In this paper, fabrication methods of metal patterns using ultraviolet nanoimprint lithography (UV-NIL) and electrodeposition are demonstrated. Since the photocurable resin patterned by UV-NIL was directly used for electrodeposition mask, the simple and high-throughput fabrication process was realized. Several examples of functional device using these methods are described.

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A simple fabrication method of Au-electrode-embedded cyclo-olefin polymer (COP) microchip was developed using hot embossing, Au wet etching and low-temperature direct bonding methods. A prototype microchip (dimension: 20 × 40 mm²) was fabricated. The Au electrode coated by electron-beam evaporation was successfully patterned on COP surface without any intermediate metal layers. The adhesion strength between the COP and the Au film was stronger than the strength between quartz and Au, and as same as between Si and Cr. The bond strength between the COP and Au coated on COP plate was strong enough not to leak flow of de-ionized water at the bonded interfaces. Flow behavior of negative-charged fluorescent microbeads indicates that the electrical continuity of Au electrode was kept after the bonding process. This technology is remarkable advantage of integrating electrode in plastic microchips.

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We fabricated a polymer chip for microchip electrophoresis-mass spectrometry (MCE—MS). As a substrate material, cycloolefin polymer (COP) was selected due to its high chemical durability and easy metallization for the electrode. A COP microchip with a conventional cross-type channel configuration for the MCE separation was fabricated by hot embossing. After bonding with a rid substrate, a nano electrospray ionization (nano-ESI) tip structure for MS detection was machined directly at the opening of the separation channel end. A gold electrode to keep the electric contact for ESI was deposited around the nanospray tip by electron beam evaporation. When the voltage of 3.0 and 2.0 kV was applied to the inlet and the ESI electrode, respectively, the formation of Taylor cone and stable electrospray were observed at the channel opening. In infusion analysis of caffeine, the MS spectrum with parent mass number of 195, which accords with that of the protonated caffeine, was successfully obtained in the positive mode. Furthermore, the MCE separation and ESI-MS detection of caffeine and arginine was also successfully achieved with resolution of 1.0. Therefore, these results demonstrated that the fabricated microchip integrated with the nano-ESI tip can be employed as the MCE—ESI-MS device.

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In this study, an experimental system for in-situ observation of the thermal imprint process was constructed, and the material behavior from the initiation of transcription to product removal was precisely studied. Based on the results obtained, effect of the temperature and pressure on the transcription behavior and the shape accuracy was investigated, and the principles to obtain good replication were discussed. In addition, the exfoliation behavior of the material from substrate in the cooling stage after the transcription was observed and its characteristics were discussed.

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Nanoimprint technology is considered one of the mass production methods of the display for cellular phone or notebook computer, with Anti-Reflection Structures (ARS) pattern and so on. In this case, the large size mold with nanometer order pattern is very important. Then, we describe the fabrication process for large size mold, and the alignment method for UV nanoimprint system. We developed the original mold fabrication process using nanoimprint method and etching techniques. In 66 × 45 mm² area, 200nm period seamless patterns were formed using this process. And, we constructed original alignment system that consists of the CCD-camera system, X-Y-θ table, method of moiré fringe, and image processing system, because the accuracy of pattern connection depends on the alignment method. This alignment system accuracy was within 20nm.

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As-grown n-type GaN has been bonded successfully to polycrystalline Al by surface activated bonding in an ultrahigh vacuum at room temperature. The microstructure, bonding strength, and electrical characteristics of the bonded GaN/Al interface have been investigated using transmission electron microscopy (TEM), tensile strength testing, and current-voltage (I-V) measurements. For producing active surfaces, argon-fast atom beam sputtering source (acceleration voltage: 1.5 kV, current: 15 mA) was used. The TEM study showed that a nearly continuous amorphous thin interlayer composed of mainly Al with a thickness of about 10 nm was observed at the bonded interface. The tensile strength of GaN/Al samples was in the range of 14-19 MPa. The results of I-V measurements showed that the n- GaN/Al interface without thermal annealing was rectifying, and became ohmic after thermal annealing in N₂ gas ambient at 600°C.

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The ultra compact optical RGB multiplexer for a pocket projector that size is 8.8(W)×6.0(D)×4.0(H)(mm) was developed by the micro-molding processing. The RGB multiplexer was constructed by the optical filter and three lenses for each RGB laser diode in the molding packaging. The interface of the optical filter and the resin was not existed an air gap by optimizations of molding conditions. We were successfully projected onto a screen using the RGB multiplexer.

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A valveless/diffuser micropump with a thin polyimide membrane was designed, fabricated using surface micromachining and characterized. The micropump was actuated by deforming the membrane with alternating air pressure. The micropump chamber had the depth of 525 μm, and the diameter was 7 mm. The top side of the chamber was covered by the polyimide membrane with the thickness of 5.4 μm, and the polyimide ftlm was deposited using the spin coating technique. The deflection of membrane was large, and was nearly 200μm at the static air pressure of 10 kPa and 350μm at 30 kPa. The residual stress in the polyimide membrane induced through the fabrication processes was estimated to be 18.9 MPa. The static pressure limit of the membrane prior to fracture was over 200 kPa. The flow rate of water in the micropump reached 310 μl/min with the applied air pressure of 10 kPa at 3 Hz. Based on the advantages of surface micromachining processes and nice mechanical characteristics of polyimide membrane, fabrication of further miniaturized micropumps such as nanoliter-level micropumps using similar fabrication processes may be possible.

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We reported on a numerical analysis of the material properties that directly control the quality of the analytic results in our previous paper. In this paper, we focus on parameter optimization for the underfill in high density products such as consumer electronics devices. We report on our methodology to optimize the underfill properties through some parameter studies with numerical analysis.
It is difficult to select the best underfill to be used for the high density packaging. In this study, some currently available underfills and a newly developed one are used in wafer level chip-sized package technology to compare the reliability of the packages against the stress and strain caused at both solder and underfill under thermal stress.

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We have analyzed the effect of penetration of the electric field into the semiconductor on the electrical and mechanical characteristics of comb-drive actuators. In this study we found two specific effects due to the depletion layer: (1) the electro-mechanical conversion factor is a function of the depletion layer and becomes smaller than that for the “ideal conductor” assumption, and (2) an additional stiffness appears in the mechanical system. Following the change in the electro-mechanical conversion factor, the resonance peak becomes lower than that of an ideal conductor. These effects are relatively small when the gap between the comb-fingers and the substrate is of the order of a micrometer. However if the gap is 0.1μm, the electro-mechanical conversion factor decreases by about 2.8%. In this analysis, we have taken only the depletion effect into account; however, for a more complete analysis we should also consider the surface traps induced by unpassivated surface bonds.

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We have developed and characterized a technique of patterning PEDOT:PSS (poly(3,4-ethylenedioxythiophene): polystyrenesulfonate) film with a Parylene peel-off method. PEDOT:PSS has characteristics of transparency and high conductivity which are expected to replace transparent ITO (indium tin oxide) electrodes for flat panel displays. But existing technology of inkjet printing decreased its conductivity by mixing a binder, while the other method with electrochemical etching could not completely remove PEDOT:PSS film. To solve these problems, we proposed a process which consisted of negative patterning of Parylene film, coating of PEDOT:PSS and peeling off of Parylene film with the undesired-area of PEDOT:PSS. To peel off the Parylene from the substrates, the control of heating process of PEDOT:PSS under Parylene glass transition temperature was found to be required. The proposed process revealed that the conductivity was almost the same even after the process and its resolution reached down to 20 μm. Finally, the 300-μm-wide electrodes were fabricated through the process, which leads to replacement of ITO for displays.

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Environmental factors such as dust adsorption effects and humidity generally result in drifts of the sensor output signal and lead to malfunctions of the sensor and/or reduction in sensitivity. So a sensor package is necessary to protect hydrogen sensors in order to operate the sensors in an actual use environment. In this study, a Pt-FET hydrogen sensor covered with a polytetrafluoroethylene (PTFE) porous membrane was developed. The PTFE porous membrane with different pore sizes of 5 μm, 20 μm, and 30 μm was applied and the effects of humidity on sensor sensitivity were evaluated. The results indicate the effects of humidity on the sensitivity were reduced in the relative humidity range between 20% and 80% for the sensor with the 5-μm porous membrane.

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A novel gate-structure FET-type hydrogen sensor (Pt/Ti-FET) that has an adhesion layer (Ti) between the catalytic metal (Pt) and the gate insulator was fabricated. The dependence of the response characteristics of the sensitivity and selectivity on the Ti thickness was investigated. The sensitivity showed dependence on Ti thickness, and higher sensitivity was obtained with a decrement in Ti thickness. In addition, the Pt/Ti-FET showed good selectivity against other gases (O₂, C₂H₆) compared with the Pt-FET. After annealing at 260°C for 30 min under 5 Pa in a vacuum, the Pt/Ti-FET showed different response characteristics from an as-deposited Pt/Ti-FET. The annealed Pt/Ti-FETs with a thin Ti adhesion layer (below 10 nm) showed improved hydrogen sensitivity. In particular, the Ti 5-nm sample of the Pt/Ti-FET sensor showed a higher hydrogen response when exposed to 0.8% hydrogen gas (526.2 mV) compared to that of the Pt-FET sensor (415.7 mV). However, improvement in hydrogen sensitivity was not obtained in thick Ti samples. Additionally, the annealed Pt/Ti-FET showed better selectivity against O₂ than as-deposited Pt/Ti-FET.

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Thermal conduction type gas flow sensor unified with an impurity-gas concentration sensor using the MEMS processing technique is proposed. This unified sensor has a pair of returning groove channels, and each channel has a sensor-unit composed of a central thermocouple and a pair of thermocouples formed by both sides of the central one. The central thermocouple is working as both a heater and a temperature sensor working as a current detection type thermocouple. This unified sensor can measure both carrier gas (H₂) flow and impurity-gas concentration. The impurity-gas is mixed on the way into the H₂ carrier gas. The extremely compact sensor with high sensitivity is able to realize. The carrier gas flow is measured using one of sensor-units, and the impurity-gas concentration is obtained from measurement of differential temperature difference between two central thermocouples of sensor-units in the cooling process after cease of thermocouple-heating during stopping the gas flow.

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