• Journal of Integrative Natural Science
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• v.3 no.2
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• pp.84-88
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• 2010

Photonic crystals containing rugate structures from a single crystalline silicon wafer was obtained by using a sinoidal alternating current during an electrochemical etch procedure. Photonic crystals were isolated from the silicon substrate by applying an electropolishing current and were then made into particles by using an ultrasonic fracture in an ethanol solution to give a smart dust. Smart dusts exhibited their unique nanostructures and optical characteristics. They exhibited sharp photonic band gaps in the optical reflectivity spectrum. The size of smart dust obtained was in the range of 10-20 nm.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3322-3324
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• 1999

This paper studies on the design and fabrication of a micro in-plane positioning actuator integrated with a microlens. Proposed in-plane actuator is a micro XY-stage which is composed of two linear comb drive actuators being orthogonal to each other. In the fabrication of actuator, the single crystalline silicon substrate anodically bonded with a #7740 glass substrate is used because of simple release and passivation. The structure of actuator is formed on the silicon facet of bonded fixture by chlorine-based deep RIE and then released by isotropic wet etching of glass (#7740) in hydrofluoric acid solution. Fabricated actuator has a large travel range up to $30({\pm}15){\mu}m$ and high resolution less than 0.01f1l1l in each direction. Experimented resonant frequency of this actuator is 630Hz. The micro-Fresnel lens is fabricated on the square-shape glass structure prepared in the center of actuator.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.525-531
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• 1996

(Ti1-xAlx)N films were deposited on high speed steel and silicon substrates by reactive sputtering in mixed $Ar-N_2$ discharges. Crystalline phases and microhardness of ($Ti_1_xAl_x$)N films were investigated with variation of the film composition and substrate RF bias voltage. With Al content x of about 0.6, crystalline phase of ( $Ti_1_xAl_x$N films was changed from single-phase NaCl structure to two phase mixture of NaCl and wurtzite structures: Microhardness of ($Ti_1_xAl_x$)N films was largely improved by applying RF bias voltage above 50 V during deposition. Hardness of ($Ti_1_xAl_x$)N films reached a maximum value for Al content x of about 0.4, and 1900 kg/$mm^2$ was obtained for 1$\mu m$-thick ($Ti_{0.6}Al_{0.4}$)N films.

• Korean Journal of Materials Research
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• v.24 no.7
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• pp.375-380
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• 2014

Solar cells exhibit different power outputs in different climates. In this study, the temperature dependence of open-circuit voltage(V-oc), short-circuit current(I-sc), fill factor(FF) and the efficiency of screen-printed single-crystal silicon solar cells were studied. One group was fabricated with homogeneously-doped emitters and another group was fabricated with selectively-doped emitters. While varying the temperature (25, 40, 60 and $80^{\circ}C$), the current-voltage characteristics of the cells were measured and the leakage currents extracted from the current-voltage curve. As the temperature increased, both the homogeneously-doped and selectively-doped emitters showed a slight increase in I-sc and a rapid degradation of V-oc. The FF and efficiency also decreased as temperature increased in both groups. The temperature coefficient for each factor was calculated. From the current-voltage curve, we found that the main cause of V-oc degradation was an increase in the intrinsic carrier concentration. The temperature coefficients of the two groups were compared, leading to the idea that structural effects could also affect the temperature dependence of current-voltage characteristics.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.15-21
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• 2011

In this study, flexural strength and fracture behavior of silicon die from single crystalline silicon wafer were investigated as a function of thickness. Silicon wafers with various thickness of 300, 200, 180, 160, 150, and 100 ${\mu}m$ were prepared by mechanical grinding and polishing of as-saw wafers. Flexural strength of 40 silicon dies (size: 62.5 mm${\times}$4 mm) from each wafer was measured by four point bending test, respectively. For statistical analysis of flexural strength, shape factor(i.e., Weibull modulus) and scale factor were determined from Weibull plot. Flexural strength reflecting both statistical fracture probability and size (thickness) effect of brittle silicon die was obtained as a linear function of die thickness. Fracture appearance was discussed in relation with measured fracture strength.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1509_1510
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• 2009

This paper presents the design and simulation results of ohmic contact RF MEMS silicon switch with a high isolation at high frequencies along with the position of a contact part, initial off-state and intermediate off-state including the state where a contact part is placed right over a signal line of coplanar waveguide (CPW). The ohmic contact part is connected with comb drives made of high resistivity single crystalline silicon. The released contact part is $30{\mu}m$ apart from the edge of signal line on the glass substrate along the lateral direction (x-direction) at initial off-state. The electrostatic force of the comb electrode creates the x-directional movement thus initial state is converted to the intermediate off-state. The initial off-state of the switch results in isolations of -31 dB, -24 dB and reflections of -0.45 dB, -0.67 dB at 50 GHz and 110 GHz, respectively. It shows the isolation degradation when the contact part moves right over the signal line of CPW like an initial off-state of a conventional MEMS switch. The isolations and reflections are -31 dB, -24 dB and -0.50 dB, -1.31 dB at 50 GHz and 110 GHz, respectively at the intermediate off-state.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.274-274
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• 2008

This paper describes on the fabrication and characteristics of a 3C-SiC (Silicon Carbide) micro pressure sensor for harsh environment applications. The implemented micro pressure sensor used 3C-SiC thin-films heteroepitaxially grown on SOI (Si-on-insulator) structures. This sensor takes advantages of the good mechanical properties of Si as diaphragms fabricated by D-RIE technology and temperature properties of 3C-SiC piezoresistors. The fabricated pressure sensors were tasted at temperature up to $250^{\circ}C$ and indicated a sensitivity of 0.46 mV/V*bar at room temperature and 0.28 mV/V*bar at $250^{\circ}C$. The fabricated 3C-SiC/SOI pressure sensor presents a high-sensitivity and excellent temperature stability.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.10-13
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• 2001

Effects of an anionic surfactant pentadecafluorooctanoic acid on the photoluminescence of porous silicon was investigated, which was prepared by photoelectrochemical etching at 4V of single crystalline n-type silicon (100) with the specific resistivity of $0.4\~0.8{\Omega}{\cdot}cm$. Photoluminescence shifted to shorter wavelength and its intensity decreased when the concentration of the surfactant increased. FT-IR and contact angle data supported the presence of the surfactant lying on the surface of porous silicon.

• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.369-380
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• 2020

Most mono-crystalline silicon ingots are manufactured by the Czochralski (Cz) process. But If there are oxygen impurities, These Si-ingot tends to show low-efficiency when it is processed to be solar cell substrate. For making single-crystal Si- ingot, We need Czochralski (Cz) process which melts molten Si and then crystallizing it with seed of single-crystal Si. For melts poly Si-chunk and forming of single-crystalline Si-ingot, the heat transfer plays a main role in the structure of Cz-process. In this study to obtain high-quality Si ingot, the Cz-process was modified with the process design. The crystal growth simulation was employed with pulling rate and rotation speed optimization. Studies for modified Cz-process and the corresponding results have been discussed. The results revealed that using crystal growth simulation, we optimized the oxygen concentration of single crystal silicon by the optimal design of the pulling rate, rotation speed and melt charge level of Cz-process.

• 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.