A new type of Prussian blue modified electrode is described. The Prussian blue modified electrode is electrochemically prepared in a solution of ferric‐ferricyanide. The amount of Prussian blue on electrodes such as platinum, glassy carbon, and SnO2 is easily controlled by changing the current density, the electrode potential, and the time of the electrolysis. The waves observed at +0.2 and +1.0V vs. SCE are due to the reduction and the oxidation of the ferric part and of the ferrous part in the Prussian blue crystal, KFeIIIFeII false(CN)6 or Fe4IIIfalse[FeII false(CN)6]3 , respectively. This electrode exhibits excellent stability in aqueous solution. A spectroelectrochemical property of the modified electrode is also described.

An electrochromic display based on a Prussian-blue-modified electrode is described. Prussian blues are deposited electrochemically in a solution of ferric-ferricyanide. Current flow at +0.2 and +1.0 V is due to the reduction of Fe3+ and the oxidation of Fe2+ in the Prussian-blue coating, respectively. The result is a display that switches from clear to blue, has high stability, and has a response of less than 100 ms.

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To improve the safety of the electrolyte used for lithium secondary batteries, binary mixed solvent electrolytes containing trifluoropropylene carbonate ͑TFPC͒ as cosolvent have been studied. Chloroethylene carbonate ͑ClEC͒, ethylene carbonate, and propylene carbonate were chosen as the other component of the binary mixed solvent for the electrolytes. The solution properties of these electrolytes were characterized using conductivity and nuclear magnetic resonance ͑NMR͒ spectroscopy. The chemical shift of ClEC and TFPC did not vary with the mixing ratio due to their similar enthalpies of solvation as derived by molecular orbital simulation. The ClEC/TFPC electrolyte showed higher discharge capacities with lower irreversible capacity loss in both a graphite/Li cell and Li 1ϩx Mn 2 O 4 /Li cell than other electrolyte systems. Electrochemical impedance spectroscopy measurements were made for cells composed of each electrolyte. The surface of the graphite anode was analyzed using X-ray photoelectron spectroscopy, infrared spectroscopy, and solid 7 Li-NMR spectroscopy.

The metal capping barrier deposited by the electroless cobalt tungsten boron ͑CoWB͒ alloy plating method for ultralarge scale integration applications was investigated. The CoWB film was formed directly on copper without a palladium catalyst, using dimethyl amin borane ͑DMAB͒ as a reducing agent, and it was deposited selectively on 0.25 m wide copper interconnects separated with 0.25 m spacing SiO 2 . The CoWB thin films were effective barriers against copper diffusion even at CoWB thicknesses as low as 50 nm. Compared with the CoWB film, cobalt tungsten phosphorus films deposited directly on copper using DMAB as a deposition initiator was not effective as a copper diffusion barrier. The plating films contained mainly cobalt with a significant amount of tungsten ͑up to 20 atom %͒ and a small amount of boron. Additionally, we propose a newly developed alkaline metal free electroless CoWB plating solution using tetramethyl ammonium hydroxide as a pH adjuster.

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Resistivity difference between Cu wires made with plating using high purity ͑new plating process͒ and conventional purity ͑conventional process͒ materials has been evaluated in order to develop the process for the realization of high performance LSIs. This resistivity difference is relatively small, i.e., 8% when line width is wide ͑200 nm͒. However, it increases with the decrease in line width, and it reaches about 20%, i.e., 2.8 ⍀ cm for the former and 3.5 ⍀ cm for the latter at 50 nm line width. A 50 nm wide Cu wire formed with the new plating process had more uniform and larger grain sizes and lower impurity concentrations than the wire formed with the conventional process.Copper has been used as an interconnect material for high performance ultralarge scale integrations ͑ULSIs͒ due to its low electrical resistivity and high reliability. However, the resistivity of Cu interconnects increases significantly with a decreasing line width of less than 100 nm. 1-4 This is becoming a critical issue for the realization of high speed ULSIs, and it is mainly because the line widths are comparable to the mean free path of the electron ͑40 nm͒; hence, electron scattering occurs at the grain boundaries, resulting in the higher resistivity of very narrow Cu wires. 5 To lower the resistivity, both the coarsening of the grain sizes and reduction of the thickness of high resistivity barrier metals in Cu wires are very important. Self-forming barriers using Cu-Mn or Cu-Ti alloys and atomic layer deposition are possible candidates to promote the formation of thinner barriers. 6,7 The most effective method to reduce Cu wire resistivity is to lower the resistivity of the Cu wires themselves by coarsening the grain sizes. It has been recently reported that impurities such as oxygen, sulfur, and nitrogen concentrate on the grain boundaries of Cu wires and depress their grain growth during annealing. 8,9 These results imply that low resistivity Cu wires can be formed if high purity, very narrow Cu wires can be formed.Hence, we focused our attention on the purification of Cu wires using a newly developed nominal high purity 9N anode and nominal high purity 6N-CuSO 4 ·5H 2 O electrolyte ͑new plating process͒. Resistivities of Cu wires formed with the new plating process were measured and compared to those of Cu wires formed with a conventional purity 4N anode and 3N-CuSO 4 ·5H 2 O electrolyte ͑conven-tional process͒.Using the new plating process, we achieved 50 nm Cu wires with ϳ20% lower resistivity than those made by the conventional process. In this paper, we first investigated grain sizes and textures of plated films obtained using the new plating and conventional processes. Then, the resistivities of Cu wires made with the new plating process were evaluated as a function of wire width in comparison with those of Cu wires formed with the conventional process. Finally, we considered the mechanism for achieving low resistivity by evaluating the grain sizes, impurities, and lattice images of 50 nm wide Cu wires made by both the new p...

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