발간논문

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Isothermal annealing and electromigration tests were performed at 125℃ and 125℃, 3.6×104 A/cm2 conditions, respectively, in order to compare the growth kinetics of the intermetallic compound (IMC) in the Cu/thin Sn/Cu bump. Cu6Sn5 and Cu3Sn formed at the Cu/thin Sn/Cu interfaces where most of the Sn phase transformed into the Cu6Sn5 phase. Only a few regions of Sn were not consumed and trapped between the transformed regions. The limited supply of Sn atoms and the continued proliferation of Cu atoms enhanced the formation of the Cu3Sn phase at the Cu pillar/Cu6Sn5 interface. The IMC thickness increased linearly with the square root of annealing time, and increased linearly with the current stressing time, which means that the current stressing accelerated the interfacial reaction. Abrupt changes in the IMC growth velocities at a specific testing time were closely related to the phase transition from Cu6Sn5 to Cu3Sn phases after complete consumption of the remaining Sn phase due to the limited amount of the Sn phase in the Cu/thin Sn/Cu bump, which implies that the relative thickness ratios of Cu and Sn significantly affect Cu-Sn IMC growth kinetics.

keyword : Cu/thin Sn/Cu bump, intermatallics, annealing, electromigration, scanning electron microsopy, SEM

In order to obtain a suitable back contacting electrode for Cu(InGa)Se2-based photovoltaic devices, a molybdenum thin film was deposited using a chemical vapor transport (CVT) during the hydrogen reduction of MoO3 powder. A MoO2 thin film was successfully deposited on substrates by using the CVT of volatile MoO3(OH)2 at 550℃ for 60 min in a H2 atmosphere. The Mo thin film was obtained by reduction of MoO2 at 650℃ in a H2 atmosphere. The Mo thin film on the substrate presented a low sheet resistance of approximately 1 Ω/sq.

keyword : solar cells, vapor deposition, hydrogen reduction, electrical properties, conductivity/resistivity

The multi-layered thin film with an ITO/Ag/ITO structure was produced on PET by using magnetron reactive sputtering method. First, 30 nm of ITO thin film was coated on PET by using normal temperature process. Then 20-52 nm of the Ag thin film was coated. Lastly, 30 nm of ITO thin film was coated on Ag layer. The sample of the 20 nm Ag thin film showed more than 70% transmission and a 2.7Ω/□ sheet resistance. When compared to the existing single-layered transparent conducting thin film, multi-layered film was found to be superior with about 5Ω/□ less sheet resistance. However, since the Ag layer became thinner, the band gap energy needs to be increased to more than 3.5 eV.

keyword : optical material, sputtering, electrical properties, AES