• Title/Summary/Keyword: Ni/Co composite silicide

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Characterizatics of Composite Silicides from Co/Ni Structure (코발트/니켈 적층구조 박막으로부터 형성된 복합실리사이드)

  • Song Ohsung;Cheong Seonghwee;Kim Dugjoong;Choi Yongyun
    • Korean Journal of Materials Research
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    • v.14 no.11
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    • pp.769-774
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    • 2004
  • 15 nm-Co/15 nm-Ni/P-Si(100)[Type I] and 15 nm-Ni/15 nm-Co/P-Si(100)(Type II) bilayer structures were annealed using a rapid thermal annealer for 40sec at $700/sim1100^{\circ}C$. The annealed bilayer structures developed into composite NiCo silicides and resulting changes in sheet resistance, composition and microstructure were investigated using Auger electron spectroscopy and transmission electron microscopy. Prepared NiCoSix films were further treated in a sequential annealing set up from $900\sim1100^{\circ}C$ with 30 minutes. The sheet resistances of NiCoSix from Type I maintained less than $7\;{\Omega}/sq$. even at the temperature of $1100{\circ}C$, while those of Type II showed about $5\;{\Omega}/sq$. with the thinner and more uniform thickness. With the additive post annealing, the sheet resistance for all the composite silicides remained small up to $900^{\circ}C$. The proposed NiCoSix films were superior over the conventional single-phased silicides and may be easily incorporated into the sub-0.1 ${\mu}m$ process.

Reaction Stability of Co/Ni Composite Silicide on Side-wall Spacer with Silicidation Temperatures (Co/Ni 복합 실리사이드 제조 온도에 따른 측벽 스페이서 물질 반응 안정성 연구)

  • Song, Oh-Sung;Kim, Sang-Yeob;Jung, Young-Soon
    • Journal of the Korean institute of surface engineering
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    • v.38 no.3
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    • pp.89-94
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    • 2005
  • We investigate the reaction stability of cobalt and nickel with side-wall materials of $SiO_2\;and\;Si_3N_4$. We deposited 15nm-Co and 15nm-Ni on $SiO_2(200nm)/p-type$ Si(100) and $Si_3N_4(70 nm)/p-type$ Si(100). The samples were annealed at the temperatures of $700\~1100^{\circ}C$ for 40 seconds with a rapid thermal annealer. The sheet resistance, shape, and composition of the residual materials were investigated with a 4-points probe, a field emission scanning electron microscopy, and an AES depth profiling, respectively. Samples of annealed above $1000^{\circ}C$ showed the agglomeration of residual metals with maze shape and revealed extremely high sheet resistance. The Auger depth profiling showed that the $SiO_2$ substrates had no residual metallic scums after $H_2SO_4$ cleaning while $Si_3N_4$ substrates showed some metallic residuals. Therefore, the $SiO_2$ spacer may be appropriate than $Si_3N_4$ for newly proposed Co/Ni composite salicide process.

Sheet Resistance and Microstructure Evolution of Cobalt/Nickel Silicides with Annealing Temperature (코발트/니켈 복합실리사이드의 실리사이드온도에 따른 면저항과 미세구조 변화)

  • Jung Young-soon;Cheong Seong-hwee;Song Oh-sung
    • Korean Journal of Materials Research
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    • v.14 no.6
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    • pp.389-393
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    • 2004
  • The silicide layer used as a diffusion barrier in microelectronics is typically required to be below 50 nm-thick and, the same time, the silicides also need to have low contact resistance without agglomeration at high processing temperatures. We fabricated Si(100)/15 nm-Ni/15 nm-Co samples with a thermal evaporator, and annealed the samples for 40 seconds at temperatures ranging from $700^{\circ}C$ to $1100^{\circ}C$ using rapid thermal annealing. We investigated microstructural and compositional changes during annealing using transmission electron microscopy and auger electron spectroscopy. Sheet resistance of the annealed sample stack was measured with a four point probe. The sheet resistance measurements for our proposed Co/Ni composite silicide was below 8 $\Omega$/sq. even after annealing $1100^{\circ}C$, while conventional nickel-monosilicide showed abrupt phase transformation at $700^{\circ}C$. Microstructure and auger depth profiling showed that the silicides in our sample consisted of intermixed phases of $CoNiSi_{x}$ and NiSi. It was noticed that NiSi grew rapidly at the silicon interface with increasing annealing temperature without transforming into $NiSi_2$. Our results imply that Co/Ni composite silicide should have excellent high temperature stability even in post-silicidation processes.

Characteristics and Microstructure of Co/Ni Composite Silicides on Polysilicon Substrates with Annealing Temperature (폴리실리콘 기판 위에 형성된 코발트 니켈 복합실리사이드 박막의 열처리 온도에 따른 물성과 미세구조변화)

  • Kim, Sang-Yeob;Song, Oh-Sung
    • Korean Journal of Materials Research
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    • v.16 no.9
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    • pp.564-570
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    • 2006
  • Silicides have been required to be below 40 nm-thick and to have low contact resistance without agglomeration at high silicidation temperature. We fabricated composite silicide layers on the wafers from Ni(20 nm)/Co(20 nm)/poly-Si(70 nm) structure by rapid thermal annealing of $700{\sim}1100^{\circ}C$ for 40 seconds. The sheet resistance, surface composition, cross-sectional microstructure, and surface roughness were investigated by a four point probe, a X-ray diffractometer, an Auger electron spectroscopy, a field emission scanning electron microscope, and a scanning probe microscope, respectively. The sheet resistance increased abruptly while thickness decreased as silicidation temperature increased. We propose that the fast metal diffusion along the silicon grain boundary lead to the poly silicon mixing and inversion. Our results imply that we may consider the serious thermal instability in designing and process for the sub-0.1 um CMOS devices.

Micro-pinholes in Composite Cobalt Nickel Silicides (코발트 니켈 합금 구조에서 생성된 실리사이드의 마이크로 핀홀의 발생)

  • Song, Oh-Sung;Kim, Sang-Yeob;Jeon, Jang-Bae;Kim, M.J.
    • Korean Journal of Materials Research
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    • v.16 no.10
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    • pp.656-662
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    • 2006
  • We fabricated thermal evaporated 10 nm-$Ni_xCo_{1-x}$ (x=0.2, 0.5 and 0.8) /(poly)Si films to form nanothick cobalt nickel composite silicides by a rapid thermal annealing at $700{\sim}1100^{\circ}C$ for 40 seconds. A field emission scanning electron microscope and a micro-Raman spectrometer were employed for microstructure and silicon residual stress characterization, respectively. We observed self-aligned micro-pinholes on single crystal silicon substrates silicidized at $1100^{\circ}C$. Raman silicon peak shift indicates that the residual tensile strain of $10^{-3}$ in single crystal silicon substrates existed after the silicide process. We propose thermal stress from silicide exothermic reaction and high temperature silicidation annealing may cause the pinholes. Those pinholes are expected to be avoided by lowering the silicidation temperature. Our results imply that we may use our newly proposed composite silicides to induce the appropriate strained layer in silicion substrates.

Silicidation Reaction Stability with Natural Oxides in Cobalt Nickel Composite Silicide Process (자연산화막 존재에 따른 코발트 니켈 복합실리사이드 공정의 안정성)

  • Song, Oh-Sung;Kim, Sang-Yeob;Kim, Jong-Ryul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.1
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    • pp.25-32
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    • 2007
  • We investigated the silicide reaction stability between 10 nm-Col-xNix alloy films and silicon substrates with the existence of 4 nm-thick natural oxide layers. We thermally evaporated 10 nm-Col-xNix alloy films by varying $x=0.1{\sim}0.9$ on naturally oxidized single crystal and 70 nm-thick polycrystalline silicon substrates. The films structures were annealed by rapid thermal annealing (RTA) from $600^{\circ}C$ to $1100^{\circ}C$ for 40 seconds with the purpose of silicidation. After the removal of residual metallic residue with sulfuric acid, the sheet resistance, microstructure, composition, and surface roughness were investigated using a four-point probe, a field emission scanning electron microscope, a field ion bean4 an X-ray diffractometer, and an Auger electron depth profiling spectroscope, respectively, to confirm the silicide reaction. The residual stress of silicon substrate was also analyzed using a micro-Raman spectrometer We report that the silicide reaction does not occur if natural oxides are present. Metallic oxide residues may be present on a polysilicon substrate at high silicidation temperatures. Huge residual stress is possible on a single crystal silicon substrate at high temperature, and these may result in micro-pinholes. Our results imply that the natural oxide layer removal process is of importance to ensure the successful completion of the silicide process with CoNi alloy films.

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Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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