Capacitive sensor with minimized dielectric drift
First Claim
1. A capacitive sensor of the silicon-dielectric-silicon type used to sense physical changes, such as, for example, pressure changes, comprising:
- a conductive silicon substrate;
a conductive, elastic, flexible silicon diaphragm having an exterior side, said diaphragm being capable of flexing movement due to physical changes being sensed; and
a non-conductive, dielectric wall spacer layer between said silicon substrate and said silicon diaphragm, said layer providing peripheral wall(s) extending substantially above said silicon substrate and joining said silicon substrate and said silicon diaphragm together;
an evacuated, closed, hermetically sealed chamber being formed between said silicon substrate and said silicon diaphragm and being closed off at the sides above said substrate by said wall(s) formed by said dielectric layer between said silicon substrate and said silicon diaphragm;
the flexing movement of said silicon diaphragm due to the physical changes being sensed causing the capacitance of the sensor to vary;
the capacitance contribution of said dielectric layer to the total capacitance of the sensor being no more than about twenty-to-twenty-five percent of the total capacitance of the sensor.
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Accused Products
Abstract
Pressure sensors utilizing capacitance variations to sense pressure variations of the silicon-on-silicon type in which dielectric drift, which occurs in such sensors due to the changing characteristics primarily of the dielectric wall support layer (16) extending up from the silicon substrate (12) between it and the silicon diaphragm (11), is minimized by in turn minimizing the contribution of the dielectric layer to the total capacitance of the sensor (10), reducing the dielectric contribution of the capacitance from, for example, about fifty (50%) percent down to a range of no more than about twenty to twenty-five (20-25%) percent and down typically to sixteen to about ten (16%-10%) percent of the total capacitance or lower. Three exemplary approaches are illustrated, namely, etching the outer edges of the dielectric layer, making the wall(s) it form(s) thinner (FIG. 2); reducing the horizontal thickness of the effective peripheral, lower edge(s) of the silicon diaphragm where it interfaces in contact with the wall(s) formed by the dielectric layer (FIG. 3); and/or reducing the horizontal thickness of the effective peripheral, upper edge(s) of the silicon base or substrate where it interfaces with the wall(s) formed by the dielectric layer (FIUG. 4); and/or a combination of one or more of these approaches or any other approach that minimizes the effective capacitive contribution of the peripheral dielectric layer to the total capacitance of the sensor and hence to long term drift.
32 Citations
16 Claims
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1. A capacitive sensor of the silicon-dielectric-silicon type used to sense physical changes, such as, for example, pressure changes, comprising:
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a conductive silicon substrate; a conductive, elastic, flexible silicon diaphragm having an exterior side, said diaphragm being capable of flexing movement due to physical changes being sensed; and a non-conductive, dielectric wall spacer layer between said silicon substrate and said silicon diaphragm, said layer providing peripheral wall(s) extending substantially above said silicon substrate and joining said silicon substrate and said silicon diaphragm together;
an evacuated, closed, hermetically sealed chamber being formed between said silicon substrate and said silicon diaphragm and being closed off at the sides above said substrate by said wall(s) formed by said dielectric layer between said silicon substrate and said silicon diaphragm;
the flexing movement of said silicon diaphragm due to the physical changes being sensed causing the capacitance of the sensor to vary;
the capacitance contribution of said dielectric layer to the total capacitance of the sensor being no more than about twenty-to-twenty-five percent of the total capacitance of the sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of minimizing the dielectric drift of a capacitive, silicon-dielectric-silicon sensor used to sense physical changes, such as, for example, pressure changes, which sensor includes
a conductive silicon substrate; -
a conductive, elastic, flexible, silicon diaphragm having an exterior side, said diaphragm being capable of flexing movement due to he physical changes being sensed; and a non-conductive, dielectric wall spacer layer between said silicon substrate and said silicon diaphragm, said layer providing peripheral wall(s) extending substantially above said silicon substrate and joining said silicon substrate and said silicon diaphragm together;
an evacuated, closed, hermetically sealed chamber being formed between said silicon substrate and said silicon diaphragm and being closed off at the sides above said substrate by said wall(s) formed by said kielectric layer between said silicon substrate and said silicon diaphragm;
the flexing movement of said silicon diaphragm due to the physical changes being sensed causing the capacitance of the sensor to vary;
comprising the following step(s);limiting the capacitive contribution of said dielectric wall spacer layer to the total capacitance of the sensor to no more than about twenty to twenty-five percent of the total capacitance of the sensor. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification