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

• US 20060291129A1
• Filed: 06/22/2006
• Published: 12/28/2006
• Est. Priority Date: 06/23/2005
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Inventors: Divoux, Claire, Chappaz, Cedrick
• Granted Patent: US 7,679,261 B2
• Time in Patent Office: Days
• US Class Current: 361/207
• 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

This invention mainly relates to: an electrostatic actuator,

• • at least one fixed electrode (2) with respect to a substrate (4),
  • at least one flexible electrode (6) arranged facing the substrate,
  • at least one means forming the pivot of the flexible electrode, the said means being fixed to the flexible electrode on its face facing the fixed electrode (2) and made from a conducting material,
  • at least one means of suspension (11) of the flexible electrode, holding the said flexible electrode at rest at a distance from the substrate (4). Another purpose of this invention is a method for making such an actuator.

Claims

1. Electrostatic actuator comprising:

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

at least one flexible electrode arranged facing the substrate,

at least one means forming the pivot (30,330) of the flexible electrode, the said means being fixed to the flexible electrode on its face facing the fixed electrode and made from a conducting material,

at least one means of suspension of the flexible electrode, holding the said flexible electrode at rest at a distance from the substrate, the suspension means and the means forming the pivot being different.

2. Actuator according to claim 1, in which the suspension means is formed from a suspension beam fixed at one end to a support projecting from the substrate.

3. Actuator according to claim 1 or claim 2, in which the means forming the pivot is shaped like a pad.

4. Device according to claim 1 or claim 2, in which the flexible electrode at least partly zigzags between its first and its second ends.

5. Actuator according to claim 1 or claim 2, in which one face of the flexible electrode opposite the facing face of the fixed electrode, is designed to support an object to be moved.

6. Actuator according to claim 1 or claim 2, in which the flexible electrode and/or the fixed electrode is (are) coated with a layer of a dielectric material.

7. Actuator according to claim 1 or claim 2, comprising two fixed electrodes and two means forming a pivot, each of the fixed electrodes being arranged between one end of the flexible electrode and a means forming a pivot.

8. Electrostatic actuation device, comprising a first and a second actuators according to claim 1.

9. Electrostatic actuation device according to the previous claim, in which the flexible electrodes of the two actuators are suspended by the associated suspension means from a common support projecting from the substrate.

10. Electrostatic actuation device comprising at least one actuator of the first type according to claim 1, and at least one actuator of a second type comprising a fixed electrode and a flexible electrode held at a distance from the fixed electrode, the said actuators being uniformly distributed at an equal angular spacing.

11. Device according to the previous claim, in which the suspension means are distributed at an equal angular spacing between the actuators.

12. Device according to the previous claim, comprising three actuators of the first type and three actuators of the second type arranged alternately.

13. Device according to the previous claim, in which there are three suspension means distributed at an equal angular spacing between an actuator of the first type and an actuator of the second type.

14. Device according to claim 11, in which the actuators of the first type and the second type are arranged on each side of an axis fixed at one end to the object to be moved and forming a suspension means.

15. Device according to the previous claim, comprising a plurality of actuators of the first type and the second type on each side of the axis, arranged alternately parallel to each other.

16. Device according to the previous claim in which the adjacent actuators of the first and second types are carried by the legs of a U, one U arranged on one side of the axis being connected to another U arranged on the other side of the axis through a central leg fixed to the axis and connecting the bottoms of the U shapes.

17. Device according to claim 14, comprising at least two axes, advantageously six axes distributed at an equal angular spacing around the object to be moved.

18. Device according to claim 1, in which the flexible electrodes are provided with pull-in zones so as to facilitate displacement of the flexible electrodes towards the substrate.

19. Microsystem comprising an object to be moved and an electrostatic actuation device according to claims 8 to 18.

20. Microsystem according to the previous claim, in which the object to be moved is a mirror.

21. Method for making an electrostatic actuator on a substrate, according to any one of claims 1 to 7, comprising the following steps:

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

b) deposit a sacrificial layer,

c) structure the said sacrificial layer to form at least one flexible electrode, at least one suspension means and at least one means forming the pivot,

d) deposit a conducting layer (218) forming the flexible electrode and the means forming the pivot, and eliminate the sacrificial layer.

22. Method according to the previous claim, in which an oxide layer is deposited on the front face of the substrate, for example made of silicon oxide, before the fixed electrode is formed.

23. Method according to claim 21 or 22, in which during step a), a metallic layer is deposited on the oxide and structuring layer by lithography and etching of the said metallic layer.

24. Method according to claim 21 or 22, in which a layer of dielectric material is deposited after the metallic layer has been etched.

25. Method according to claim 21 or 22 in which step c) is done by double lithography and etching of the sacrificial layer.

26. Method according to the claim 21, in which step c) is done by double lithography and etching of the sacrificial layer and in which at the end of step c), the sacrificial layer comprises through channels reaching the insulating layer for the connection between the substrate and the flexible electrode and at least one non-through channel for formation of the means forming the pivot.

27. Method according to the claim 22, in which step c) is done by double lithography and etching of the sacrificial layer and in which at the end of step c), the sacrificial layer comprises through channels reaching the insulating layer for the connection between the substrate and the flexible electrode and at least one non-through channel for formation of the means forming the pivot.