Silicon Accelerometer for high temperature applications with Double SOI structure

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In this study, an accelerometers for high temperature application have been developed using SOI structure and micromachining technology. At first, an ultrahigh-vacuum chemical vapor deposition (UHV-CVD) with a hot wall heating system have developed to grow double SOI structure [Si/Al203/Si]. The epitaxial Al203 (100) film grown on a Si (100) substrate can be used as etching stop layr and as an electric-isolation layr of an SOI device. Another important technologies for the SOI devices were developed : the one is a new etching method of chemically stable A1203 films and sapphire wafers by Si ion implantation method, and the another is the selective epitaxial growth of Si (100) on Al203 (100) by electron-beam-irradiation method to make fine pattern. As the result, the fundamental technologies for double SOI structure has been developed for accelerometers for high temperature applications.Then, a novel piezoresistive silicon accelerometer and a capacitive accelerometer were designed with finite element method (FEM) of ANSYS.These acoelerometers were fabricated with micromachining technology and integrated circuit technology. The accelerometers can be detect three dimensional acceleration. Next, a package and a measurement system for high temperature up to 400ﾟC were developed, and the characteristics of accelerometers were evaluated. The accelerometer successfully worked at up to 400ﾟC stably, so that it was confirmed that the SOI structure greatly improve the characteristics at high temperature. The temperature characteristics and the output characteristics were compared with simulated result, and it well agrees with simulated result.