Ultrasonic sensor was fabricated from silicon membrane of about 1.5 /spl mu/m thick by using ion implantation and anisotropic etching technique. This thin membrane is strong and the 4 mm square membrane is not broken by the atmospheric pressure (760 Torr). The sensor has a condenser-microphone structure with glass balls of about 10 /spl mu/m diameter as spacers. The sensitivity of the sensor having a 4 mm square membrane for the 10 kHz ultrasonic wave is 67 /spl mu/V/Pa when the applied voltage to the sensor is 18 V. The frequency dependence of the sensitivity is flat in the frequency region over 1 kHz. Angular dependence of the sensitivity for 40 kHz ultrasonic wave is close to that of the line antenna and the sensitivity becomes sharp as the membrane becomes large. The noise from the sensor can be effectively reduced by using MOSFET on the SOS substrate, which is used as an opposite electrode.
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机译:通过使用离子注入和各向异性蚀刻技术,通过约1.5 / SPL MU / M厚的硅膜制成超声波传感器。这种薄膜强,4mm方形膜不会被大气压(760托)破裂。该传感器具有冷凝器 - 麦克风结构,具有约10 / SPL MU / M直径的玻璃球作为间隔物。当施加电压到传感器为18V时,具有4mm平方膜的传感器的灵敏度为67 / spl mu / v / pa。频率区域的频率依赖性在频率区域的频率依赖性1 kHz。对于40kHz超声波的灵敏度的角度依赖性接近线天线的敏感性,并且随着膜变大,灵敏度变得敏锐。通过在SOS基板上使用MOSFET可以有效地减少来自传感器的噪声,其用作相对电极。
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