 확인하였다. Three-dimensional integrated circuit(3D IC) technology has become increasingly important due to the demand for high system performance and functionality. In this work, BOE and HF wet etching of Cu line surfaces after CMP were conducted for Cu-Cu pattern direct bonding. Step height of Cu and $SiO_2$ as well as Cu dishing after Cu CMP were analyzed by the 3D-Profiler. Step height increased and Cu dishing decreased with increasing BOE and HF wet etching times. XPS analysis of Cu surface revealed that Cu surface oxide layer was partially removed by BOE and HF wet etching treatment. BOE treatment showed not only the effective $SiO_2$ etching but also reduced dishing and Cu surface oxide rather than HF treatment, which can be used as an meaningful process data for reliable Cu-Cu pattern bonding characteristics.

실리콘 실험실에 구리 오염을 방지 할 수 있는 고밀도/고균일의 Solder Bump 형성방법

김성진,주철원,박성수,백규하,이희태,송민규 한국마이크로전자및패키징학회 2000 마이크로전자 및 패키징학회지 Vol.7 No.4

사용되는 metal구분 없이 반도체 공정장비들을 사용함으로써 cross-contamination을 유발시킬 수 있다. 특히, copper(Cu)는 확산이 쉽게 되어 cross-contamination에 의해 수 ppm정도가 wafer에 오염되더라도 트랜지스터의 leakage current발생 요인으로 작용할 수 있기 때문에 Si-IC성능에 치명적인 영향을 미칠 수 있는데, Si-LSI 실험실에서 할 수 있는 공정과 Si-LSI 실험실을 나와 할 수 있는 공정으로 구분하여 최대한 Si-LSI 장비를 공유함으로써 최소한의 장비로 Cu cross-contamination문제를 해결할 수 있다. 즉, 전기도금을 할 때 전극으로 사용되어지는 TiW/Al sputtering, photoresist (PR) coating, solder bump형성을 위한 via형성까지는 Si-LSI 실험실에서 하고, 독립적인 다른 실험실에서 Cu-seed sputtering, solder 전기도금, 전극 etching, reflow공정을 하면 된다. 두꺼운 PR을 얻기 위하여 PR을 수회 도포(multiple coaling) 하고, 유기산 주석과 유기산 연의 비를 정확히 액 조성함으로서 Sn:Pb의 조성비가 6 : 4인 solder bump를 얻을 수 있었다. solder를 도금하기 전에 저속 도금으로 Cu를 도금하여, PR 표면의 Cu/Ti seed층을 via와 PR표면과의 저항 차를 이용하여 PR표면의 Cu-seed를 Cu도금 중에 etching 시킬 수 있다. 이러한 현상을 이용하여 선택적으로 via만 Cu를 도금하고 Ti층을 etching한 후, solder를 도금함으로써 저 비용으로 folder bump 높이가 60 $\mu\textrm{m}$ 이상 높고, 고 균일/고 밀도의 solder bump를 형성시킬 수 있었다. We demonstrate the fabrication method of high-density and high-quality solder bump solving a copper (Cu) cross-contamination in Si-LSI laboratory. The Cu cross-contamination is solved by separating solder-bump process by two steps. Former is via-formation process excluding Cu/Ti under ball metallurgy (UBM) layer sputtering in Si-LSI laboratory. Latter is electroplating process including Ti-adhesion and Cu-seed layers sputtering out of Si-LSI laboratory. Thick photoresist (PR) is achieved by a multiple coating method. After TiW/Al-electrode sputtering for electroplating and via formation in Si-LSI laboratory, Cu/Ti UBM layer is sputtered on sample. The Cu-seed layer on the PR is etched during Cu-electroplating with low-electroplating rate due to a difference in resistance of UBM layer between via bottom and PR. Therefore Cu-buffer layer can be electroplated selectively at the via bottom. After etching the Ti-adhesion layer on the PR, Sn/Pb solder layer with a composition of 60/40 is electroplated using a tin-lead electroplating bath with a metal stoichiometry of 60/40 (weight percent ratio). Scanning electron microscope image shows that the fabricated solder bump is high-uniformity and high-quality as well as symmetric mushroom shape. The solder bumps with even 40/60 $\mu\textrm{m}$ in diameter/pitch do not touch during electroplating and reflow procedures. The solder-bump process of high-uniformity and high-density with the Cu cross-contamination free in Si-LSI laboratory will be effective for electronic microwave application.

Cu가 도핑된 LSM의 구조분석과 열팽창특성 연구

노태민,류지승,김진성,정철원,이희수,Noh, Tai-Min,Ryu, Ji-Seung,Kim, Jin-Seong,Jeong, Cheol-Weon,Lee, Hee-Soo 한국결정성장학회 2011 한국결정성장학회지 Vol.21 No.4

이종 원자가를 가시는 Cu의 도핑이 LSM에 미치는 영향을 구조적인 분석과 열팽창계수를 통해서 고찰하였다. 고상반응을 이용하여 $La_{0.8}Sr_{0.2}Mn_{1-x}Cu_xO_3$($0{\leq}x{\leq}0.3$)음 제조하였으며, Cu의 도핑 함량에 따른 결정구조 및 열팽창계수를 확인하였다. Cu 함량이 증가함에 따라서 격자상수외 열팽창계수가 감소하는 경향을 나타냈지만, x = 0.3인 경우에는 증가 하였다. 이러한 격자상수와 열팽창계수의 변화는 Cu 이온의 B-site에서의 Mn 자리에 치환될 때 $0{\leq}x{\leq}0.2$의 범위에서는 $Cu^{3+}$의 존재로 인한 이온 반성의 감소에 의한 것으로 판단되었고, x=0.3인 경우에는 $Cu^{2+}$와 $Mn^{4+}$의 존재로 인한 산소 공공의 증가에 기인한 것이었다. The doping effect of Cu in the Sr-doped lanthan manganites (LSM) has been investigated in terms of structural analysis and thermal expansion coefficient (TEC). The $La_{0.8}Sr_{0.2}Mn_{1-x}Cu_xO_3$ ($0{\leq}x{\leq}0.3$) were prepared by solid state reaction method and their crystal structure and TEC were measured. A decrease in the lattice parameters and the TEC were observed with increase eu content, whereas they were decreased for x = 0.3. For $0{\leq}x{\leq}0.2$, the decrease of the lattice parameter and the TEC with increase Cu content were attributed to the reduction of ionic radius of Cu ions due to the presence of $Cu^{3+}$ ions. For x = 0.3, however, the increase was originated from the formation of oxygen vacancies due 10 the presence of $Cu^{2+}$ and $Mn^{4+}$.

Cu(Mg) alloy의 표면과 계면에서 형성된 MgO의 확산방지능력 및 표면에 형성된 MgO의 전기적 특성 연구

조흥렬,조범석,이재갑,Jo, Heung-Ryeol,Jo, Beom-Seok,Lee, Jae-Gap 한국재료학회 2000 한국재료학회지 Vol.10 No.2

Sputter Cu(1-4.5at.%Mg) alloy를 100mTorr이하의 산소압력에서 온도를 증가시키며 열처리하였을 때 표연과 계면에서 형성된 MgO의 확산방지막 특성을 살펴보았다 먼저, $Cu(Mg)/SiO_2/Si$ 구조의 샘플을 열처리했을 때 계면에서는 $2Mg+SiO_2{\rightarrow}2MgO+Si$의 화학반응에 의해 MgO가 형성되는데 이 MgO충에 의해 Cu가 $SiO_2$로 확산되는 것이 현저하게 감소하였다. TiN/Si 기판 위에서도 Cu(Mg)과 TiN 계면에 MgO가 형성되어 Cu(4.5at.%Mg)의 경우 $800^{\circ}C$까지 Cu와 Si의 확산을 방지할 수 있었다. 표면에 형성된 MgO위에 Si을 증착하여 $Si/MgO(150\;{\AA})/Cu(Mg)/SiO_2/Si$구조로 만든 후 열처리했을 때 $150\;{\AA}$의 MgO는 $700^{\circ}C$까지 Si과 Cu의 확산을 방지할 수 있었다. 표면에 형성된 MgO($150\;{\AA}$)의 누설전류특성은 break down 5V, 누설전류 $10^{-7}A/\textrm{cm}^2$의 값을 나타냈다. 또한 $Si_3N_4/MgO$ 이중구조에서는 매우 낮은 누설전류밀도를 나타냈으며 MgO에 의해 $Si_3N_4$ 증착시 안정적인 계면이 형성됨을 확인하였다. We have investigated the electrical and diffusion barrier properties of MgO produced on the surface of Cu (Mg) alloy. Also the diffusion barrier property of the interfacial MgO between Cu alloy and $SiO_2$ has been examined. The results show that the $150\;{\AA}$-MgO layer on the surface remains stable up to $700^{\circ}C$, preventing the interdiffusion of C Cu and Si in Si/MgO/Cu(Mg) structure. It also has the breakdown voltage of 4.5V and leakage current density of $10^{-7}A/\textrm{cm}^2/$. In addition, the combined structure of $Si_3N4(100{\AA})/MgO(100{\AA})$ increases the breakdown voltage up to lOV and reduces the leakage current density to $8{\tiems}10^{-7}A/\textrm{cm}^2$. Furthermore, the interfacial MgO formed by the chemical reac­t tion of Mg and $SiO_2$ reduces the diffusion of copper into $SiO_2$ substrate. Consequently, Cu(Mg) alloy can be applied as a g gate electrode in TFT /LCDs, reducing the process steps.

전기폭발법에 의한 CU/CUO 나노분말의 제조 및 분말특성

맹덕영,이창규,이남희,박중학,김흥회,이은구,Maeng, D.Y.,Rhee, C.K.,Lee, N.H.,Park, J.H.,Kim, W.W.,Lee, E.G. 한국재료학회 2002 한국재료학회지 Vol.12 No.12

Both Cu and Cu-oxide nanopowders have great potential as conductive paste, solid lubricant, effective catalysts and super conducting materials because of their unique properties compared with those of commercial micro-sized ones. In this study, Cu and Cu-oxide nanopowders were prepared by Pulsed Wire Evaporation (PWE) method which has been very useful for producing nanometer-sized metal, alloy and ceramic powders. In this process, the metal wire is explosively converted into ultrafine particles under high electric pulse current (between $10^4$ and $10^{ 6}$ $A/mm^2$) within a micro second time. To prevent full oxidations of Cu powder, the surface of powder has been slightly passivated with thin CuO layer. X-ray diffraction analysis has shown that pure Cu nanopowders were obtained at $N_2$ atmosphere. As the oxygen partial pressure increased in $N_2$ atmosphere, the gradual phase transformation occurred from Cu to $Cu_2$O and finally CuO nanopowders. The spherical Cu nanopowders had a uniform size distribution of about 100nm in diameter. The Cu-oxide nanopowders were less than 70nm with sphere-like shape and their mean particle size was 54nm. Smaller size of Cu-oxide nanopowders compared with that of the Cu nanopowders results from the secondary explosion of Cu nanopowders at oxygen atmosphere. Thin passivated oxygen layer on the Cu surface has been proved by XPS and HRPD.

Cu-NO 복합체에 대한 DFT 계산에 따른 Cu의 자동차 촉매변환기 적합성

하광아,이민주 대한화학회 2018 대한화학회지 Vol.62 No.5

The purpose of this study is to show the possibility of using Cu catalyst in removal of NOx from automobile exhaust which is regarded as the primary source of fine dust PM2.5. The energy and the bond lengths of the three possible structures of Cu-NO complex, which is formed by binding NO molecule to Cu, and the changes in IR and Raman spectra are calculated using MPW1PW91 method on the level of 6-311(+)G(d,p) of basis sets with Gaussian 09 program. As a result, the enthalpy of formation of the Cu-NO complexes are obtained as ΔH = 104.89, 91.98, -127.48 kJ/mol for the linear, bent, and bridging forms of them, respectively. And the bond lengths between N and O in NO complexes, which becomes longer than NO molecule, indicates that O is easily reduced from Cu-NO. In addition, the Cu-NO complexes using Cu catalyst can be easily measured by infrared or Raman spectroscopy because in the IR and Raman spectra of the NO and Cu-NO complexes the positon and the intensity of bands are definitely different in each vibration mode. 화석연료의 사용과 그 2차오염으로 인해 매년 수도권의 초미세먼지(PM2.5)는 점점 증가하는 추세에 있다. 본 연구는 초 미세먼지의 주된 원인물질이라고 알려져 있는 자동차의 매연에서 발생하는 NOx의 제거에 저렴한 Cu 촉매의 이용 가능성에 초 점을 두었다. 이를 위하여 일산화질소(NO) 분자가 Cu에 결합하여 형성할 수 있는 Cu-NO 복합체의 가능한 3가지 구조에서의 에 너지와 결합길이, IR 및 라만 스펙트럼의 변화를 알아보기 위하여 Gaussian 09 프로그램에서 MPW1PW91 법을 이용하여 기저 함수 6-311(+)G(d,p) 수준에서 계산을 수행하였다. 그 결과, Cu-NO 복합체의 생성 엔탈피는 선형, 굽은형, 다리형 구조에 대하여 각각 ΔH = 104.89, 91.98, -127.48 kJ/mol의 값을 얻었고, NO 결합길이는 복합체가 되었을 때 약 0.03~0.10 Å 정도 NO 분자보다 길어지는 경향을 보여 Cu-NO 결합으로부터 O가 보다 쉽게 환원될 수 있음을 보여준다. 또한 NO와 Cu-NO 복합체의 IR 및 라만 스펙트럼은 각 진동 모드에 대한 피크의 위치와 세기가 확연히 달라져 Cu 촉매에서 Cu-NO 복합체의 생성 여부도 적외선 또는 라만 분광법으로 손쉽게 확인될 수 있음을 알 수 있었다.