Capacitive pressure sensor with third encircling plate
First Claim
1. A capacitive pressure sensor of the conductive dielectric-conductive type, comprising:
- a conductive substrate forming a first capacitive plate;
a conductive flexible, elastic diaphragm having an exterior side, said diaphragm being capable of flexing movement due to changes in pressure on its exterior side and forming a second capacitive plate; and
a non-conductive, dielectric layer between said conductive substrate and said conductive diaphragm, said layer providing peripheral wall spacer(s) extending between and joining said conductive substrate and said conductive diaphragm;
an evacuated chamber being formed between said substrate and said diaphragm and being closed off by spacer wall(s) formed by said dielectric layer between said substrate and said diaphragm;
the flexing movement of said diaphragm due to the changes in pressure on its exterior side causing the capacitance of the sensor to vary;
said chamber being at least generally cylindrical in its outer configuration defining a central region; and
a third, conductive plate located in said wall(s) spaced and separated from both said conductive substrate and said conductive diaphragm by said dielectric layer and forming a third capacitive plate, said third conductive plate encircling said central region but being located substantially outside of said central region.
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Accused Products
Abstract
A pressure sensor (210) utilizing capacitance variations to sense pressure variations of the silicon-glass-silicon type (FIG. 3) including a conductive silicon substrate (212), a conductive silicon diaphragm (211) and a glass dielectric layer (213) therebetween forming a spacing wall (216) between them, in which dielectric drift and parasitic (non-pressure sensitive) capacitance is minimized by including a very thin, third, symmetrical, silicon, capacitive plate (220) in the glass wall (216). The third conductive plate encircles the central region (Cc) of the sensor and is located outside of it. Improved assembly techniques, including all symmetrical planar layers, for higher manufacturing yield and better long term reliability are also disclosed.
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Citations
14 Claims
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1. A capacitive pressure sensor of the conductive dielectric-conductive type, comprising:
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a conductive substrate forming a first capacitive plate; a conductive flexible, elastic diaphragm having an exterior side, said diaphragm being capable of flexing movement due to changes in pressure on its exterior side and forming a second capacitive plate; and a non-conductive, dielectric layer between said conductive substrate and said conductive diaphragm, said layer providing peripheral wall spacer(s) extending between and joining said conductive substrate and said conductive diaphragm;
an evacuated chamber being formed between said substrate and said diaphragm and being closed off by spacer wall(s) formed by said dielectric layer between said substrate and said diaphragm;
the flexing movement of said diaphragm due to the changes in pressure on its exterior side causing the capacitance of the sensor to vary;
said chamber being at least generally cylindrical in its outer configuration defining a central region; anda third, conductive plate located in said wall(s) spaced and separated from both said conductive substrate and said conductive diaphragm by said dielectric layer and forming a third capacitive plate, said third conductive plate encircling said central region but being located substantially outside of said central region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of minimizing the parasitic capacitance of a capacitive pressure sensor, which sensor includes--
a conductive substrate; -
a conductive diaphragm having an exterior side, said diaphragm being capable of flexing movement due to changes in pressure on its exterior side; and a non-conductive, dielectric layer between said conductive substrate and said conductive diaphragm, said layer providing peripheral spacer wall(s) extending between and joining said substrate and said diaphragm;
an evacuated chamber being formed between said substrate and said diaphragm and being closed off by said peripheral spacer wall(s) formed by said dielectric layer between said substrate and said diaphragm;
the flexing movement of said diaphragm due to the changes in pressure on its exterior side causing the capacitance of the sensor to vary;comprising the following step(s); providing a third, conductive plate in said spacer wall(s) spaced and separated from both said conductive substrate and said conductive diaphragm by said dielectric layer, with said third conductive plate encircling said central region but being located substantially outside of said central region. - View Dependent Claims (11, 12, 13, 14)
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Specification