When accelerated electrons enter a semiconductor device, each of them produces thousands of electron-hole pairs. This electron-bombarded multiplication is successfully used to establish a photon sensor in conjunction with a photocathode emitting electrons. An operational principle of the electron-bombarded multiplication and performance of photon sensors adopted this technology are described.

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This paper presents a self-generation piezoelectric sensor device for a wireless alarm system. A piezo-generator composed of a steel ball and piezoelectric vibrators senses the impact-induced vibration, and transforms its mechanical energy into electric energy to drive a wireless transmitter. First, the thickness and poling direction / electrode connection of the piezoelectric vibrator are examined to improve the efficiency of the piezo-generator. Next, the mechanical oscillations of a cantilever spring are used to repeat the impact and accumulate the electric energy up to the level enough for driving a micro-computer and a radio transmitter. A prototype wireless alarm system was assembled and worked successfully.

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The DRIE (Deep Reactive Ion Etching) process is one of the most important processes for MEMS field. Especially, a high aspect ratio etching is essential for state-of-the-art devices. This paper describes a new DRIE process that drastically improves the highest aspect ratio of conventional DRIE process. The conventional process deposits a protection layer not only on a trench sidewall, but also on a trench bottom. This isotropic deposition causes a limitation of aspect ratio. To avoid this situation, we have developed a new process that alternately repeats the conventional DRIE process and a O₂ plasma irradiation which forms a thin SiO₂ layer inside the trench within a same chamber. The SiO₂ layer remains on the sidewall during the DRIE proceeds while it on the bottom is removed at the beginning of each DRIE. Therefore, the etching anisotropy is improved. A switching between the conventional DRIE and the O₂ plasma irradiation needs only to change introducing gasses. This simple process can widen a possibility of the conventional DRIE.

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The combination of PZT ceramics with excellent ferroelectric, piezoelectric, and pyroelectric properties with Si micromachining techniques promises the creation of various microdevices including sensors and actuators. The most important technique is the preparation of functionally combined wafers of PZT ceramics and Si single crystals. Three useful techniques that are the fabrication of PZT thin films on Si, the fabrication of PZT thick films on Si and the wafer bonding of PZT and Si are discussed from the point of view of the properties and micromachining of PZT. Thin PZT films on Si are most suitable for microdevices because of their micromachining capability. Thick PZT films on Si are useful for microactuators which create a large force. The wafer bonding of PZT and Si has an advantage in that it delivers the excellent functionalities of PZT ceramics, though its micromachining is difficult.

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A new method of chemical bonding for GaAs on Si has been developed using SeS₂. The bonding between GaAs and Si is very robust and withstands many processing steps. Using the epitaxial lift off (ELO) technique the thin film of GaAs is grafted to Si substrate. The film bonded by this method has longer minority carrier lifetime than heteroepitaxial GaAs film on Si. The current-voltage(I-V)characteristics of p-GaAs/n-Si, n-GaAs/n-Si, p-GaAs/p-Si and n-GaAs/p-Si were measured at room temperature. The I-V curve did not show a rectifying behavior when GaAs was bonded to Si with SeS₂ because of the formation of a high-resistance layer at the interface. The characteristics were greatly improved bsuby small additions of Sn to SeS₂ during the bonding process. The very low resistance is obtained with adding Sn in SeS₂ during the bonding. The properties of solar cells using this method were compared with those grown on Si substrate by heteroepitaxy and GaAs substrate.

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Technological problems for realization of Micro Electro-mechanical System (MEMS) are discussed and an introduction of smart materials (PZT) is encouraged. The film formation and micromachining technology are discussed in integration of PZT thin films into MEMS. Further developments are proposed on PZT micro sensors and actuators with special emphasis laid on exploration of new application fields of MEMS, such as scanning mirror. Internal stress is estimated and analyzed for the improvement of device performance.

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A new type of PLC (Planar Lightwave Circuit)-Optical circulator arranged in a straight line has been successfully fabricated. This device shifts the light propagation direction aside by using blazed diffraction grating, which is realized by MEMS fine fabrication technique. The device is inherently small, and eliminates precise alignment and a magnetic garnet crystal required in conventional bulk devices.

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In order to realize long-term stable multi-channel neural recording, a micro probe array based on a flexible polyimide substrate was designed and fabricated. Each probe was formed by etching a silicon wafer using a Deep RIE equipment. This type of flexible microelectrode can be attached around the soft nervous tissue. This paper shows the fabrication process and the analysis on the flexibility of the electrode to estimate the utility for the application to tissues (brain, nerve, retina, and so on).

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Young’s modulus of polysilicon thin film was measured by means of a tensile tester equipped with electrostatic force grip system. The images of gauge marks on a specimen were captured by a high-speed digital CCD camera and the tensile strain was calculated from the images. Polysilicon thin film specimens were tensile tested for evaluating the resolution of the measurement system. The polysilicon specimens were 1.7 µm thick, 20 and 50 µm wide, and 100 and 500 µm in gauge length. The linear stress-strain curve was obtained and Young’s modulus was measured. The mean Young’s modulus ranged from 162 to 175 GPa, which agreed with the theoretical value and the measured values using the bulge method. The resolution and the comparison to the differential method were discussed.

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In this paper, a suppression method of generated distortion on the beam structures due to thermal stress is investigated for reduction of remainder thermal drift in three-axis accelerometer for high temperatures. An arrangement of piezoresistors for acceleration detection is presented to further reduction of thermal drift. Thermal drift analysis and design of advanced three-axis accelerometer for high temperatures without temperature dependence has been carried out with the finite element method (FEM) program, ANSYS. Experimental results agreed well with these theoretical results. Design considerations that enable the three-axis accelerometer to have stable sensitivity and offset are described with the simulated results.

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This paper reports a new proposal on PZT film formation technology both on planar and non-planar surface with use of spray coating method. SEM observation shows the film formation on non-planar and edged surface of Si-wafer. Ferroelectric properties is confirmed with ferroelectric test system. Several kinds of applications of this method is also shown for the future target.

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