• Title/Summary/Keyword: Zn selective etching

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Fabrication of Porous Cu Layers on Cu Pillars through Formation of Brass Layers and Selective Zn Etching, and Cu-to-Cu Flip-chip Bonding (황동층의 형성과 선택적 아연 에칭을 통한 구리 필라 상 다공성 구리층의 제조와 구리-구리 플립칩 접합)

  • Wan-Geun Lee;Kwang-Seong Choi;Yong-Sung Eom;Jong-Hyun Lee
    • Journal of the Microelectronics and Packaging Society
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    • v.30 no.4
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    • pp.98-104
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    • 2023
  • The feasibility of an efficient process proposed for Cu-Cu flip-chip bonding was evaluated by forming a porous Cu layer on Cu pillar and conducting thermo-compression sinter-bonding after the infiltration of a reducing agent. The porous Cu layers on Cu pillars were manufactured through a three-step process of Zn plating-heat treatment-Zn selective etching. The average thickness of the formed porous Cu layer was approximately 2.3 ㎛. The flip-chip bonding was accomplished after infiltrating reducing solvent into porous Cu layer and pre-heating, and the layers were finally conducted into sintered joints through thermo-compression. With reduction behavior of Cu oxides and suppression of additional oxidation by the solvent, the porous Cu layer densified to thickness of approximately 1.1 ㎛ during the thermo-compression, and the Cu-Cu flip-chip bonding was eventually completed. As a result, a shear strength of approximately 11.2 MPa could be achieved after the bonding for 5 min under a pressure of 10 MPa at 300 ℃ in air. Because that was a result of partial bonding by only about 50% of the pillars, it was anticipated that a shear strength of 20 MPa or more could easily be obtained if all the pillars were induced to bond through process optimization.

Selective fabrication and etching of vertically aligned Si nanowires for MEMS

  • Kar, Jyoti Prakash;Moon, Kyeong-Ju;Das, Sachindra Nath;Kim, Sung-Yeon;Xiong, Junjie;Choi, Ji-Hyuk;Lee, Tae-Il;Myoung, Jae-Min
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2010.05a
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    • pp.27.2-27.2
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    • 2010
  • In recent years, there is a strong requirement of low cost, stable microelectro mechanical systems (MEMS) for resonators, microswitches and sensors. Most of these devices consist of freely suspended microcantilevers, which are usually made by the etching of some sacrificial materials. Herein, we have attempted to use Si nanowires, inherited from the parent Si wafer, as a sacrificial material due to its porosity, low cost and ease of fabrication. Prior to the fabrication of the Si nanowires silver nanoparticles were continuously formed on the surface of Si wafer. Vertically aligned Si nanowires were fabricated from the parent Si wafers by aqueous chemical route at $50^{\circ}C$. Afterwards, the morphological and structural characteristics of the Si nanowires were investigated. The morphology of nanowires was strongly modulated by the resistivity of the parent wafer. The 3-step etching of nanowires in diluted KOH solution was carried out at room temperature in order to control the fast etching. A layer of $Si_3N_4$ (300 nm) was used for the selective fabrication of nanowires. Finally, a freely suspended bridge of zinc oxide (ZnO) was fabricated after the removal of nanowires from the parent wafer. At present, we believe that this technique may provide a platform for the inexpensive fabrication of futuristic MEMS.

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Synthesis and Formation Mechanism of ZnO Nanotubes via an Electrochemical Method (전기화학적 방법에 의한 산화아연 나노튜브의 합성과 형성 기구)

  • Moon, Jin Young;Kim, Hyunghoon;Lee, Ho Seong
    • Korean Journal of Metals and Materials
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    • v.49 no.5
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    • pp.400-405
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    • 2011
  • ZnO nanotube arrays were synthesized by a two-step process: electrodeposition and selective dissolution. In the first step, ZnO nanorod arrays were grown on an Au/Si substrate by using a homemade electrodeposition system. ZnO nanorod arrays were then selectively dissolved in an etching solution composed of 0.125 M NaOH, resulting in hollow ZnO nanotube arrays. It is suggested that the formation mechanism of the ZnO nanotube arrays might be attributed to the preferred surface adsorption of hydroxide ion ($OH^{-1}$) on a positive polar surface followed by selective dissolution of the metastable Zn-terminated ZnO (0001) polar surface caused by the difference in the surface energy per unit area between the ZnO nanorod and nanotube.

Self-assembly of ZnO Stripes Prepared by Anodization in an Ethanolic Sulfuric Acid (에탄올/황산 혼압액에서 양극산화법을 이용한 자기정렬된 ZnO 줄무늬 구조 제조 연구)

  • Kim, Sung Joong;Choi, Jinsub
    • Korean Chemical Engineering Research
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    • v.46 no.4
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    • pp.686-691
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    • 2008
  • There are no many research reports on the preparation of ZnO by electrochemical oxidation since the zinc oxide is very easily dissolved in an acidic or basic environment, even though zinc oxides have attracted many attentions because of their optical/electrical properties. In this paper, we describe the fabrication of self-ordered stripes of ZnO by anodization of Zn in an ethanolic sulfuric acid. The formation of stripes of ZnO originating from Zn is attributed to water-selective dissolution of ZnO during anodization. We study in detail the effects of concentration of $H_2SO_4$, applied potential, anodization time, and addition of a small amount of water on the fabrication of stripes of ZnO. Mechanisms for the fabrication of ZnO stripes are discussed in terms of the above-mentioned effects.

Conformal coating of Al-doped ZnO thin film on micro-column patterned substrate for TCO (TCO 응용을 위한 패턴된 기판위에 증착된 AZO 박막의 특성 연구)

  • Choi, M.K.;Ahn, C.H.;Kong, B.H.;Cho, H.K.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.28-28
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    • 2009
  • Fabrications of antireflection structures on solar cell were investigated to trap the light and to improve quantum efficiency. Introductions of patterned substrate or textured layer for Si solar cell were performed to prevent reflectance and to increase the path length of incoming light. However, it is difficult to deposit conformally flat electrode on perpendicular plane. ZnO is II-VI compound semiconductor and well-known wide band-gap material. It has similar electrical and optical properties as ITO, but it is nontoxic and stable. In this study, Al-doped ZnO thin films are deposited as transparent electrode by atomic layer deposition method to coat on Si substrate with micro-scale structures. The deposited AZO layer is flatted on horizontal plane as well as perpendicular one with conformal 200 nm thickness. The carrier concentration, mobility and resistivity of deposited AZO thin film on glass substrate were measured $1.4\times10^{20}cm^{-3}$, $93.3cm^2/Vs$, $4.732\times10^{-4}{\Omega}cm$ with high transmittance over 80%. The AZO films were coated with polyimide and performed selective polyimide stripping on head of column by reactive ion etching to measure resistance along columns surface. Current between the micro-columns flows onto the perpendicular plane of deposited AZO film with low resistance.

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Energy band gap of $Zn_{0.86}Mn_{0.14}Te$ epilayer grown on GaAs(100) substrates (GaAs(100)기판 위에 성장된 $Zn_{0.86}Mn_{0.14}Te$에피막의 띠 간격 에너지)

  • 최용대;안갑수;이광재;김성구;심석주;윤희중;유영문;김대중;정양준
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.3
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    • pp.122-126
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    • 2003
  • In this study, $Zn_{0.86}Mn_{0.14}$Te epilayer of 0.7 $\mu\textrm{m}$-thickness was grown on GaAs(100) substrate by using hot wallepitaxy. GaAs(100) substrate was removed from $Zn_{0.86}Mn_{0.14}$Teepilayer by the selective etching solution. The crystal structure and the lattice constant of only Z $n_{0.86}$ M $n_{0.14}$Te epilayer were investigated to be zincblende and 6.140 $\AA$ from X-ray diffraction pattern, respectively. Mn composition x of $Zn_{1-x}Mn_x$Te epilayer was found to be 0.14 using this lattice constant and Vegard's law. The crystal quality of the epilayer was confirmed to be very good due to 256 arcsec-full-width at half-maximum of the double crystal rocking curve. The absorption spectra from the transmission ones were obtained to measure the band gap energy of $Zn_{0.86}Mn_{0.14}$Te epilayer from 300 K to 10 K. With the decreasing temperature,. strong absorption regions in the absorption spectra were shifted to higher energy side and the absorption peak meaning the free exciton formation appeared near the absorption edge. The band gap energy values of $Zn_{0.86}Mn_{0.14}$Te epilayer at 0 K and 300 K were found to be almost 2.4947 eV and 2.330 eV from the temperature dependence of the free exciton peak position energy of $Zn_{0.86}Mn_{0.14}$Te epilayer, respectively. The free exciton peak position energy of $Zn_{0.86}Mn_{0.14}$Te epilayer without GaAs substrate was larger 15.4 meV than photoluminescence peak position energy at 10 K. This energy difference between two peaks was analysed to be Stokes shift.