Abstract
A bulk micromachined accelerometer based on an area variation capacitive sensing for low-g applications was developed. The accelerometer was designed with ribbed-style fingers structure on the movable mass connected in parallel and suspended over stationary electrodes composed of differential comb fingers by means of suspension beams anchored onto the substrate. A folded, rigid truss suspension design with low spring constant and low cross-axis sensitivity was chosen. The simulation was performed using Coventorware software. A three- mask bulk micromachining wafer bonding fabrication process was utilized to realize the 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 0.47 pF/g with an acceleration range of ±5 g.
Highlights
The interest in the development of low-g MEMS accelerometer has increased lately
In accelerometers utilizing varying air-gap, the deflection of the proof mass produces a change in the air gap between electrodes that causes the change in capacitance
Area-changed accelerometers uses a ribbed fingers structure on the movable mass as a differential capacitor and suspended over stationary electrodes composed of differential comb fingers by means of suspension beams [8,9,10]
Summary
The interest in the development of low-g MEMS accelerometer has increased lately. Low-g accelerometer has potential applications in the automotive field such as vehicle stability enhancement, roll-over detection, inclination/theft detection and vehicle dynamics such as potential wheel skid while turning. High sensitivity can be obtained either by increasing the mass of the proof mass or lowering the spring constant of the suspension beam. Folded suspension designs can be used to achieve high sensitivity by offering a low spring constant in the sensing direction.
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