Copper bottom-up deposition in 200 nm trenches by an acid-copper sulfate with only two additives ͓poly͑ethylene glycol͒ ͑PEG͒ and Cl Ϫ ] is achieved. The inhibiting effect of electrodeposition by PEG is strongly related to Cl Ϫ concentration. Secondary-ion mass spectroscopy measurements show that Cl Ϫ is consumed in the electroplating process. The explanation of bottom-up deposition realized in copper superfilling, in which the decrease of Cl Ϫ concentration causes rapid electrodeposition on trench bottoms, is verified experimentally.Copper on-chip interconnection is a current topic in the semiconductor industry. It became possible by copper superfilling 1 of trenches and vias in the damascene process. The superfilling is achieved by the presence of additives in the acid-copper sulfate electroplating bath. Many studies based on the diffusion-adsorption theory 2-11 have been carried out to understand the superfilling process. In those studies, it is assumed that additives inhibit the electrodeposition and are consumed on the plating surface. Due to the diffusional limitation, concentration of additives is decreased in the trench bottom and rapid deposition from the bottom occurs. However, the mole fraction of additive-derived impurities ͑C, O, S, Cl͒ measured by secondary-ion mass spectroscopy ͑SIMS͒ is smaller than the expected value from the diffusion-adsorption based theories. 12-14 So far, poly͑ethylene glycol͒ ͑PEG, Mw about 3000͒ is considered a main inhibitor. The expected diffusion coefficient of the inhibitor is the same order of Cu 2ϩ 8 and it is large for the size of the additives. Then, recent studies showed interest in catalytic additives like bis͑3-sulfopropyl͒disulfide ͑SPS͒ or 3-mercapto-1-propanesulfonate ͑MPSA͒. [15][16][17] In this study, to understand the superfilling mechanism, the inhibition by PEG and Cl Ϫ is carefully investigated by measuring overpotential of an electrode being electroplated. Overpotential MeasurementThe cell for the electroplating experiments is a 500 mL beaker submerged in a water bath at 298 Ϯ 0.5 K. The working electrode ͑WE͒ is a polished platinum disk in an epoxy resin. To assume a one-dimensional flow of current, ions, and additives, the WE is covered by a resin plate which has a cylindrical hole ( ϭ 3 mm). The WE is preplated with copper at 200 A/m 2 for 20 s in the electrolyte of interest before each experiment. After preplating, the electrolyte of the bath is spit out from a thin tube connected to a pump for supplying fresh electrolyte in the hole. To avoid contamination of Cl Ϫ , a copper plate in the cover resin is used as a reference electrode which is expected to work as a stable Cu/CuSO 4 electrode. The composition of the standard electrolyte is 225 g/L CuSO 4 •5H 2 O and 55 g/L H 2 SO 4 . All electrodes are connected to a potentiostat ͑Hokuto Denko, HABF501͒ and constant current is applied for copper electrodeposition on the WE. Figure 1 shows the time variation of overpotential when Cl Ϫ is added to a 3000 Mw PEG containing electroplating bath. The concent...

A fabrication technique of miniature fuel cell electrodes was developed from Si wafers. The fuel channels, porous layer, and catalyst layer were formed in the Si wafer. The fuel channels were fabricated by photolithographic patterning and subsequent wet etching on the Si. The porous layer was formed by anodization of Si from the polymer electrolyte membrane side through the bottom of the fuel channels. Catalyst metals were deposited inside the porous layer by wet plating. The two electrodes were hot-pressed with a Nafion 112 sheet. Open-circuit voltage of 840 mV and maximum power density of 1.5 mW/cm 2 were observed by hydrogen feed.The increasing interest for portable electronic systems drives the research toward integrated regenerating power sources with small dimensions and miniaturized fuel cells are attractive. The microfabrication technology of Si is an important tool to reduce the fuel cell structure to micrometer sizes and have been employed by several research groups. 1-11 Those miniaturized fuel cells using various degrees of microfabrication techniques have been reported. Lee et al. 1 created flowfields on Si substrate and formed hydrogen feed fuel cell array on a Si wafer. Kelley et al. 4 created catalyst layer supporter on a Si chip and demonstrated that the miniaturized direct methanol fuel cell ͑DMFC͒ has almost same performance as state-of-the-art larger fuel cells. However, those miniaturized fuel cells uses conventional catalyst layers, in which Pt/Ru on activated carbon is splayed on the gold sputter deposited silicon electrodes or conventional membrane electrode assembly ͑MEA͒ is used, and treating powders such as activated carbon is not suitable for silicon batch fabrication process. To adapt the construction process to more Si processing steps, various approaches have been tried. In those studies, catalyst metals were deposited by physical vapor deposition ͑PVD͒ on porous layers formed by photolithographic patterning or anodization of Si. 5-8 Generally, it is difficult to deposit materials inside a porous layer by PVD and the catalyst deposits only on the surface of the porous layer and the performance of the catalyst will be poor. Therefore, a different approach to forming a catalyst layer should be developed. Recently, D'Ariggo et al. 9 proposed a novel Si-based electrode fabrication technique, although the power generation is not reported yet. In this technique, the fuel channels were formed inside the Si substrate by depositing an epitaxial Si layer after wet etching of a Si substrate, then the deposited epitaxial Si layer was anodized and the porous Si layer was obtained. Pt and Ru were electrodeposited into the porous layer and the catalyst layer was formed. Generally, resistivity of porous Si is high and it has been supposed to be difficult to use a porous Si layer as a catalyst support layer. However, porous Si has a large surface area up to 1700 m 2 /cm 3 which is comparable with that of activated carbon 12 and porous Si is attractive if it works as a catalyst support layer, becaus...

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Concentration of real tumor cells leaking into blood from cancer was attempted by a deterministic lateral displacement (DLD) microfluidic device. Spiked cultured cell line tumor cells are often used to verify performance of the circulating tumor cells (CTCs) separation methods. Cultured tumor cells are obviously larger than most of hematocytes and considered not to be appropriate as CTC mimics, while there is uncertainty in identifying real CTCs from clinical samples and there is no practical way to examine CTCs leakage into benign cells during the sorting. In this work, blood samples were prepared from tumor-bearing mice whose tumors were induced by implanting cells with GFP expression to living mice. Therefore, CTCs were identified by their fluorescence emission. We succeeded in the enrichment of tumor cells to 0.05% from the blood, in which CTCs were negligibly detected among three million blood cells, and little loss of CTCs was observed.

In this article, we report on the synthesis and characterization of porous platinum layers on top of highly doped ͑0.007-0.02 and 0.001-0.003 ⍀ cm͒ n-type porous silicon by immersion plating. Porous silicon samples of different morphologies were prepared by electrochemical etching. Plating was performed by simple immersion of the porous samples in HF-containing hexachloroplatinate solutions for some minutes. Scanning electron microscopy showed that the deposits attained up to 8 m depth. Moreover, the achieved platinum deposits have a random pore structure, whereas the original porous silicon substrates show an organized honeycomb-like parallel pore array. Electron probe microanalysis measurements showed that the deposits have very good in-depth homogeneity, indicating also that almost all silicon originally present was etched away by platinum. The electrochemically active surface area of the platinum deposits was determined to be on the order of 80 m 2 /cm 3 by cyclic voltammetry.