• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.985-988
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• 2008

Metal induced crystallization of a-Si with a source of Ni/Si oxide was studied. Its mechanism to induce crystallization was discussed. It was found that new source behaves an effect of self-released nickel and reducing nickel residua, so can provide a wider process tolerance; improve the uniformity and stability of TFTs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.358-361
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• 2002

Self-aligned MOSFETS using a polysilicon gate are widely fabricated in silicon technology. The polysilicon layer acts as a mask for the source and drain implants and does as gate electrode in the final product. However, the usage of polysilicon gate as a self-aligned mask is restricted in fabricating SiC MOSFETS since the following processes such as dopant activation, ohmic contacts are done at the very high temperature to attack the stability of the polysilicon layer. A metal instead of polysilicon can be used as a gate material and even can be used for ohmic contact to source region of SiC MOSFETS, which may reduce the number of the fabrication processes. Co-formation process of metal-source/drain ohmic contact and gate has been examined in the 4H-SiC based vertical power MOSFET At low bias region (<20V), increment of leakage current after RTA was detected. However, the amount of leakage current increment was less than a few tens of ph. The interface trap densities calculated from high-low frequency C-V curves do not show any difference between w/ RTA and w/o RTA. From the C-V characteristic curves, equivalent oxide thickness was calculated. The calculated thickness was 55 and 62nm for w/o RTA and w/ RTA, respectively. During the annealing, oxidation and silicidation of Ni can be occurred. Even though refractory nature of Ni, 950$^{\circ}C$ is high enough to oxidize it. Ni reacts with silicon and oxygen from SiO$_2$ 1ayer and form Ni-silicide and Ni-oxide, respectively. These extra layers result in the change of capacitance of whole oxide layer and the leakage current

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.458-465
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• 2022

Interest in the use of semiconductor-based photocatalyst materials for the degradation of organic pollutants in a liquid phase has grown, due to their excellent performance and response to the light source. Herein, we fabricated a NiO-SiC-TiO₂ ternary structured photocatalyst which had reduced bandgap energy, with strong activation under UV-light irradiation. The synthesized samples were examined using XRD, SEM, EDX, TEM, DRS, EIS techniques and photocurrent measurement. The results confirmed that the two types of metal oxides were well bonded to the SiC fiber surface. The junction of the new photocatalyst exhibited a large number of photoexcited electrons and holes. The holes tended to oxidize the water and form a hydroxyl radical, which promoted the decomposition of methylene blue. The close contact between the 2D SiC fiber and metal oxide semiconductors expanded the scope of absorption wavelength, and enhanced the usability of the ternary photocatalyst for the degradation of methylene blue. Among three synthesized samples, the NiO-SiC-TiO₂ showed the best photocatalytic effect, and was considered to have excellent photoelectron transfer due to the synergy effect between the metal oxide and SiC.

• Transactions on Electrical and Electronic Materials
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• v.16 no.4
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• pp.187-189
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• 2015

A charge-trap flash (CTF) thin film transistor (TFT) memory is proposed at a low-temperature process (≤ 450℃). The memory cell consists of a sputtered oxide-nitride-oxide (ONO) gate dielectric and Schottky barrier (SB) source/drain (S/D) junctions using nickel silicide. These components enable the ultra-low-temperature process to be successfully achieved with the ONO gate stacks that have a substrate temperature of room temperature and S/D junctions that have an annealing temperature of 200℃. The silicidation process was optimized by measuring the electrical characteristics of the Ni-silicided Schottky diodes. As a result, the Ion/Ioff current ratio is about 1.4×10⁵ and the subthreshold swing and field effect mobility are 0.42 V/dec and 14 cm²/V·s at a drain voltage of −1 V, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.355-355
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• 2010

We studied the dependence of the performance of schottky barrier metal-oxide-field effect transistors(SB MOSFETs) on the work function of source/drain metals. A strong impact of the various work functions and the light wavelengths on the transistor characteristics is found and explained using experimental data. We used an insulator of a high thickness (100nm) and back gate issues in SOI substrate, subthreshold swing was measured to 300~400[mV/dec] comparing with a ideal subthreshold swing of 60[mV/dec]. Excellent characteristics of Al/Si was demonstrated higher on/off current ratios of ${\sim}10^7$ than others. In addition, extensive photoresponse analysis has been performed using halogen and deuterium light sources(200<$\lambda$<2000nm).

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.450-455
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• 2004

NiCr thin films were fabricated by thermal evaporation method using NiCr alloy as evaporating source. NiCr thin films were annealed at various temperatures in air atmosphere in order to investigate effects of annealing conditions on phase change, composition, and microstructures of NiCr films. Typical multilayer was formed after annealing in air atmosphere. This results from the diffusion and oxidation of Cr toward surface during annealing. In the case of annealing at 700$^{\circ}C$, large columnar grains of NiO were formed on Cr-oxide layer through the diffusion and oxidation of Ni over Cr-oxide layer. Especially, NiO layer was formed additionally on surface, sustaining the underlayer structure with the formation of porous Ni layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.341-341
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• 2012

Recently, oxide semi-conductor materials have been investigated as promising candidates replacing a-Si:H and poly-Si semiconductor because they have some advantages of a room-temperature process, low-cost, high performance and various applications in flexible and transparent electronics. Particularly, amorphous indium-gallium-zinc-oxide (a-IGZO) is an interesting semiconductor material for use in flexible thin film transistor (TFT) fabrication due to the high carrier mobility and low deposition temperatures. In this work, we demonstrated improvement of flexibility in IGZO TFTs, which were fabricated on polyimide (PI) substrate. At first, a thin poly-4vinyl phenol (PVP) layer was spin coated on PI substrate for making a smooth surface up to 0.3 nm, which was required to form high quality active layer. Then, Ni gate electrode of 100 nm was deposited on the bare PVP layer by e-beam evaporator using a shadow mask. The PVP and $Al_2O_3$ layers with different thicknesses were used for organic/inorganic multi gate dielectric, which were formed by spin coater and atomic layer deposition (ALD), respectively, at $200^{\circ}C$. 70 nm IGZO semiconductor layer and 70 nm Al source/drain electrodes were respectively deposited by RF magnetron sputter and thermal evaporator using shadow masks. Then, IGZO layer was annealed on a hotplate at $200^{\circ}C$ for 1 hour. Standard electrical characteristics of transistors were measured by a semiconductor parameter analyzer at room temperature in the dark and performance of devices then was also evaluated under static and dynamic mechanical deformation. The IGZO TFTs incorporating hybrid gate dielectrics showed a high flexibility compared to the device with single structural gate dielectrics. The effects of mechanical deformation on the TFT characteristics will be discussed in detail.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.438-439
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• 2013

Microelectronic devices의 접촉저항의 향상을 위해 Metal silicides의 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 지난 수십년에 걸쳐, Ti silicide, Co silicide, Ni silicide 등에 대한 개발이 이루어져 왔으나, 계속적인 저저항 접촉 소재에 대한 요구에 의해 최근에는 Rare earth silicide에 관한 연구가 시작되고 있다. Rare-earth silicide는 저온에서 silicides를 형성하고, n-type Si과 낮은 schottky barrier contact (~0.3 eV)를 이룬다. 또한, 비교적 낮은 resistivity와 hexagonal AlB2 crystal structure에 의해 Si과 좋은 lattice match를 가져 Si wafer에서 high quality silicide thin film을 성장시킬 수 있다. Rare earth silicides 중에서 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 낮은 schottky barrier 응용에서 쓰이고 있다. 이로 인해, n-channel schottky barrier MOSFETs의 source/drain으로써 주목받고 있다. 특히 ytterbium과 molybdenum co-deposition을 하여 증착할 경우 thin film 형성에 있어 안정적인 morphology를 나타낸다. 또한, ytterbium silicide와 마찬가지로 낮은 면저항과 electric work function을 갖는다. 그러나 ytterbium silicide에 molybdenum을 화합물로써 높은 농도로 포함할 경우 높은 schottky barrier를 형성하고 epitaxial growth를 방해하여 silicide film의 quality 저하를 야기할 수 있다. 본 연구에서는 ytterbium과 molybdenum의 co-deposition에 따른 silicide 형성과 전기적 특성 변화에 대한 자세한 분석을 TEM, 4-probe point 등의 다양한 분석 도구를 이용하여 진행하였다. Ytterbium과 molybdenum을 co-deposition하기 위하여 기판으로 $1{\sim}0{\Omega}{\cdot}cm$의 비저항을 갖는 low doped n-type Si (100) bulk wafer를 사용하였다. Native oxide layer를 제거하기 위해 1%의 hydrofluoric (HF) acid solution에 wafer를 세정하였다. 그리고 고진공에서 RF sputtering 법을 이용하여 Ytterbium과 molybdenum을 동시에 증착하였다. RE metal의 경우 oxygen과 높은 반응성을 가지므로 oxidation을 막기 위해 그 위에 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, 진공 분위기에서 rapid thermal anneal(RTA)을 이용하여 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium silicides를 형성하였다. 전기적 특성 평가를 위한 sheet resistance 측정은 4-point probe를 사용하였고, Mo doped ytterbium silicide와 Si interface의 atomic scale의 미세 구조를 통한 Mo doped ytterbium silicide의 형성 mechanism 분석을 위하여 trasmission electron microscopy (JEM-2100F)를 이용하였다.