SCREAM micromachined high-aspect-ratio low-g microaccelerometer

Abstract

A low-cost open loop differential capacitive accelerometer with a resolution of 5mg and high sensitivity has been designed with a ful measurement range of +/- 2g. By using the single crystal reactive ion etching and metallization process, beams with high aspect ratio, small air gap for large capacitance variation and low parasitic capacitance have been attained. The fabricated micro accelerometer also offers high voltage output and it has successfully survived a shock of 1000g. The effects of electrostatic spring constant on the natural frequency and sensitivity of the accelerometer have been thoroughly discussed, and obliqueness of the beam cross-section has also been taken into consideration. The radiometric error for this system has been optimized and is well below 2 percent with a cross axis sensitivity of less than 3 percent. The operating voltage is 5V DC. The construction is based on a hybrid two- chip design and the sensing element is wire bonded to a CMOS ASIC.