Parylene Accelerometer Utilizing Spiral Beams

This paper reports a Parylene accelerometer utilizing spiral beams. Since Parylene has intrinsic tensile stress, the resonant frequency ωnof sensor structure is higher than that under no tensile stress. Considering the sensitivity of accelerometer is 1 n/ωn², the investigation of ωnof a suspended structure supported by straight beams is carried out both theoretically and experimentally. As a result, it is proved that comparatively long beams are necessary for realizing the high sensitivity of a Parylene sensor with tensile stress. A spiral beam is effective for not only realizing a long beam in a limited space, but also realizing stress relaxation. Both Parylene accelerometer with straight beams and that with spiral beams are fabricated. Sensitivity of them is characterized, and the effectiveness of utilizing spiral beam is confirmed.