# US 12,111,284 B2 · Gas sensors with negligible response to humidity and temperature

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- Number: US 12,111,284 B2
- Document ID: US12111284B2
- Status: Granted
- Kind: B2
- Application number: 17/594,605
- Filed: 2020-04-23
- Published: 2022-06-30
- Granted: 2024-10-08
- Earliest claimed: 2019-04-24
- Assignees: The Regents of the University of California
- Applicants: The Regents of the University of California
- Inventors: Niharika Gupta; Ali Javey; Hossain Mohammad Fahad
- Web page: https://patentgrep.com/patent/US12111284B2

## CPC

- G01N 27/4141: {specially adapted for gases}
- G01N 27/4146: {involving nanosized elements, e.g. nanotubes, nanowires}
- G01N 33/0009: {General constructional details of gas analysers, e.g. portable test equipment (devices for withdrawing samples in the gaseous state G01N1/22)}
- G01N 33/0037: {NOx}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

In one example, a gas sensor is provided. The gas sensor includes a substrate, an isolation region formed on outer edges of the substrate, a micro-heater formed on the isolation region, a sensing layer formed on the substrate inside of the isolation region, and a source and drain formed around the sensing layer and inside of the isolation region.

## Claims

### Claim 1

A gas sensor, comprising:
a substrate;
an isolation region formed on outer edges of the substrate;
a micro-heater formed on the isolation region;
a sensing layer formed on the substrate inside of the isolation region; and
a source and drain formed around the sensing layer and inside of the isolation region.

### Claim 2 (depends on 1)

The gas sensor of claim 1, wherein the micro-heater comprises a layer of tungsten.

### Claim 3 (depends on 2)

The gas sensor of claim 2, wherein the layer of tungsten comprises approximately 200 nanometers.

### Claim 4 (depends on 1)

The gas sensor of claim 1, wherein the sensing layer comprises platinum nanoparticles on trichloro (1H,1H,2H,2H-perfluorooctyl) silane (FOTS) for a hydrogen sensor.

### Claim 5 (depends on 4)

The gas sensor of claim 4, wherein the platinum nanoparticles in the sensing layer are approximately 1 nanometer thick.

### Claim 6 (depends on 1)

The gas sensor of claim 1, wherein the sensing layer comprises indium oxide particles for a nitrogen oxide sensor.

### Claim 7 (depends on 6)

The gas sensor of claim 6, wherein the indium oxide particles in the sensing layer are approximately 1.5 nanometers thick.

### Claim 8 (depends on 1)

The gas sensor of claim 1, wherein the source and drain each further comprise nickel and tungsten contacts.

### Claim 9 (depends on 1)

The gas sensor of claim 1, wherein the micro-heater is powered with a constant voltage to heat the gas sensor to a temperature that is above a room temperature.

### Claim 10 (depends on 9)

The gas sensor of claim 9, wherein the temperature comprises approximately 37 degrees Celsius+/−3 degrees.

### Claim 11 (depends on 9)

The gas sensor of claim 9, wherein the micro-heater is operated at a power of approximately 372 milliWatts (mW).

### Claim 12 (depends on 1)

The gas sensor of claim 1, wherein a drain bias of approximately 0.6 Volts (V) to 0.7 V is applied to the source and drain.

### Claim 13 (depends on 1)

The gas sensor of claim 1, further comprising:
a controller coupled to the micro-heater to adjust an amount of voltage to the micro-heater in response to an ambient temperature change to maintain the gas sensor at a constant operating temperature.

### Claim 14

A method for fabricating a gas sensor, comprising:
providing a substrate;
forming a silicon dioxide isolation region on outer edges of the substrate;
doping source and drain regions on the substrate;
patterning a sensing layer region between the source and drain regions;
doping the sensing layer region;
defining source and drain contacts on the source and drain regions, wherein each of the source and drain contacts comprises a layer of nickel and tungsten;
forming a tungsten micro-heater on the silicon dioxide isolation region; and
depositing a sensing layer on the sensing layer region.

### Claim 15 (depends on 14)

The method of claim 14, wherein the sensing layer comprises platinum nanoparticles on trichloro (1H,1H,2H,2H-perfluorooctyl) silane (FOTS) for a hydrogen sensor or indium oxide particles for a nitrogen oxide sensor.