CMOS INTEGRATED MICROSENSOR WITH A PRECISION MEASUREMENT CIRCUIT

摘要

Improved microsensors are provided by combining surface micromachined substrates (48), including integrated CMOS circuitry (50), together with bulk micromachined wafer bonded substrates (16) which include at least part of a microelectromechanical sensing element. In the case of an accelerometer (46), the proof mass (52) is included within the wafer bonded bulk machined substrate, which is bonded to the CMOS surface machine substrate, which has corresponding etch pits (62) defined therein over which the wafer bonded substrate is disposed, and in the case of accelerometer, the proof mass or thin film membranes in the case of other types of detectors such as acoustical detectors or infrared detectors. A differential sensor electrode (60) is suspended over the etch pits (62) so that the parasitic capacitance of the substrate is removed from the capacitance sensor, or in the case of an infrared sensor, to provide a low thermal conductance cavity under the pyroelectric refractory thin film. Where a membrane suspended electrode is utilized over an etch pit, one or more apertures are defined therethrough to avoid squeeze film damping.