Capacitance pressure sensor

A batch fabricated capacitive sensor comprising:

• a dielectric layer of rigid material having first and second surfaces;
• a diaphragm assembly comprising a second layer comprising an edge supported diaphragm sealingly bonded to the first side of the dielectric layer and forming a capacitor plate;
• said dielectric layer having an opening therethrough in registry with the diaphragm and a metal layer formed on both sides of the dielectric layer and through the opening;
• and
• a third layer having a peripheral rim overlying the diaphragm assembly's edge to form a peripheral support sealingly bonded to the metal layer on the second surface of the dielectric layer to overlie and seal the opening, a portion of said third layer being removed to expose the metal layer on the second side of the dielectric layer to provide an exposed metal surface for attachment of leads to such metal layer on the second side of the dielectric layer.

A pressure sensor for sensing the magnitude of a pressure comprising:

• a support layer having a opening therethrough and having a metal layer formed on both sides of the layer and through the opening;
• a layer of material including a diaphragm member surrounded by a diaphragm rim mounted on said support layer, said diaphragm and support layer having facing surfaces forming capacitive sensing means, and being spaced apart to provide capacitive spacing, said diaphragm being deflected toward said support layer when subjected to a pressure;
• a sealing layer disposed on the support layer having a peripheral rim overlying the diaphragm rim to form a peripheral support, the peripheral rim having a sealing surface thereon bonded to the metal layer for sealing the opening;
• means forming a dampening chamber on a side of said diaphragm opposite from said support layer, said means comprising a cover member overlying said diaphragm and being fixed with respect to the edges of the diaphragm to form a small volume dampening chamber disposed directly over the diaphragm, and
• opening means comprising a control orifice leading from said dampening chamber to the exterior, a filling of fluid provided within said dampening chamber, the pressure applied to said diaphragm causing flow of the filling of fluid in the dampening chamber through the control orifice such that the response of the diaphgragm is dampened.

A capacitive sensor for sensing the magnitude of a pressure, comprising:

• a rigid support;
• a brittle diaphragm member mounted on said support, said diaphragm member and said support having facing surfaces closely spaced from each other;
• sensing means for sensing diaphragm deflection, said diaphragm member being deflected toward said support when subjected to a pressure;
• means forming a small volume dampening chamber on a side of said diaphragm opposite from said support comprising a cover member overlying said diaphragm and being fixed with respect to the edges thereof to form said small volume chamber;
• opening means comprising a passageway leading from said dampening chamber to the exterior;
• a filling of oil provided in said chamber, the pressure applied to said diaphragm acting only through said chamber and the filling of oil in the chamber to cause deflection of the diaphragm whereby movement of the diaphragm is directly related to fluid flow through the passageway;
• and
• circuit means for sampling the signal of the capacitive sensor at a desired frequency, the control orifice restricting the dynamic response of the diaphragm to a frequency not substantially greater than one-half of the sampling frequency.

A capacitive pressure sensor for connection to a capacitance sensing circuit providing an output representative of a sensed pressure comprising:

• a dielectric layer having an aperture extending therethrough between a substantially planar surface and an opposite second surface thereon;
• electrical conductive means for forming a first capacitor plate on the planar surface and forming an electrical contact on the second surface spaced away from the aperture and connecting through the aperture to the first capacitor plate;
• a semiconductor layer having a rim surrounding a diaphragm responsive to the pressure sealingly bonded to the planar surface around the first capacitor plate, said diaphragm forming a second capacitor plate facing and spaced from the first capacitor plate, the semiconductor layer also having a metal ohmic contact thereon;
• a sealing layer having a sealing surface thereon bonded to the electrical contact on the second surface of the dielectric layer for sealing the aperture to provide a reference pressure to the diaphragm;
• a fourth layer bonded to the semiconductor layer opposite the dielectric layer, said fourth layer having a neck substantially smaller than the width of the sensor with an aperture therethrough permitting the sensed pressure to act on the diaphragm;
• and
• a reference capacitor disposed in the sensor comprising a first reference capacitor plate disposed on the substantially planar surface and being coupled capacitively to a portion of the rim.

A capacitive pressure sensor for connection to a capacitance sensing circuit providing an output representative of a sensed pressure comprising:

• a dielectric layer having an aperture extending therethrough between a substantially planar surface and an opposite second surface thereon;
• electrical conductive means for forming a first capacitor plate on the planar surface and forming an electrical contact on the second surface spaced away from the aperture and connecting through the aperture to the first capacitor plate;
• a semiconductor layer having a rim surrounding a diaphragm responsive to the pressure sealingly bonded to the planar surface around the first capacitor plate, said diaphragm forming a second capacitor plate facing and spaced from the first capacitor plate, the semiconductor layer also having a metal ohmic contact thereon;
• a sealing layer having a sealing surface thereon bonded to the electrical contact and overlying the aperture for sealing the aperture to provide a reference pressure to the diaphragm;
• a fourth layer bonded to the semiconductor layer opposite the dielectric layer, said fourth layer having a neck substantially smaller than the width of the sensor with an aperture therethrough permitting the sensed pressure to act on the diaphragm;
• a base member bonded to the neck;
• and
• a reference capacitor bonded to the base member and spaced away from the fourth layer and coupled to the sensing circuit such that vibration sensitivity of the output is reduced.