We have developed through-hole interconnections in silicon substrates, which can be applied for Micro Electro-Mechanical System (MEMS) devices or high-density packaging. The through-holes were formed by Deep Reactive Ion Etching (DRIE) and filled with Au-Sn solder by Molten Metal Suction Method (MMSM). The MMSM we have proposed is an unique and distinctive technology to fill high aspect ratio through-holes with conductive metal. We could make more than 18,000 conductive through-holes, 30μm in diameter and 300μm in depth, in a 4 inch silicon wafer by the MMSM. We report principle, filling process and optimization of the MMSM. We also present structure, fabrication processes and electrical characteristics of the conductive through-holes.

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We propose a new concept for anisotropic single crystalline silicon (Si) etching simulation. Our approach combines three calculation modules, a molecular dynamics calculation module to define chemical reaction probability, a Cellular-Automaton module to calculate etching rate, and a Wulff-Jaccodine graphical method module to predict an etched shape. This configuration allows mm scale process simulation based on atomic scale physical chemistry of anisotropic Si etching. In this paper, the performance of a newly developed Cellular-Automata module, called CAES (Cellular-Automata Etching simulator), is presented as a first step towards the realization of our simulation concept.

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Polycrystalline Si films are a promising structural material for microsensing devices. On its application, mechanical fatigue phenomena may be worrying in view of long-term reliability. For revealing its mechanism, it is necessary to understand the structural behavior of its correlative grain boundaries (GBs). In the present study, using a conventional admittance spectroscopic technique, we have systematically clarified the formation process and the thermally induced behavior of interface states at GBs in chemical vapor deposited amorphous Si films after thermal annealing. As an unique trial, we have also investigated the correlation between the GBs states and the mechanical properties using polycrystalline Si membranes fabricated. The results indicate that a deeper energy shift of the GBs states is caused by adding an external stress and that its quantity depends on Young’s modulus of the films. We expect that our findings contribute to the solution of fatigue problems of polycrystalline Si films in the near future.

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We have newly developed a prototype model of silicon microfabricated piggyback actuator for positioning a read/write head of magnetic hard-disk drive, which is usually referred to as a dual servo system because the piggyback actuator for fine control is used in collaboration with the voice-coil motor for coarse control. The actuator is made of a 50-micron-thick SOI (silicon on insulator) wafer processed by deep RIE (reactive ion etching) of high-aspect ratio. Actuation mechanism is based upon electrostatic force generated by multiple parallel plates. Maximum displacement of 0.2μ with a dc driving voltage of 20V has been achieved with a 1mm × 0.3mm actuator of its resonance at 25kHz. An analytical model for predicting electromechanical performance has also been developed.

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Rectangular column state titanium oxide particles were prepared by hydrolysis of titanium alkoxides in alcohol solutions. The sizes and the aspect-ratio of the particles were varied depending on a reaction period. The particles obtained were amorphous before heating treatment. The particles posessed anatase structure after being heat-treated at 500 °C for 1 hour.

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The electrical and mechanical properties of piezoelectrics for power generation in wearable electronic devices were measured using an experimental apparatus. With a 40 N applied load, the peak output power of PZT system transducers was measured at 3 μW, comprising 1.8 V and 1.7 μA. The electro-mechanical coupling constant was measured at 0.53 using PZT in the same apparatus in short- and open-circuit conditions. It is possible to harness mW power by installing piezoelectric transducers on the soles of footwear, where the total weight of a human is applied most efficiently.

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