• Title, Summary, Keyword: NiSi

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Effect of Co substitution on NiSi and $NiSi_2$: ab initio calculation (NiSi와 $NiSi_2$에 대한 Co 치환의 영향: ab initio 계산)

  • Kim, Yeong-Cheol;Seo, Hwa-Il
    • Journal of the Semiconductor & Display Technology
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    • v.6 no.3
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    • pp.13-17
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    • 2007
  • Effect of Co substitution on crystal structures of two nickel silicides, NiSi and $NiSi_2$, is investigated by using an ab initio calculation. Relaxed NiSi and $NiSi_2$ structures are calculated and the calculated lattice parameters are in good agreement with experimentally determined lattice parameters within about 2%. A Co atom substitutes a Ni and Si site, respectively, to evaluate the preferable site between them. Co prefers Ni site to Si site in both NiSi and $NiSi_2$. The calculated total energy also indicates that the Co substitution to Ni site stabilizes both the NiSi and $NiSi_2$ structures. Co also prefers Ni site in $NiSi_2$ to that in NiSi, indicating that $NiSi_2$ becomes more stable than NiSi with Co substitution. As Co addition to NiSi improves its thermal stability experimentally, this indicates that the energy barrier between the two phases is high enough to prevent the phase transformation from NiSi to $NiSi_2$ up to high temperature.

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Interdiffusion in Cu/Capping Layer/NiSi Contacts (Cu/Capping Layer/NiSi 접촉의 상호확산)

  • You, Jung-Joo;Bae, Kyoo-Sik
    • Korean Journal of Materials Research
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    • v.17 no.9
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    • pp.463-468
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    • 2007
  • The interdiffusion characteristics of Cu-plug/Capping Layer/NiSi contacts were investigated. Capping layers were deposited on Ni/Si to form thermally-stable NiSi and then were utilized as diffusion barriers between Cu/NiSi contacts. Four different capping layers such as Ti, Ta, TiN, and TaN with varying thickness from 20 to 100 nm were employed. When Cu/NiSi contacts without barrier layers were furnace-annealed at $400^{\circ}C$ for 40 min., Cu diffused to the NiSi layer and formed $Cu_3Si$, and thus the NiSi layer was dissociated. But for Cu/Capping Layers/NiSi, the Cu diffusion was completely suppressed for all cases. But Ni was found to diffuse into the Cu layer to form the Cu-Ni(30at.%) solid solution, regardless of material and thickness of capping layers. The source of Ni was attributed to the unreacted Ni after the silicidation heat-treatment, and the excess Ni generated by the transformation of $Ni_2Si$ to NiSi during long furnace-annealing.

Epitaxial Growth of Nickel Silicide $(NiSi_2)$ in Vacuum Deposited Nickel and Gold Films on (III) Silicon Single Crystals (규소(III) 단 결정에 진공 증착한 닉켈과 금 박막에서 $NiSi_2$의 적층성장)

  • 윤기현;이희수
    • Journal of the Korean Ceramic Society
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    • v.13 no.3
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    • pp.55-62
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    • 1976
  • 순수한 닉켈과 금 박막을 (III)규소 단 결정위에 진공 증착시켰다. Ni/Au/Si나 Au/Ni/Si시료를 진공중에서 약 55$0^{\circ}C$로 가열하였을 때 육방정 혹은 변형된 육방정의 미소 결정들이 규소 기질위에 형성되었다. 이들 미소 결정들의 형성과정 및 조성은 X-선 회절법, scanning electron microscopy 및 scanning Auger microprobe 법을 사용하여 결정하였다. 이들 미소 결정은 NiSi2임이 확인되었다. Ni/Au/Si 시료에서는 Au-Si 공융점(37$0^{\circ}C$) 이상으로 온도가 증가됨에 따라 닉켈과 규소가 Au-Si 공융체 속으로 이동한 후 반응하여 NiSi2를 형성하였다. Au/Ni/Si 시료에 있어서의 Au-Si 공융체 형성은 닉켈 박막에 있는 바늘구멍형의 표면 결함과 관련 지을 수 있겠다. 금이 닉켈 박막의 grain boundary를 통하여 Ni/Si 계면으로 확산되어 그 계면을 습윤시킨 다음 Au-Si 공융체를 형성하였다. 이런 Au-Si 공용체는 닉켈과 규소 원자에 대한 높은 확산 매질로서 작용하여 NiSi2 형성을 촉진시켰다. 표면에 평행한 (III)규소면 위의 NiSi2 미소 결정은 유사한 육방정으로 나타났으며, 경사진 미소결정은 부등변 사변형과 유사하였다. Auger 스펙트럼 및 Ni, Au 및 Si에 대한 내층조성(indepth Composition Profiles)은 NiSi2 미소 결정이 Au-Si 공융체의 matrix에 미소 부분으로 나타났음을 보여주었다.

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A Study on the Thermal Stability of Cu/Ti(Ta)/NiSi Contacts (Cu/Ti(Ta)/NiSi 접촉의 열적안정성에 관한 연구)

  • You, Jung-Joo;Bae, Kyoo-Sik
    • Korean Journal of Materials Research
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    • v.16 no.10
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    • pp.614-618
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    • 2006
  • The thermal stability of Cu/Ti(or Ta)/NiSi contacts was investigated. Ti(Ta)-capping layers deposited to form NiSi was utilized as the Cu diffusion barrier. Ti(Ta)/NiSi contacts was thermally stable upto $600^{\circ}C$. However when Cu/Ti(Ta)/NiSi contacts were furnace-annealed at $300{\sim}400^{\circ}C$ for 40 min., the Cu diffusion was found to be effectively suppressed, but NiSi was dissociated and then Ni diffused into the Cu layer to form Cu-Ni solutions. On the other hand, the Ni diffusion did not occur for the Al/Ti/NiSi system. The thermal instability of Cu/Ti(Ta)/NiSi contacts was attributed to the high heat of solution of Ni in Cu.

Structural Study of Interface Layers in Tetragonal-NiSi (010)/Si using Density Functional Theory (밀도범함수를 이용한 정방정계-NiSi (010)/Si 계면 층의 구조 연구)

  • Kim, Dae-Hee;Kim, Dae-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.5
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    • pp.377-381
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    • 2009
  • Tetragonal-NiSi (010)/Si superstructures were calculated for studying the interface structure using density functional theory, The orthorhombic-NiSi was changed to the tetragonal-NiSi to be matched with the Si surface for epitaxy interface. The eight interface models were produced by the type of the Si surfaces, The tetragonal-NiSi (010)/Si (020)[00-1] superstructure was energetically the most favorable, and the interface thickness of this superstructure was the shortest among the tetragonal-NiSi (010)/Si superstructures. However, in the case of tetragonal-NiSi (010)/Si (010)[00-1] superstructure, it was energetically the most unfavorable, and the interface thickness was the longest. The energies and interface thicknesses of tetragonal-NiSi (010)/Si superstructures were influenced by the coordination number of Ni atoms and the bond length between atoms located at the interface.

Structural Study of Tetragonal-Ni1-xPdxSi/Si (001) Using Density Functional Theory (DFT) (Density Functional Theory (DFT)를 이용한 Tetragonal-Ni1-xPdxSi/Si (001)의 구조 연구)

  • Kim, Dae-Hee;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Korean Journal of Materials Research
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    • v.18 no.9
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    • pp.482-485
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    • 2008
  • Tetragonal-$Ni_{1-x}Pd_x$Si/Si (001) structure was studied by using density functional theory (DFT). An epitaxial interface between $2{\times}2{\times}4$ (001) tetragonal-NiSi supercell and $1{\times}1{\times}2$ (001) Si supercell was first constructed by adjusting the lattice parameters of B2-NiSi structure to match those of the Si structure. We chose Ni atoms as a terminating layer of the B2-NiSi; the equilibrium gap between the tetragonal-NiSi and Si was calculated to be 1.1 ${\AA}$. The Ni atoms in the structure moved away from the original positions along the z-direction in a systematic way during the energy minimization. Two different Ni sites were identified at the interface and the bulk, respectively. The two Ni sites at the interface have 6 and 7 coordination numbers. The Ni sites with coordination number 6 at the interface were located farther away from the interface, and were more favorable for Pd substitution.

Study of Pd substitution in orthorhombic-NiSi/Si (010) structure: First principles calculation (Orthorhombic-NiSi/Si (010) 구조의 Pd 치환 연구: 제 1 원리 계산)

  • Kim, Dae-Hee;Kim, Dae-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Semiconductor & Display Technology
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    • v.7 no.4
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    • pp.41-44
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    • 2008
  • NiSi is less stable than the previously-used $CoSi_2$ at high temperature. Some noble metals, such as Pd and Pt, have been added to NiSi to improve its thermal stability. We employed a first principles calculation to understand the Pd segregation at the interface. An orthorhombic structure of NiSi was used to construct an orthorhombic-NiSi/Si (010). Lattice parameters along a- and c-axes in orthorhombic-NiSi were matched with those of Si for epitaxy contact. The optimized $1\times4\times1$ orthorhombic-NiSi (010) and $1\times2\times1$ Si (010) superstructures were put together to construct the orthorhombic-NiSi/Si (010), and the superstructure was relieved in calculation to minimize its total free energy. The optimized interface thickness of the superstructure was $1.59\AA$. Pd atom was substituted in Ni and Si sites located near interface. Both Ni and Si sites located at the interface were favorable for Pd substitution.

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Fabrications and Characterization of High Temperature, High Voltage Ni/6H-SiC and Ni/4H-SiC Schottky Barrier Diodes (고온, 고전압 Ni/4H-SiC 및 Ni/6H-SiC Schottky 다이오드의 제작 및 전기적 특성 연구)

  • Lee, Ho-Seung;Lee, Sang-Wuk;Shin, Dong-Hyuk;Park, Hyun-Chang;Jung, Woong
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.35D no.11
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    • pp.70-77
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    • 1998
  • Ni/SiC Schottky diodes have been fabricated using epitaxial 4H-SiC and 6H-SiC wafers. The epitaxial n-type layers were grown on $n^{+}$ substrates, with a doping density of 4.0$\times$10$^{16}$ c $m^{-3}$ and a thickness of 10${\mu}{\textrm}{m}$. Oxide-termination has been adopted in order to obtain high breakdown voltage and low leakage current. The fabricated Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes show excellent rectifying characteristics up to the measured temperature range of 55$0^{\circ}C$. In case of oxide-terminated Schottky barrier diodes, breakdown voltage of 973V(Ni/4H-SiC) and 920V(Ni/6H-SiC), and a very low leakage current of less than 1nA at -800V has been observed at room temperature. On non-terminated Schottky barrier diodes, breakdown voltages were 430V(Ni/4H-SiC) and 160v(Ni/6H-SiC). At room temperature, SBH(Schottky Barrier Height), ideality factor and specific on-resistance were 1.55eV, 1.3, 3.6$\times$10$^{-2}$ $\Omega$.$\textrm{cm}^2$ for Ni/4H-SiC Schottky barrier diodes, and 1.24eV, 1.2, 2.6$\times$10$^{-2}$$\Omega$.$\textrm{cm}^2$/ for Ni/SH-SiC Schottky barrier diodes, respectively. These results show that both Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes are very promising for high-temperature and high power applications.s..

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Enhancement of Crystallinity and Exchange Bias Field in NiFe/FeMn/NiFe Trilayer with Si Buffer Layer Fabricated by Ion-Beam Deposition (이온 빔 증착법으로 제작한 NiFe/FeMn/NiFe 3층박막의 버퍼층 Si에 따른 결정성 및 교환결합세기 향상)

  • Kim, Bo-Kyung;Kim, Ji-Hoon;Hwang, Do-Guwn;Lee, Sang-Suk
    • Journal of the Korean Magnetics Society
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    • v.12 no.4
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    • pp.132-136
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    • 2002
  • Enhancement of crystallinity and exchange bias characteristics for NiFe/FeMn/NiFe trilayer with Si buffer layer fabricated by ion-beam deposition were examined. A Si buffer layer promoted (111) texture of fcc crystallities in the initial growth region of NiFe layer deposited on it. FeMn layers deposited on Si/NiFe bilayer exhibited excellent (111) crystal texture. The antiferromagnetic FeMn layer between top and bottom NiFe films with the buffer Si 50 ${\AA}$-thick induced a large exchange coupling field Hex with a different dependence. It was found that H$\sub$ex/ of the bottom and top NiFe films with Si buffer layer revealed large value of about 110 Oe and 300 Oe, respectively. In the comparison of two Ta and Si buffer layers, the NiFe/FeMn/NiFe trilayer with Si could possess larger exchange coupling field and higher crystallinity.

A Study on the Formation of Ti-capped NiSi and it′s Thermal Stability (Ti-capped NiSi 형성 및 열적안정성에 관한 연구)

  • 박수진;이근우;김주연;배규식
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.288-291
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    • 2002
  • Application of metal silicides such as TiSi$_2$ and CoSi$_2$ as contacts and gate electrodes are being studied. However, TiSi$_2$ due to the linewidth-dependance, and CoSi$_2$ due to the excessive Si consumption during silicidation cannot be applied to the deep-submicron MOSFET device. NiSi shows no such problems and can be formed at the low temperature. But, NiSi shows thermal instability. In this investigation, NiSi was formed with a Ti-capping layer to improve the thermal stability. Ni and Ti films were deposited by the thermal evaporator. The samples were then annealed in the N$_2$ ambient at 300-800$^{\circ}C$ in a RTA (rapid thermal annealing) system. Four point probe, FESEM, and AES were used to study the thermal properties of Ti-capped NiSi layers. The Ti-capped NiSi was stable up to 700$^{\circ}C$ for 100 sec. RTA, while the uncapped NiSi layers showed high sheet resistance after 600$^{\circ}C$. The AES results revealed that the Ni diffusion further into the Si substrate was retarded by the capping layer, resulting in the suppression of agglomeration of NiSi films.

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