• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.665-672
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• 1997

We applied mechanical alloying process by ball milling to produce molybdenum silicides $MoSi_2$ and $Mo_5Si_3$ using a mixture of elemental molybdenum and silicon powders at room temperature. The intermetallic compound MoSi$_3$ have been obtained by ball milling of $Mo_{33}Si_{67}$ mixture powders for 100 h, which is transformed to single $MoSi_2$ phase by subsequent heat treatment up to $725^{\circ}C$. The grain size of the $MoSi_2$ powders thus obtained was 19 nm, being approximately four times smaller than that of the commercial alloy. The intermetallic compound $MoSi_2$ with grain size of 30 nm have been also obtained by ball milling of $Mo_{62}Si_{38}$ mixture powders for 500 h, which is transformed to single $MoSi_2$ phase by heating up to $1000^{\circ}C$. We believe that the retarded ball milling time for the formation of $MoSi_2$ phase is attributed to its complicated crystal structure and large unit cell. The finer grain size in the ball-milled molybdenum silicides powders is expected to improve room-temperature mechanical properties for high-temperature structural materials.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.195-200
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• 2007

We fabricated thermally-evaporated 10 nm-Ni/70 w-Poly-Si/200 $nm-SiO_2/Si$ and $10nm-Ni_{0.5}Co_{0.5}/70$ nm-Poly-Si/200 $nm-SiO_2/Si$ structures to investigate the microstructure of nickel monosilicide at the elevated temperatures required fur annealing. Silicides underwent rapid anneal at the temperatures of $600{\sim}1100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process formed on top of the polycrystalline silicon substrate mimicking the gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope and an Auger depth profile scope were employed for the determination of cross sectional microstructure and thickness. 20nm thick nickel cobalt composite silicides on polycrystalline silicon showed low resistance up to $900^{\circ}C$, while the conventional nickle silicide showed low resistance below $900^{\circ}C$. Through TEM analysis, we confirmed that the 70nm-thick nickel cobalt composite silicide showed a unique silicon-silicide mixing at the high silicidation temperature of $1000^{\circ}C$. We identified $Ni_3Si_2,\;CoSi_2$ phase at $700^{\circ}C$ using an X-ray diffractometer. Auger depth profile analysis also supports the presence of this mixed microstructure. Our result implies that our newly proposed NiCo composite silicide from NiCo alloy films process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.27-36
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• 2006

We fabricated thermally evaporated 10 nm-Ni/(poly)Si, 10 nm-Ni/l nm-Ir/(poly)Si and 10 nm-Ni/l nm-Pt/(poly)Si films to investigate the thermal stability of nickel monosilicides at the elevated temperatures by rapid annealing them at the temperatures of $300{\sim}1200^{\circ}C$ for 40 seconds. Silicides of 50 nm-thick were formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to examine sheet resistance. A scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An X-ray diffractometer and an Auger depth profiler were used for phase and composition analysis, respectively. Nickel silicides with platinum have no effect on widening the NiSi stabilization temperature region. Nickel silicides with iridium farmed on single crystal silicon showed a low resistance up to $1200^{\circ}C$ while the ones formed on polycrystalline silicon substrate showed low resistance up to $850^{\circ}C$. The grain boundary diffusion and agglomeration of silicides lowered 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.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.84-84
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• 1993

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2830-2844
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• 2012

This review covers recent developments in our group regarding the synthesis, characterization and applications of single-crystalline one-dimensional nanostructures based on a wide range of material systems including noble metals, metal silicides and metal germanides. For the single-crystalline one-dimensional nanostructures growth, we have employed chemical vapor transport approach without using any catalysts, capping reagents, and templates because of its simplicity and wide applicability. Au, Pd, and Pt nanowires are epitaxially grown on various substrates, in which the nanowires grow from seed crystals by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. We also present the synthesis of numerous metal silicide and germanide 1D nanostructures. By simply varying reaction conditions, furthermore, nanowires of metastable phase, such as $Fe_5Si_3$ and $Co_3Si$, and composition tuned cobalt silicides (CoSi, $Co_2Si$, $Co_3Si$) and iron germanides ($Fe_{1.3}Ge$ and $Fe_3Ge$) nanowires are synthesized. Such developments can be utilized as advanced platforms or building blocks for a wide range of applications such as plasmonics, sensings, nanoelectronics, and spintronics.

• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.44-48
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• 2005

We prepared nickel silicide layers from p-Si(l00)/SiO₂(2000 Å)/poly-Si(700 Å)/Ni(400 Å) structures, feasible for gates in MOSFETs, by annealing them from 500℃～900℃ for 30 minutes. We measured the color coordination in visible range, cross sectional micro-structure, and surface topology with annealing temperature by an UV-VIS-IR spectrometer, field effect scanning electron microscope(FE-SEM), and scanning probe micro-scope respectively. We conclude that we may identify the nickel silicide by color difference of 0.90 and predict the silicide process reliability by color coordination measurement. The nickel silicide layers showed similar thickness while the columnar grains size and surface roughness increased as annealing temperature increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.79-79
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• 2013

Quantum-structures with nanoparticles have been attractive for various electronic and photonic devices [1,2]. In recent, nonvolatile memories such as nano-floating gate memory (NFGM) and resistance random access memory (ReRAM) have been studied using silicides, metals, and metal oxides nanoparticles [3,4]. In this study, we fabricated nonvolatile memories with silicides (WSi2, Ti2Si, V2Si) and metal-oxide (Cu2O, Fe2O3, ZnO, SnO2, In2O3 and etc.) nanoparticles embedded in polyimide matrix, and photovoltaic device also with SiC nanoparticles. The capacitance-voltageand current-voltage data showed a threshold voltage shift as a function of write/erase voltage, which implies the carrier charging and discharging into the metal-oxide nanoparticles. We have investigated also the electrical properties of ReRAM consisted with the nanoparticles embedded in ZnO, SiO2, polyimide layer on the monolayered graphene. We will discuss what the current bistability of the nanoparticle ReRAM with monolayered graphene, which occurred as a result of fully functional operation of the nonvolatile memory device. A photovoltaic device structure with nanoparticles was fabricated and its optical properties were also studied by photoluminescence and UV-Vis absorption measurements. We will discuss a feasibility of nanoparticles to application of nonvolatile memories and photovoltaic devices.

• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.3-14
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• 1996

High temperature anneal of W-rich silicides, inferior to adherence compared with Si-rich silicides, resulted in the film peeling off from the Si-substrate when WSix thickness reached more than critical thickness. Investigation of the W-rich silicide films peeling off from the substrate revealed that the voids underneath the $WSi_2$ produced through silicide reaction were responsible for the poor adherence of W-rich silicide. In addition, internal stress in the film increased as the silicide thickness increased. In order to promote the adhesion of WSix to Si-substrate, thin Ti-layer was formed between WSi and Si-substrate(WSix/Ti/Si). No voids were observed in $WSi_2$/Ti/Si $N_2$-annealed at $1000^{\circ}C$, thereby leading to an increase of the critical thickness from ～1700$\AA$ to more than 2500$\AA$. However, higher resisiti-vity was obtained in WSix/Ti/Si than in WSix/Si. Finally, different silicide reaction mechanism for the structures(WSix/Si, WSix/Ti/Si) was proposed to explain the formation of voids as well as the role of thin Ti-layer.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.197-204
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• 2007

Ultra thin Er-silicide layers formed by Er deposition on the clean p-silicon and in situ post annealing technique were investigated with respect to change of the Schottky barrier height. The formation of Er silicides was confirmed by XPS results. UPS measurements revealed that the workfunction of the silicide decreased and was saturated as the deposited Er thickness increased up to $10{\AA}$. We found that the silicides were mainly composed of Er5Si3 phase through the XRD experiments. After Schottky diodes were fabricated with the Er silicide/p-Si junctions, the Schottky barrier heights were calculated $0.44{\sim}0.78eV$ from the I-V measurements of the Schottky diodes. There was large discrepancy in the Schottky barrier heights deduced from the UPS with the ideal junction condition and the real I-V measurements, so that we attributed the discrepancy to the $Er_5Si_3$ phase in the Er-silicides and the large interfacial density of trap state of it.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.16-22
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• 2008

We fabricated thermally-evaporated 10 nm-Ni/30 nm and 70 nm Poly-Si/200 nm-$SiO_2/Si$ structures to investigate the thermal stability of nickel silicides formed by rapid thermal annealing(RTA) of the temperature of $300{\sim}1100^{\circ}C$ for 40 seconds. We employed for a four-point tester, field emission scanning electron microscope(FE-SEM), transmission electron microscope(TEM), high resolution X-ray diffraction(HRIXRD), and scanning probe microscope(SPM) in order to examine the sheet resistance, in-plane microstructure, cross-sectional microstructure evolution, phase transformation, and surface roughness, respectively. The silicide on 30 nm polysilicon substrate was stable at temperature up to $900^{\circ}C$, while the one on 70 nm substrate showed the conventional $NiSi_2$ transformation temperature of $700^{\circ}C$. The HRXRD result also supported the existence of NiSi-phase up to $900^{\circ}C$ for the Ni silicide on the 30 nm polysilicon substrate. FE-SEM and TEM confirmed that 40 nm thick uniform silicide layer and island-like agglomerated silicide phase of $1{\mu}m$ pitch without residual polysilicon were formed on 30 nm polysilicon substrate at $700^{\circ}C\;and\;1000^{\circ}C$, respectively. All silicides were nonuniform and formed on top of the residual polysilicon for 70 nm polysilicon substrates. Through SPM analysis, we confirmed the surface roughness was below 17 nm, which implied the advantage on FUSI gate of CMOS process. Our results imply that we may tune the thermal stability of nickel monosilicide by reducing the height of polysilicon gate.