Organic photovoltaics (OPVs) and dye-sensitized solar cells (DSSCs) have drawn great interest from both academics and industry, due to the possibility of low-cost conversion of photovoltaic energy at reasonable efficiencies. This review focuses on recent progress in molecular engineering and technological aspects of fused-thiophene-based organic dye molecules for applications in solar cells. Particular attention has been paid to the design principles and stability of these dye molecules, as well as on the effects of various electrolyte systems for DSSCs. Importantly, it has been found that incorporation of a fused-thiophene unit into the sensitizer has several advantages, such as red-shift of the intramolecular charge transfer band, tuning of the frontier molecular energy level, and improvements in both photovoltaic performance and stability. This work also examines the correlation between the physical properties and placement of fused-thiophene in the molecular structure with regard to their performance in OPVs and DSSCs. OPEN ACCESSPolymers 2014, 6 2646

In semiconductor metallization processes, the galvanic corrosion of metals should be controlled to improve the process integrity. Refractory metals such as tantalum and tantalum nitride ͑TaN x ͒ are widely used as a barrier metal to prevent the copper ͑Cu͒ metal from diffusing into the dielectric layers. In this study, the galvanic effect between the Cu seed and the TaN x film, which is deposited with different nitrogen ͑N 2 ͒ gas flow rates was investigated using chemical mechanical polishing slurries. It was found that the galvanic corrosion of the TaN x films decreased whereas the galvanic corrosion of the Cu seed increased as the N 2 gas flow rate increased. The whole Cu corrosion rate was higher than that of the TaN x films because the intrinsic corrosion of the Cu seed dominated the overall Cu corrosion rate in the acidic slurry, but for the TaN x films the galvanic corrosion dominated. This study also proposed a model to reveal the galvanic effect between the Cu seed and various TaN x films.In sub-130 nm semiconductor device manufacturing, copper ͑Cu͒ has been used as the interconnection metal as a replacement for aluminum because the Cu metal has higher electromigration resistance and lower resistivity. Different from the metal-etching patternization in the aluminum metallization process, the Cu metal lines are produced by the damascene process including the deposition of diffusion barriers and Cu metals and the removal of overburden metals by chemical mechanical polishing ͑CMP͒. 1-13 For the Cu metallization, a barrier layer is necessary to prevent Cu metal from diffusing into dielectric layer. The materials used as barrier layers should not only be thin enough to reduce effective metal resistance but also have compatible adhesion between the Cu metals and dielectric layers. 14-22 In addition, good step-coverage is necessary for the barrier deposition to form a uniform layer along the feature surfaces and corners. Tantalum and tantalum nitride ͑Ta/TaN x ͒ films have been widely used as the diffusion barriers for Cu metallization because of their excellent chemical and thermal stability. The physical properties of TaN x films deposited with different nitrogen ͑N 2 ͒ gas flow rates have been widely investigated in prior literatures. [22][23][24][25] Some researchers have investigated the roles of the nitrogen content on the mechanical properties, microstructures, and electrical characteristics of the TaN x barriers. 7-9 As the N content in the TaN x films increased, the barrier property against the Cu diffusion was improved by blocking Cu diffusion paths, but the film resistivity increased in the meanwhile. Our previous study has reported that as the N 2 flow rate increased from 0 to 10 sccm, the phase of the TaN x gradually transformed from ␤-Ta to body-centered cubic-Ta. Further increase in the N 2 flow rate from 10 to 24 sccm resulted in the phase transformation of the TaN x films to hexagonal Ta 2 N. Finally, the face-centered cubic-TaN phase composed mainly of an amorphous phase was observed when the ...

The composition of the plating electrolyte is important in a copper (Cu) electroplating process. The consumption rate of bis(3-sodiumsulfopropyl disulfide) (SPS) has a strong correlation with the electroplating current density. The decomposition of SPS is relative to the electroplating charge and to the age of the Cu anode. The cathodic current density improves SPS breakdown, and it increases the generation of by-products resulting from SPS decomposition. The aged bath is examined using potentiodynamic polarization and electrochemical impedance spectroscopy. The aged bath helps increase cupric ion reduction because the concentration of cupric ions increases with time after Cu electroplating. The SPS species reacted with cuprous ions to produce the Cu-accelerator complex, which increased the depolarization effect.

Boron and zinc oxide (ZnBO) glass added in dielectric materials have drawn a great attention recently due to the low firing temperature. Microwave dielectric properties of the Ba 2 Ti 9 O 20 -based ceramics with ZnBO addition up to 3 wt% were investigated at the sintering temperatures ranging from 900 to 960 C. Effects of the ZnBO addition on the bulk density, microstructure, and dielectric properties of the Ba 2 Ti 9 O 20 -based ceramics at microwave frequency were elucidated. X-ray diffraction (XRD) results show the presence of five crystalline phases, in the sintered ceramics, depending upon the amount of ZnBO addition. Optimum dielectric properties were obtained for the Ba 2 Ti 9 O 20 -based ceramic with 1 wt% ZnBO addition and sintered in air at 940 C for 2 h, having the dielectric properties: Q ¼ 1137 (Q Â f ¼ 8300), " r value ¼ 27:3, and f ¼ 2:5 ppm/ C.

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The effects of Bi2O3 addition on the microwave dielectric properties and the microstructures of Zn0.95Mg0.05TiO3 + 0.25TiO2 with 1 wt% 3ZnO–B2O3 (ZnBO–ZMT') ceramics prepared by conventional solid-state routes have been investigated. In a preliminary study, it was shown that ZnBO–ZMT' ceramics can be sintered to a theoretical density higher than 95% at 900°C. In this study, the effects of Bi2O3 additions of up to 10 wt% on the sintering characteristics of the ZnBO–ZMT' ceramics was investigated at the sintering temperatures ranging from 860 to 960°C. Sintered ceramic samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). It was found that as the content of Bi2O3 increases, the density of the sintered ceramics increases, and the sintering temperature can be lowered to 880°C by adding 5 wt% Bi2O3. The ZnBO–ZMT' ceramic with 5 wt% Bi2O3 addition sintered at 880°C exhibits the optimum dielectric properties: Q×f=4000 GHz, ε r=24.6, and τf=-14 ppm/°C. Unlike the ZnBO–ZMT' ceramic without Bi2O3 addition sintered at above 920°C, the ceramics with Bi2O3 additions show no Zn2TiO4 existence at 960°C sintering. It is therefore demonstrated that the addition of Bi2O3 can suppress the formation of Zn2TiO4 in ZnBO–ZMT' ceramics.

In this letter, microwave annealing over a wide range of power (300–2700 W) in nitrogen ambient was performed on TiN/Al/TiN/HfO2/Si metal-oxide-semiconductor capacitors. Capacitors with rapid thermal annealing at 500 °C were also fabricated for comparison at the same wafer temperature measured during microwave annealing at 2700 W. For microwave annealed capacitors, key parameters such as equivalent oxide thickness, interface state density, oxide trapped charge, leakage current density, and breakdown voltage were all improved with increasing microwave annealing power. For the capacitor with rapid thermal annealing at 500 °C, diffusion of Al into TiN and growth of the interfacial oxide layer are detected, leading to the shift in flat-band voltage and increase in equivalent oxide thickness, respectively. The results further indicate that it is more effective to remove the charged traps by microwave annealing than by rapid thermal annealing, and the reduction in leakage current density after microwave annealing corresponds to the reduction in charge traps based on a trap-assisted tunneling model. With no trade-off relationship between the electrical characteristics and no undesired effect such as diffusion of species, microwave annealing demonstrates great potential for the post-metallization annealing process for the high-k/metal gate structure.

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