HIGHLY SENSITIVE CAPACITIVE SENSOR AND METHODS OF MANUFACTURING THE SAME
First Claim
1. A capacitive sensor, comprising:
- a substrate;
a mass;
a plurality of spring beams coupling the mass to the substrate;
at least one first electrode extending from the mass; and
at least one second electrode attached to the substrate,wherein the first electrode is disposed adjacent to the second electrode to form a substantially invariable gap between the first and second electrodes, andwherein each of the first and second electrodes has a tooth profile including a plurality of teeth, each of the plurality of teeth having a predetermined geometric shape.
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Abstract
Micro-machined capacitive sensors implemented in micro-electro-mechanical system (MEMS) processes that have higher sensitivity, while providing an increased linear capacitive sensing range. Capacitive sensing is achieved via variable-area sensing, which employs a transduction mechanism in which the relationship between changes in the capacitance of variable, parallel-plate capacitors and displacements of a proof mass is generally linear. Each respective variable, parallel-plate capacitor is formed by a finger/electrode pair, in which both the finger and the electrode have rectangular tooth profiles that include a plurality of rectangular teeth. Because changes in the overlapping area of the finger and the electrode are multiplied by the number of rectangular teeth, while the standing capacity of the micro-machined capacitive sensor remains relatively high, the sensitivity of the micro-machined capacitive sensor employing variable-area sensing is significantly increased per unit area of the finger and the electrode.
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Citations
15 Claims
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1. A capacitive sensor, comprising:
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a substrate; a mass; a plurality of spring beams coupling the mass to the substrate; at least one first electrode extending from the mass; and at least one second electrode attached to the substrate, wherein the first electrode is disposed adjacent to the second electrode to form a substantially invariable gap between the first and second electrodes, and wherein each of the first and second electrodes has a tooth profile including a plurality of teeth, each of the plurality of teeth having a predetermined geometric shape. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of fabricating a capacitive sensor, comprising the steps of:
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covering a surface of a substrate with a protection film; transferring a predetermined pattern to the protection film to obtain a mask for forming at least one electrode in the substrate, the electrode having a tooth profile including a plurality of teeth, each of the plurality of teeth having a predetermined geometric shape; in a first etching step, etching, using the mask, the electrode having the tooth profile to a specified depth in the substrate; removing portions of the protection film to expose a plurality of regions on the surface of the substrate, the plurality of regions corresponding to locations between the plurality of teeth of the tooth profile; in a second etching step, at least partly etching the exposed regions of the substrate to obtain the predetermined geometric shape of the plurality of teeth of the tooth profile; and in a third etching step, etching the substrate to release the at least one electrode having the tooth profile from the substrate. - View Dependent Claims (12, 13, 14, 15)
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Specification