Silicon micromachined capacitive pressure sensor and method of

Abstract

A capacitive pressure sensor that uses polysilicon as an electrostatic bonding medium and as a lead transfer to make an electrical connection to an electrode within a vacuum sealed chamber. The heavily doped P++ region of a silicon wafer defines a movable diaphragm that is bonded to a glass substrate of the sensor. The diaphragm is one electrode of the capacitor and includes a recess that defines the sealed chamber. An internal electrode is patterned on the glass substrate in the sealed chamber, and is the other electrode of the capacitor. An internal lead within the chamber is electrically connected to the internal electrode and a polysilicon layer that seals the diaphragm electrode to the glass substrate. Dielectric isolation layers are provided to electrically isolate the polysilicon sealing layer in the diaphragm electrode, and isolate the polysilicon sealing layer from an etchant that removes a polysilicon region around the diaphragm electrode during fabrication. The diaphragm electrode makes electrical contact through an isolated polysilicon region to connect the diaphragm electrode to an outside lead. A series of contact areas are provided through the dielectric layer between the diaphragm electrode and the polysilicon sealing layer, where the contact areas are outside of the diaphragm electrode, to provide an electrical connection for electrostatic bonding purposes.