고감지전압 및 가지전극을 이용한 고정도 정전용량형 미소가속도계

한기호; 조영호

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This paper presents a navigation garde capacitive microaccelerometer, whose low-noise high-resolution detection capability is achieved by a new electrode design based on a high-amplitude anti-phase sense voltage. We reduce the mechanical noise of the microaccelerometer to the level of 5.5ug/ ??HZ by increasing the proof-mass based on deep RIE process of an SOl wafer. We reduce the electrical noise as low as 0.6ug/ ??Hz by using an anti-phase high-amplitude square-wave sense voltage of 19V. The nonlinearity problem caused by the high-amplitude sense voltage is solved by a new electrode design of branched finger type. Combined use of the branched finger electrode and high-amplitude sense voltage generates self force-balancing effects, resulting in an 140% increase of the bandwidth from 726Hz to 1,734Hz. For a fixed sense voltage of 10V, the total noise is measured as 2.6ug/ ??HZ at the air pressure of 3.9torr, which is the 51 % of the total noise of 5.1ug/ ??Hz at the atmospheric pressure. From the excitation test using I g, 10Hz sinusoidal acceleration, the signal-to-noise ratio of the fabricated microaccelerometer is measured as 105dB, which is equivalent to the noise level of 5.7ug/ ??Hz. The sensitivity and linearity of the branched finger capacitive microaccelerometer are measured as 0.638V /g and 0.044%, respectively.