• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.592-597
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• 2004

Porous silicon(PS) has received much attention as a sensitive material of chemical sensors because of its large internal surface area. In this work, we fabricated gas-sensing devices based on the porous silicon layer which could be applicable to the measurement of blood alcohol content(BAC), and estimated their electrical properties. The structure of the sensor is similar to an MIS (metal-insulator-semiconductor) diode and consists of thin Au/oxidized PS/PS/p-Si/Al, where the p-Si substrate is etched anisotropically to reduce the thickness. We measured C-V curves from two types of the samples with the PS layer treated by the different anodization current density of 60 or 100 mA/cm$^2$, in order to compare the sensitivity. As a result, the magnitude and variation of capacitances from the devices with the PS formed under the current density of 100 mA/cm$^2$ were found to be more detectable due to the larger internal surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.848-852
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• 2008

Characteristics of microcrystalline-silicon thin-films deposited by plasma-enhanced chemical-vapor deposition (PECVD) method were studied. There were optimum values of RF power density and $H_2$ dilution ratio $(H_2/(SiH_4+H_2))$; maximum grain size of about 35 nm was obtained at substrate temperature of 250 $^{\circ}C$ with RF power density of 1.1 W/$cm^2$ and $H_2$ dilution ratio of 0.91. Larger grain was obtained with higher substrate temperature up to 350 $^{\circ}C$. Grain size dependence on RF power density and $H_2$ dilution ratio could be explained by etching effects of hydrogen ions and changes of species of reactive precursors on growing surface. Surface-mobility activation of reactive precursors by temperature could be a reason of grain-size dependence on the substrate temperature. Microcrystalline-silicon thin-films that could be used for flat-panel electronics such as active-matrix organic-light-emitting-diodes are expected to be fabricated successfully using these results.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.322-322
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• 2010

Recently, anti-reflective films (AR) are one of the most studied parts of a solar cell since these films improve the efficiency of photovoltaic devices. Also, anti-reflection films on the textured silicon solar cells reduce the amount of reflection of the incident light, which improves the device performance due to light trapping of incident light into the cell. Therefore, we preformed two step processes to get textured Si (100) substrate in this experiment. Pyramid size of textured silicon had approximately $2{\sim}9\;{\mu}m$. A well-textured silicon surface can lower the reflectance to 10%. For more reduced reflection, TiO2 anti-reflection films on the textured silicon were deposited at $600^{\circ}C$ using titanium tetra-isopropoxide (TTIP) as a precursor by metal-organic chemical vapor deposition (MOCVD), and the deposited TiO2 layers were then treated by annealing for 2 h in air at 600 and $1000^{\circ}C$, respectively. In this process, the treated samples by annealing showed anatase and rutile phases, respectively. The thickness of TiO2 films was about $75{\pm}5\;nm$. The reflectance at specific wavelength can be reduced to 3% in optimum layer.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.547-552
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• 2019

In the present study, the thermal conductivity of a silicon nitride($Si_3N_4$) thin-film is evaluated using the dual-wavelength pump-probe technique. A 100-nm thick $Si_3N_4$ film is deposited on a silicon (100) wafer using the radio frequency plasma enhanced chemical vapor deposition technique and film structural characteristics are observed using the X-ray reflectivity technique. The film's thermal conductivity is measured using a pump-probe setup powered by a femtosecond laser system of which pump-beam wavelength is frequency-doubled using a beta barium borate crystal. A multilayer transient heat conduction equation is numerically solved to quantify the film property. A finite difference method based on the Crank-Nicolson scheme is employed for the computation so that the experimental data can be curve-fitted. Results show that the thermal conductivity value of the film is lower than that of its bulk status by an order of magnitude. This investigation offers an effective way to evaluate thermophysical properties of nanoscale ceramic and dielectric materials with high temporal and spatial resolutions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.440-440
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• 2009

Semiconductor nanowires offer exciting possibilities as components of solar cells and have already found applications as active elements in organic, dye-sensitized, quantum-dot sensitized, liquid-junction, and inorganic solid-state devices. Among many semiconductors, silicon is by far the dominant material used for worldwide photovoltaic energy conversion and solar cell manufacture. For silicon wire to be used for solar device, well aligned wire arrays need to be fabricated vertically or horizontally. Macroscopic silicon wire arrays suitable for photovoltaic applications have been commonly grown by the vapor-liquid-solid (VLS) process using metal catalysts such as Au, Ni, Pt, Cu. In the case, the impurity issues inside wire originated from metal catalyst are inevitable, leading to lowering the efficiency of solar cell. To escape from the problem, the wires of purity of wafer are the best for high efficiency of photovoltaic device. The fabrication of wire arrays by the electrochemical etching of silicon wafer with photolithography can solve the contamination of metal catalyst. In this presentation, we introduce silicon wire arrays by electrochemical etching method and then fabrication methods of radial p-n junction wire array solar cell and the various merits compared with conventional silicon solar cells.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.112-117
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• 2008

Vertical interconnection scheme using novel silicon-through-via for 3D MEMS devices or stacked package is proposed and fabricated to demonstrate its feasibility. The suggested silicon-through-via replaces electroplated copper, which is used as an interconnecting material in conventional through-via, with doped silicon. Adoption of doped silicon instead of metal eliminates thermal-mismatch-induced stress, which can make troubles in high temperature MEMS processes, such as wafer bonding and LP-CVD(low pressure chemical vapor deposition). Two silicon layers of $30{\mu}m$ thickness are stacked on the substrate. The through-via arrays with spacing $40{\mu}m$ and $50{\mu}m$ are fabricated successfully. Electrical characteristics of the through-via are measured and analyzed. The measured resistance of the silicon-through-via is $169.9\Omega$.

• Korean Journal of Materials Research
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• v.26 no.1
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• pp.47-53
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• 2016

Silicon nitride ($SiN_x:H$) films made by plasma enhanced chemical vapor deposition (PECVD) are generally used as antireflection layers and passivation layers on solar cells. In this study, we investigated the properties of silicon nitride ($SiN_x:H$) films made by PECVD. The passivation properties of $SiN_x:H$ are focused on by making the antireflection properties identical. To make equivalent optical properties of silicon nitride films, the refractive index and thickness of the films are fixed at 2.0 and 90 nm, respectively. This limit makes it easier to evaluate silicon nitride film as a passivation layer in realistic application situations. Next, the effects of the mixture ratio of the process gases with silane ($SiH_4$) and ammonia ($NH_3$) on the passivation qualities of silicon nitride film are evaluated. The absorption coefficient of each film was evaluated by spectrometric ellipsometry, the minority carrier lifetimes were evaluated by quasi-steady-state photo-conductance (QSSPC) measurement. The optical properties were obtained using a UV-visible spectrophotometer. The interface properties were determined by capacitance-voltage (C-V) measurement and the film components were identified by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectroscopy detection (RBS) - elastic recoil detection (ERD). In hydrogen passivation, gas ratios of 1:1 and 1:3 show the best surface passivation property among the samples.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.154-157
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• 2011

Hydrogenated silicon nitride deposited by LF-PECVD is commonly used for anti-reflection coating and passivation in silicon solar cell fabrication. The deposition of the optimized silicon nitride on the surface is elemental in crystalline silicon solar cell. In this work, the carrier lifetimes were measured while the thicknesses of $SiN_x$ were changed from 700 ${\AA}$ to 1150 ${\AA}$ with the gas flow of $SiH_4$ as 40 sccm and $NH_3$ as 120 sccm,. The carrier lifetime enhanced as the thickness of $SiN_x$ increased due to improved passivation effect. To study the characteristics of $SiN_x$ with various gas ratios, the gas flow of $NH_3$ was changed from 40 sccm to 200 sccm with intervals of 40 sccm. The thickness of $SiN_x$ was fixed as 1000 ${\AA}$ and the gas flow of $SiH_4$ as 40 sccm. The refractive index of SiNx and the carrier lifetime were measured before and after heat treating at $650^{\circ}C$ to investigate their change by the firing process in solar cell fabrication. The index of refraction of SiNx decreased as the gas ratios increased and the longest carrier lifetime was measured with the gas ratio $NH_3/SiH_4$ of 3.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.58.2-58.2
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• 2010

본 연구에서는 n-type wafer에 비정질 실리콘을 증착한 이종접합 태양전지를 열처리 방법을 이용하여 열처리의 효과를 분석함으로써 이종접합 태양전지에 효율적인 열처리 효과에 대하여 연구하였다. P, N-layer는 PECVD(Plasma-enhanced chemical vapor deposition) I-layer는 HWCVD(Hot wire chemical vapor deposition), ITO는 RF 마그네트론 스퍼터링법으로 동일한 조건에서 제작하였고 rapid thermal process를 이용하여 진공 중에서 $150^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$, $250^{\circ}C$까지 열처리를 하였다. 열처리 전과 후 QSSPC로 minority carrier life time, 자외 가시선 분광분석 장치로 투과 반사도를, Ellipsometer로 흡수 계수 등의 변화를 조사하였다. 열처리 후 Minority carrier life time, Voc 및 광변환 효율이 증가하였다.

• Electrical & Electronic Materials
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• v.16 no.9
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• pp.65.2-65
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• 2003

Praseodymium oxid ($Pr_2$$O_3$) thin films have been deposited on Si(100) substrates by metalorganic chemical vapor deposition using praseodymium tris-2,2,6,6-tetramethyl-3,5-heptandionate as source material. Film structural, morphological, and compositional characterizations have been carried out. Dielectric properties have been studied as well by capacitance-voltage and current-voltage measurements on metal-oxide-semiconductor capacitors of several areas. The $Pr_2$$O_3$ films have shown a dielectric constant = 23-25 and a leakage current density of $8.8{\times}10$-e $A/\textrm{mm}^2$ at ＋1 V.