• Journal of Welding and Joining
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• v.28 no.3
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• pp.49-58
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• 2010

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites (diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature $940^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.175.1-175.1
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• 2015

CuSn thin films were deposited by rf magnetron co-sputtering method with pure Cu and Sn metal targets with a variety of rf powers. CuSn thin films were studied with a surface profiler (alpha step), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), X-ray diffraction (XRD), and contact angle measurement. The thickness of CuSn thin films was fixed at $200{\pm}10nm$ and deposition rate was calculated by the measured with a surface profiler. From the survey XPS spectra, the characteristic peaks of Cu and Sn were observed. Therefore, CuSn thin films were successfully synthesized on the Si (100) substrate. The oxidation state and chemical environment of Cu and Sn were investigated with the binding energy regions of Cu 2p XPS spectra, Sn 3d XPS spectra, and Cu LMM Auger spectra. Change of the crystallinity of the films was observed with XRD spectra. Using contact angle measurement, surface free energy (SFE) and wettability of the CuSn thin films were studied with distilled water (DW) and ethylene glycol (EG).

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.29-33
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• 2003

Material and electrical properties of copper-based ohmic contacts on n-type 4H-SiC were investigated for the effects of the post-annealing and the metal covering conditions. The ohmic contacts were prepared by sequential sputtering of Cu and Si layers on SiC substrate. The post-annealing treatment was performed using RTP (rapid thermal process) in vacuum and reduction ambient. The specific contact resistivity ($p_{c}$), sheet resistance ($R_{s}$), contact resistance ($R_{c}$), transfer length ($L_{T}$), were calculated from resistance (RT) versus contact spacing (d) measurements obtained from TLM (transmission line method) structure. The best result of the specific contact resistivity was obtained for the sample annealed in the reduction ambient as $p_{c}= 1.0 \times 10^{-6}\Omega \textrm{cm}^2$. The material properties of the copper contacts were also examined by using XRD. The results showed that copper silicide was formed on SiC as a result of intermixing Cu and Si layer.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.9-15
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• 2009

Compared to the flip-chip process using solder bumps, Cu pillar bump technology can accomplish much finer pitch without compromising stand-off height. Flip-chip process with Cu pillar bumps can also be utilized in radio-frequency packages where large gap between a chip and a substrate as well as fine pitch interconnection is required. In this study, Cu pillars with and without Sn caps were electrodeposited and flip-chip-bonded together to form the Cu-Sn-Cu sandwiched joints. Contact resistances and die shear forces of the Cu-Sn-Cu sandwiched joints were evaluated with variation of the height of the Sn cap electrodeposited on the Cu pillar bump. The Cu-Sn-Cu sandwiched joints, formed with Cu pillar bumps of $25-{\mu}m$ diameter and $20-{\mu}m$ height, exhibited the gap distance of $44{\mu}m$ between the chip and the substrate and the average contact resistance of $14\;m{\Omega}$/bump without depending on the Sn cap height between 10 to $25\;{\mu}m$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.192-193
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• 2007

An evaporated Ti/Pd/Ag contact system is most widely used to make high-efficiency silicon solar cells, however, the system is not cost effective due to expensive materials and vacuum techniques. Commercial solar cells with screen-printed contacts formed by using Ag paste suffer from a low fill factor and a high shading loss because of high contact resistance and low aspect ratio. Low-cost Ni and Cu metal contacts have been formed by using electro less plating and electroplating techniques to replace the Ti/Pd/Ag and screen-printed Ag contacts. Ni/Cu alloy is plated on a silicon substrate by electro-deposition of the alloy from an acetate electrolyte solution, and nickel-silicide formation at the interface between the silicon and the nickel enhances stability and reduces the contact resistance. It was, therefore, found that nickel-silicide was suitable for high-efficiency solar cell applications. Cu was electroplated on the Ni layer by using a light induced plating method. The Cu electroplating solution was made up of a commercially available acid sulfate bath and additives to reduce the stress of the copper layer. In this paper, we investigated low-cost Ni/Cu contact formation by electro less and electroplating for crystalline silicon solar cells.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.548-551
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• 2007

Organic field-effect transistors (OFETs) are of interest for use in widely area electronic applications. We fabricated a copper phthalocyanine (CuPc) based field-effect transistor with different substrate temperature. The CuPc FET device was made a top-contact type and the substrate temperature was room temperature and $150^{\circ}C$. The CuPc thickness was 40nm, and the channel length was $50{\mu}m$, channel width was 3mm. We observed a typical current-voltage (I-V) characteristics in CuPc FET.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.67-73
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• 2009

Compared to the chip-bonding process utilizing solder bumps, flip chip process using Cu pillar bumps can accomplish fine-pitch interconnection without compromising stand-off height. Cu pillar bump technology is one of the most promising chip-mounting process for RF packages where large gap between a chip and a substrate is required in order to suppress the parasitic capacitance. In this study, Cu pillar bumps and Sn bumps were electroplated on a chip and a substrate, respectively, and were flip-chip bonded together. Contact resistance and chip shear force of the Cu pillar bump joints were measured with variation of the electroplated Sn-bump height. With increasing the Sn-bump height from 5 ${\mu}m$ to 30 ${\mu}m$, the contact resistance was improved from 31.7 $m{\Omega}$ to 13.8 $m{\Omega}$ and the chip shear force increased from 3.8 N to 6.8 N. On the contrary, the aspect ratio of the Cu pillar bump joint decreased from 1.3 to 0.9. Based on the variation behaviors of the contact resistance, the chip shear force, and the aspect ratio, the optimum height of the electroplated Sn bump could be thought as 20 ${\mu}m$.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.225-229
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• 2009

The front metal contact is one of the most important element influences in efficiency in the silicon solar cell. First of all selective of the material and formation method is important in metal contacts. Commercial solar cells with screen-printed contacts formed by using Ag paste process is simple relatively and mass production is easy. But it suffer from a low fill factor and a high shading loss because of high contact resistance. Besides Ag paste too expensive. because of depends income. This paper applied for Ni/Cu metallization replace for paste of screen printing front metal contact. Low cost Ni and Cu metal contacts have been formed by using electroless plating and electroplating techniques to replace the screen-printed Ag contacts. Ni has been proposed as a suitable silicide for the salicidation process and is expected to replace conventional silicides. Copper is a promising material for the electrical contacts in solar cells in terms of conductivity and cost. In experiments Ni/Cu metal contact applied same grid formation of screen-printed solar cell. And it has variation of different grid spacing. It was verified that the wide spacing of grid finger could increase the series resistance also the narrow spacing of grid finger also implies a grid with a higher density of grid fingers. Through different grid spacing found alteration of efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.166-169
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• 2006

We fabricated hexagonal copper sulfide $Cu_2S$ nanowires to obtain a larger contact area of $Cu_2S/CdS$ solar cell. Copper sulfide nanowires were grown on Cu foil at room temperature by gas-sol id reaction. The size, density and shape of nanowires seemed to be affected by the change or reaction time temperature, crystallographic orientation of Cu foil, and molar ratio of the mixed gas. We controled the length and the diameter of the nanowires and we obtained suitable nanowire arrays which has fitting size for uniform deposition with n-type CdS. CdS layer was deposited on the nanowire array by electrodeposition and it seemed to be uniform. The $Cu_2S/CdS$ nanowires/CdS junction showed diode characteristics, A large contact area is expected with the $Cu_2S/CdS$ nanowire structure as compared with the $Cu_2S/CdS$ thin film.

• Proceedings of the KWS Conference
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• v.43
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• pp.94-96
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• 2004