Electrostatic actuator, device comprising such actuators, microsystem comprising such a device and method for making such an actuator

• US 7,679,261 B2
• Filed: 06/22/2006
• Issued: 03/16/2010
• Est. Priority Date: 06/23/2005
• Status: Expired due to Fees

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Divoux, Claire, Chappaz, Cedrick
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US11/472,377
• Publication Number:
  US 20060291129A1
• Time in Patent Office: 1,363 Days
• Field of Search: 310/309
• US Class Current: 310/309
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0062 Devices moving in two or more dimensions, i.e. having special features which allow movement in more than one dimension
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence

Abstract

An electrostatic actuator including: at least one fixed electrode, fixed with respect to a substrate; at least one flexible electrode arranged to face the substrate; a pivot member extending from the flexible electrode, the pivot member being fixed to a face of the flexible electrode facing the fixed electrode, and the pivot member being made from a conducting material; and at least one suspending unit suspending the flexible electrode and holding the flexible electrode at rest at a distance from the substrate, wherein the suspending unit and the pivot member are different.

Claims

1. An electrostatic actuator comprising:

at least one fixed electrode, fixed with respect to a substrate;

at least one flexible electrode arranged to face the substrate;

a pivot member fixed to a face of the flexible electrode facing the fixed electrode, and said pivot member being made from a conducting material; and

at least one means for suspending the flexible electrode and holding said flexible electrode at rest at a distance from the substrate,

wherein the means for suspending and the pivot member are different.

2. The electrostatic actuator according to claim 1, wherein the means for suspending includes a suspension beam fixed at one end to a support projecting from the substrate.

3. The electrostatic actuator according to claim 1 or claim 2, wherein the pivot member is pad shaped.

4. The electrostatic actuator according to claim 1 or claim 2, wherein the flexible electrode at least partly zigzags between first and second ends of the flexible electrode.

5. The electrostatic actuator according to claim 1 or claim 2, wherein another face of the flexible electrode opposite the face of the flexible electrode facing the fixed electrode is configured to support an object to be moved.

6. The electrostatic actuator according to claim 1 or claim 2, wherein at least one of the flexible electrode or the fixed electrode is coated with a layer of a dielectric material.

7. The electrostatic actuator according to claim 1 or claim 2, wherein there are two fixed electrodes and two pivot members fixed to the flexible electrode, each of the two fixed electrodes being arranged between one end of the flexible electrode and one of the pivot members.

8. An electrostatic actuation device, comprising:

a first electrostatic actuator according to claim 1; and

a second electrostatic actuator according to claim 1.

9. The electrostatic actuation device according to claim 8, wherein the flexible electrode of the first electrostatic actuator and the flexible electrode of the second electrostatic actuator are suspended by their respective means for suspending from a common support projecting from the substrate.

10. An electrostatic actuation device comprising:

at least one first electrostatic actuator according to claim 1; and

at least one second actuator including a second fixed electrode, and a second flexible electrode held at a distance from the second fixed electrode, wherein said at least one electrostatic actuator and said second actuator are uniformly distributed at an equal angular spacing.

11. The electrostatic actuation device according to claim 10, wherein plural means for suspending are distributed at an equal angular spacing between the at least one electrostatic actuator and the second actuator.

12. The electrostatic actuation device according to claim 11, wherein there are three of the first electrostatic actuators and three of the second actuators arranged alternately.

13. The electrostatic actuation device according to claim 12, wherein there are three of the means for suspending distributed at an equal angular spacing between the first electrostatic actuators and the second actuators.

14. The electrostatic actuation device according to claim 11, wherein the at least one first electrostatic actuator and the at least one second actuator are arranged on each side of an axis fixed at one end to the object to be moved, said axis forming a suspension member.

15. The electrostatic actuation device according to claim 14, wherein there are a plurality of the first electrostatic actuators and a plurality of the second actuators on each side of the axis, arranged alternately parallel to each other.

16. The electrostatic actuation device according to claim 15, wherein adjacent actuators of the first electrostatic actuators and the second actuators are carried by a legs of a U shaped member, one leg of the U shaped member being arranged on one side of the axis being connected to another leg of the U shaped member being arranged on the other side of the axis through a central leg fixed to the axis and connecting bottoms of the one leg and the another leg of the U shaped member.

17. The device according to claim 14, wherein there are two or more axes distributed at an equal angular spacing around the object to be moved.

18. The electrostatic actuator according to claim 1, wherein the at least one flexible electrode is provided with a pull-in zone so as to facilitate displacement of the at least one flexible electrode towards the substrate.

20. The microsystem according to claim 18, wherein the object to be moved is a mirror.

19. A microsystem comprising:

an actuator; and

an object to be moved by the actuator, wherein the actuator includes,

at least one fixed electrode, fixed with respect to a substrate,

at least one flexible electrode arranged to face the substrate,

a pivot member fixed to a face of the flexible electrode facing the fixed electrode, and said pivot member being made from a conducting material, and

at least one means for suspending the flexible electrode and holding said flexible electrode at rest at a distance from the substrate,

wherein the means for suspending and the pivot member are different.

21. A method for making an electrostatic actuator on a substrate, comprising:

making at least one fixed electrode on a front face of the substrate,

depositing a sacrificial layer on the substrate,

structuring said sacrificial layer to form at least one flexible electrode, at least one suspension member and at least one pivot member, the suspension member being different from the pivot member,

depositing a conducting layer forming the flexible electrode and the pivot member, and

eliminating the sacrificial layer.

22. The method according to claim 21, further comprising:

depositing an oxide layer on the front face of the substrate before the fixed electrode is formed.

23. The method according to claim 22, wherein the making the at least one fixed electrode includes depositing a metallic layer on the oxide, forming a lithography mask on the metallic layer, and etching said metallic layer.

24. The method according to claim 23, further comprising:

depositing a layer of dielectric material after the metallic layer has been etched.

25. The method according to claim 21 or 22, wherein the structuring includes applying double lithography and etching of the sacrificial layer.

26. The method according to the claim 21, wherein the structuring includes applying double lithography and etching of the sacrificial layer, and at an end of the structuring, the sacrificial layer comprises through channels reaching an insulating layer for a connection between the substrate and the flexible electrode and at least one non-through channel for formation of the pivot member.

27. The method according to the claim 22, wherein the structuring includes applying double lithography and etching of the sacrificial layer, and at an end of the structuring, the sacrificial layer comprises through channels reaching an insulating layer for a connection between the substrate and the flexible electrode and at least one non-through channel for formation of the pivot member.