ELECTROSTATIC ACTUATOR DEVICE AND METHOD OF MAKING THE DEVICE

• US 20080048520A1
• Filed: 08/28/2006
• Published: 02/28/2008
• Est. Priority Date: 08/28/2006
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Gulvin, Peter M., Nystrom, Peter J.
• Granted Patent: US 8,450,902 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

The present application is directed to novel electrostatic actuators and methods of making the electrostatic actuators. In one embodiment, the electrostatic actuator comprises a substrate, an electrode formed on the substrate and a deflectable member positioned in proximity to the electrode so as to provide a gap between the electrode and the deflectable member. The deflectable member is anchored on the substrate via one or more anchors. The gap comprises at least one first region having a first gap height positioned near the one or more anchors and at least one second region having a second gap height positioned farther from the anchors than the first region. The first gap height is smaller than the second gap height.

Claims

1. An electrostatic actuator comprising:

a substrate;

an electrode formed on the substrate, and

a deflectable member positioned in proximity to the electrode so as to provide a gap between the electrode and the deflectable member, the deflectable member being anchored on the substrate via one or more anchors;

wherein the gap comprises at least one first region having a first gap height positioned near the one or more anchors and at least one second region having a second gap height positioned farther from the anchors than the first region, the first gap height being smaller than the second gap height.

2. The electrostatic actuator of claim 1, wherein the size of the gap in the first region ranges from about 0.1 um to about 3.0 um, and the size of the gap in the second region ranges from about 0.125 to about 4.0 um.

3. The electrostatic actuator of claim 1, wherein the dimensions of the gap are chosen so as to maintain a gap which is not reduced below a desired distance when deflectable member 40 is deflected.

4. The electrostatic actuator of claim 1, wherein the gap comprises a fluid dielectric material chosen from at least one of air, nitrogen gas, and SF₆.

5. The electrostatic actuator of claim 4, wherein the gap comprises a vacuum.

6. The electrostatic actuator of claim 5, wherein at least one insulator chosen from silicon oxide and silicon nitride is positioned within the gap.

7. The electrostatic actuator of claim 1, wherein the deflectable member is in the form of a membrane.

8. The electrostatic actuator of claim 1, wherein the deflectable member is in the form of a cantilever.

9. The electrostatic actuator of claim 1, wherein the deflectable member comprises at least one conductor chosen from polysilicon and metals.

10. The electrostatic actuator of claim 1, wherein that the size of the gap varies continuously over the majority of the gap, the gap varying in size between the first gap height and the second gap height.

11. The electrostatic actuator of claim 1, wherein the gap comprises a third region having a third gap height which is different from both the first gap height and the second gap height.

12. A method for forming an electrostatic actuator, the method comprising:

providing a substrate;

forming an electrode on the substrate;

forming a sacrificial layer on the electrode;

depositing a deflectable member on the sacrificial layer so that the deflectable member is anchored on the substrate via one or more anchors; and

removing at least a portion of the sacrificial layer to form a gap between the electrode and the deflectable member, wherein the gap comprises a first region positioned near the anchors and a second region positioned farther from the anchors than the first region, the gap in the first region being smaller than the gap in the second region.

13. The method of claim 12, wherein forming the sacrificial layer comprises:

forming a first sacrificial layer portion over the electrode;

patterning the first sacrificial layer portion to remove it from over part of the electrode; and

forming a second sacrificial layer portion over the remaining first sacrificial layer portion and over the part of the electrode from which the first sacrificial layer portion was removed.

14. The method of claim 13, further comprising forming one or more additional sacrificial layer portions over the electrode so as to create a sacrificial layer having three or more thickness regions.

15. The method of claim 12, wherein forming the sacrificial layer comprises:

depositing a sacrificial layer;

forming a photoresist of continuously varying thickness on the sacrificial layer; and

etching back the photoresist and a portion of the sacrificial layer.

16. The method of claim 12, further comprising:

forming an insulating layer on the substrate prior to forming the electrodes, the insulating layer being formed to have at least one lower region and at least one upper region;

depositing the electrode so that portions of the electrode are positioned on both the upper and lower regions; and

planarizing the sacrificial layer after it is deposited on the electrode.

17. The method of claim 16, wherein the planarizing is carried out using a chemical mechanical polishing process.

18. The method of claim 16, wherein the thickness of the insulating layer varies continuously from the at least one lower region to the at least one upper region to form a concave surface.

19. The method of claim 12, wherein forming the sacrificial layer comprises:

determining a desired gap distance between the electrode and the deflectable member for achieving a desired electric field when the deflectable member is fully deflected;

determining a non-deflected shape of the deflectable member that is capable of achieving the desired gap distance when the deflectable member is fully deflected; and

forming the sacrificial oxide to have a shape that results in the deflectable member being deposited to have the non-deflected shape.

20. A method for determining the shape of a gap between an electrode and a deflectable member of an electrostatic actuator, the method comprising:

determining a desired gap distance between the electrode and the deflectable member for achieving a desired electric field when the deflectable member is fully deflected; and

determining a non-deflected shape of the deflectable member that is capable of achieving the desired gap distance when the deflectable member is fully deflected.