Post-Processing Micromachined Pull-In Accelerometer

This paper reports the first pull-in time accelerometer made by post-processing surface micromachining technology. As the pull-in time is a semi digital signal, the output of the device can be measured with a fully digital circuit. The sensitivity and nonlinearity are comparable with the differential capacitive sensing devices. Aluminium was used for the mechanical layer, while phosphosilicate glass was used as the sacrificial material. Measurements show the change in pull-in time of 5 mus from 0 to 1G.