Micromachined device with enhanced dimensional control

• US 6,282,960 B1
• Filed: 06/16/1998
• Issued: 09/04/2001
• Est. Priority Date: 03/15/1996
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Samuels, Howard R., Farash, Jeffrey A.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/097,839
• Time in Patent Office: 1,176 Days
• Field of Search: 735/143.2, 735/141.8, 735/141.6, 735/140.1, 738/626.1, 738/626.21, 738/626.36, 738/626.37, 361/280, 361/283.3
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A micromachined device is provided that establishes select dimensional relationships between micromachined structures to achieve correlation in dimensional variation among these structures.

Claims

1. A micromachined device comprising:

a substrate;

a movable mass suspended over the substrate and having a central member extending along an axis;

a spring structure coupled to the movable mass for performing a mechanical spring function, the spring structure including a first leg and a second leg;

a first structure having an elongated portion extending parallel and next to the first leg and spaced a distance d from the first leg, the first structure not performing the spring function;

a plurality of sense fingers extending perpendicular to the axis away from the central member; and

a plurality of fixed fingers, each disposed next to a respective sense finger at approximately the distance d.

2. The device of claim 1, wherein the first leg is parallel to and spaced from the second long leg a distance equal to approximately the distance d.

3. The device of claim 1, further comprising a second structure having an elongated portion parallel to the second leg of the spring structure at approximately the distance d, wherein the second structure does not perform the spring function.

4. The device of claim 1, wherein each of the sense fingers is disposed between a first fixed finger and a second fixed finger, the fixed fingers being fixed relative to the substrate, each sense finger and adjacent first and second fixed finger forming a differential capacitor.

5. The device of claim 4, wherein each sense finger is spaced a distance d from the first and second fixed fingers.

6. The device of claim 5, wherein the first fixed fingers are electrically coupled together, and the second fixed fingers are electrically coupled together.

7. The device of claim 4, wherein the distance d is about 1.3 microns.

8. The device of claim 1, wherein the first and second legs extend perpendicular to the axis.

9. The device of claim 1, wherein the first and second legs extend parallel to the axis.

10. The device of claim 1, wherein the spring includes at least third and fourth legs, the first, second, third, and fourth legs being parallel to each other and connected to form a folded spring with at least four parallel legs.

11. The device of claim 10, wherein each leg is spaced the distance d from an adjacent leg.

12. A micromachined device comprising:

a substrate;

a first structure suspended over the substrate and performing a mechanical function, the first structure having a first side and a second side, the first structure being positioned relative to any nearby components such that the spacing to other components in the device next to the first and second sides is set at a predefined distance; and

a second structure suspended over the substrate and coupled to the first structure, the second structure performing an electrical function and having a first external side that faces outwardly from the second structure, the second structure being laid out so that the spacing to components next to the external side is set at the predefined distance, whereby a dimensional relationship is established between the first and second structures.

13. The device of claim 12, wherein the first structure is a spring.

14. The device of claim 13, wherein the spring includes a first leg having the first side, and a second leg having the second side, wherein the second leg is parallel to the first leg.

15. The device of claim 14, wherein the first leg is spaced from the second leg approximately the predefined distance.

16. The device of claim 14, wherein the spring further includes a third leg and a fourth leg, the four legs forming at least part of a folded spring.

17. The device of claim 14, wherein the second structure includes a sense finger, the device further comprising fixed fingers that are fixed relative to the substrate, the sense finger between the fixed fingers to form a differential capacitor.

18. The device of claim 17, wherein the sense finger is spaced from each fixed finger a distance d, and the first and second legs are spaced the distance d.

19. The device of claim 12, wherein the first structure is a spring, wherein the second operating structure includes a sense finger, the device further comprising fixed fingers that are fixed relative to the substrate, the sense finger between the fixed fingers to form a differential capacitor.

20. A micromachined device comprising:

a substrate;

a movable mass suspended in a plane over and parallel to the substrate and movable along a first axis, the movable mass including

a beam elongated along the first axis, and

a plurality of parallel movable fingers arranged in a row extending away from the beam and perpendicular to the first axis;

a first plurality of fixed fingers that are stationary with respect to the substrate, the first plurality of fixed fingers being on one side of the row of movable fingers to form a first capacitance, each of the first plurality of fixed fingers being spaced a distance d from one of the movable fingers;

a second plurality of fixed fingers that are stationary with respect to the substrate, the second plurality of fixed fingers being on the other side of the row of movable fingers to form a second capacitance, each of the second plurality of fixed fingers being spaced a distance d from one of the movable fingers;

spring anchored to the substrate and coupled to the movable mass to allow the mass to move relative to the substrate, the spring having first and second legs parallel to each other and perpendicular to the first axis for performing a spring function; and

a dimensional control structure having an elongated side and formed next to the first long leg of the spring and spaced from the first leg by the distance d, wherein the dimensional control structure does not perform the spring function.

21. The device of claim 20, wherein the first and second legs are parallel and spaced apart the distance d.

22. The device of claim 20, wherein the first and second legs are part of a folded spring structure.