Two Si Wafers were bonded using SiO₂//Si₃N₄ direct bonding technology, where a bridge structure of a composite dielectric film (SiO₂//Si₃N₄/SiO₂) was formed in the bond area. In the center of this bridge structure, a single crystal Si was left in the shape of an island, on which a Schottky Barrier Diode (SBD) with Cr silicide was fabricated and used as a detector part. On the other hand, another Si wafer was used as a cap wafer having anti-reflection coating to improve the light transmittivity in the wavelength range from 8 to 12μm up to more than 90%. This cap wafer and the above mentioned main wafer were bonded together using water glass bonding technology at 80°C to encapsulate the detector part in a vacuum. A bolometer type infrared radiation microsensor was thus made on an experiment basis. It has a self-package type structure to protect the detector part from mechanical damages and secure the operational environment. Its size and weight could be extremely reduced down to 2.0mm×2.0mm×0.8mm and 10mg, respectively. The response time is as fast as 4ms which is about 1/100 of that of a conventional bolometer. Other important electric characteristics of this element are as follows: NEP (noise equivalent power)=5.90×10^-10W/Hz^1/2, NETD_200-205 (noise equivalent temperature difference)=0.02°C, R (sensitivity)=1.69×10⁵V/W.

抄録全体を表示

The relationship between the sintering temperature and the electrical properties was investigated for SiC ceramic in order to realize a micro thermistor. The SiC powder containing boron and carbon was sintered in the temperature range of 1973K-2473K in vacuum. The electrical properties of the sample depended on the sintering temperature. The resistivity of the samples sintered below 2273K was independent of the temperature measured, whereas the resistivity of the samples sintered above 2273K depended on the temperature. The samples sintered at 2323K showed the most uniform resistivity compared to those sintered at other tempertures. In order to explain the above mentioned results, two electrical mechanisms were proposed; (1) current along grain boundaries which was dominant in the samples sintered below 2273K and (2) current across grain boundaries which was dominant in the sample sintered above 2273K.

抄録全体を表示

Several simulations were performed in order to investigate the effects of the device size of SiC ceramic thermistors of which materials have nonuniform microstructure on their electrical properties quantitatively. The boundary potential model and the energy band model were used to express the electrical characteristics of the grain boundaries in the simulations. These simulations show that the reduction of device size tends to widen the variation of the resistivity and the variation of the B constant. Furthermore, it was found that the device size reduction tends to decrease the average of the resistivity and average of the B constant. These are explained by the percolation theory. The uniformalization of the microstructure and/or the increase of the number of grain boundary between the electrodes are necessary for the manufacturing of the devices that have uniform electrical properties.

抄録全体を表示

We propose a surface micromachined simple resonant accelerometer based on the principle of a resonator rigidity change. The sensor consists of a parallel beam resonator and a mass. The rigidity change of the resonator is induced with a change in the cross-sectional shape of the resonator. The feasibility of this sensing principle was confirmed by FEM analysis. The FEM analysis revealed that a frequency change ratio of 10%/g and 5%/g were obtained for the basic structure and the double resonator structure, respectively. Furthermore, we confirmed that the double resonator structure had a lower cross-axis sensitivity.

抄録全体を表示

A new bulk silicon micromachining suitable for accelerometer and other micromechanical structures is developed. By combining deep RIE, P ⁺⁺ diffusion and anisotropic wet etching, surface thin beam structures can be fabricated. This process is applied for small sized and high performance capacitive accelerometer packaged by anodic bonding.

抄録全体を表示

As the microfabrication technique of LiNbO₃ that utilized electric field sensor, the wet etching by fluorine acid solution and the dry etching by plasma have been used. However, etching condition and etching profile need to be examined in detail. We have studied a plasma etching characteristic of LiNbO₃. The etch rate of LiNbO₃ increases drastically by interaction of physical and chemical etching. The maximum etch rate was 31.8nm/min for 60% Ar in CF₄+Ar plasma and 29.6nm/min for 37% H₂ in NF₃+H₂ plasma. This etch rate increases by 3 times in comparison with that in CF₄ only plasma and 10 times in comparison with that in fluorine acid solution (10%). The analytical results by XPS show that LiNbO₃ absorbs F radical and forms the mixing layer in the surface and the etch rate of LiNbO₃ increases by the ion bombardment effect. It is found out that Ni metal is adequate as the mask material. The Ridge type optical waveguide with the height of 3μm could be formed.

抄録全体を表示