The National R&D Project “Micromachine Technology” was launched in 1990 by the Ministry of International Trade and Industry. The target was to establish a technological paradigm of micromachine, which was supposed to be applied for a variety of domains, i.e. maintenance in complex industrial facilities, less invasive medical treatment and diagnosis, less energy consumption manufacturing system. The R&D approach originated from miniaturization of machine system and was different from those in the overseas. The Project run over the last decade of 20th century in the depressed economy and ended in March 2001 with many technological results and substantial impact on the public as well as research society. This paper summarizes background of Project initiation, implementation approach and major technological results. And also it takes a look at a foreseeable course in future.

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When a micromachine works in a narrow space inside of tubes and equipments such as a microfactory, a microdevice that has a visual function is indispensable. To monitor the minute shapes of microfabrication and microassembly process that are impossible to observe, inspection mechanism (environmental recognition devices) has been developed. The devices are designed to allow stereoscopic and microscopic observation and to measure the dimensions of microparts. To achieve these goals and to realize minute structures and functions, we developed a fiber-optic tactile sensor for microscopic observation, fiber-optic actuators for stereoscopic observation and tip articulation. The environmental recognition devices that integrate stereoscopic observation, tactile sensing and tip articulation mechanism have been developed. In microfactory, inspection mechanism such as measuring size of micro-gear molds fabricated by electrochemical processing and the assembly of the gear train have been confirmed using the devices.

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High-density 3D packaging technology for a CCD micro-camera system module consisting of an experimental wireless micromachine for inspection of 10 mmφ inner surface of tubes in electric power generators has been developed by applying high-density interconnection stack-unit modules that have fine-pitch flip-chip interconnections within copper-column-based solder bumps and high-aspect-ratio sidewall footprints for vertical interconnections. Copper-column-based solder bump design and underfill encapsulation resin characteristics were optimized to reduce the strain in the bump and to achieve fine-pitch flip-chip interconnection with high-reliability. High-aspect-ratio sidewall footprints were realized by the copper-filled stacked vias at the edge of the substrate. High-precision distribution of sidewall footprints was achieved by laminating multiple stack-unit substrates simultaneously. The fabricated 3D package has operated satisfactorily as the CCD imaging data transmission circuit module and it has been confirmed that the output CCD images have high resolution which enables 20μm objects to be distinguish inside 10mmφ tubes. The technology was confirmed to be effective for incorporating many devices of different sizes at far higher packaging density than it is possible to attain using conventional technology.

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We developed a technique that prevents the leakage of the liquid from a channel and applied it to micro-trochoid pump. When a minute texture is formed on the interior wall of a channel and is coated by a low-surface-energy material that is much thinner than the texture, the wettability of the surface can be greatly reduced. This technique is effective in sealing liquid in a channel. And it can seal the water at a pressure difference of 18.1 kPa in a gap of 5 μm. This seal can then be used in high-output micro-trochoid pump.

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We propose a new digital all-in-focus microscope system using a quick-response dynamic focusing lens suitable for micro parts assembling. This microscope system realizes real-time observation for micro parts with a deep depth of field, as well as three-dimensional shape measurement using only one image sensor. This system consists of a quick response deformable lens using a multi-layered piezoelectric bimorph micro actuator, a CCD camera, an image data processor and a display. In this paper, we report a newly developed real-time algorithm called one pixel method for generating clear image having a deep depth of field. This method is able to process one original picture (640×480 pixels per frame) in approximately 1.0 ms. We also report the results three-dimensional shape measurement in high accuracy using the contrast of brightness method.

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We have developed a compact and low power consumed control circuit for a wireless in-pipe inspection micromachine. The micromachine consists of a CCD camera, a locomotive device, a system control circuit and wireless energy supply and communication devices, and moves in a 10mm diameter pipe without wire and observes the inner surface of the pipe using the installed CCD camera. The developed control circuit controls all installed devices in the micromachine by commands from outside and transmits the image data from the CCD camera. As for the control circuit, the power consumption and the size are greatly restricted in order to be installed in the micromachine. In order to reduce the size of the circuit, we have newly developed an image data communication LSI based on a new architecture. The LSI has the size of 3.9mm by 3.9mm and the power consumption of 45mW. To make the control circuit compact, we used a flip chip assembly for the LSI and eight more ICs in the system. Through a fabricated prototype of the micromachine, we have successfully confirmed the wireless in-pipe locomotion and wireless image data communication of 2.25 frames per second.

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This paper investigates a new process for assembling micro components by bonding element using magnetic polarity and attraction. The components can be connected mechanically and electrically by these bonding elements without accurate component positioning. The new bonding elements which have a larger permanent magnet area with an electrode function have been developed. A new process for the bonding element using negative tone resist(SU-8) has also been developed. The linearity of the tapered angle was improved by adjusting the roughness of substrate ground. The bonding elements with taper shape of 160 μm in thickness and tapered angle of 15 degrees were fabricated and the mechanical and electrical performance was verified.

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This paper discusses a fundamental research project aimed at developing. The project was motivated by the need for better microactuator technology that can be used for micro-robots and other micro applications. A range of artificial muscle technologies was investigated, and a class of electroactive polymers based on the electric field-activated deformation of dielectric elastomers was selected as the most promising approach for an in-depth-study. The dielectric elastomer polymers are sandwiched between two compliant electrodes. Actuation is accomplished by the application of a voltage difference between the two electrodes, which squeezes and stretches the film. A variety of polymer and electrode materials have been tested. Excellent actuator performance has been achieved by this approach, with actuated strains over 300%, actuation pressures of 1-8 MPa, response times of less than 0.5 ms, and theoretical efficiencies of over 80%. Corresponding specific energy densities exceeded 3 J/g, and are believed to be the highest ever observed for a field-actuated material, based on the available literature.

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Heteroepitaxial BaTiO₃ thin films were prepared by RF magnetron sputtering under various gas pressures ranging from 0.08 to 27 Pa. Influence of the gas pressure was investigated through characterization of X-ray diffraction analyses and ferroelectric properties of the epitaxial BaTiO₃ films. When the substrates were placed at a position directly above the sputtering target and the epitaxial films were grown under lower gas pressures, the epitaxial films were crystallographically damaged and no ferroelectricity was observed due to ionic bombardment of particles which are generated at the surface of the target and accelerated by plasma sheath voltage. When the films were grown under higher pressures, the lattice misfit strain was relaxed and ferroelectric properties were degraded, because of a lack of assistance from the irradiated sputtering particles. Sputtering under intermediate gas pressure of 6.3 Pa resulted in optimized crystallinity and ferroelectric properties, in which lattice misfit strain and remanent polarization, 2P_r, were 5% and 43 μC/cm², respectively. We concluded that control of energy and/or amount of the irradiated particles at the film surface during heteroepitaxial growth is essential to improve ferroelectric properties of BaTiO₃ thin films.

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A radical-source molecular beam epitaxy (RS-MBE) apparatus was used to grow ZnO films on Si substrates. The surface nitridation of the Si substrates prior to the ZnO growth was found to be critical for improving the film quality. The ZnO films with strong c-axis orientation and predominant near bandedge emissions have been successfully grown.

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Conductive interconnection through Silicon (Si) substrate has been required as one of the essential elements for high-density packages, module assemblies and/or system integration for many years. In this paper, we demonstrated to form metal filled Through-Holes (THs) from the front to the back of thick Si wafer (∼500 μm) by Optical Excitation Electro-polishing Method (OEEM) and Molten Metal Suction Method (MMSM). The conductive interconnections through thick Si substrate formed by the both technologies have more than 500V dielectric breakdown voltage of insulator between the Si substrate and the filled metal and leakage free structure between the front and the back of the substrate. In our experiments, 3,500THs/mm² were formed in a thick Si substrate, and Sn was filled after the formation of insulation layers in the THs. These metal filled THs can be applied for Si terraces, Si Optical Bench (SiOB), 3D-stacked IC or other System In Package (SIP). In addition, water glass bonding is proposed as a low temperature and stress free sealing technique for the 3D-stacking IC fabrication.

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