CADDIE-CORNER SINGLE PROOF MASS XYZ MEMS TRANSDUCER

• US 20090165558A1
• Filed: 12/28/2007
• Published: 07/02/2009
• Est. Priority Date: 12/28/2007
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Schultz, Peter S.
• Granted Patent: US 7,793,542 B2
• Time in Patent Office: Days
• US Class Current: 73/510
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass
• CPC Class Codes: 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

Abstract

A three-axis MEMS transducer featuring a caddie-corner proof mass comprises a planar main body portion of conductive material and a planar extra mass caddie-corner feature. The main body portion includes a width, length, and at least four side edges. An x-axis sense direction is defined from a first side edge to an opposite first side edge and a y-axis sense direction is defined from a second side edge to an opposite second side edge. The x-axis sense direction is perpendicular to the y-axis sense direction. The main body portion further includes at least two corners. The caddie-corner feature is positioned about at least one of the two corners of the main body portion. The caddie-corner feature and the main body portion comprise a single proof mass having a z-sense pivot axis disposed at an angle of ninety degrees to a diagonal extending from the caddie-corner feature to an opposite corner of the main body portion. The proof mass is configured to teeter-totter corner to corner about the z-sense pivot axis in response z-axis acceleration and/or z-axis deceleration.

Claims

1. A three-axis MEMS transducer featuring a caddie-corner proof mass, the proof mass comprising:

a planar main body portion of conductive material, the main body portion having a width and a length dimension and at least four side edges, wherein an x-axis sense direction is defined from a first side edge to an opposite first side edge and a y-axis sense direction is defined from a second side edge to an opposite second side edge, the x-axis sense direction being perpendicular to the y-axis sense direction, the main body portion further having at least two corners; and

a planar extra mass caddie-corner feature positioned about at least one of the two corners of the main body portion, wherein the extra mass caddie-corner feature and the main body portion comprise a single caddie-corner proof mass having a z-sense pivot axis disposed at an angle of ninety degrees to a diagonal extending from the extra mass caddie-corner feature to an opposite corner of the main body portion, wherein the proof mass is configured to teeter-totter corner to corner about the z-sense pivot axis in response to one of a z-axis acceleration and a z-axis deceleration.

2. The transducer of claim 1, wherein the planar main body portion includes four corners, wherein the extra mass caddie-corner feature is disposed on a diagonal extending between a first one of the four corners and a third one of the four corners, and wherein the z-sense pivot axis is defined along a diagonal extending between a second one of the four corners and a fourth one of the four corners.

3. The transducer of claim 2, further wherein the second one of the four corners and the fourth one of the four corners comprise reduced corners.

4. The transducer of claim 1, wherein the planar main body portion of conductive material further comprises (i) at least two pair of x-axis sense openings, wherein one pair is disposed in a first half of the main body portion of conductive material along the x-axis sense direction and the other pair is disposed in a second half of the main body portion along the x-axis sense direction opposite the first half, and (ii) at least two pair of y-axis sense openings in a first half of the main body portion of conductive material along the y-axis sense direction and the other pair is disposed in a second half of the main body portion along the y-axis sense direction opposite the first half, the transducer further comprising:

a substrate including at least two pairs of x-axis sense plates, at least two pairs of y-axis sense plates, and at least two z-axis sense plates; and

four springs coupled between the substrate and the main body portion, wherein the at least two pairs of x-axis sense plates align to and are positioned within the at least two pair of x-axis sense openings, the at least two pairs of y-axis sense plates align to and are positioned within the at least two pair of y-axis sense openings, and the at least two z-axis sense plates align with the extra mass caddie-corner feature and the corresponding opposite corner of the main body portion.

5. The transducer of claim 4, wherein the four springs comprise planar springs, each planar spring configured to allow movement of the main body portion and the extra mass caddie-corner feature (i) in an x-axis sense direction in response to at least one of an x-axis acceleration and an x-axis deceleration, (ii) in a y-axis sense direction in response to at least one of a y-axis acceleration and a y-axis deceleration, and (i) in a z-axis sense direction about the z-sense pivot axis in response to at least one of a z-axis acceleration and a z-axis deceleration.

6. The transducer of claim 1, wherein the z-sense pivot axis comprises a well-defined pivot axis disposed within the planar main body portion of conductive material at an angle of forty-five degrees from the x-axis and at an angle of forty-five degrees from the y-axis.

7. The transducer of claim 6, further wherein the z-sense pivot axis passes through a central point of the main body portion.

8. The transducer of claim 1, wherein the caddie-corner feature comprises a length portion that extends along an adjacent side edge by an amount less than or equal to one-half of a maximum length of a side edge of the main body portion.

9. The transducer of claim 1, wherein the caddie-corner feature comprises a width portion that extends from an adjacent side edge by an amount less than or equal to one-third of a maximum length of a side edge of the main body portion.

10. The transducer of claim 1, further comprising:

additional mass overlying the caddie-corner portion.

11. The transducer of claim 1, wherein the extra mass caddie-corner feature is disposed in the x-y plane at an angle less than ninety degrees off-axis from the x-axis sense direction and at an angle less than ninety degrees off-axis from the y-axis sense direction.

12. The transducer of claim 1, further wherein the extra mass caddie-corner feature is disposed at an angle of forty-five degrees off-axis from the x-axis sense direction and at an angle of forty-five degrees off-axis from the y-axis sense direction.

13. A three-axis MEMS transducer featuring a caddie-corner proof mass, the proof mass comprising:

a planar main body portion of conductive material, the main body portion having a width and a length dimension and at least four side edges, wherein an x-axis sense direction is defined from a first side edge to an opposite first side edge and a y-axis sense direction is defined from a second side edge to an opposite second side edge, the x-axis sense direction being perpendicular to the y-axis sense direction, the main body portion further having at least two corners; and

a planar extra mass caddie-corner feature positioned about at least one of the two corners of the main body portion, wherein the extra mass caddie-corner feature and the main body portion comprise a single caddie-corner proof mass having a z-sense pivot axis disposed at an angle of ninety degrees to a diagonal extending from the extra mass caddie-corner feature to an opposite corner of the main body portion, wherein the proof mass is configured to teeter-totter corner to corner about the z-sense pivot axis in response to one of a z-axis acceleration and a z-axis deceleration, wherein the planar main body portion includes four corners, wherein the extra mass caddie-corner feature is disposed on a diagonal extending between a first one of the four corners and a third one of the four corners, and wherein the z-sense pivot axis is defined along a diagonal extending between a second one of the four corners and a fourth one of the four corners, wherein the planar main body portion of conductive material further comprises (i) at least two pair of x-axis sense openings, wherein one pair is disposed in a first half of the main body portion of conductive material along the x-axis sense direction and the other pair is disposed in a second half of the main body portion along the x-axis sense direction opposite the first half, and (ii) at least two pair of y-axis sense openings in a first half of the main body portion of conductive material along the y-axis sense direction and the other pair is disposed in a second half of the main body portion along the y-axis sense direction opposite the first half, the transducer further comprising;

a substrate including at least two pairs of x-axis sense plates, at least two pairs of y-axis sense plates, and at least two z-axis sense plates; and

four springs coupled between the substrate and the main body portion, wherein the at least two pairs of x-axis sense plates align to and are positioned within the at least two pair of x-axis sense openings, the at least two pairs of y-axis sense plates align to and are positioned within the at least two pair of y-axis sense openings, and the at least two z-axis sense plates align with the extra mass caddie-corner feature and the corresponding opposite corner of the main body portion.

14. The transducer of claim 13, wherein the four springs comprise planar springs, each planar spring configured to allow movement of the main body portion and the extra mass caddie-corner feature (i) in an x-axis sense direction in response to at least one of an x-axis acceleration and an x-axis deceleration, (ii) in a y-axis sense direction in response to at least one of a y-axis acceleration and a y-axis deceleration, and (i) in a z-axis sense direction about the z-sense pivot axis in response to at least one of a z-axis acceleration and a z-axis deceleration.

15. The transducer of claim 14, wherein the z-sense pivot axis comprises a well-defined pivot axis disposed within the planar main body portion of conductive material at an angle of forty-five degrees from the x-axis and at an angle of forty-five degrees from the y-axis.

16. The transducer of claim 15, wherein the caddie-corner feature comprises a length portion that extends along an adjacent side edge by an amount less than or equal to one-half of a maximum length of a side edge of the main body portion, and wherein the caddie-corner feature comprises a width portion that extends from an adjacent side edge by an amount less than or equal to one-third of a maximum length of a side edge of the main body portion.

17. The transducer of claim 16, wherein the extra mass caddie-corner feature is disposed in the x-y plane at an angle of forty-five degrees off-axis from the x-axis sense direction and at an angle of forty-five degrees off-axis from the y-axis sense direction.

18. The transducer of claim 17, further wherein the second one of the four corners and the fourth one of the four corners comprise reduced corners.

19. A three-axis MEMS transducer featuring a caddie-corner proof mass, the proof mass comprising:

a planar main body portion of conductive material, the main body portion having a width and a length dimension and at least four side edges, wherein an x-axis sense direction is defined from a first side edge to an opposite first side edge and a y-axis sense direction is defined from a second side edge to an opposite second side edge, the x-axis sense direction being perpendicular to the y-axis sense direction, the main body portion further having at least two corners;

a planar extra mass caddie-corner feature positioned about at least one of the two corners of the main body portion, wherein the extra mass caddie-corner feature and the main body portion comprise a single proof mass having a z-sense pivot axis disposed at an angle of ninety degrees to a diagonal extending from the extra mass caddie-corner feature to an opposite corner of the main body portion, wherein the proof mass is configured to teeter-totter corner to corner about the z-sense pivot axis in response to one of a z-axis acceleration and a z-axis deceleration, wherein the z-sense pivot axis comprises a well-defined pivot axis disposed within the planar main body portion of conductive material at an angle of forty-five degrees from the x-axis and at an angle of forty-five degrees from the y-axis, further wherein the z-sense pivot axis passes through a central point of the main body portion, wherein the extra mass caddie-corner feature comprises a length portion that extends along an adjacent side edge by an amount less than or equal to one-half of a maximum length of a side edge of the main body portion, wherein the extra mass caddie-corner feature comprises a width portion that extends from an adjacent side edge by an amount less than or equal to one-third of a maximum length of a side edge of the main body portion, further wherein the extra mass caddie-corner feature is disposed in the x-y plane at an angle of forty-five degrees off-axis from the x-axis sense direction and at an angle of forty-five degrees off-axis from the y-axis sense direction, wherein the planar main body portion includes four corners, wherein the extra mass caddie-corner feature is disposed on a diagonal extending between a first one of the four corners and a third one of the four corners, and wherein the z-sense pivot axis is defined along a diagonal extending between a second one of the four corners and a fourth one of the four corners, wherein the planar main body portion of conductive material further comprises (i) at least two pair of x-axis sense openings, wherein one pair is disposed in a first half of the main body portion of conductive material along the x-axis sense direction and the other pair is disposed in a second half of the main body portion along the x-axis sense direction opposite the first half, and (ii) at least two pair of y-axis sense openings in a first half of the main body portion of conductive material along the y-axis sense direction and the other pair is disposed in a second half of the main body portion along the y-axis sense direction opposite the first half;

a substrate including at least two pairs of x-axis sense plates, at least two pairs of y-axis sense plates, and at least two z-axis sense plates; and

four springs coupled between the substrate and the main body portion, wherein the at least two pairs of x-axis sense plates align to and are positioned within the at least two pair of x-axis sense openings, the at least two pairs of y-axis sense plates align to and are positioned within the at least two pair of y-axis sense openings, and the at least two z-axis sense plates align with the extra mass caddie-corner feature and the corresponding opposite corner of the main body portion, wherein the four springs comprise planar springs, each planar spring configured to allow movement of the main body portion and the extra mass caddie-corner feature (i) in an x-axis sense direction in response to at least one of an x-axis acceleration and an x-axis deceleration, (ii) in a y-axis sense direction in response to at least one of a y-axis acceleration and a y-axis deceleration, and (i) in a z-axis sense direction about the z-sense pivot axis in response to at least one of a z-axis acceleration and a z-axis deceleration.

20. The transducer of claim 19, further wherein the second one of the four corners and the fourth one of the four corners comprise reduced corners.