High sensitivity pressure actuated switch based on MEMS-fabricated silicon diaphragm and having electrically adjustable switch point

• US 7,360,429 B1
• Filed: 01/31/2007
• Issued: 04/22/2008
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: Brooks Automation Incorporated (Azenta, Inc.)
• Inventors: Filippelli, Albert R.
• Primary Examiner(s): Allen; Andre J.
• Application Number:
  US11/700,303
• Time in Patent Office: 447 Days
• Field of Search: 737/15, 737/24, 737/18, 200/83
• US Class Current: 73/715
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01H 35/34 actuated by diaphragm

Abstract

A pressure actuated switch for a pressure control region includes a diaphragm with a first electrically conductive surface and a second conductive surface electrically isolated from the first conductive surface. The switch also includes an evacuated cavity disposed between the first conductive surface and the second conductive surface and includes a piezoelectric assembly on which is mounted the second conductive surface. A controller applies a control signal to the piezoelectric assembly. The piezoelectric assembly in response to the control signal translates the second conductive surface to set a trip point of the switch. The diaphragm is exposed to the pressure of the pressure control region. In response to the pressure applied to the first conductive surface, the first conductive surface deflects in a direction toward the second conductive surface. The first conductive surface communicates with the second conductive surface to produce a signal when the applied pressure is sufficiently large.

Claims

1. A pressure actuated switch for a pressure region that can be operable over a range of pressures comprising:

a diaphragm including a first electrically conductive surface;

a second conductive surface electrically isolated from the first conductive surface and having an evacuated cavity disposed between the first conductive surface and the second conductive surface;

a piezoelectric assembly mechanically coupled to the second conductive surface;

a controller applying a control signal to the piezoelectric assembly, the piezoelectric assembly in response to the control signal shifting a location of second conductive surface to set a trip point of the switch; and

the diaphragm being exposed to the region and in response to pressure causing the first conductive surface to deflect in a direction toward the second conductive surface, the first conductive surface communicating with the second conductive surface to produce a signal.

2. The pressure actuated switch of claim 1, wherein the diaphragm is doped with a second material to make the diaphragm electrically conductive.

3. The pressure actuated switch of claim 1, wherein the diaphragm comprises a single crystal silicon diaphragm.

4. The pressure actuated switch of claim 1, wherein the diaphragm comprises an elastic material.

5. The pressure actuated switch of claim 1, wherein the diaphragm is a micro-electro-mechanical system fabricated as a boron doped single crystal silicon diaphragm.

6. The pressure actuated switch of claim 1, wherein the evacuated cavity disposed between the first conductive surface and the second conductive surface includes a gap distance of about three micrometers.

7. The pressure actuated switch of claim 1, wherein the diaphragm and backing plate are micro-electro-mechanical system components.

8. The pressure actuated switch of claim 1, further comprising an electrode, the electrode being connected to the second conductive surface.

9. The pressure actuated switch of claim 1, wherein the diaphragm has a thickness of about three micrometers.

10. The pressure actuated switch of claim 1, wherein the first conductive surface contacts the second conductive surface at a predetermined pressure by deforming elastically in response to the predetermined pressure.

11. The pressure actuated switch of claim 10, wherein the predetermined pressure is in a range between about 1 Torr to about 1×

10<sup>−

7</sup> Torr.

12. The pressure actuated switch of claim 1, further comprising an amplifier configured to amplify the signal.

13. The pressure actuated switch of claim 1, further comprising a coating disposed on the diaphragm to protect the diagram.

14. The pressure actuated switch of claim 1, wherein the second conductive surface comprises a conductive film, and wherein the controller applies the control signal to the piezoelectric assembly to translate the conductive film toward the first conductive surface, the translation setting a gap therebetween and being proportional to the control signal to configure the trip point of the switch.

15. A pressure actuated switch for a process control region comprising:

a boron doped single crystal silicon diaphragm including a first electrically conductive surface, the diaphragm being exposed to an applied pressure in the process control region;

a second conductive surface electrically isolated from the first conductive surface and having an evacuated cavity disposed between the first conductive surface and the second conductive surface;

a piezoelectric assembly mechanically coupled to the second conductive surface, the piezoelectric assembly being coupled to an controller and configured to selectively adjust a trip point of the pressure actuated switch by moving the second conductive surface toward the first conductive surface; and

the controller applying a control signal to the piezoelectric assembly, the piezoelectric assembly in response to the control signal shifting the second conductive surface to set the trip point, the first conductive surface deflecting in a direction toward the second conductive surface in response to the applied pressure, the first conductive surface communicating with the second conductive surface in response to the applied pressure to produce a signal, the trip point being settable in a range that includes 100 Torr to 1×

10<sup>−

7</sup> Torr.

16. The pressure actuated switch of claim 15, wherein the diaphragm is coated on a surface in contact with gas to protect the diaphragm.

17. The pressure actuated switch of claim 15, further comprising a substrate connected to the diaphragm to define the evacuated cavity therebetween, and wherein the piezoelectric assembly increases in length when a voltage is applied to the piezoelectric assembly, the increase translating an electrode connected to the second conductive surface in the evacuated cavity.

18. The pressure actuated switch of claim 15, further comprising an amplifier configured to receive the signal.

19. The pressure actuated switch of claim 15, wherein the boron doped single crystal silicon diaphragm and second conductive surface are micro-electro-mechanical system components.

20. A pressure actuated switch for a process control comprising:

a coated conductive diaphragm;

a conductive surface electrically isolated from the coated conductive diaphragm and having an evacuated cavity disposed between the coated conductive diaphragm and the conductive surface;

a piezoelectric assembly moving the conductive surface, the piezoelectric assembly being coupled to a controller and configured to selectively adjust a trip point of the pressure actuated switch; and

the controller applying a control signal to the piezoelectric assembly, the piezoelectric assembly in response to the control signal moving the conductive surface to set the trip point, the coated conductive diaphragm deflecting in a direction toward the conductive surface in response to an applied pressure, the conductive diaphragm communicating with the conductive surface to produce a signal, the trip point being settable in a range that includes to 100 Torr to 1×

10<sup>−

7</sup> Torr.

21. A method for actuating a switch in response to an applied pressure, the method comprising:

electrically setting a trip point of the switch by apply a signal to a piezoelectric actuator, the piezoelectric actuator configured to move the second conductive surface toward the first conductive diaphragm to adjust a predetermined gap between the first conductive diaphragm and the second conductive surface;

applying a signal to the first conductive diaphragm;

applying a signal to the second conductive surface;

exposing the first conductive diaphragm to the applied pressure; and

developing a signal when the applied pressure exceeds a predetermined pressure threshold, the predetermined pressure threshold being when the first conductive diaphragm contacts the second conductive surface.