Electrostatic actuator, and electrostatic microrelay and other devices using the same

• US 20030102771A1
• Filed: 11/04/2002
• Published: 06/05/2003
• Est. Priority Date: 11/06/2001
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Sano, Koji, Seki, Tomonori, Akiba, Akira, Uno, Keisuke, Jojima, Masao
• Granted Patent: US 7,161,273 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: H01H 2001/0084 with perpendicular movement of the movable contact relative to the substrate
• CPC Class Codes: H01H 2059/0018 Special provisions for avoiding charge trapping, e.g. insulation layer between actuating electrodes being permanently polarised by charge trapping so that actuating or release voltage is altered
• CPC Class Codes: H01H 2059/0072 with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A fixed voltage and a movable electrode are placed face to face with each other, and an insulating film is formed on the surface of the fixed electrode. The insulating film is made of a nitride film (SiN) as a main material, with oxide films (SiO₂) being formed on the front and rear surfaces of the nitride film. Moreover, a plurality of protrusions are formed on an area facing the movable electrode of the upper face of the insulating film. The charge quantity in the insulating film is mainly determined by a film thickness of the oxide film, and the nitride film is used for maintaining a sufficient film thickness required for the voltage proof characteristic. Thereby, it is possible to suppress variations in operational voltage characteristics such as on-voltage and off-voltage in an electrostatic actuator so as to prevent phenomena in which the electrostatic actuator fails to turn on even when a rated voltage is applied to the electrostatic actuator and in which the electrostatic actuator fails to turn off even when the driving voltage is turned off.

Claims

1. An electrostatic actuator, comprising:

a first electrode and a second electrode disposed face to face with each other; and

an insulating film formed on an opposite face of at least one of the first electrode and the second electrode at an area where the first electrode and the second electrode are made face to face with each other so that at least one of the first electrode and the second electrode is driven by an electrostatic force that is exerted when a voltage is applied between the first electrode and the second electrode to allow the first electrode and the second electrode to contact each other with the insulating film being interpolated in between, wherein

at least one of the first electrode and the second electrode has a structure for controlling charge quantity.

2. The electrostatic actuator according to claim 1, wherein

the structure for controlling charge quantity is adapted such that the quantities of positive and negative charges, exerted when a voltage is applied between the first and second electrodes, are respectively controlled so that the sum of the quantities of charge in the insulating film is desirably controlled.

3. The electrostatic actuator according to claim 2, wherein

the thickness of the insulating film is selected such that the charge quantity in the insulating film is controlled.

4. The electrostatic actuator according to claim 3, wherein

the insulating film comprises a plurality of layers, and wherein the charge quantity in the insulating film is controlled based upon the thickness of a layer that is in direct contact with at least one of the first electrode and the second electrode.

5. The electrostatic actuator according to claim 3, wherein

the insulating film comprises an oxide film and a nitride film.

6. The electrostatic actuator according to claim 5, wherein

the nitride film has a surface coated with the oxide film.

7. The electrostatic actuator according to claim 3, wherein

the insulating layer is a single material.

8. The electrostatic actuator according to claim 2, wherein

the charge quantity in the insulating film is controlled based upon a contact area of a portion which the first electrode and the second electrode are made in contact with the insulating film being interpolated in between.

9. The electrostatic actuator according to claim 8, wherein

at least one protrusion is formed on at least one of the surfaces of the first or second electrodes, wherein the contact area is controlled by the at least one protrusion.

10. The electrostatic actuator according to claim 9, wherein

the protrusion has a surface formed into a spherical shape.

11. The electrostatic actuator according to claim 1, wherein

an area which corresponds to a contact surface at a portion with and from which the first electrode and the second electrode are made in contact and separated with the insulating film being interpolated in between lacks at least one of the electrodes.

12. An electrostatic micro-relay, comprising:

a fixed contact, a movable contact, and an electrostatic actuator, wherein the fixed and movable contacts are made in contact with and separated from each other by utilizing the electrostatic actuator, wherein the electrostatic actuator comprises a first electrode and a second electrode disposed face to face with each other; and

an insulating film formed on an opposite face of at least one of the first electrode and the second electrode at an area where the first electrode and the second electrode are made face to face with each other so that at least one of the first electrode and the second electrode is driven by an electrostatic force that is exerted when a voltage is applied between the first electrode and the second electrode to allow the first electrode and the second electrode to contact each other with the insulating film being interpolated in between, wherein

at least one of the first electrode and the second electrode has a structure for controlling charge quantity.

13. A radio device, comprising:

an antenna, an inner circuit, and an electrostatic microrelay, the electrostatic microrelay comprising a fixed contact, a movable contact, and an electrostatic actuator, wherein the fixed and movable contacts are made in contact with and separated from each other by utilizing the electrostatic actuator, wherein the electrostatic actuator comprises a first electrode and a second electrode disposed face to face with each other; and

an insulating film formed on an opposite face of at least one of the first electrode and the second electrode at an area where the first electrode and the second electrode are made face to face with each other so that at least one of the first electrode and the second electrode is driven by an electrostatic force that is exerted when a voltage is applied between the first electrode and the second electrode to allow the first electrode and the second electrode to contact each other with the insulating film being interpolated in between, wherein

at least one of the first electrode and the second electrode has a structure for controlling charge quantity.

14. A measuring device, wherein

a measuring subject and an inner circuit, and an electrostatic microrelay, the electrostatic microrelay comprising a fixed contact, a movable contact and an electrostatic actuator, wherein the fixed and movable contacts are made in contact with and separated from each other by utilizing the electrostatic actuator, wherein the electrostatic actuator comprises a first electrode and a second electrode disposed face to face with each other;

and

an insulating film formed on an opposite face of at least one of the first electrode and the second electrode at an area where the first electrode and the second electrode are made face to face with each other so that at least one of the first electrode and the second electrode is driven by an electrostatic force that is exerted when a voltage is applied between the first electrode and the second electrode to allow the first electrode and the second electrode to contact each other with the insulating film being interpolated in between, wherein

at least one of the first electrode and the second electrode has a structure for controlling charge quantity.

15. A personal digital assistant, comprising:

a fixed contact, a movable contact and an electrostatic actuator, wherein the fixed and movable contracts are made in contact with and separated from each other by utilizing the electrostatic actuator, wherein the electrostatic actuator comprises a first electrode and a second electrode disposed face to face with each other; and

an insulating film formed on an opposite face of at least one of the first electrode and the second electrode at an area where the first electrode and the second electrode are made face to face with each other so that at least one of the first electrode and the second electrode is driven by an electrostatic force that is exerted when a voltage is applied between the first electrode and the second electrode to allow the first electrode and the second electrode to contact each other with the insulating film being interpolated in between, wherein

at least one of the first electrode and the second electrode has a structure for controlling charge quantity is placed so as to open and close an electric signal inside thereof.