# US 11,111,135 B2 · Methods and devices for microelectromechanical pressure sensors

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- Number: US 11,111,135 B2
- Document ID: US11111135B2
- Status: Granted
- Kind: B2
- Application number: 14/790,225
- Filed: 2015-07-02
- Published: 2016-01-07
- Granted: 2021-09-07
- Earliest claimed: 2014-07-02
- Assignees: My01 IP Holdings Inc.
- Applicants: MY01 IP Holdings Inc.
- Inventors: Vamsy Chodavarapu; Adel Merdassi; Charles Allan
- Web page: https://patentgrep.com/patent/US11111135B2

## CPC

- B81C 1/00182: {Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer}
- B81B 7/007: {Interconnections between the MEMS and external electrical signals}
- B81C 1/00269: {Bonding of solid lids or wafers to the substrate}
- B81C 1/00301: {Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias}
- 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 9/0073: {using a semiconductive diaphragm}
- G01L 9/12: by making use of variations in capacitance {, i.e. electric circuits therefor}
- H03H 3/0072: {of microelectro-mechanical resonators or networks (micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C)}
- H03H 3/0073: {Integration with other electronic structures}
- H03H 9/0561: {consisting of a multilayered structure}
- H03H 9/1057: {for microelectro-mechanical devices}
- H03H 9/2405: {of microelectro-mechanical resonators}
- H03H 9/2426: {in combination with other electronic elements}
- H03H 9/2431: {Ring resonators}
- H03H 9/2436: {Disk resonators}
- B81B 2203/0307: Anchors
- H03H 9/2452: {Free-free beam resonators}
- H03H 9/2463: {Clamped-clamped beam resonators}
- H03H 9/2473: {Double-Ended Tuning Fork [DETF] resonators}
- H03H 9/2478: {Single-Ended Tuning Fork resonators}
- H03H 2009/2442: {Square resonators}
- B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01)
- B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00)
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

MEMS based sensors, particularly capacitive sensors, potentially can address critical considerations for users including accuracy, repeatability, long-term stability, ease of calibration, resistance to chemical and physical contaminants, size, packaging, and cost effectiveness. Accordingly, it would be beneficial to exploit MEMS processes that allow for manufacturability and integration of resonator elements into cavities within the MEMS sensor that are at low pressure allowing high quality factor resonators and absolute pressure sensors to be implemented. Embodiments of the invention provide capacitive sensors and MEMS elements that can be implemented directly above silicon CMOS electronics.

## Claims

### Claim 1

A method for post-fabrication of a MEMS device, the method comprising:
providing the MEMS device comprising (i) a handling layer, (ii) a top layer, and (iii) a device layer located between the handling layer and the top layer, wherein the handling layer comprises a first trench on a top face of the handling layer adjacent to the device layer, wherein the top layer comprises a second trench on a bottom face of the top layer adjacent to the device layer, the second trench facing the first trench, wherein a first portion of the top layer is electrically insulated from a second portion of the top layer, wherein the first portion of the top layer extends to the second trench, wherein the device layer comprises a section of silicon positioned between the first trench and the second trench;
etching a back face of the handling layer until reaching the first trench, thereby forming an opening extending through the handling layer; and
etching the section of silicon of the device layer through the opening in the handling layer, thereby thinning the section of silicon of the device layer to form a flexible membrane that is (i) positioned between the opening and the second trench and (ii) capacitively coupled with the first portion of the top layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein etching the section of silicon of the device layer comprises dry etching the section of silicon of the device layer or wet etching the section of silicon of the device layer.

### Claim 3 (depends on 1)

The method of claim 1, wherein etching the back face of the handling layer comprises wet etching the back face of the handling layer or dry etching the back face of the handling layer.

### Claim 4 (depends on 1)

The method of claim 1, wherein the second trench is at a vacuum pressure.

### Claim 5 (depends on 2)

The method of claim 2, wherein the MEMS device further comprises an insulating layer deposited on the top face of the handling layer adjacent to the device layer, and wherein forming the opening further comprises etching through the insulating layer.

### Claim 6 (depends on 1)

The method of claim 1, further comprising securing a CMOS electronics wafer to a top face of the top layer opposite the bottom face of the top layer.

### Claim 7 (depends on 1)

The method of claim 1, wherein thinning the section of silicon of the device layer to form the flexible membrane comprises (i) etching a central portion of the section of silicon of the device layer to a first thickness and (ii) etching an outer portion of the section of silicon of the device layer to a second thickness that is thinner than the first thickness.

### Claim 8 (depends on 1)

The method of claim 1, wherein etching the section of silicon of the device layer through the opening in the handling layer comprises deep reactive-ion etching the section of silicon of the device layer.

### Claim 9 (depends on 1)

The method of claim 1, wherein providing the MEMS device comprises (i) forming the first trench on the top face of the handling layer and (ii) bonding the device layer to the handling layer.

### Claim 10 (depends on 9)

The method of claim 9, wherein providing the MEMS device further comprises (i) forming the second trench on the bottom face of the top layer and (ii) bonding the top layer to the device layer.

### Claim 11 (depends on 10)

The method of claim 10, wherein the top layer is bonded to the device layer while under a vacuum pressure.

### Claim 12 (depends on 10)

The method of claim 10, wherein the device layer comprises a first plurality of fingers protruding toward the top layer into the second trench, wherein the top layer comprises a second plurality of fingers protruding toward the device layer into the second trench, and wherein bonding the top layer to the device layer comprises bonding the top layer to the device layer such that the first plurality of fingers and the second plurality of fingers are interdigitated.

### Claim 13 (depends on 10)

The method of claim 10, wherein bonding the top layer to the device layer comprises bonding the second portion of the top layer to the device layer.

### Claim 14 (depends on 9)

The method of claim 9, wherein the top layer further comprises an annulus with finite thickness that insulates the first portion of the top layer from the second portion of the top layer.

### Claim 15 (depends on 14)

The method of claim 14, wherein the first portion of the top layer is electrically connected to a first electrode of the MEMS device, wherein the second portion of the top layer is electrically connected to a second electrode of the MEMS device.

### Claim 16 (depends on 14)

The method of claim 14, further comprising forming a first electrical contact on the first portion of the top layer and a second electrical contact on the second portion of the top layer.

### Claim 17 (depends on 16)

The method of claim 16, further comprising bonding the first electrical contact and the second electrical contact to a CMOS circuit.