저유전체 고분자 접착 물질을 이용한 웨이퍼 본딩을 포함하는 웨이퍼 레벨 3차원 집적회로 구현에 관한 연구

Kwon, Yongchai,Seok, Jongwon,Lu, Jian-Qiang,Cale, Timothy,Gutmann, Ronald 한국화학공학회 2007 Korean Chemical Engineering Research(HWAHAK KONGHA Vol. No.

웨이퍼 레벨(WL) 3차원(3D) 집적을 구현하기 위해 저유전체 고분자를 본딩 접착제로 이용한 웨이퍼 본딩과, 적층된 웨이퍼간 전기배선 형성을 위해 구리 다마신(damascene) 공정을 사용하는 방법을 소개한다. 이러한 방법을 이용하여 웨이퍼 레벨 3차원 칩의 특성 평가를 위해 적층된 웨이퍼간 3차원 비아(via) 고리 구조를 제작하고, 그 구조의 기계적, 전기적 특성을 연속적으로 연결된 서로 다른 크기의 비아를 통해 평가하였다. 또한, 웨이퍼간 적층을 위해 필수적인 저유전체 고분자 수지를 이용한 웨이퍼 본딩 공정의 다음과 같은 특성 평가를 수행하였다. (1) 광학 검사에 의한 본딩된 영역의 정도 평가, (2) 면도날(razor blade) 시험에 의한 본딩된 웨이퍼들의 정성적인 본딩 결합력 평가, (3) 4-점 굽힘시험(four point bending test)에 의한 본딩된 웨이퍼들의 정량적인 본딩 결합력 평가. 본 연구를 위해 4가지의 서로 다른 저유전체 고분자인 benzocyclobutene(BCB), Flare, methylsilsesquioxane(MSSQ) 그리고 parylene-N을 선정하여 웨이퍼 본딩용 수지에 대한 적합성을 검토하였고, 상기 평가 과정을 거쳐 BCB와 Flare를 1차적인 본딩용 수지로 선정하였다. 한편 BCB와 Flare를 비교해 본 결과, Flare를 이용하여 본딩된 웨이퍼들이 BCB를 이용하여 본딩된 웨이퍼보다 더 높은 본딩 결합력을 보여주지만, BCB를 이용해 본딩된 웨이퍼들은 여전히 칩 back-end-of-the-line (BEOL) 공정조건에 부합되는 본딩 결합력을 가지는 동시에 동공이 거의 없는 100%에 가까운 본딩 영역을 재현성있게 보여주기 때문에 본 연구에서는 BCB가 본딩용 수지로 더 적합하다고 판단하였다. A technology platform for wafer-level three-dimensional integration circuits (3D-ICs) is presented, and that uses wafer bonding with low-k polymeric adhesives and Cu damascene inter-wafer interconnects. In this work, one of such technical platforms is explained and characterized using a test vehicle of inter-wafer 3D via-chain structures. Electrical and mechanical characterizations of the structure are performed using continuously connected 3D via-chains. Evaluation results of the wafer bonding, which is a necessary process for stacking the wafers and uses low-k dielectrics as polymeric adhesive, are also presented through the wafer bonding between a glass wafer and a silicon wafer. After wafer bonding, three evaluations are conducted; (1) the fraction of bonded area is measured through the optical inspection, (2) the qualitative bond strength test to inspect the separation of the bonded wafers is taken by a razor blade, and (3) the quantitative bond strength is measured by a four point bending. To date, benzocyclobutene (BCB), $Flare^{TM}$, methylsilsesquioxane (MSSQ) and parylene-N were considered as bonding adhesives. Of the candidates, BCB and $Flare^{TM}$ were determined as adhesives after screening tests. By comparing BCB and $Flare^{TM}$, it was deduced that BCB is better as a baseline adhesive. It was because although wafer pairs bonded using $Flare^{TM}$ has a higher bond strength than those using BCB, wafer pairs bonded using BCB is still higher than that at the interface between Cu and porous low-k interlevel dielectrics (ILD), indicating almost 100% of bonded area routinely.

BCB 수지로 본딩한 웨이퍼의 본딩 결합력에 관한 연구

Kwon, Yongchai,Seok, Jongwon,Lu, Jian-Qiang,Cale, Timothy,Gutmann, Ronald 한국화학공학회 2007 Korean Chemical Engineering Research(HWAHAK KONGHA Vol. No.

BCB 수지를 이용하여 본딩한 웨이퍼의 BCB 두께, 본딩 촉진제의 사용여부 및 이웃하는 적층 물질의 종류에 따른 본딩 결합력에 대한 영향을 4-점 굽힘방법을 이용하여 규명한다. 실험결과 본딩 결합력은 BCB 두께에 선형 비례하는데, 이는 BCB의 소성 변형의 정도가 두께에 비례하는 반면에 BCB의 항복 강도에는 영향을 미치지 않기 때문이다. 본딩한 BCB의 두께가 각각 $2.6{\mu}m$ 및 $0.4{\mu}m$인 경우에 대하여 본딩 촉진제를 사용 했을 때, 본딩 촉진제와 본딩된 물질의 표면에서는 공유 결합이 형성되기 때문에 본딩 결합력이 증가한다. 산화 규소막이 증착된 실리콘 웨이퍼와 BCB 사이 계면에서의 본딩 결합력은 글래스 웨이퍼와 BCB 사이의 계면에서 보다 약 3배 정도 높다. 이러한 본딩 결합력의 차이는 각 계면에서 Si-O 본드의 본딩 밀도 및 본드 파단 에너지의 차이에 기인한다. PECVD 산화 규소막을 증착한 실리콘 웨이퍼와 BCB 사이 계면의 경우, 기 측정된 $18J/m^2$ 및 $22J/m^2$의 본드 파단 에너지를 얻기 위해 각각 약 $12{\sim}13bonds/nm^2$ 및 $15{\sim}16bonds/nm^2$의 Si-O 본드 밀도가 필요하다. 반면에, 글래스 웨이퍼와 BCB 사이 계면의 경우에는 기 측정된 $5J/m^2$의 본드 파단 에너지를 얻기 위해 약 $7{\sim}8bonds/nm^2$의 Si-O 본드 밀도가 필요하다. Four point bending is used to study the dependences of bond strength of benzocyclobutene(BCB) bonded wafers and BCB thickness, the use of an adhesion promoter, and the materials being bonded. The bond strength depends linearly on BCB thickness, due to the thickness-dependent contribution of the plastic dissipation energy of the BCB and thickness independence of BCB yield strength. The bond strength increases by about a factor of two with an adhesion promoter for both $2.6{\mu}m$ and $0.4{\mu}m$ thick BCB, because of the formation of covalent bonds between adhesion promoter and the surface of the bonded materials. The bond strength at the interface between a silicon wafer with deposited oxide and BCB is about a factor of three higher than that at the interface between a glass wafer and BCB. This difference in bond strength is attributed to the difference in Si-O bond density at the interfaces. At the interfaces between plasma enhanced chemical vapor deposited (PECVD) oxide coated silicon wafers and BCB, and between thermally grown oxide on silicon wafers and BCB, 12~13 and $15{\sim}16bonds/nm^2$ need to be broken. This corresponds to the observed bond energies, $G_0s$, of 18 and $22J/m^2$, respectively. Maximum 7~8 Si-O $bonds/nm^2$ are needed to explain the $5J/m^2$ at the interfaces between glass wafers and BCB.

Evaluation of direct formic acid fuel cells with catalyst layers coated by electrospray

Kwon, Yongchai,Baek, Seungmin,Kwon, Byungwan,Kim, Jinsoo,Han, Jonghee Springer-Verlag 2010 Korean Journal of Chemical Engineering Vol.27 No.3

Electrochemical Activity Studies of Glucose Oxidase (GOx)‐Based and Pyranose Oxidase (POx)‐Based Electrodes in Mesoporous Carbon: Toward Biosensor and Biofuel Cell Applications

Kwon, Ki Young,Kim, Jae Hyun,Youn, Jongkyu,Jeon, Chulmin,Lee, Jinwoo,Hyeon, Taeghwan,Park, Hyun Gyu,Chang, Ho Nam,Kwon, Yongchai,Ha, Su,Jung, Hee‐,Tae,Kim, Jungbae WILEY‐VCH Verlag 2014 Electroanalysis Vol.26 No.10

<P><B>Abstract</B></P><P>A simple study using a fixed amount of mesoporous carbon (MSU‐F‐C) was performed for the comparison of pyranose oxidase (POx) and glucose oxidase (GOx) in their electrochemical performance under biosensor and biofuel cell operating modes. Even though the ratio of POx to GOx in the glucose oxidation activity per unit weight of MSU‐F‐C was 0.35, the ratios of POx to GOx in sensitivity and power density were reversed to be 6.2 and 1.4, respectively. POx with broad substrate specificity and an option of large scale production using recombinant <I>E. coli</I> has a great potential for various electrochemical applications, including biofuel cells.</P>

Current trends for the floating liquefied natural gas (FLNG) technologies

원왕연,Yongchai Kwon,Sun Keun Lee,Kwangho Choi 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.5

Natural gas (NG) and liquefied NG (LNG), which is one trade type of NG, have attracted great attentionbecause their use may alleviate rising concerns about environmental pollution produced by classical fossil fuels andnuclear power plants. However, when gas reserves are located in stranded areas and a portion of the offshore reserves isa significant amount of the total gas reserves, LNG is not suitable because (i) installation of pipelines for the transferof NG to onshore LNG facilities is expensive and difficult, and (ii) it still has environmental and security problems. As a result, there are many efforts to excavate and monetize these stranded and offshore reserves with floating facilitieswhere offshore liquefaction of NG is possible. Therefore, the development of floating LNG (FLNG) technology is becomingimportant. Although the FLNG technologies have advantages over conventional LNG technologies, there arestill several roadblocks. To overcome the challenges, modular designs related to the main and typical stages of the FLNGprocess – gas pretreatment, liquefaction and regasification topsides, hulls, mooring, and transfer systems should beenhanced. Regarding FLNG ongoing operations and future plans, there are six nations (Argentina, Brazil, Kuwait, UAE,UK, and USA) operating FLNG, and a variety of FLNG liquefaction projects will be finished soon. Shell and Petrobrasare making rapid strides to build FLNG facilities, and Flex LNG, Hoegh LNG, SBM Linde, MODEC, and Saipem arealso building their FLNGs. In this review paper, we initially review the LNG concept and compare it with FLNG. Inturn, new and typical FLNG technologies are introduced and the main challenges are also explained with insight intohow these challenges are overcome. The main market drivers for FLNG industry are also considered.

Effect of nafion membrane thickness on performance of vanadium redox flow battery

Sanghyun Jeong,Yongchai Kwon,Sunhoe Kim,Lae-Hyun Kim 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.11

The performance of vanadium redox ow batteries (VRFBs) using different membrane thicknesses wasevaluated and compared. The associated experiments were conducted with Nafion® 117 and 212 membranes that have175 and 50 µm of thickness, respectively. The charge efficiency (CE) and energy efficiency (EE) of VRFB using Nafion®117 were higher than those of VRFB using Nafion® 212, while power efficiency was vice versa. In terms of amountsof charge and discharge that are measured in different charging current densities, the amounts in VRFB using Nafion®212 are more than that in VRFB using Nafion® 117. To further characterize the effect of membrane thickness on VRFBperformance, electrochemical impedance spectroscopy (EIS) and UV-vis. spectrophotometer (UV-vis) were used. InEIS measurements, VRFB using Nafion® 117 was more stable than that using Nafion® 212, while in UV-vis meas-urements, vanadium crossover rate of VRFB usingNafion® 212 (0.0125 M/hr) was higher than that of VRFB usingNafion® 117 (0.0054M/hr). These results are attributed to high crossover rate of vanadium ion in VRFB using Nafion®212. With these results, vanadium crossover plays more dominant role than electrochemical reaction resistance in de-ciding performance of VRFB in condition of different membranes.

Effect of the redox reactivity of vanadium ions enhanced by phosphorylethanolamine based catalyst on the performance of vanadium redox flow battery

Noh, Chanho,Kwon, Byeong Wan,Chung, Yongjin,Kwon, Yongchai Elsevier 2018 Journal of Power Sources Vol.406 No.-

<P><B>Abstract</B></P> <P>Phosphorylethanolamine (PHOS) doped carbon nanotube (CNT) is newly suggested as a catalyst for enhancing the redox reactions of vanadium ions and vanadium redox flow battery (VRFB) performance. For synthesizing the catalyst, CNT is linked to the phosphate group of the PHOS, forming phosphate functionalized carbon nanotube (POH-CNT). Its catalytic activity is then compared with those of pure CNT and carboxylic acid functionalized CNT (CA-CNT) catalysts. Regarding the redox reactivity of vanadium ions, POH-CNT exhibits superior catalytic activity and reaction reversibility for VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> reaction to CNT and CA-CNT because of (i) the chelation ability of phosphate group, (ii) its low electron delocalization capability and (iii) its high acid dissociation constant. By the role as chelating agent of phosphate group, the density of active sites for reaction of VO<SUP>2+</SUP> and VO<SUB>2</SUB> <SUP>+</SUP> ions in POH-CNT increase. Also, the low electron delocalization and high acid dissociation constant induce effective adsorption and desorption of VO<SUP>2+</SUP> and VO<SUB>2</SUB> <SUP>+</SUP> ions. Such effects facilitate the VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> reaction. In contrast, regarding V<SUP>2+</SUP>/V<SUP>3+</SUP> reaction, POH-CNT shows equivalent reactivity to CA-CNT because phosphate and carboxyl groups form similar active sites for the V<SUP>2+</SUP>/V<SUP>3+</SUP> reaction. The above results are supported by calculating kinetic parameters, such as charge transfer resistance and diffusion coefficient, while chemical bonding of the catalysts is examined by XPS. Finally, as the POH-CNT is used as catalyst for positive electrode prompting the VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> reaction, performance of VRFB single cell is improved.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phosphorylethanolamine doped carbon nanotube (POH-CNT) is suggested as catalyst. </LI> <LI> POH-CNT exhibits superior catalytic activity for VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox reaction. </LI> <LI> Chelation ability of phosphate group promotes VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox reaction rate. </LI> <LI> Electron delocalization capability and acid dissociation constant are key factors. </LI> <LI> Performance of VRFB single cell using POH-CNT catalyst is improved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A study on the stability and sensitivity of mediator-based enzymatic glucose sensor measured by catalyst consisting of multilayer stacked via layer-by-layer

이준영,현규환,Yongchai Kwon 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.93 No.-

A catalyst consisting of carbon nanotube, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), polyacrylicacid (PAA), polyethylenimine (PEI), and glucose oxidase (GOx) (CNT/[TEMPO-PAA]/PEI/GOx) isdeveloped to improve the stability and sensitivity of mediator based glucose sensor. In this catalyst,TEMPO is bonded with PAA to prevent the leaching out of TEMPO, which plays a crucial role inincreasing the glucose sensitivity by instilling charges in it. The TEMPO-PAA composite is then linked toother components by electrostatic force. To confirm the chemical structure of the catalyst, its chemicalbonds and surface charge are investigated by Fourier-transform infrared spectroscopy and zetapotential. When the stability and glucose sensitivity are measured, this catalyst preserves 80% of itsinitial catalytic activity for one week although other similar catalysts show far worse stability. Inaddition, the linear relationship of glucose concentration and reactivity of glucose oxidation shown in1–10 mM glucose range that corresponds to actual blood glucose concentration of human beingindicates that this catalyst can induce excellent glucose sensitivity. In terms of selectivity, this catalystreacts with blood glucose highly selectively, whereas this is not reacted with other eight differentsaccharides.

Effect of Carboxylic Acid-Doped Carbon Nanotube Catalyst on the Performance of Aqueous Organic Redox Flow Battery Using the Modified Alloxazine and Ferrocyanide Redox Couple

Lee, Wonmi,Kwon, Byeong Wan,Kwon, Yongchai American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.43

<P>Alloxazine and ferrocyanide are suggested as the redox couple for an aqueous organic redox flow battery (AORFB). Alloxazine is further modified by carboxylic acid (COOH) groups (alloxazine-COOH) to increase the aqueous solubility and to pursue a desirable shift in the redox potential. For obtaining a better AORFB performance, the overall redox reactivity of AORFB should be improved by the enhancement of the rate-determining reaction of the redox couple. A carboxylic acid-doped carbon nanotube (CA-CNT) catalyst is considered for increasing the reactivity. The utilization of CA-CNT allows for the induction of a better redox reactivity of alloxazine-COOH because of the role of COOH within alloxazine-COOH as a proton donor, the fortified hydrophilic attribute of alloxazine-COOH, and the increased number of active sites. With the assistance of these attributes, the mass transfer of aqueous alloxazine-COOH molecules can be promoted. However, CA-CNT does not have an effect on the increase of the redox reactivity of ferrocyanide because the redox reaction is not affected by the same influence of protons that the redox reactivity of alloxazine-COOH is affected by. Such a behavior is proven by measuring the electron transfer rate constant and diffusivity. With regard to AORFB full cell testing, when CA-CNT is used as a catalyst for the negative electrode, the performance of the AORFB increases. Specifically, the charge-discharge overpotential and infrared drop potential are improved. As a result, the voltage efficiency affected by the potentials increases to 64%. Furthermore, the discharging capacity reaches 26.7 A h·L<SUP>-1</SUP>, and the state of charge attains 83% even after 30 cycles.</P> [FIG OMISSION]</BR>

Enzyme precipitate coatings of glucose oxidase onto carbon paper for biofuel cell applications

Fischback, Mike,Kwon, Ki Young,Lee, Inseon,Shin, Su Jeong,Park, Hyun Gyu,Kim, Byoung Chan,Kwon, Yongchai,Jung, Hee‐,Tae,Kim, Jungbae,Ha, Su Wiley Subscription Services, Inc., A Wiley Company 2012 Biotechnology and bioengineering Vol.109 No.2

<P><B>Abstract</B></P><P>Enzymatic biofuel cells (BFC) have a great potential as a small power source, but their practical applications are being hampered by short lifetime and low power density. This study describes the direct immobilization of glucose oxidase (GOx) onto the carbon paper in the form of highly stable and active enzyme precipitation coatings (EPCs), which can improve the lifetime and power density of BFCs. EPCs were fabricated directly onto the carbon paper via a three‐step process: covalent attachment (CA), enzyme precipitation, and chemical crosslinking. GOx‐immobilized carbon papers via the CA and EPC approaches were used as an enzyme anode and their electrochemical activities were tested under the BFC‐operating mode. The BFCs with CA and EPC enzyme anodes produced the maximum power densities of 50 and 250 µW/cm<SUP>2</SUP>, respectively. The BFC with the EPC enzyme anode showed a stable current density output of >700 µA/cm<SUP>2</SUP> at 0.18 V under continuous operation for over 45 h. When a maple syrup was used as a fuel under ambient conditions, it also produced a stable current density of >10 µA/cm<SUP>2</SUP> at 0.18 V for over 25 h. It is anticipated that the direct immobilization of EPC on hierarchical‐structured electrodes with a large surface area would further improve the power density of BFCs that can make their applications more feasible. Biotechnol. Bioeng. 2012; 109:318–324. © 2011 Wiley Periodicals, Inc.</P>