• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.131-135
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• 2005

This paper describes the ohmic contact formation of single crystalline 3C-SiC thin films heteroepitaxially grown on Si(001) wafers. In this work, a TiW (Titanium-tungsten) film as a contact matieral was deposited by RF magnetron sputter and annealed with the vacuum and RTA (rapid thermal anneal) process respectively. Contact resistivities between the TiW film and the n-type 3C-SiC substrate were measured by the C-TLM (circular transmission line model) method. The contact phases and interface the TiW/3C-SiC were evaulated with XRD (X-ray diffraction), SEM (scanning electron microscope) and AES (Auger electron spectroscopy) depth-profiles, respectively. The TiW film annealed at $1000^{\circ}C$ for 45 sec with the RTA play am important role in formation of ohmic contact with the 3C-SiC substrate and the contact resistance is less than $4.62{\times}10^{-4}{\Omega}{\cdot}cm^{2}$. Moreover, the inter-diffusion at TiW/3C-SiC interface was not generated during before and after annealing, and kept stable state. Therefore, the ohmic contact formation technology of single crystalline 3C-SiC using the TiW film is very suitable for high temperature MEMS applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.434-435
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• 2009

The crystalline silicon solar cell where the solar cell market grows rapidly is occupying of about 85% or more. high-efficiency and low cost endeavors many crystalline silicon solar cells. the fabrication processes of high-efficiency crystalline silicon solar cells necessitate complicated fabrication processes and Ti/Pd/Ag contact, however, this contact formation processed by expensive materials. Ni/Cu contact formation is good alternative. in this paper, according to temperature Ni silicide makes, produced Ni/Cu contact solar cell and measured conversion efficiency.

• Economic and Environmental Geology
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• v.14 no.2
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• pp.55-76
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• 1981

Southwestern contact zone of the Boeun granodiorite occurs near the thrust fault between the Ogcheon Group and Majeonri Limestone Formation. Ogcheon Group, metasediments composed of the Munjuri Formation, Changri Formation, and unconformably overlying Hwanggangri Formation, belongs to greenschist facies of regional metamorphism accompanied with deformation of two fold axes, $N10^{\circ}E$ and $N45-65^{\circ}E$ directions. Basic metamorphic rocks occurring in the Changri and Limestone Formations are the meta-basalts and meta-diabases of tholeiitic basalt series. The meta-basalts intruded in the Changri Formation as sills, whereas the meta-diabases in the Changri and Limestone Formations as stocks in appearance. They are considered to have emplaced before the formation of two fold axes and related with the thrust fault, based on the geologic setting of the area. The metamorphic facies are identified to be greenschist facies to epidote-amphibolite facies for the meta-basalt, and epidote-amphibolite facies for the meta-diabases. It is interpreted that such a variety of facies was related from the combination of earlier deuteric alteration and later regional metamorphism. The metasediments in southwestern contact zont of the Boeun granodiorite which is a product of later syntectonic intrusion of middle Jurassic in age, show pyroxene-hornfels facies near the contact and amphibole-horenfels facies away from the contact to the mineral zoning in the contact metamorphic aureole of the Limestone Formation, based on the paragenetic analysis of mineral assemblages. The Limestone in the area appears to be considerably $SiO_2-CaO-MgO-CO_2-H_2O$ can be adopted to evaluate equilibrium conditions of the mineral assemblages in each mineral zone. It is revealed that a temperature gradient was existed accross the contact aureole ranging from the higher igneous side to lower sedimentary side, whereas no clear trend of $XCO_2$ variation appears but high mole fraction. The tremolite diopside-quartz-calcite assemblages occurs in common through the most mineral zones of contact aureole that is in good agreement with the equivalent reaction curve which extends over a wide range of $T-XCO_2$ conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.2075-2082
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• 2006

This paper presents modeling and optimization techniques for hish efficiency solar cell process on single-crystalline float zone (FZ) wafers. Among a sequence of multiple steps of fabrication, the followings are the most sensitive steps for the contact formation: 1) Emitter formation by diffusion; 2) Anti-reflection-coating (ARC) with silicon nitride using plasma-enhanced chemical vapor deposition (PECVD); 3) Screen-printing for front and back metalization; and 4) Contact formation by firing. In order to increase the performance of solar cells in terms of efficiency, the contact formation process is modeled and optimized using neural networks and genetic algorithms, respectively. This paper utilizes the design of experiments (DOE) in contact formation to reduce process time and fabrication costs. The experiments were designed by using central composite design which consists of 24 factorial design augmented by 8 axial points with three center points. After contact formation process, the efficiency of the fabricated solar cell is modeled using neural networks. Established efficiency model is then used for the analysis of the process characteristics and process optimization for more efficient solar cell fabrication.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.968-972
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• 2008

Ni/Ti/Al multilayer system ('/'denotes the deposition sequence) was tested for low-resistance ohmic contact formation to Al-implanted p-type 4H-SiC. Ni 30 nm / Ti 50 nm / Al 300 nm layers were sequentially deposited by e-beam evaporation on the 4H-SiC samples which were implanted with Al (norminal doping concentration = $4\times10^{19}cm^{-3}$) and then annealed at $1700^{\circ}C$ for dopant activation. Rapid thermal anneal (RTA) temperature for ohmic contact formation was varied in the range of $840\sim930^{\circ}C$. Specific contact resistances were extracted from the measured current vs. voltage (I-V) data of linear- and circular transfer length method (TLM) patterns. In constrast to Ni contact, Ni/Ti/Al contact shows perfectly linear I-V characteristics, and possesses much lower contact resistance of about $2\sim3\times10^{-4}\Omega{\cdot}cm^2$ even after low-temperature RTA at $840^{\circ}C$, which is about 2 orders of magnitude smaller than that of Ni contact. Therefore, it was shown that RTA temperature for ohmic contact formation can be lowered to at least $840^{\circ}C$ without significant compromise of contact resistance. X-ray diffraction (XRD) analysis indicated the existence of intermetallic compounds of Ni and Al as well as $NiSi_{1-x}$, but characteristic peaks of $Ti_{3}SiC_2$, a probable narrow-gap interfacial alloy responsible for low-resistance Ti/Al ohmic contact formation, were not detected. Therefore, Al in-diffusion into SiC surface region is considered to be the dominant mechanism of improvement in conduction behavior of Ni/Ti/Al contact.

• Korean Journal of Materials Research
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• v.20 no.6
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• pp.338-343
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• 2010

As an alternative to the W plug used in MOSFETs, a Cu plug with a NiSi contact using Ta / TaN as a diffusion barrier is currently being considered. Conventionally, Ni was first deposited and then NiSi was formed, followed by the barrier and Cu deposition. In this study, Ti was employed as a barrier material and simultaneous formation of the NiSi contact and Cu plug / Ti barrier was attempted. Cu(100 nm) / Ti / Ni(20 nm) with varying Ti thicknesses were deposited on a Si substrate and annealed at $4000^{\circ}C$ for 30 min. For comparison, Cu/Ti/NiSi thin films were also formed by the conventional method. Optical Microscopy (OM), Scanning Probe Microscopy (SPM), X-Ray Diffractometry (XRD), and Auger Electron Microscopy (AES) analysis were performed to characterize the inter-diffusion properties. For a Ti interlayer thicker than 50 nm, the NiSi formation was incomplete, although Cu diffusion was inhibited by the Ti barrier. For a Ti thickness of 20 nm and less, an almost stoichiometric NiSi contact along with the Cu plug and Ti barrier layers was formed. The results were comparable to that formed by the conventional method and showed that this alternative process has potential as a formation process for the Cu plug/Ti barrier/NiSi contact system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.95-101
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• 2000

The effect of surface contact angle on the behavior of frost formation in a fin-tube heat exchanger is investigated experimentally. It is shown that both heat exchangers with hydrophilic and hydrophobic surfaces appear to have a better thermal performance than bare aluminium heat exchanger, but the improvements are very small. There is a little increase in the amount of the frost deposited onto the heat exchanger with both hydrophilic and hydrophobic surface. However, the effect of contact angle on the frost density is observed ; the frost with high density forms on the heat exchanger with hydrophilic surface ; and the frost with low density is deposited onto the heat exchanger with hydrophobic surface when compared with the frost deposited onto the heat exchanger with bare aluminium surface. This may be attributed to the fact that the shape of water droplets which condense on the surface of heat exchanger at the early stage of frosting varies with contact angle, and thus makes a difference on the structure of frost formation. From the experiments with different relative humidity of inlet air, it is shown that the variations of operating parameter make no influence on the effect of surface contact angle on the frosting behavior in the heat exchanger.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.406-407
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• 2006

This paper describes the ohmic contact formation between a TiW film as a contact material deposied by RF magnetron sputter and polycrystalline 3C-SiC films deposied on thermally grown Si wafers. The specific contact resistance (${\rho}_c$) of the TiW contact was measured by using the C-TLM. The contact phase and interfacial reaction between TiW and 3C-SiC at high-temperature were also analyzed by XRD and SEM. All of the samples didn't show cracks of the TiW film and any interfacial reaction after annealing. Especially, when the sample was annealed at $800^{\circ}$ for 30min., the lowest contact resistivity of $2.90{\times}10^{-5}{\Omega}cm^2$ was obtained due to the improved interfacial adhesion.

• Journal of the Semiconductor & Display Technology
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• v.2 no.3
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• pp.7-11
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• 2003

In this research, the etching characteristics of via contact and deep contact hole have been studied using multi-pole inductively coupled plasma(MICP) etching system. We investigated Plasma density of MICP source using the Langmuir probe and etching characteristics with RF frequency, wall temperature, chamber gap, and gas chemistry containing Carbon and Fluorine. As the etching time increases, formation of the polymer increases. To improve the polymer formation, we controlled the temperature of the reacting chamber, and we found that temperature of the chamber was very effective to decrease the polymer thickness. The deep contact etch profile and high selectivity(oxide to photoresist) have been achieved with the optimum mixed gas ratio containing C and F and the temperature control of the etching chamber.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.4-5
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• 2006

This paper represents modeling and optimization techniques for solar cell process on single-crystalline float zone (FZ) wafers with high efficiency; There were the four significant processes : i)emitter formation by diffusion, anti-reflection-coating (ARC) with silicon nitride using plasma-enhanced chemical vapor deposition (PECVD); iii)screen-printing for front and back metallization; and iv)contact formation by firing. In order to increase the performance of solar cells, the contact formation process is modeled and optimized. This paper utilizes the design of experiments (DOE) in contact formation to reduce process time, fabrication costs. The experiments were designed by using central composite design which is composed of $2^4$ factorial design augmented by 8 axial points with three center points. After contact formation process, the efficiency of the solar cell is modeled using neural networks. This model is used to analyse the characteristics of the process, and to optimize the process condition using genetic algorithms (GA). Finally, find optimal recipe for solar cell efficiency.