Microrelays and microrelay fabrication and operating methods

• US 20050121298A1
• Filed: 11/02/2004
• Published: 06/09/2005
• Est. Priority Date: 09/24/2002
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Sridhar, Uppili, Zou, Quanbo
• Granted Patent: US 7,463,125 B2
• Time in Patent Office: Days
• US Class Current: 200/181
• 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 59/0009 making use of micromechanics

Abstract

Microrelays and microrelay fabrication and operating methods providing a microrelay actuator positively controllable between a switch closed position and a switch open position. The microrelays are a five terminal device, two terminals forming the switch contacts, one terminal controlling the actuating voltage on an actuator conductive area, one terminal controlling the actuating voltage on a first fixed conductive area, and one terminal controlling the actuating voltage on a second fixed conductive area deflecting the actuator in an opposite direction than the first fixed conductive area. Providing the actuating voltages as zero average voltage square waves and their complement provides maximum actuating forces, and positive retention of the actuator in both actuator positions. Various fabrication techniques are disclosed.

Claims

1. A microrelay comprising:

a micromachined deflectable actuator having first and second actuator surfaces and first and second conductive regions electrically isolated from each other;

a first cap having a first cap surface adjacent the first actuator surface, the first cap having third, fourth and fifth conductive regions electrically isolated from each other, the third conductive region being adjacent the first conductive region, the fourth and fifth conductive regions being adjacent the second conductive region;

a second cap having a second cap surface adjacent the second surface of the actuator, the second cap having a sixth conductive region adjacent the first conductive region;

the actuator being deflectable in a first direction to allow the second conductive region to contact the fourth and fifth conductive region, and the first and third conductive regions to not electrically contact each other;

the actuator being deflectable in a second direction opposite the first direction so that the first and sixth regions move closer without electrically contacting each other;

the actuator being hermetically sealed within the microrelay, the first, third, fourth, fifth and sixth conductive regions being electrically accessible externally to the microrelay;

the second, fourth and fifth conductive regions being a single layer of metal.

2. A microrelay comprising:

a micromachined deflectable actuator having first and second actuator surfaces and first and second conductive regions electrically isolated from each other;

a first cap having a first cap surface adjacent the first actuator surface, the first cap having third, fourth and fifth conductive regions electrically isolated from each other, the third conductive region being adjacent the first conductive region, the fourth and fifth conductive regions being adjacent the second conductive region;

a second cap having a second cap surface adjacent the second surface of the actuator, the second cap having a sixth conductive region adjacent the first conductive region;

the actuator being deflectable in a first direction to allow the second conductive region to contact the fourth and fifth conductive region, and the first and third conductive regions to not electrically contact each other;

the actuator being deflectable in a second direction opposite the first direction so that the first and sixth regions move closer without electrically contacting each other;

the actuator being hermetically sealed within the microrelay, the first, third, fourth, fifth and sixth conductive regions being electrically accessible externally to the microrelay;

the second, fourth and fifth conductive regions being multiple layers of more than one metal or metal alloy.

3. The microrelay of claim 2 wherein the second, fourth and fifth conductive regions comprise a layer of high melting temperature metal on a layer of higher conductivity metal.

4. The microrelay of claim 3 wherein the high melting temperature metal is selected from the group consisting of Ruthenium, Rhodium, Tungsten, Titanium/Tungsten alloy, Titanium, Palladium and Nickel, and the layer of higher conductivity metal is selected from the group consisting of Gold, Copper, Silver and Aluminum.

5. The microrelay of claim 4 wherein the high melting temperature metal has a thickness in the range of 100A to 1 micron, and the layer of higher conductivity metal has a thickness in the range of 1 micron to 10 microns.

6. A method of providing a microrelay switch function comprising:

providing a microrelay having;

an actuator having first and second actuator surfaces and first and second conductive regions electrically isolated from each other;

a first cap having a first cap surface adjacent the first actuator surface, the first cap having third, fourth and fifth conductive regions electrically isolated from each other, the third conductive region being adjacent the first conductive region, the fourth and fifth conductive regions being adjacent the second conductive region;

a second cap having a second cap surface adjacent the second surface of the actuator, the second cap having a sixth conductive region adjacent the first conductive region;

the actuator being deflectable in a first direction to allow the second conductive region to contact the fourth and fifth conductive region, and the first and third conductive regions to not electrically contact each other;

the actuator being deflectable in a second direction opposite the first direction so that the first and sixth regions move closer without electrically contacting each other;

a) when a relay switch is to be closed, providing DC voltages on the first, third and sixth regions so that the actuator is attracted toward the first cap to put the second region in electrical contact with the fourth and fifth regions; and

,

b) when the relay switch is to be opened, providing DC voltages on the first, third and sixth regions so that the actuator is attracted toward the second cap to prevent the second region from making electrical contact with the fourth and fifth regions.

7. The method of claim 6 wherein the DC voltages provided to the third and sixth regions are of opposite polarity relative to a reference voltage.

8. The method of claim 7 wherein the reference voltage is a ground voltage.

9. The method of claim 6 wherein in a), the voltage provided to the first region is equal to the voltage provided to the sixth region, and in b), the voltage provided to the first region is equal to the voltage provided to the third region.

10. The method of claim 6 wherein in a), the voltage provided to the first region is unequal to the voltage provided to the sixth region, or in b), the voltage provided to the first region is unequal to the voltage provided to the third region.

11. The method of claim 6 wherein in a), the voltage provided to the first region is unequal to the voltage provided to the sixth region, and in b), the voltage provided to the first region is unequal to the voltage provided to the third region.

12. A method of providing a microrelay switch function comprising:

providing a microrelay having;

an actuator having first and second actuator surfaces and first and second conductive regions electrically isolated from each other;

a first cap having a first cap surface adjacent the first actuator surface, the first cap having third, fourth and fifth conductive regions electrically isolated from each other, the third conductive region being adjacent the first conductive region, the fourth and fifth conductive regions being adjacent the second conductive region;

a second cap having a second cap surface adjacent the second surface of the actuator, the second cap having a sixth conductive region adjacent the first conductive region;

the actuator being deflectable in a first direction to allow the second conductive region to contact the fourth and fifth conductive region, and the first and third conductive regions to not electrically contact each other;

the actuator being deflectable in a second direction opposite the first direction so that the first and sixth regions move closer without electrically contacting each other;

a) when a relay switch is to be closed, providing AC voltages on the first, third and sixth regions so that the actuator is attracted toward the first cap to put the second region in electrical contact with the fourth and fifth regions; and

,

b) when the relay switch is to be opened, providing AC voltages on the first, third and sixth regions so that the actuator is attracted toward the second cap to prevent the second region from making electrical contact with the fourth and fifth regions.

13. The method of claim 12 wherein the AC voltages have a zero average value about a reference voltage.

14. The method of claim 13 wherein the reference value is a ground voltage.

15. The method of claim 12 wherein the AC voltages are not all of the same amplitude.

16. The method of claim 12 wherein the AC voltages are not all of the same wave shape.

17. The method of claim 12 wherein at least one of the AC voltages is a sine wave.

18. The method of claim 12 wherein at least one of the AC voltages is a square wave filtered to attenuate the higher frequency components in the waveform.

19. The method of clam 12 wherein the AC waveforms applied to the third and sixth regions are 180°

out of phase with each other.

20. The method of claim 19 wherein the AC voltage applied to the first region in a) and b) is of a different amplitude than the AC waveforms applied to the third and sixth regions.