Surface micromachined capacitive accelerometer with comb electrodes
(in-plane accelerations):

only a half of a symmetrical sensing element is shown

Basic features:

• Accelerometer was designed for crash sensing in automotive airbag electronic control units
• Sensing element structure realized on an SOI separation by ion implantation of oxygen (SIMOX) epitaxial wafer
• SIMOX technology, primarily developed as a substrate for high temperature or radiation hardened semiconductors, has been found to be very interesting for sensor applications
• Central seismic mass, supported by four suspension arms, can move along the sensitive axis parallel to the substrate
• Interdigitated capacitances are formed between the seismic mass fingers and the fixed electrode fingers
• Arrangement of the fingers is such that the variations of the capacitances are opposite
• Overload protection is provided by two bumpers limiting the displacement along the sensitive axis