• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.260-260
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• 2009

In high-efficiency crystalline silicon solar cell, If high-efficiency solar cells are to be commercialized, It is need to develop superior contact formation method and material that can be inexpensive and simple without degradation of the solar cells ability. For reason of plated metallic contact is not only high metallic purity but also inexpensive manufacture. It is available to apply mass production. Especially, Nickel, Copper are applied widely in various electronic manufactures as easily formation is available by plating. Ni is shown to be a suitable barrier to Cu diffusin as well as desirable contact metal to silicon. Nickel monosilicide has been suggested as a suitable silicide due to its lower resistivitym lower sintering temperature and lower layer stress than $TiSi_2$. In this paper, Nickel as a seed layer and diffusion barrier is plated by electroless plating to make nickel monosilicide.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.571-577
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• 2006

We fabricated thermal evaporated 10 nm-Ni/(poly)Si and 10 nm-Ni/1 nm-Ir/(poly)Si films to investigate the thermal stability of nickel monosilicide at the elevated temperatures by rapid annealing them at the temperatures of $300{\sim}1200^{\circ}C$ for 40 seconds. Silicides for salicide process was formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester is used for sheet resistance. Scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An x-ray diffractometer and an auger depth profile scope were used for phase and composition analysis, respectively. Nickel silicides with iridium on single crystal silicon actives and polycrystalline silicon gates showed low resistance up to $1200^{\circ}C$ and $800^{\circ}C$, respectively, while the conventional nickel monosilicide showed low resistance below $700^{\circ}C$. The grain boundary diffusion and agglomeration of silicides led to lower the NiSi stable temperature with polycrystalline silicon substrates. Our result implies that our newly proposed Ir added NiSi process may widen the thermal process window for nano CMOS process.

• Korean Journal of Materials Research
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• v.17 no.4
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• pp.207-214
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• 2007

We fabricated thermally-evaporated 10 -Ni/(poly)Si and 10 -Ni/1 -Ir/(poly)Si structures to investigate the microstructure of nickel monosilicide at the elevated temperatures required for annealing. Silicides underwent rapid at the temperatures of 300-1200 for 40 seconds. Silicides suitable for the salicide process formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope(TEM) and an Auger depth profile scope were employed for the determination of vertical section structure and thickness. Nickel silicides with iridium on single crystal silicon actives and polycrystalline silicon gates shoed low resistance up to 1000 and 800, respectively, while the conventional nickle monosilicide showed low resistance below 700. Through TEM analysis, we confirmed that a uniform, 20 -thick silicide layer formed on the single-crystal silicon substrate for the Ir-inserted case while a non-uniform, agglomerated layer was observed for the conventional nickel silicide. On the polycrystalline silicon substrate, we confirmed that the conventional nickel silicide showed a unique silicon-silicide mixing at the high silicidation temperature of 1000. Auger depth profile analysis also supports the presence of thismixed microstructure. Our result implies that our newly proposed iridium-added NiSi process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.69-79
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• 2008

A composition consisting of 10 nm-Ni/1 nm-Pd/(30 nm or 70 nm-poly)Si was thermally annealed using rapid thermal for 40 seconds at $300{\sim}1100^{\circ}C$ to improve the thermal stability of conventional nickel monosilicide. The annealed bilayer structure developed into $Ni(Pd)Si_x$, and the resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness were investigated. The silicide, which formed on single crystal silicon, could defer the transformation of $NiSi_2$, and was stable at temperatures up to $1100^{\circ}C$. It remained unchanged on polysilicon substrate compared with the sheet resistance of conventional nickel silicide. The silicides annealed at $700^{\circ}C$, formed on single crystal silicon and 30 nm polysilicon substrates exhibited 30 nm-thick uniform silicide layers. However, silicide annealed at $1,000^{\circ}C$ showed preferred and agglomerated phase. The high resistance was due to the agglomerated and mixed microstructures. Through X-ray diffraction analysis, the silicide formed on single crystal silicon and 30 nm polysilicon substrate, showed NiSi phase on the entire temperature range and mixed phases of NiSi and $NiSi_2$ on 70 nm polysilicon substrate. Through scanning probe microscope (SPM) analysis, we confirmed that the surface roughness increased abruptly until 36 nm on 30 nm polysilicon substrate while not changed on single crystal and 70 nm polysilicon substrates. The Pd-inserted nickel monosilicide could maintain low resistance in a wide temperature range and is considered suitable for nano-thick silicide processing.

• Journal of the Korean institute of surface engineering
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• v.32 no.6
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• pp.703-708
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• 1999

Silicides have been used extensively in ULSI logic device fabrication as contact materials for the active areas as well as the poly- Si gates. NiSi is a promising candidate for submicron device application due to less volume expansion, low formation temperature, little silicon consumption, and large stable processing temperature window. In this report, the microstructure of nickel silicides fabricated with a thermal evaporator has been investigated. We observed systematic transformation of Ni silicides of $Ni_2$Si, NiSi, $NiSi_2$, as annealing temperature increases. All the silicides have been identified by a X-ray diffractometer (XRD). The cross-sectional microstructure of silicides was examined by a transmission electron microscope (TEM) equipped with a energy dispersive spectrometer(EDS). The surface roughness of silicides was measured by scanning probe microscope(SPM). Although we observed thin oxide layer existed at the $Ni/NiSi_{x}$ interface, we fabricated successfully $550\AA$-thick planar Ni-monosilicide at the temperature range of$ 400~700^{\circ}C$.

• 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.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.159-168
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• 2008

Thermally-evaporated 10 nm-Ni/1 nm-Ru/(30 nm or 70 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Ru-inserted nickel monosilicide. The silicide samples underwent rapid thermal anne aling at $300{\sim}1,100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution X-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope(SPM) were used to determine the cross-sectional structure and surface roughness. The silicide, which formed on single crystal silicon and 30 nm polysilicon substrate, could defer the transformation of $Ni_2Si $i and $NiSi_2 $, and was stable at temperatures up to $1,100^{\circ}C$ and $1,100^{\circ}C$, respectively. Regarding microstructure, the nano-size NiSi preferred phase was observed on single crystalline Si substrate, and agglomerate phase was shown on 30 nm-thick polycrystalline Si substrate, respectively. The silicide, formed on 70 nm polysilicon substrate, showed high resistance at temperatures >$700^{\circ}C$ caused by mixed microstructure. Through SPM analysis, we confirmed that the surface roughness increased abruptly on single crystal Si substrate while not changed on polycrystalline substrate. The Ru-inserted nickel monosilicide could maintain a low resistance in wide temperature range and is considered suitable for the nano-thick silicide process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.4
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• pp.308-317
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• 2007

We fabricated thermally-evaporated 10 nm-Ni/(poly)Si and 10 nm-$Ni_{0.5}Co_{0.5}$/(Poly)Si structures to investigate the microstructure of nickel silicides at the elevated temperatures required lot annealing. Silicides underwent rapid annealing at the temperatures of $600{\sim}1100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope and an Auger depth profilescope were employed for the determination of vortical microstructure and thickness. Nickel silicides with cobalt on single crystal silicon actives and polycrystalline silicon gates showed low resistance up to $1100^{\circ}C$ and $900^{\circ}C$, respectively, while the conventional nickle monosilicide showed low resistance below $700^{\circ}C$. Through TEM analysis, we confirmed that a uniform, $10{\sim}15 nm$-thick silicide layer formed on the single-crystal silicon substrate for the Co-alloyed case while a non-uniform, agglomerated layer was observed for the conventional nickel silicide. On the polycrystalline silicon substrate, we confirmed that the conventional nickel silicide showed a unique silicon-silicide mixing at the high silicidation temperature of $1000^{\circ}C$. Auger depth profile analysis also supports the presence of this mixed microstructure. Our result implies that our newly proposed NiCo-alloy composite silicide process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.444-445
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• 2009

The metallic contact system of silicon solar cell must have several properties, such as low contact resistance, easy application and good adhesion. Ni is shown to be a suitable barrier to Cu diffusion as well as desirable contact metal to silicon. Nickel monosilicide(NiSi) has been suggested as a suitable silicide due to its lower resistivity, lower sintering temperature and lower layer stress than $TiSi_2$. Copper and Silver can be plated by electro & light-induced plating method. Light-induced plating makes use the photovoltaic effect of solar cell to deposit the metal on the front contact. The cell is immersed into the electrolytic plating bath and irradiated at the front side by light source, which leads to a current density in the front side grid. Electroless plated Ni/ Electro&light-induced plated Cu/ Light-induced plated Ag contact solar cells result in an energy conversion efficiency of 16.446 % on $0.2\sim0.6\;{\Omega}{\cdot}cm$, $20\;\times\;20\;mm^2$, CZ(Czochralski) wafer.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.219-219
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• 2010

Silicides have been commonly used in the Si technology due to the compatibility with Si. Recently the silicide has been applied in solar cells [1] and nanoscale interconnects [2]. The modulation of Ni silicide phase is an important issue to satisfy the needs. The excellent electric-conductive nickel monosilicide (NiSi) nanowire has proven the low resistive nanoscale interconnects. Otherwise the Ni disilicide (NiSi2) provides a template to grow a crystalline Si film above it by the little lattice mismatch of 0.4% between Si and NiSi2. We present the formation of Ni silicide phases performed by the single deposition and the co-deposition methods. The co-deposition of Ni and Si provides a stable Ni silicide phase at a reduced processing temperature comparing to the single deposition method. It also discusses the Schottky contact formation between the Ni silicide and the grown crystalline Si film for the solar cell application.