# US 10,481,025 B2 · Piezoresistive sensor with spring flexures for stress isolation

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- Number: US 10,481,025 B2
- Document ID: US10481025B2
- Status: Granted
- Kind: B2
- Application number: 15/416,801
- Filed: 2017-01-26
- Published: 2018-07-26
- Granted: 2019-11-19
- Earliest claimed: 2017-01-26
- Assignees: Rosemount Aerospace Inc.
- Applicants: Rosemount Aerospace Inc.
- Inventors: Timothy Thomas Golly; David P. Potasek; Cuong Tho Huynh
- Web page: https://patentgrep.com/patent/US10481025B2

## CPC

- G01L 9/0048: {Details about the mounting of the diaphragm to its support or about the diaphragm edges, e.g. notches, round shapes for stress relief}
- G01L 9/0042: {Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms (details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively)}
- G01L 9/0052: {of piezoresistive elements (circuits therefor G01L9/06)}
- G01L 9/0055: {bonded on a diaphragm}
- G01L 19/146: {using flexible element between the transducer and the support}
- G01L 19/147: {Details about the mounting of the sensor to support or covering means}
- G01L 9/0054: {integral with a semiconducting diaphragm}
- G01L 9/008: {using piezoelectric devices (piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025)}
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)

## Abstract

A MEMS device includes a backing wafer with a support portion and central back plate connected to the support portion with spring flexures, a diaphragm wafer with a support portions and a sensing portion connected to the support portion with spring flexures, a passivation layer on the diaphragm, and a topping wafer. The device allows for stress isolation of a diaphragm in a piezoresistive device without a large MEMS die.

## Claims

### Claim 1

A sensor device comprising:
a backing wafer comprising:
a backing support portion, and
a central backing plate connected to the backing support portion by one or more backing springs;
a diaphragm wafer connected to the backing wafer, the diaphragm wafer comprising:
a diaphragm support portion, and
a sensing portion connected to the diaphragm support portion by one or more diaphragm springs;
a passivation layer on the diaphragm wafer opposite the backing wafer; and
a topping wafer connected to the passivation layer opposite the backing wafer;
wherein the backing wafer and the diaphragm wafer are connected with frit, and wherein the diaphragm wafer and the topping wafer are connected with frit.

### Claim 2 (depends on 1)

The sensor device of claim 1, further comprising a base wafer connected to the backing wafer opposite the diaphragm wafer.

### Claim 3 (depends on 2)

The sensor device of claim 2, wherein the base wafer is secured to a package base opposite the backing wafer.

### Claim 4 (depends on 1)

The sensor device of claim 1, wherein the diaphragm springs are connected to the support portion of the diaphragm wafer.

### Claim 5 (depends on 1)

The sensor device of claim 1, wherein the sensing portion of the diaphragm wafer contains a diaphragm.

### Claim 6 (depends on 1)

The sensor device of claim 1, wherein the diaphragm wafer is attached to the backing wafer such that a reference pressure cavity is enclosed between the diaphragm wafer and the backing wafer.

### Claim 7 (depends on 6)

The sensor device of claim 6, further comprising a Wheatstone bridge on the diaphragm wafer opposite the diaphragm.

### Claim 8 (depends on 1)

The sensor device of claim 1, wherein the passivation layer comprises:
a first insulation layer attached to the diaphragm wafer,
a thin metal film attached to the first insulation layer opposite the diaphragm wafer,
a piezoresistive layer, and
a second insulation layer attached to the thin metal film and the piezoresistive layer opposite the first insulation layer.

### Claim 9 (depends on 8)

The sensor device of claim 8, wherein the passivation layer includes an opening in the second insulation layer such that an electrical connection can be made to the thin metal film.

### Claim 10 (depends on 9)

The sensor device of claim 9, further comprising one or more wire bonds connected to the thin metal film through the opening, the wire bonds connected to one or more electrical feedthrough pins.

### Claim 11 (depends on 10)

The sensor device of claim 10, wherein the one or more electrical feedthrough pins are sealed by a hermetic seal and run through a package base.