A new process is developed for a surface micromachine fabrication with a small sticking problem. Electroplated Ni film is used as maicromachine material and a resist for the image reversal process is used as a sacrificial layer. The processes for the image reversal are carried out before making movable structures. The resist is developed after making movable structures. Movable structures are fixed by small resist columns when the development of the sacrificial layer resist is finished. Finally, the small columns are removed by O₂ plasma. Cantilevers with long and wide beam are fabricated by the new process. The cantilever with 1000μm length and 100μm width beam can be fabricated without the sticking problem. The mechanical properties of the electroplated Ni film are examined. It is found that the mechanical properties of the electroplated Ni film is almost same as those of a bulk Ni.

View full abstract

Recovery of stiction-failed micro-cantilevers by using electrical heating has been proposed and confirmed for silicon oxide cantilevers. Micro-cantilevers with various lengths have been fabricated by surface micromachining process. Recovery of stiction-failed micro-cantilevers with heating elements is possible on cantilevers made of silicon oxide. By using a thermal model that considers the sum of elastic force and thermoelastic force as restoring force, the freestanding yield after heating is calculated. The theoretical results exhibit qualitative agreement with the experimental data of both silicon oxide and silicon cantilevers. The results suggest validity of the present model, and the feasibility of the proposed device.

View full abstract

The capacitive-type sensor with a new microelectrode to suppress the swelling of the humidity sensitive polymer film was developed for prototype purpose utilizing the MEMS ( Micro Electro Mechanical Systems ) technology to overcome one of the weak points of conventional sensors. The first trial sample made as a prototype sensor showed a steep standing up of the sensor capacitance output at the lower humidity region. In addition, the sensor capacitance output has increased steeply in the high humidity region after the sensor was left in a hot and humid atmosphere for a long time. It is explained that one of the causes is the water adsorption on the surface of the sensor, due to the change of the state of the polymer surface from hydrophobic into hydrophilic. The influence of the polymer surface on the sensor performance was suppressed by applying an additional shield metal film on top of the polymer surface. As a result the sensor with improved sensor structure showed an excellent performance within the range of 10-50 %RH after the exposure to a hot and humid atmosphere.

View full abstract

A new structure for display device is proposed and fabricated by MEMS process. The device is based on physical contact and evanescent coupling between a sheet waveguide and electrostatically driven multi-cantilevers. When incident light is propagated into the waveguide and the cantilevers are contacted to the waveguide by applying dc voltage, the switched light is emitted from side-edges of the contacted multi-cantilevers resulting in display device. The device contributes to expansion of switching-area, removal of unnecessary scattered light and high contrast due to the simple fabrication and structure with corner spacers for optical-separation between cantilevers and the waveguide. From experimental result of the device, a contrast of 0.9 is obtained at 170V, and stable drive is realized up to 1kHz. Therefore, the device can be expected to apply to display device by the fabrication of an array structure.

View full abstract

We proposed a new analysis of the quartz crystal chemical sensors by using both the elastic and the electric equivalent circuit theories. We applied it to determine the frequency-temperature characteristics of the crystal resonators in solution, so that we were able to confirm that our analysis could be effective to explain the experimental characteristics in the network analyzer.

View full abstract