• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.968-972
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• 2008

Ni/Ti/Al multilayer system ('/'denotes the deposition sequence) was tested for low-resistance ohmic contact formation to Al-implanted p-type 4H-SiC. Ni 30 nm / Ti 50 nm / Al 300 nm layers were sequentially deposited by e-beam evaporation on the 4H-SiC samples which were implanted with Al (norminal doping concentration = $4\times10^{19}cm^{-3}$) and then annealed at $1700^{\circ}C$ for dopant activation. Rapid thermal anneal (RTA) temperature for ohmic contact formation was varied in the range of $840\sim930^{\circ}C$. Specific contact resistances were extracted from the measured current vs. voltage (I-V) data of linear- and circular transfer length method (TLM) patterns. In constrast to Ni contact, Ni/Ti/Al contact shows perfectly linear I-V characteristics, and possesses much lower contact resistance of about $2\sim3\times10^{-4}\Omega{\cdot}cm^2$ even after low-temperature RTA at $840^{\circ}C$, which is about 2 orders of magnitude smaller than that of Ni contact. Therefore, it was shown that RTA temperature for ohmic contact formation can be lowered to at least $840^{\circ}C$ without significant compromise of contact resistance. X-ray diffraction (XRD) analysis indicated the existence of intermetallic compounds of Ni and Al as well as $NiSi_{1-x}$, but characteristic peaks of $Ti_{3}SiC_2$, a probable narrow-gap interfacial alloy responsible for low-resistance Ti/Al ohmic contact formation, were not detected. Therefore, Al in-diffusion into SiC surface region is considered to be the dominant mechanism of improvement in conduction behavior of Ni/Ti/Al contact.

• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.25-28
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• 2007

Electroless Ni-P coating is widely used for chemical, electronic, and semiconductor equipment parts because of its corrosion resistance. The incorporation of chemically-inert PTFE particles into the Ni-P films improves properties such as, non-stick, anti-adhesive and better corrosion resistance. However, soft PTFE particles degrade the hardness, wear and abrasion resistance. In this study, effects of PTFE and W addition to the Ni-P-coatings were compared by the XRD, SEM, sheet resistance, contact angle, and microhardness measurements. The change in sheet resistance was negligible, but contact angle was doubled by the addition of PTFE and W. The microhardness was lower for Ni-P-PTFE, but higher for Ni-P-PTFE-W coatings, compared to that of Ni-P coatings.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.10
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• pp.495-499
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• 2004

Characteristics of ohmic Ni/Si/Ni contacts to n-type 4H-SiC are investigated systematically. The ohmic contacts were formed by annealing Ni/Si/Ni sputtered sequentially The annealings were performed at 950℃ using RTP in vacuum ambient and N₂ ambient, respectively. The specific contact resistivity(p/sub c/), sheet resistance(R/sub s/), contact resistance (R/sub c/) transfer length(L/sub T/) were calculated from resistance(R/sub T/) versus contact spacing(d) measurements obtained from TLM(transmission line method) structure. While the resulting measurement values of sample annealed at vacuum ambient were p/sub c/ = 3.8×10/sup -5/Ω㎠, R/sub c/ = 4.9 Ω and R/sub T/ = 9.8 Ω, those of sample annealed at N₂ ambient were p/sub c/ = 2.29×10/sup -4/Ω㎠, R/sub c/ = 12.9 Ω and R/sub T/ = 25.8 Ω. The physical properties of contacts were examined using XRD 3nd AES. The results showed that nickel silicide was formed on SiC and Ni was migrated into SiC. This result indicates that Ni/Si/Ni ohmic contact would be useful in high performance electronic devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.6-10
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• 2018

Ni germanide (NiGe) is a promising alloy material with small contact resistance at the source/drain (S/D) of Ge MOSFETs. However, it is necessary to reduce the specific contact resistance between NiGe and the doped Ge S/D region in high-performance MOSFETs. In this study, a novel method is proposed to reduce the specific contact resistance between NiGe and p-type Ge (p-Ge) using a Tb interlayer. The specific contact resistance between NiGe and p-Ge was successfully decreased with the introduction of the Tb interlayer. To investigate the mechanism behind the reduction in the specific contact resistance, the elemental distribution and crystalline structure of NiGe were analyzed using secondary ion mass spectroscopy and X-ray diffraction. It is likely that the reduction in specific contact resistance was caused by an increase in the concentration of boron in the space between NiGe and p-Ge due to the influence of the Tb interlayer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.208-209
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• 2008

Ni/Ti/Al multilayer system was tested for low-resistance ohmic contact formation to Al-implanted p-type 4H-SiC. Compared with conventional process using Ni, Ni/Ti/Al contact shows perfect ohmic behavior, and possesses much lower contact resistance of about $2.5\times10^{-4}\Omega{\cdot}cm^2$ after $930^{\circ}C$ RTA, which is about 2 orders of magnitude smaller than that of Ni contact. Contact resistance gradually increased as the RTA temperature was lowered in the range of 840 ~ $930^{\circ}C$, and about $3.4\times10^{-4}\Omega{\cdot}cm^2$ was obtained at the lowest RTA temperature of $840^{\circ}C$. Therefore, it was shown that RTA temperature for ohmic contact formation can be lowered to at least $840^{\circ}C$ without significant compromise of contact resistance.

• Korean Journal of Materials Research
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• v.16 no.7
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• pp.430-434
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• 2006

Au/Ni coatings are widely used in the electrical interconnect system, such as connectors, sockets and wire crimps. But due to repeated mechanical contacts, fretting corrosion occurs and causes a rapid increase in resistance. As an attempt to resolve these problem, application of Ni-P-PTFE to replace Ni undercoats was proposed, for which basic materials properties of Ni-P-PTFE coatings for preventing fretting corrosion was examined in this study. The Ni-P-PTFE coatings were formed by electroless Ni plating and PTFE coating followed by the heat-treatment. PTFE particles were found to be uniformly distributed in the Ni-P matrix. The Ni-P-PTFE coatings showed the excellent anti-adherent property with the contact angle of $104.3^{\circ}$, microhardness of 144.3 Hv comparable to that of Ni-P, and electric conductivity equivalent to that of Ni-P.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.717-723
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• 2009

Ni/Al ('/' denotes deposition sequence) contacts were deposited on Al-implanted 4H-SiC for ohmic contact formation, and the conduction properties were characterized and compared with those of Ni-only contacts. The thicknesses of the Ni and Al thin film were 30 nm and 300 nm, respectively, and the films were sequentially deposited bye-beam evaporation without vacuum breaking. Rapid thermal anneal (RTA) temperature was varied as follows : $840^{\circ}C$, $890^{\circ}C$, and $940^{\circ}C$. The specific contact resistivity of the Ni contact was about $^{\sim}2\;{\pm}\;10^{-2}\;{\Omega}{\cdot}cm^2$, However, with the addition of Al overlayer, the specific contact resistivity decreased to about $^{\sim}2\;{\pm}\;10^{-4}\;{\Omega}{\cdot}cm^2$, almost irrespective of RTA temperature. X-ray diffraction (XRD) analysis of the Ni contact confirmed the existence of various Ni silicide phases, while the results of Ni/Al contact samples revealed that Al-contaning phases such as $Al_3Ni$, $Al_3Ni_2$, $Al_4Ni_3$, and $Ab_{3.21}Si_{0.47}$ were additionally formed as well as the Ni silicide phases. Energy dispersive spectroscopy (EDS) spectrum showed interfacial reaction zone mainly consisting of Al and Si at the contact interface, and it was also shown that considerable amounts of Si and C have diffused toward the surface. This indicates that contact resistance lowering of the Ni/Al contacts is related with the formation of the formation of interfacial reaction zone containing Al and Si. From these results, possible mechanisms of contact resistance lowering by the addition of Al were discussed.

• Electrical & Electronic Materials
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• v.3 no.4
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• pp.325-331
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• 1990

본 연구는 텅스텐 소결에 저온 활성제로 작용하는 Ni-P 공정합금을 미량첨가하여 제조공정의 간단화를 통한 새로운 W-Cu계 전기접점제조를 목표로 하였다. 이를 위해 1회 용침공정을 통해 제조한 W(Ni-P)-Cu 합금에 대한 전기접점특성을 조사하여 접점의 미세구조 관점에서 논의하였다. Ni-P 합금첨가한 접점은 기존의 순수 W-Cu 합금에 비해 낮은 접촉저항 및 낮은 아크소모를 나타내는 우수한 접점성능을 보여주었다. 이것은 Ni-P합금이 Cu용침이 개시되기전 짧은 승온단계에서 분말간의 강한 결합과 Cu용침에 유리한 기공통로를 갖는 W 분말 골격체의 형성을 유도하기 때문인 것으로 판단된다.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.443-446
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• 2009

This study develops a highly transparent ohmic contact scheme using indium oxide doped ZnO (IZO) as a current spreading layer for p-GaN in order to increase the optical output power of nitride-based lightemitting diodes (LEDs). IZO based contact layers of IZO, Ni/IZO, and NiO/IZO were prepared by e-beam evaporation, followed by a post-deposition annealing. The transmittances of the IZO based contact layers were in excess of 80% throughout the visible region of the spectrum. Specific contact resistances of $3.4\times10^{-4}$, $1.2\times10^{-4}$, $9.2\times0^{-5}$, and $3.6\times10^{-5}{\Omega}{\cdot}cm^2$ for IZO, Ni/Au, Ni/IZO, and NiO/IZO, respectively were obtained. The forward voltage and the optical output power of GaN LED with a NiO/IZO ohmic contact was 0.15 V lower and was increased by 38.9%, respectively, at a forward current of 20 mA compared to that of a standard GaN LED with an Ni/Au ohmic contact due to its high transparency, low contact resistance, and uniform current spreading.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.55-60
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• 2012

In order to develop electroless-plated Nickel Phosphate (Ni-P) as a contact material for high efficient low-cost silicon solar cells, we evaluated the effect of ambient thermal annealing on the degradation behavior of interfacial adhesion energy between electroless-plated Ni-P and silicon solar cell wafers by applying 4-point bending test method. Measured interfacial adhesion energies decreased from 14.83 to 10.83 J/$m^2$ after annealing at 300 and $600^{\circ}C$, respectively. The X-ray photoelectron spectroscopy analysis suggested that the bonding interface was degraded by environmental residual oxygen, in which the oxidation inhibit the stable formation of Ni silicide phase between electroless-plated Ni-P and silicon interface.