This paper presents the design, simulation and performance evaluation of an area-changed capacitive accelerometer for low-g applications. The movable mass of the accelerometer was designed with many fingers connected in parallel and suspended over stationary electrodes composed of differential comb fingers by means of suspension beams anchored onto the substrate. An area-changed differential capacitance method was used to sense the deflection of the proof mass. A folded suspension design with low spring constant and low cross-axis sensitivity was chosen. The simulation was performed using Coventorware2001.3 software. A 3-mask bulk micromachining wafer bonding fabrication process was utilized to produce this accelerometer. Silicon-on-glass was used to achieve high sensitivity and low mechanical noise while maintaining a simple structure. The general concept, main design considerations, fabrication procedure and performance of the resulted accelerometer was elaborated and presented. A linear relationship between the differential capacitance and acceleration was obtained. The accelerometer sensitivity was calculated to be 0.47pF/g with an acceleration range of ±5g.
This paper presents an area-changed capacitive accelerometer using a 3-mask fabrication process. The accelerometer is designed as finger structures connected in parallel that have a differential capacitor arrangement. The movable electrodes are mounted on a proof mass of silicon and a pair of stationary electrodes of polysilicon is formed under the mass with a 3 μm air gap. The fabrication process utilizes silicon/glass anodic bonding and deep reactive ion etching (DRIE) for high aspect ratio etching. The simulated mass displacement change rate is 0.076 μm/g and the overall sensitivity is -0.04/μm. This type of accelerometer will be characterized for low-g as well as for medium-g applications.