Suspension arrangement for semiconductor accelerometer

• US 6,223,598 B1
• Filed: 06/18/1997
• Issued: 05/01/2001
• Est. Priority Date: 06/18/1997
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Judy, Michael W.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US08/878,213
• Time in Patent Office: 1,413 Days
• Field of Search: 73/514.32, 73/514.18, 73/514.24, 73/514.16, 73/510, 73/514.38, 73/504.04, 73/504.12, 73/504.14, 73/504.02, 361/280
• US Class Current: 73/514.32
• 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

Abstract

A suspension mounting arrangement for a suspended layer in a semiconductor accelerometer, the layer being suspended above and spaced apart from a substrate. The arrangement includes a common anchor point associated with the substrate; first and second anchor points associated with the suspended layer; a first flexible serpentine arm coupled between the first anchor point and the common anchor point; and a second flexible serpentine arm coupled between the second anchor point and the common anchor point. The first and second flexible serpentine arms are symmetrically configured with respect to one another.

Claims

1. A semiconductor device comprising:

a substrate;

a layer suspended above and spaced apart from the surface of said substrate, said layer including at least one first capacitive element;

at least one second capacitive element associated with said substrate positioned in parallel juxtaposition with said at least one first capacitive element so as to define first gaps between each of said at least one first capacitive element and adjoining said at least one second capacitive element; and

a plurality of suspension members coupled between said substrate and said layer to allow limited movement of said layer relative to a plane parallel to said substrate, each of said suspension members including a plurality of symmetrically configured flexible serpentine arms having second gaps defined therebetween, wherein

said first and second gaps are configured to track one another so as to maintain constant gap widths, and each of said suspension members has spring constants such that the response in a first direction is equal to the response in a second direction orthogonal to said first direction, and said device is configured with 4-fold symmetry in the plane of the substrate.

2. The device of claim 1, wherein said suspension members are compliant and provide flexure to said layer.

3. The device of claim 1, wherein said suspension members are coupled to four corners of said layer.

4. The device of claim 1, wherein said device comprises an accelerometer.

5. A semiconductor accelerometer comprising:

a semiconductor substrate;

a layer of conductive material suspended above and spaced apart from the surface of said substrate, said layer including at least one first capacitive element;

at least one second capacitive element associated with said substrate positioned in parallel juxtaposition with said at least one first capacitive element so as to define first gaps between each of said at least one first capacitive element and adjoining said at least one second capacitive element, said first and second capacitive elements forming variable capacitances which vary in accordance with acceleration of movement of said first layer; and

a plurality of suspension members coupled between said substrate and said layer to allow limited movement of said layer relative to a plane parallel to said substrate, each of said suspension members including a plurality of symmetrically configured flexible serpentine arms having second gaps defined therebetween, wherein

said first and second gaps are configured to track one another so as to maintain constant gap widths, and each of said suspension members has spring constants such that the response in a first direction is equal to the response in a second direction orthogonal to said first direction, and said accelerometer is configured with 4-fold symmetry in the plane of the substrate.

6. The accelerometer of claim 5, wherein said suspension members are compliant and provide flexure to said layer.

7. The accelerometer of claim 5, wherein said suspension members are coupled to four corners of said layer.

8. The accelerometer of claim 5, wherein said accelerometer comprises a multi-axis accelerometer.

9. The accelerometer of claim 5, wherein the acceleration of movement of said layer is measured in accordance with a differential capacitance generated between said at least one first capacitive element and said at least one second capacitive element.

10. A mounting arrangement for a suspended layer in a semiconductor accelerometer, said layer being suspended above and spaced apart from a substrate to allow limited movement of said layer relative to a plane parallel to said substrate, said layer including a plurality of first capacitive elements, a plurality of second capacitive elements being associated with said substrate positioned in parallel juxtaposition with said first capacitive elements so as to define first gaps between each of said first capacitive elements and said adjoining second capacitive elements, said arrangement comprising:

a common anchor associated with said substrate;

first and second connection points associated with said suspended layer;

a first flexible serpentine arm coupled between said first connection point and said common anchor; and

a second flexible serpentine aim coupled between said second connection point and said common anchor, wherein said first and second flexible serpentine arms are symmetrically configured with respect to one another and having second gaps defined therebetween, wherein

said first and second gaps are configured to track one another so as to maintain constant gap widths, said first and second serpentine arms comprise spring constants such that the response in a first direction is equal to the response in a second direction orthogonal to said first direction, and said accelerometer is configured with 4-fold symmetry in the plane of the substrate.

11. The accelerometer of claim 10, wherein said serpentine arms are compliant and provide flexure to said layer.

12. The accelerometer of claim 10, wherein said serpentine arms are coupled to four corners of said layer.

13. The accelerometer of claim 10, wherein said accelerometer comprises a multi-axis accelerometer.