PRESSURE SENSOR WITH PRESSURE-ACTUATED SWITCH

• US 20120167659A1
• Filed: 01/05/2011
• Published: 07/05/2012
• Est. Priority Date: 01/05/2011
• Status: Active Grant

• Current Assignee: ScioSense B.V. (Ams-Osram AG)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Besling, Willem Frederik Adrianus, Steeneken, Peter Gerard, Wunnicke, Olaf
• Granted Patent: US 9,016,133 B2
• Time in Patent Office: Days
• US Class Current: 73/1.57
• CPC Class Codes: G01L 9/0047 Diaphragm with non uniform thickness, e.g. with grooves, bosses or continuously varying thickness
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: H01H 35/346 in which the movable contact is formed or directly supported by the diaphragm

Abstract

Various embodiments relate to a pressure sensor and related methods of manufacturing and use. A pressure sensor may include an electrical contact included in a flexible membrane that deflects in response to a measured ambient pressure. The electrical contact may be separated from a signal path through a cavity formed using a sacrificial layer and PVD plugs. At one or more defined touch-point pressure thresholds, the membrane of the pressure sensor may deflect so that the state of contact between an electrical contact and one or more sections of a signal path may change. In some embodiments, the change of state may cause the pressure sensor to trigger an alarm in the electrical circuit. Various embodiments also enable the operation of the electrical circuit for testing and calibration through the use of one or more actuation electrode layers.

Claims

1. A pressure sensor comprising:

a substrate including a first metallic contact;

a membrane attached to the substrate, the membrane including a second metallic contact and responding to pressure by deflection;

a cavity wherein the first and second metallic contacts are located;

a contact area between the first and second metallic contacts that enables contact between the first and second contacts when the membrane deflects at a defined pressure; and

a signal path that allows a current flow when the first metallic contact makes contact with the second metallic contact.

2. The pressure sensor of claim 1, wherein one of the first or second metallic contacts further comprises an interconnect including the contact area that makes contact with the other metallic contact when the membrane is deflected through the height of the cavity.

3. The pressure sensor of claim 2, wherein:

the interconnect further comprises a second contact area, and

the signal path comprises two separate portions on one of the substrate or the membrane, wherein the interconnect makes contact with the two portions of the signal path when the membrane is deflected through the height of the cavity.

4. The pressure sensor of claim 1, wherein the first metallic contact initially does not make contact with the second metallic contact, and further wherein the first metallic contact makes contact with the second metallic contact when the pressure exceeds the defined pressure.

5. The pressure sensor of claim 1, wherein the first metallic contact initially makes contact with the second metallic contact, and further wherein the first metallic contact breaks contact with the second metallic contact when the pressure exceeds the defined pressure.

6. The pressure sensor of claim 5, further comprising:

a lever that causes the first metallic contact to break contact with the second metallic contact when the membrane deflects through the height of the cavity.

7. The pressure sensor of claim 4, further comprising:

a series of metallic contact pairs, each metallic contact pair comprising;

a membrane metallic contact, and

a substrate metallic contact, wherein each metallic contact pair makes contact when the membrane deflects at distinct pressures.

8. The pressure sensor of claim 1, further comprising:

a first actuation electrode layer on the substrate; and

a second actuation electrode layer on the membrane.

9. The pressure sensor of claim 8, further comprising:

a pressure-actuated switch that deflects the pressure-sensitive membrane in response to an applied electric potential difference between the first and second actuation electrode layers.

10. The pressure sensor of claim 8, further comprising:

a pressure indicator that measures an applied pressure based on a capacitive measurement between the first and second actuation electrode layers.

11. The pressure sensor of claim 8, further comprising:

a user-controlled system that applies an electric potential difference between the first and second actuation electrode layers until the first and second metallic contacts make contact.

12. The pressure sensor of claim 8, further comprising:

a transistor whose state is based on contact between the first and second metallic contacts.

13. The pressure sensor of claim 12, wherein the transistor is connected to an electrical circuit, and further wherein current flow in the electrical circuit is based on the state of the transistor.

14. The pressure sensor of claim 13, wherein active current flow in the electrical circuit triggers an alarm.

15. The pressure sensor of claim 8, further comprising:

a configuration system that;

applies an electric potential difference between the first and second actuation electrode layers to deflect the membrane;

detects a change in capacitance after the deflection of the membrane;

compares the detected change in capacitance to stored calibration data; and

applies a correction voltage between the first and second actuation electrode layers to deflect the membrane to a corrective position.

16. The pressure sensor of claim 1, wherein the cavity is sealed during manufacture and further wherein a cavity pressure inside the cavity is a vacuum or is less than the defined pressure.

17. The pressure sensor of claim 16, further comprising:

a metallic plug that seals the cavity, comprising at least one of Al, Ti, TiW, W, Ta, TaN, or Cu.

18. The pressure sensor of claim 1, wherein the metallic contacts comprise one of:

a noble metal from the group of Au, Ag, Pt, Pd, Ru, Os, Ir, or Rh;

an alloy of the noble metals;

or

an alloy of the noble metal with a refractory metals from the group of Al, Ti, Zr, Hf, Ta, Nb, V, W, Mo, Cr, Co, Mn, Cu, or Ni.

19. A method comprising:

providing, by a substrate, a first metallic contact;

measuring, by a pressure sensor having a membrane including a second metallic contact, a defined pressure;

deflecting, by the membrane in response to the defined pressure, through a height of a cavity to the substrate;

making, by the second metallic contact, contact with the first metallic contact when the membrane deflects at the defined pressure; and

conducting, by a signal path, a current flow when the first metallic contact makes contact with the second contact.

20. A method of producing a pressure sensor comprising:

depositing and patterning a first metallic layer on a substrate;

depositing and patterning a sacrificial layer upon the first metallic layer and substrate;

depositing and patterning a second metallic layer on the sacrificial layer;

etching a hole to the sacrificial layer;

removing the sacrificial layer; and

plugging the etched hole with a plug.

21. The method of claim 20, further comprising:

depositing a membrane layer upon the sacrificial layer and first metallic layer, wherein the second metallic layer is deposited and patterned on the membrane layer.