Differential capacitive low-g microaccelerometer with m g resolution

Abstract

A low-cost differential capacitive accelerometer with a resolution of 5 mg (1 g = 9.81 m/s2) and high sensitivity (800 mV/g) has been designed with a full measurement range of ±2 g. By using the single crystal reactive ion etching and metallization (SCREAM) process, beams with high aspect ratio, small air gap for large capacitance variation and low parasitic capacitance have been attained. The fabricated microaccelerometer also offers high output and it has successfully survived a shock of 1000 g. The effects of electrostatic spring constant on the natural frequency and sensitivity of the accelerometer have been thoroughly discussed, and obliqueness of the beams has also been taken into consideration. The ratiometric error has been studied, and is well below 2% with a cross axis sensitivity of less than 3%. The operating voltage is 5 V DC. The construction is based on a two-chip design and the sensing element is connected to a CMOS ASIC by wire bonding.