Piezoelectric micromachined transducer and device

Patent metadata

Field	Value
Publication number	US-12161507-B2
Application number	US-202318387043-A
Country	US
Kind code	B2
Filing date	Nov 5, 2023
Priority date	Dec 13, 2019
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

An ultrasonic transducer device comprises a piezoelectric micromachined ultrasonic transducer (PMUT), a transmitter with first and second differential outputs, and a controller. The PMUT includes a membrane layer. A bottom electrode layer, comprising a first bottom electrode and a second bottom electrode, is disposed above the membrane layer. The piezoelectric layer is disposed above the bottom electrode layer. The top electrode layer is disposed above the piezoelectric layer and comprises a segmented center electrode disposed above a center of the membrane layer and a segmented outer electrode spaced apart from the segmented center electrode. The controller, responsive to the PMUT being placed in a transmit mode, is configured to couple the first and second segments of the bottom electrode layer with ground, couple the first output of the transmitter with the segments of the segmented center electrode, and couple the second output with the segments of the segmented outer electrode.

First claim

What is claimed is:

1. A method of manufacturing a piezoelectric micromachined transducer, the method comprising:
depositing a bottom electrode layer above a membrane layer;
depositing a piezoelectric layer disposed above the bottom electrode layer;
depositing a top electrode layer above the piezoelectric layer, the top electrode layer comprising a center electrode disposed above a center of the membrane layer and an outer electrode spaced apart from the center electrode and disposed away from the center of the membrane layer in a ring around the center electrode; and
etching through the top electrode layer, the piezoelectric layer, and the bottom electrode layer to create:
a first bottom electrode and a second bottom electrode from the bottom electrode layer, wherein the first bottom electrode and the second bottom electrode are substantially equal in surface area;
a first piezoelectric portion and a second piezoelectric portion from the piezoelectric layer, the first piezoelectric portion disposed above the first bottom electrode and the second piezoelectric portion disposed above the second bottom electrode;
a first outer electrode segment and a second outer electrode segment from the outer electrode, wherein the first outer electrode segment is disposed above the first bottom electrode and the second outer electrode segment is disposed above the second bottom electrode; and
a first center electrode segment and a second center electrode segment from the center electrode, wherein the first center electrode segment is disposed above the first bottom electrode and the second center electrode segment is disposed above the second bottom electrode.

2. The method as recited in claim 1 , wherein the depositing the top electrode layer above the piezoelectric layer comprises:
depositing the outer electrode and the center electrode such that they are substantially equal in surface area.

3. The method as recited in claim 1 , wherein the etching through the top electrode layer, the piezoelectric layer, and the bottom electrode layer to create the first center electrode segment and the second center electrode segment from the center electrode comprises:
creating the first center electrode segment and the second center electrode segment to be substantially equal in surface area to the first outer electrode segment and the second outer electrode segment.

4. The method as recited in claim 1 , wherein the etching through the top electrode layer, the piezoelectric layer, and the bottom electrode layer to create the first piezoelectric portion and the second piezoelectric portion from the piezoelectric layer, the first piezoelectric portion disposed above the first bottom electrode and the second piezoelectric portion disposed above the second bottom electrode comprises:
creating the first piezoelectric portion and the second piezoelectric portion to be substantially equal in surface area.

5. The method as recited in claim 1 , wherein the depositing the top electrode layer above the piezoelectric layer, the top electrode layer comprising the center electrode disposed above the center of the membrane layer and the outer electrode spaced apart from the center electrode and disposed away from the center of the membrane layer in the ring around the center electrode further comprises:
depositing the center electrode such that it is disposed above a portion of the piezoelectric layer in which a Laplacian of an out-of-plane displacement in the piezoelectric layer has a positive sign in a given displaced shape; and
depositing the outer electrode such that it is disposed above a second portion of the piezoelectric layer in which the Laplacian of the out-of-plane displacement in the piezoelectric layer has a negative sign in the same given displaced shape.

6. The method as recited in claim 1 , wherein the depositing the top electrode layer above the piezoelectric layer, the top electrode layer comprising the center electrode disposed above the center of the membrane layer and the outer electrode spaced apart from the center electrode and disposed away from the center of the membrane layer in the ring around the center electrode further comprises:
depositing the center electrode such that it is disposed above a portion of the piezoelectric layer in which a sum of the normal components of an in-plane strain in the piezoelectric layer has a positive sign in a given displaced shape; and
depositing the outer electrode such that it is disposed above a second portion of the piezoelectric layer in which the sum of the normal components of the in-plane strain in the piezoelectric layer has a negative sign in the same given displaced shape.

7. A method of manufacturing a piezoelectric micromachined transducer, the method comprising:
depositing a bottom electrode layer such that it is disposed above and coupled with a membrane layer, wherein the bottom electrode layer comprises a first bottom electrode and a second bottom electrode, and wherein the first bottom electrode and the second bottom electrode are substantially equal in surface area;
depositing a piezoelectric layer such that it is disposed above and coupled with the bottom electrode layer, wherein the piezoelectric layer comprises a first piezoelectric portion disposed above the first bottom electrode and a second piezoelectric portion disposed above the second bottom electrode, and wherein the first piezoelectric portion and the second piezoelectric portion are substantially equal in surface area; and
depositing a top electrode layer such that it is disposed above and coupled with the piezoelectric layer, wherein:
the top electrode layer comprises a segmented center electrode disposed above a center of the membrane layer and a segmented outer electrode which is spaced apart from the segmented center electrode;
the segmented outer electrode is disposed away from the center of the membrane layer in a ring around the segmented center electrode;
a first segment of the segmented outer electrode and a first segment of the segmented center electrode are disposed above the first bottom electrode;
a second segment of the segmented outer electrode and a second segment of the segmented center electrode are disposed above the second bottom electrode; and
individual segments of the segmented center electrode and individual segments of the segmented outer electrode are all substantially equal in surface area.

8. The method as recited in claim 7 , wherein the depositing the top electrode layer such that it is disposed above and coupled with the piezoelectric layer further comprises:
depositing the segmented center electrode such that it is disposed above a portion of the piezoelectric layer in which a Laplacian of an out-of-plane displacement in the piezoelectric layer has a positive sign in a given displaced shape; and
depositing the segmented outer electrode such that it is disposed above a second portion of the piezoelectric layer in which the Laplacian of the out-of-plane displacement in the piezoelectric layer has a negative sign in the same given displaced shape.

9. The method as recited in claim 7 , wherein the depositing the top electrode layer such that it is disposed above and coupled with the piezoelectric layer further comprises:
depositing the segmented center electrode such that it is disposed above a portion of the piezoelectric layer in which a sum of the normal components of an in-plane strain in the piezoelectric layer has a positive sign in a given displaced shape; and
depositing the segmented outer electrode such that it is disposed above a second portion of the piezoelectric layer in which the sum of the normal components of the in-plane strain in the piezoelectric layer has a ne

Assignees

• Invensense Inc

Inventors

• Goericke Fabian T
• Przybyla Richard J
• Eovino Benjamin E

Classifications

• H10N30/87

  Electrodes or interconnections, e.g. leads or terminals · CPC title

• B06B1/0688

  with foil-type piezoelectric elements, e.g. PVDF · CPC title

• G01N29/2437

  Piezoelectric probes · CPC title

• G01S7/521

  Constructional features · CPC title

• B06B1/0696

  with a plurality of electrodes on both sides · CPC title