Capacitive humidity sensor
First Claim
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1. A capacitive humidity sensor comprising:
- a semiconductor substrate;
circuit devices formed on a surface of the semiconductor substrate;
two detection electrodes, which are isolated from one another and are opposed to one other, wherein the detection electrodes are formed on the surface of the semiconductor substrate; and
a humidity-sensitive film, the capacitance of which changes in response to humidity, placed between the detection electrodes and formed on the surface of the semiconductor substrate, wherein;
the capacitance between the detection electrodes changes in response to changes in the surrounding humidity;
the circuit devices make up switched capacitor circuits comprising a reference capacitor and feedback capacitor that convert changes in capacitance between the detection electrodes into voltage signal output; and
at least one of the reference capacitor and the feedback capacitor is an underlying capacitor and is located beneath one of the detection electrodes.
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Abstract
A humidity sensor has two detection electrodes located on a semiconductor substrate and a humidity sensitive film. The capacitance of the film changes in response to humidity. The sensor includes a reference capacitor and a feedback capacitor. An electrode of each capacitor is located beneath one of the detection electrodes to limit the size of the device.
56 Citations
12 Claims
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1. A capacitive humidity sensor comprising:
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a semiconductor substrate;
circuit devices formed on a surface of the semiconductor substrate;
two detection electrodes, which are isolated from one another and are opposed to one other, wherein the detection electrodes are formed on the surface of the semiconductor substrate; and
a humidity-sensitive film, the capacitance of which changes in response to humidity, placed between the detection electrodes and formed on the surface of the semiconductor substrate, wherein;
the capacitance between the detection electrodes changes in response to changes in the surrounding humidity;
the circuit devices make up switched capacitor circuits comprising a reference capacitor and feedback capacitor that convert changes in capacitance between the detection electrodes into voltage signal output; and
at least one of the reference capacitor and the feedback capacitor is an underlying capacitor and is located beneath one of the detection electrodes. - View Dependent Claims (2, 3, 4, 5, 6)
MOS transistors, which are parts of the switched capacitor circuits; and
gate electrodes, wherein the gate electrodes include polysilicon.
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5. The capacitive humidity sensor of claim 2, wherein the one electrode of the underlying capacitor is formed with a diffusion layer that is formed at the surface of the semiconductor substrate.
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6. The capacitive humidity sensor of claim 1, wherein each of the detection electrodes is comb shaped and has tooth like parts, and the tooth-like parts of one of the detection electrodes are interdigitated with the tooth-like parts of the other detection electrode.
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7. A capacitive humidity sensor comprising:
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a semiconductor substrate;
circuit devices formed on a surface of the semiconductor substrate;
a first insulating film formed on the surface of the semiconductor substrate;
two detection electrodes formed in isolation from each other and opposed to each other on the first insulating film;
a second insulating film formed to cover the detection electrodes; and
a humidity-sensitive film, the capacitance of which changes in response to humidity, formed on the second insulating film to cover the detection electrodes and an area between the detection electrodes, wherein;
the capacitance between the detection electrodes changes in response to changes in surrounding humidity;
the circuit devices make up switched capacitor circuits comprising a reference capacitor and a feedback capacitor for converting changes in capacitance between the detection electrodes into voltage signal output; and
at least one of the reference capacitor and the feedback capacitor is an underlying capacitor that is formed beneath one of the detection electrodes. - View Dependent Claims (8, 9, 10, 11, 12)
MOS transistors, which are parts of the switched capacitor circuits; and
gate electrodes, wherein the gate electrodes include polysilicon.
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11. The capacitive humidity sensor of claim 8, wherein the one electrode of the underlying capacitor is formed with a diffusion layer that is formed at the surface of the semiconductor substrate.
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12. The capacitive humidity sensor of claim 7, wherein each of the detection electrodes is comb shaped and has tooth like parts, and the tooth-like parts of one of the detection electrodes are interdigitated with the tooth-like parts of the other detection electrode.
Specification