Selective conductive coating for MEMS sensors

• US 10,427,931 B2
• Filed: 06/28/2017
• Issued: 10/01/2019
• Est. Priority Date: 06/28/2016
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Kaanta, Bradley C.
• Primary Examiner(s): Booth, Richard A
• Application Number:
  US15/635,846
• Publication Number:
  US 20170369304A1
• Time in Patent Office: 825 Days
• CPC Class Codes: B81B 2201/0221 Variable capacitors
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: B81C 1/00698 Electrical characteristics, e.g. by doping materials
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

A capacitive microelectromechanical systems (MEMS) sensor is provided, having conductive coatings on opposing surfaces of capacitive structures. The capacitive structures may be formed of silicon, and the conductive coating is formed of tungsten in some embodiments. The structure is formed in some embodiments by first releasing the silicon structures and then selectively coating them in the conductive material. In some embodiments, the coating may result in encapsulating the capacitive structures.

Claims

1. A microelectromechanical systems (MEMS) sensor, comprising:

a first capacitor plate with a top, bottom, and side surface all covered with a metal, the first capacitor plate comprising a semiconductor material;

a second capacitor plate in-plane with the first capacitor plate in a first plane, spaced apart from the first capacitor plate, and covered with the metal; and

a third capacitor plate covered with the metal and spaced apart from the first capacitor plate in a second plane different from the first plane.

2. The MEMS sensor of claim 1, wherein the first capacitor plate is on or part of a movable mass.

3. The MEMS sensor of claim 2, wherein the second and third capacitor plates are on or part of a substrate.

4. The MEMS sensor of claim 1, wherein the first capacitor plate is part of a movable mass and is encapsulated by the metal.

5. The MEMS sensor of claim 1, wherein the second and third capacitor plates are on or part of a substrate.

6. The MEMS sensor of claim 1, wherein the metal is tungsten.

7. A microelectromechanical systems (MEMS) device, comprising:

a movable mass having a first electrode formed of a semiconductor material with a top, bottom, and side surface all covered by a metal; and

a second electrode spaced apart from and facing the side surface of the first electrode, the second electrode being covered by the metal.

8. The MEMS device of claim 7, wherein the second electrode is on or part of a substrate above which the movable mass is suspended.

9. The MEMS device of claim 8, wherein the first electrode is formed of silicon and the metal is tungsten.

10. The MEMS device of claim 7, further comprising a third electrode spaced from and facing the bottom surface of the movable mass, the third electrode being covered by the metal.

11. The MEMS device of claim 10, wherein the first electrode, second electrode, and third electrode are formed of silicon, and the metal is tungsten.

12. A microelectromechanical systems (MEMS) device, comprising:

a movable mass having a first electrode formed of a semiconductor material with a top, bottom, and side surface each having a conductive coating disposed thereon; and

a second electrode spaced apart from and facing the side surface of the first electrode, the second electrode having the conductive coating disposed thereon.

13. The MEMS device of claim 12, wherein the second electrode is on or part of a substrate above which the movable mass is suspended.

14. The MEMS device of claim 13, wherein the first electrode is formed of silicon and the conductive coating comprises a metal.

15. The MEMS device of claim 14, wherein the metal is tungsten.

16. The MEMS device of claim 12, further comprising a third electrode spaced from and facing the bottom surface of the movable mass, the third electrode having a conductive coating disposed thereon.

17. The MEMS device of claim 16, wherein the first electrode, second electrode, and third electrode are formed of silicon, and the conductive coating comprises a metal.

18. The MEMS device of claim 17, wherein the metal is tungsten.

19. The MEMS device of claim 12, wherein the top, bottom, and side surface of the first electrode all are encapsulated by the conductive coating.

20. The MEMS device of claim 19, wherein the conductive coating comprises tungsten.