Piezoelectric cantilever pressure sensor array

• US 7,032,454 B2
• Filed: 03/05/2004
• Issued: 04/25/2006
• Est. Priority Date: 03/05/2004
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Amano, Jun
• Primary Examiner(s): Noori, Max
• Assistant Examiner(s): JENKINS, JERMAINE L
• Application Number:
  US10/792,891
• Publication Number:
  US 20050193823A1
• Time in Patent Office: 781 Days
• Field of Search: 73700-756
• US Class Current: 73/704
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A piezoelectric cantilever pressure sensor array is disclosed. The piezoelectric cantilever pressure sensor array contains a substrate, a readout circuit, and piezoelectric cantilever pressure sensors electrically connected to the readout circuit. Each piezoelectric cantilever pressure sensor contains an elongate piezoelectric cantilever mounted at one end on the substrate and extending over a cavity. The piezoelectric cantilever contains a piezoelectric layer sandwiched between two electrodes and generates a measurable voltage when deformed under pressure. The piezoelectric cantilever pressure sensor array can be manufactured at low cost and used in various applications including fingerprint identification devices.

Claims

1. A piezoelectric cantilever pressure sensor array, comprising:

a substrate;

a readout circuit, and

piezoelectric cantilever pressure sensors electrically connected to the readout circuit, each piezoelectric cantilever pressure sensor comprising an elongate piezoelectric cantilever mounted at one end on the substrate and extending over a cavity, the piezoelectric cantilever comprising;

a first electrode;

a second electrode; and

a piezoelectric element between the first electrode and the second electrode and electrically connected thereto.

2. The piezoelectric cantilever sensor array of claim 1, wherein each piezoelectric cantilever pressure sensor additionally comprises an access transistor.

3. The piezoelectric cantilever sensor array of claim 2, wherein:

the access transistor comprises a source contact, a gate contact and a drain contact;

the drain contact is connected to the first electrode;

the source contact is connected to receive a reference voltage; and

the gate contact is connected to receive an activation signal.

4. The piezoelectric cantilever sensor array of claim 1, wherein the wherein the piezoelectric cantilever additionally comprises an elastic element between the piezoelectric layer and the substrate.

5. The piezoelectric cantilever sensor array of claim 4, wherein:

the elastic element comprises one of silicon and silicon nitride; and

the piezoelectric element comprises one of PZT, PMN-PZT, PZN-PZT, AlN and ZnO.

6. The piezoelectric cantilever sensor array of claim 5, wherein the piezoelectric element comprises PZT with a zirconate to titanate molar ration of about 0.4 to about 0.6.

7. The piezoelectric cantilever sensor array of claim 4, wherein:

the substrate has a top surface on which the piezoelectric cantilever pressure sensors are located; and

the cavity is located between the elastic element and the top surface of the substrate.

8. The piezoelectric cantilever sensor array of claim 4, wherein the elastic element is shaped to define a pedestal.

9. The piezoelectric cantilever sensor array of claim 1, wherein:

the piezoelectric element is a first piezoelectric element; and

the piezoelectric cantilever additionally comprises;

a third electrode; and

a second piezoelectric element between the second and the third electrodes and electrically connected thereto.

10. The piezoelectric cantilever sensor array of claim 1, wherein the substrate comprises glass.

11. The piezoelectric cantilever sensor array of claim 1, additionally comprising a protective layer covering the piezoelectric cantilever pressure sensors.

12. The piezoelectric cantilever sensor array of claim 1, wherein:

the substrate has a top surface and a bottom surface opposite thereto; and

the cavity extends through the substrate between the top surface and the bottom surface.

13. The piezoelectric cantilever sensor array of claim 1, wherein:

the substrate has a top surface on which the piezoelectric cantilever is located; and

the cavity extends into the substrate from the top surface.

14. The piezoelectric cantilever sensor array of claim 1, wherein:

the substrate has a top surface on which the piezoelectric cantilever is located; and

the cavity is located between the piezoelectric cantilever and the top surface of the substrate.

15. The piezoelectric cantilever pressure sensor of claim 14, wherein:

the piezoelectric cantilever additionally comprises an elastic element between the

piezoelectric element and the substrate; and

the cavity is located between the elastic element and the top surface of the substrate.

16. The piezoelectric cantilever sensor array of claim 1, wherein at least one of the first electrode and the second electrode comprises a metal selected from gold, silver, platinum, palladium, copper, aluminum, and alloys thereof.

17. The piezoelectric cantilever sensor array of claim 1, wherein at least one of the first electrode and the second electrode comprises a layer of platinum and a layer of titanium or titanium oxide.

18. The piezoelectric cantilever sensor array of claim 1, wherein at least one of the first electrode and the second electrode comprises a layer of platinum and a layer of titanium or titanium oxide.

19. A piezoelectric cantilever pressure sensor array comprising:

a substrate;

a readout circuit,

piezoelectric cantilever pressure sensors electrically connected to the readout circuit, each piezoelectric cantilever pressure sensor comprising an access transistor and an elongate piezoelectric cantilever mounted at one end on the substrate and extending over a cavity,

wherein the piezoelectric cantilever comprising a first electrode, a second electrode, and a piezoelectric element between the first electrode and the second electrode and electrically connected thereto, and wherein the access transistor comprises a source contact, a gate contact and a drain contact;

the drain contact is connected to the first electrode;

the source contact is connected to receive a reference voltage; and

the gate contact is connected to receive an activation signal;

first conductive lines each extending between the readout circuit and the second electrodes of ones of the piezoelectric cantilever pressure sensors arrayed in a first direction; and

,

second lines each extending between the readout circuit and the gates of the access transistors electrically connected to ones of the piezoelectric cantilever pressure sensors arrayed in a second direction, orthogonal to the first direction.

20. The piezoelectric cantilever sensor array of claim 19, additionally comprising reference lines electrically connected to the sources of the access transistors electrically connected to the piezoelectric cantilever pressure sensors.