MEMS pressure sensor

A MEMS pressure sensor comprising:

• a MEMS electrically conductive silicon wafer having first and second opposite sides, the MEMS electrically conductive silicon wafer having formed therein a frame and a membrane that separates at least one cavity from a recess with a hermetic seal, the membrane being deflectable in response to a change in fluid pressure on at least one of a first side and a second side of the membrane;
• an electrically conductive silicon cap wafer having inner and outer sides, the electrically conductive silicon cap wafer being fusion bonded on the inner side to the first side of the MEMS electrically conductive silicon wafer, the inner side of the electrically conductive silicon cap wafer having the recess defining, with the membrane, at least one capacitance gap, the electrically conductive silicon cap wafer having formed therein at least one cap electrode located relative to the membrane and forming, together with the membrane, at least one capacitor to detect a deflection of the membrane and wherein the at least one cap electrode is defined by an insulated region patterned in the electrically conductive silicon cap wafer;
• at least a first electrical contact and a second electrical contact on or over the electrically conductive cap wafer, the first electrical contact being connected to the at least one cap electrode and the second electrical contact being connected to the membrane with an insulated conducting pathway extending through the MEMS conductive silicon wafer and that includes a deflecting portion of the membrane and through a portion of the electrically conductive silicon cap wafer that is electrically insulated from the at least one cap electrode;
• a vent in fluid communication with the capacitance gap on the first side of the membrane or in fluid communication with the at least one cavity on the second side of the membrane.

A method of measuring pressure comprising:

• measuring pressure with a MEMS pressure sensor comprising:
• a MEMS electrically conductive wafer having first and second opposite sides, the MEMS electrically conductive wafer having a frame and a pressure sensor membrane, the frame defining at least one cavity, the pressure sensor membrane suspended by the frame to define a portion of said at least one cavity on the first side of the MEMS electrically conductive wafer;
• an electrically conductive cap wafer having an inner side and an outer side, the electrically conductive cap wafer being bonded on the inner side to the first side of the MEMS electrically conductive wafer, the inner side of the electrically conductive cap wafer having at least one recess defining, with the pressure sensor membrane, at least one capacitance gap, the electrically conductive cap wafer having formed therein at least one cap electrode located relative to the pressure sensor membrane and forming, together with the pressure sensor membrane, at least one capacitor to detect a deflection of the pressure sensor membrane;
• at least a first electrical contact and a second electrical contact positioned on or over the electrically conductive cap wafer, the first electrical contact being connected to said at least one cap electrode and the second electrical contact being connected to the pressure sensor membrane by an insulated conducting pathway extending from the pressure sensor membrane and through the electrically conductive cap wafer;
• and
• a vent extending from outside of the MEMS pressure sensor into one of said at least one cavity and said at least one capacitance gap;
• and
• processing pressure sensor signals generated by the MEMS pressure sensor with processing circuitry connected to the electrical contacts.