# US 10,502,759 B2 · MEMS device with two-stage motion limit structure

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- Number: US 10,502,759 B2
- Document ID: US10502759B2
- Status: Granted
- Kind: B2
- Application number: 15/791,673
- Filed: 2017-10-24
- Published: 2019-04-25
- Granted: 2019-12-10
- Earliest claimed: 2017-10-24
- Assignees: NXP USA, Inc.
- Applicants: NXP USA, Inc.
- Inventors: Aaron A. Geisberger
- Web page: https://patentgrep.com/patent/US10502759B2

## CPC

- G01P 15/125: by capacitive pick-up
- B81B 3/0051: {For defining the movement, i.e. structures that guide or limit the movement of an element (mechanical arrangements for preventing or damping vibration or shock H01H3/60)}
- B81B 2201/025: Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
- G01P 2015/0831: {the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration}
- G01P 2015/0871: {using stopper structures for limiting the travel of the seismic mass}
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})
- B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00)

## Abstract

A MEMS device includes a substrate, a proof mass capable of moving relative to the substrate, and a motion limit structure. The motion limit structure includes an arm structure flexibly coupled to the proof mass or the substrate. The arm structure has a first contact region and a second contact region. In response to a shock force that causes the proof mass to move, the first contact region contacts a first stop region on the other one of the proof mass and the substrate. Following contact of the first contact region with the first stop region and upon continuation of the shock force, the second contact region contacts a second stop region on the other one of the proof mass and the substrate such that the contact between the second contact and stop regions reduces a contact force between the first contact and stop regions.

## Claims

### Claim 1

A microelectromechanical systems (MEMS) device comprising:
a substrate;
a proof mass spaced apart from the substrate and capable of moving relative to the substrate, wherein the proof mass is configured to move in a first direction substantially parallel to a surface of the substrate; and
a motion limit structure comprising an arm structure flexibly coupled to a first one of the proof mass and the substrate, the arm structure extending from the first one of the proof mass and the substrate proximate an edge of the proof mass, the arm structure being configured to pivot about an axis of rotation that is perpendicular to the surface of the substrate, and the arm structure having a first contact region and a second contact region, wherein:
in response to a shock force imposed upon the proof mass that causes the proof mass to move, the first contact region is configured to contact a first stop region on a second one of the proof mass and the substrate; and
following contact of the first contact region with the first stop region and upon a continuation of the shock force imposed upon the proof mass, the second contact region is configured to contact a second stop region on the second one of the proof mass and the substrate such that contact of the second contact region with the second stop region reduces a contact force between the first contact region and the first stop region.

### Claim 2 (depends on 1)

The MEMS device of claim 1 wherein the arm structure is a cantilevered arm structure having a first end that is flexibly coupled to the first one of the proof mass and the substrate at a pivot location.

### Claim 3 (depends on 1)

The MEMS device of claim 1 wherein a first end of the arm structure is flexibly coupled to the first one of the proof mass and the substrate at a pivot location, and the second contact region is positioned closer to the pivot location than the first contact region.

### Claim 4 (depends on 1)

The MEMS device of claim 1 wherein:
one of the first contact region and the first stop region includes a first bump extending toward the other of the first contact region and the first stop region; and
one of the second contact region and the second stop region includes a second bump extending toward the other of the second contact region and the second stop region.

### Claim 5 (depends on 1)

The MEMS device of claim 1 wherein prior to imposition of the shock force on the proof mass, a first gap exists between the first contact region and the first stop region, the first gap having a first gap width, and a second gap exists between the second contact region and the second stop region, the second gap having a second gap width that is greater than the first gap width.

### Claim 6 (depends on 1)

The MEMS device of claim 1 wherein:
when the arm structure extends from the proof mass, a pivot location of the axis of rotation is at a junction between the edge of the proof mass and a first end of the arm structure; and
when the arm structure extends from the substrate, the pivot location of the axis of rotation is at a junction between an anchor coupled to the substrate and the first end of the arm structure.

### Claim 7 (depends on 6)

The MEMS device of claim 6 wherein:
the first contact region is displaced away from the axis of rotation by a first distance in a second direction parallel to a surface of the substrate, the second direction being perpendicular to the first direction; and
the second contact region is displaced away from the axis of rotation by a second distance in the second direction, the second distance being less than the first distance.

### Claim 8 (depends on 1)

The MEMS device of claim 1 wherein the arm structure comprises:
a first segment having a first width parallel to the direction of the movement of the proof mass; and
a second segment longitudinally extending from and aligned with the first segment, wherein the first segment is interposed between the axis of rotation and the second segment, the second segment has a second width parallel to the direction of the movement of the proof mass that is greater than the first width, and the first and second contact regions are located on the second segment.

### Claim 9

A microelectromechanical systems (MEMS) device comprising:
a substrate;
a proof mass spaced apart from the substrate and capable of moving relative to the substrate, wherein the proof mass is configured to pivot about a first axis of rotation, and the proof mass includes a first section on one side of the first axis of rotation and a second section on an opposing side of the first axis of rotation, the first section being formed with greater mass than the second section; and
a motion limit structure comprising an arm structure flexibly coupled to a first one of the proof mass and the substrate, the arm structure extending from the first one of the proof mass and the substrate proximate the first section of the proof mass, the arm structure is configured to pivot about a second axis of rotation that is parallel to the first axis of rotation, and the arm structure has a first contact region and a second contact region, wherein the first contact region and the first stop region are displaced away from the second axis of rotation by a first distance in a direction parallel to a surface of the substrate, the second contact region and the second stop region are displaced away from the second axis of rotation by a second distance in the direction parallel to the surface of the substrate, the second distance being less than the first distance, wherein:
in response to a shock force imposed upon the proof mass that causes the proof mass to move, the first contact region is configured to contact a first stop region on a second one of the proof mass and the substrate; and
following contact of the first contact region with the first stop region and upon a continuation of the shock force imposed upon the proof mass, the second contact region is configured to contact a second stop region on the second one of the proof mass and the substrate such that contact of the second contact region with the second stop region reduces a contact force between the first contact region and the first stop region.

### Claim 10 (depends on 9)

The MEMS device of claim 9 wherein the second axis of rotation is displaced away from the first axis of rotation in a direction parallel to a surface of the substrate.

### Claim 11

A microelectromechanical systems (MEMS) device comprising:
a substrate;
a proof mass spaced apart from the substrate and capable of moving relative to the substrate, the proof mass is configured to pivot about a first axis of rotation, and the proof mass includes a first section on one side of the first axis of rotation and a second section on an opposing side of the first axis of rotation, the first section being formed with greater mass than the second section; and
a motion limit structure comprising a cantilevered arm structure having a first end flexibly coupled to the proof mass at a pivot location, wherein the arm structure extends from the first section of the proof mass and is configured to pivot about a second axis of rotation that is parallel to the first axis of rotation, the second axis of rotation is displaced away from the first axis of rotation in a direction parallel to a surface of the substrate, and the arm structure has a first contact region and a second contact region, the second contact region being positioned closer to the pivot location than the first contact region, wherein the first contact region and the first stop region are displaced away from the second axis of rotation by a first distance in a direction parallel to a surface of the substrate, the second contact region and the second stop region are displaced away from the second axis of rotation by a second distance in the direction parallel to the surface of the substrate, the second distance being less than the first distance, and wherein:
in response to a shock force imposed upon the proof mass that causes the proof mass to move, the first contact region is configured to contact a first stop region on a second one of the proof mass and the substrate; and
following contact of the first contact region with the first stop region and upon a continuation of the shock force imposed upon the proof mass, the second contact region is configured to contact a second stop region on the second one of the proof mass and the substrate such that contact of the second contact region with the second stop region reduces a contact force between the first contact region and the first stop region.

### Claim 12

A microelectromechanical systems (MEMS) device comprising:
a substrate;
a proof mass spaced apart from the substrate and capable of moving relative to the substrate, wherein the proof mass is configured to move in a first direction substantially parallel to a surface of the substrate; and
a motion limit structure comprising a cantilevered arm structure having a first end flexibly coupled to a first one of the proof mass and the substrate at a pivot location, the arm structure extending from the first one of the proof mass and the substrate proximate a first edge of the proof mass, the arm structure is configured to pivot about an axis of rotation that is perpendicular to the surface of the substrate, and the arm structure has a first contact region and a second contact region, the second contact region being positioned closer to the pivot location than the first contact region, wherein:
in response to a shock force imposed upon the proof mass that causes the proof mass to move, the first contact region is configured to contact a first stop region on a second one of the proof mass and the substrate; and
following contact of the first contact region with the first stop region and upon a continuation of the shock force imposed upon the proof mass, the second contact region is configured to contact a second stop region on the second one of the proof mass and the substrate such that contact of the second contact region with the second stop region reduces a contact force between the first contact region and the first stop region.

### Claim 13 (depends on 12)

The MEMS device of claim 12 wherein:
when the arm structure extends from the proof mass, a pivot location of the axis of rotation is at a junction between the edge of the proof mass and a first end of the arm structure; and
when the arm structure extends from the substrate, the pivot location of the axis of rotation is at a junction between an anchor coupled to the substrate and the first end of the arm structure.

### Claim 14 (depends on 13)

The MEMS device of claim 13 wherein:
the first contact region is displaced away from the axis of rotation by a first distance in a second direction parallel to a surface of the substrate, the second direction being perpendicular to the first direction; and
the second contact region is displaced away from the axis of rotation by a second distance in the second direction, the second distance being less than the first distance.

### Claim 15 (depends on 12)

The MEMS device of claim 12 wherein the arm structure comprises:
a first segment having a first width parallel to the direction of the movement of the proof mass; and
a second segment longitudinally extending from and aligned with the first segment, wherein the first segment is interposed between the axis of rotation and the second segment, the second segment has a second width parallel to the direction of the movement of the proof mass that is greater than the first width, and the first and second contact regions are located on the second segment.