Method of making piezoelectric cantilever pressure sensor array

• US 20050210988A1
• Filed: 03/05/2004
• Published: 09/29/2005
• Est. Priority Date: 03/05/2004
• Status: Abandoned Application

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Theil, Jeremy A., Amano, Jun, Matta, Farid, Gilbert, Stephen R.
• Application Number:
  US10/792,778
• Publication Number:
  US 20050210988A1
• Time in Patent Office: Days
• US Class Current: 73/704
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: H10N 39/00 Integrated devices, or assemblies of multiple devices, comprising at least one piezoelectric, electrostrictive or magnetostrictive element covered by groups H10N30/00 – H10N35/00

Abstract

A method for making piezoelectric cantilever pressure sensor array is disclosed. The method contains forming a layer structure comprising a substrate, an elastic layer, a first electrode layer, a piezoelectric layer, and a second electrode layer, defining piezoelectric cantilevers in the layer structure, defining Y-lines in the first electrode layer, forming X-lines; and creating a cavity under each piezoelectric cantilever. The piezoelectric cantilever pressure sensor array can be used in various applications including fingerprint identification devices.

Claims

1. A method of making a piezoelectric cantilever sensor array, the method comprising:

forming a layer structure comprising a substrate, an elastic layer, a first electrode layer, a piezoelectric layer, and a second electrode layer,

defining piezoelectric cantilevers in the layer structure;

defining Y-lines in the first electrode layer;

forming X-lines; and

creating a cavity under each piezoelectric cantilever.

2. The method of claim 1, wherein:

the substrate comprises a top surface on which the elastic layer, the first electrode layer, the piezoelectric layer, and the second electrode layer are deposited, and additionally comprises a bottom surface opposite the top surface; and

creating the cavity comprises etching through the substrate from the bottom surface to the top surface.

3. The method of claim 1, wherein:

the substrate comprises a top surface on which the elastic layer, the first electrode layer, the piezoelectric layer, and the second electrode layer are deposited;

the method additionally comprises forming releasing holes in and around the piezoelectric cantilevers; and

creating the cavity comprises etching the top surface of the substrate through the releasing holes.

4. The method of claim 1, wherein:

the layer structure additionally comprises;

a coating layer adjacent the substrate, and

a sacrificial mesa corresponding to each of the piezoelectric cantilevers;

defining the piezoelectric cantilevers comprises defining each of the piezoelectric cantilevers partially over a respective one of the sacrificial mesas; and

creating the cavity comprises removing the sacrificial mesas.

5. The method of claim 4, wherein the removing comprises etching away the sacrificial mesas.

6. The method of claim 1, wherein the forming the X-lines comprises:

forming a protective coating;

forming contact openings in the first protective coating;

depositing an X-line metal layer on the first protective coating; and

defining the X-lines in the X-line metal layer.

7. The method of claim 6, wherein defining the X-lines in the X-line metal layer additionally comprises defining in the X-metal layer X-pads electrically connected to the X-lines.

8. The method of claim 1, wherein the forming the layer structure comprises depositing the elastic layer, the first electrode layer, the piezoelectric layer, and the second electrode layer on the substrate.

9. The method of claim 8, additionally comprising mounting access transistors on the substrate prior to the depositing.

10. The method of claim 9, wherein:

the access transistors each comprise a source contact, a gate contact and a drain contact; and

the method additionally comprises interconnecting the source contacts of the access transistors.

11. The method of claim 10, wherein defining the piezoelectric cantilevers comprises:

performing a first etching process to define the piezoelectric cantilevers in the second electrode layer and the piezoelectric layer; and

performing a second etching process to define the piezoelectric cantilevers in the first electrode layer and the elastic layer.

12. The method of claim 11, wherein:

performing the second etching process defines a first electrode in the first electrode layer and additionally defines an electrical connection between the first electrode and the drain of the access transistor in the first electrode layer; and

defining Y-lines in the first electrode layer comprises performing the second etching process additionally to define the Y-lines in the first electrode layer.

13. The method of claim 8, wherein:

the piezoelectric layer is a first piezoelectric layer; and

depositing the elastic layer comprises depositing a third electrode layer and a second piezoelectric layer on the substrate.

14. The method of claim 1, additionally comprising depositing a protective layer over the piezoelectric cantilevers.

15. The method of claim 14, wherein the protective layer comprises a flexible material.

16. The method of claim 7, additionally comprising depositing a protective layer over the piezoelectric cantilever sensor array.

17. The method of claim 16, additionally comprising exposing the Y-pads and the X-pads by etching away the protective layer on top of the Y-pads and the X-pads.

18. The method of claim 10, wherein the source contacts of the access transistors are interconnected to a source pad.

19. The method of claim 18, additionally comprising depositing a protective layer over the piezoelectric cantilever sensor array.

20. The method of claim 19, additionally comprising exposing the source pad by etching away the protective layer on top of the source pad.