Fabrication methods for silicon/glass capacitive absolute pressure

Abstract

A method for making pressure sensors is disclosed. A wafer of doped silicon or other semiconductive material is selectively chemically etched (micromachined) on both sides to form a plurality of diaphragms, a thicker silicon rim surrounding each diaphragm, and a feedthrough hole corresponding to each diaphragm external to the silicon rim. A small metallized area of the upper surface of the silicon substrate on the rim adjacent each diaphragm permits external electrical connection to the silicon plate. Capacitor plates are formed by depositing a metallized film or other conductive material on a dielectric substrate in locations corresponding to the diaphragms of the silicon wafer. To permit external electrical connection to the conductive material, contact pads electrically connected to the conductive material are formed on the dielectric substrate external to the area corresponding to the diaphragms. A buffer layer of nonconductive material is disposed over the entire dielectric substrate, and then selectively removed from the contact pads. The lower surface of the silicon substrate is joined to the dielectric substrate, such that the diaphragms formed in the semiconductor material are in alignment with the conductive areas of the dielectric substrate and the contact pads on the dielectric substrate are in alignment with the feedthrough holes in the silicon wafer. The resulting assembly comprises a plurality of electric capacitors and may be cut into individual capacitive pressure sensors.