Micromachined device with enhanced dimensional control

• US 5,880,369 A
• Filed: 03/15/1996
• Issued: 03/09/1999
• 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): Williams, Hezron E.
• Assistant Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/616,713
• Time in Patent Office: 1,089 Days
• Field of Search: 73/514.32, 73/514.18, 73/514.16, 73/514.01, 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. Such dimensional relationships are achieved through consistent spacing between desired operating structures and by adding new structures (i.e., dimensional control structures) which provide additional consistent spacing at desired locations within the micromachined device.

Claims

1. A micromachined device comprising:

a first dimensional-control structure;

a first operating structure having a first side and a second side, said first side disposed proximate to said first dimensional-control structure at a predefined distance; and

a second dimensional-control structure disposed proximate to said second side at approximately said predefined distance;

wherein the dimensional-control structures are structures whose sole purpose is to provide dimensional control, and wherein the first operation structure performs at least one of a mechanical and electrical function.

2. The micromachined device of claim 1 wherein said first operating structure is a spring.

3. The micromachined device of claim 2 wherein said spring comprises:

a first spring leg having said first side; and

a second spring leg having said second side, wherein said second spring leg is disposed proximate to said first spring leg at approximately said predefined distance.

4. The micromachined device of claim 2 further comprising:

a second operating structure coupled to said first operating structure, said second operating structure having a third side and a fourth side;

a third operating structure disposed proximate to said third side at approximately said predefined distance; and

a fourth operating structure disposed proximate to said fourth side at approximately said predefined distance.

5. The micromachined device of claim 4 wherein said second operating structure is a sense finger.

6. The micromachined device of claim 5 wherein said third and fourth operating structures are fixed fingers, the sense finger and fixed fingers forming a capacitor.

7. A micromachined device comprising:

a first operating structure performing a first function;

a dimensional-control structure disposed proximate to said first operating structure at a predefined distance;

a second operating structure coupled to said first operating structure, said second operating structure performing a second function; and

a third operating structure disposed proximate to said second operating structure at approximately said predefined distance, said third operating structure performing said second function;

wherein the dimensional-control structures are structures whose sole purpose is to provide dimensional control, and wherein the first operation structure performs at least one of a mechanical and electrical function.

8. The micromachined device of claim 7 wherein said first function is mechanical.

9. The micromachined device of claim 8 wherein said second function is electrical.

10. The micromachined device of claim 9 wherein said first operating structure is a spring and said second operating structure is a sense finger in a sense capacitor.

11. A micromachined device comprising:

a substrate;

a central member suspended over the substrate;

a spring structure coupled to said central member, the spring structure having a first side and a second side;

a first dimensional-control structure disposed proximate to said first side at a predefined distance;

a second dimensional-control structure disposed proximate to said second side at approximately said predefined distance, wherein the first and second dimensional-control structures are structures whose sole purpose is to provide dimensional control; and

a first sense capacitor including a first sense finger coupled to said central member and a first fixed finger disposed proximate to said first sense finger at approximately said predefined distance.

12. The micromachined device of claim 11 wherein said spring structure is a folded spring comprising a first long leg, a second long leg disposed parallel to said first long leg, and a short leg intercoupling said first and second long legs, said first side being on said first long leg, and said second side being on said second long leg.

13. The micromachined device of claim 12 wherein said first long leg is spaced from said second long leg a distance equal to approximately said predefined distance.

14. The micromachined device of claim 13 further comprising a second sense capacitor coupled to said member, said second capacitor including said first sense finger and a second fixed finger disposed proximate to said first sense finger at approximately said predefined distance, wherein said first sense finger is disposed between said first and second fixed fingers.

15. A micromachined device comprising:

a first operating structure performing a first function that is at least one of an electrical and mechanical function, said first operating structure having a first side and a second side and being laid out so that spacing disposed immediately proximate to said first and second sides is set at a predefined distance; and

a second operating structure coupled to said first operating structure and performing a second function that is at least one of an electrical and mechanical function different from the first function, said second operating structure having a first external side that faces outwardly from said second operating structure, the second operating structure being laid out so that spacing disposed immediately proximate to said first external side is set at said predefined distance, whereby a dimensional relationship is established between said first and said second structures, said relationship providing control of dimensional variation between said first and second structures.

16. The micromachined device of claim 15 wherein said spacing disposed immediately proximate to said first side of said first operating structure is between said first operating structure and a third operating structure that performs at least one of a mechanical and an electrical function.

17. The micromachined device of claim 16 wherein said spacing disposed immediately proximate to said first external side is between said second operating structure and a first dimensional-control structure, wherein the dimensional control structure has a sole purpose of providing dimensional control.

18. The micromachined device of claim 17 wherein said spacing disposed immediately proximate to said second side is between said first operating structure and a fourth operating structure that performs at least one of a mechanical and an electrical function.

19. The micromachined device of claim 18 wherein said second operating structure has a second external side that faces away from said second operating structure and is laid out so spacing disposed immediately proximate to said second external side is set at said predefined distance between said second operating structure and a second dimensional-control structure, wherein the dimensional control structure has a sole purpose of providing dimensional control.

20. The micromachined device of claim 19 wherein said first operating structure is a sense finger in a sense capacitor, said second operating structure is a spring and said third and fourth operating structures are fixed fingers.

21. 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 in the plane, the movable mass including a plurality of movable fingers extending along parallel axes in the plane and orthogonal to the first axis;

a plurality of fixed fingers that are stationary with respect to the substrate and interleaving with the movable fingers to form a differential capacitor, the fixed fingers being spaced a distance d from the fingers on the mass;

spring members anchored to the substrate and extending to the movable mass to allow the mass to move relative to the substrate; and

dimensional control members formed next to the spring members and spaced from the spring members by the distance d, the dimensional control members performing substantially only a dimensional control function.

22. 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 in the plane, the movable mass including a plurality of movable fingers extending along parallel axes in the plane and orthogonal to the first axis, the plurality of movable fingers being arranged in a row from a first finger to an n-th finger;

a plurality of fixed fingers that are stationary with respect to the substrate and interleaving with and parallel to the movable fingers to form a differential capacitor, the fixed fingers including a first group of n fingers electrically coupled together, with each spaced a distance d from a corresponding one of the movable fingers and each on one side of the corresponding movable finger, and a second group of n fingers electrically coupled together, with each spaced a distance d from a corresponding movable finger and each on the other side of the corresponding movable finger, such that a plurality of differential capacitive cells is formed, with each cell having a movable finger between a fixed finger in the first group and a fixed finger in the second group and spaced a distance d from the fixed finger in the first group and from the fixed finger in the second group, the cells being ordered from a first cell to an n-th cell corresponding to the number of the movable finger in the cell;

a first dimensional control finger electrically coupled to the second group of fixed fingers and positioned a distance d from the fixed finger in the first group in the first cell, such that the fixed finger in the first group in the first cell is between the first movable finger and the first dimensional control finger; and

a second dimensional control finger electrically coupled to the first group of fixed fingers and positioned a distance d from the fixed finger in the second group in the n-th cell, such that the fixed finger in the second group in the n-th cell is between the n-th movable finger and the second dimensional control finger.