# US 9,437,802 B2 · Multi-layered thin film piezoelectric devices and methods of making the same

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- Number: US 9,437,802 B2
- Document ID: US9437802B2
- Status: Granted
- Kind: B2
- Application number: 13/972,814
- Filed: 2013-08-21
- Published: 2015-02-26
- Granted: 2016-09-06
- Earliest claimed: 2013-08-21
- Assignees: FUJIFILM Dimatix, Inc.
- Applicants: Youming Li
- Inventors: Youming Li
- Web page: https://patentgrep.com/patent/US9437802B2

## CPC

- H10N 30/871: {Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes}
- H10N 30/05: Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes
- H10N 30/2047: {Membrane type}
- H10N 30/2048: {having non-planar shape}
- H10N 30/50: having a stacked or multilayer structure
- H10N 30/704: {based on piezoelectric or electrostrictive films or coatings}
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

Multi-layered thin film piezoelectric material stacks and devices incorporating such stacks. In embodiments, an intervening material layer is disposed between two successive piezoelectric material layers in at least a portion of the area of a substrate over which the multi-layered piezoelectric material stack is disposed. The intervening material may serve one or more function within the stack including, but not limited to, inducing an electric field across one or both of the successive piezoelectric material layers, inducing a discontinuity in the microstructure between the two successive piezoelectric materials, modulating a cumulative stress of the piezoelectric material stack, and serving as a basis for varying the strength of an electric field as a function of location over the substrate.

## Claims

### Claim 1

A thin film piezoelectric device, comprising:
a piezoelectric element including:
a lower electrode disposed over a first region of a substrate;
a first piezoelectric layer having a first polarization disposed over the lower electrode;
a second piezoelectric layer having the first polarization disposed over the first piezoelectric layer;
an intervening layer disposed between the first and second piezoelectric layers in at least a portion of the first region, wherein the intervening layer is of a different composition than that of the first and second piezoelectric layers; and
an upper electrode disposed over the second piezoelectric layer;
wherein the piezoelectric element is in fluid communication with a pumping chamber, or wherein the piezoelectric element is disposed over a sealed cavity of an ultrasonic transducer.

### Claim 2 (depends on 1)

The device of claim 1, wherein the intervening layer is an inner electrode comprising conductive material capable of sustaining a voltage different than that of either the lower or upper electrode.

### Claim 3 (depends on 1)

The device of claim 1, wherein the intervening layer includes at least one of Pt, Ir, an alloy thereof, or an oxide thereof in direct contact with both the first and second piezoelectric layers.

### Claim 4 (depends on 3)

The device of claim 3, wherein each of the first and second piezoelectric layers comprise PZT, and wherein both of the lower electrode and intervening layer further comprises a Pt or Ir containing layer disposed in direct contact with a piezoelectric layer.

### Claim 5 (depends on 1)

The device of claim 1, wherein the first and second piezoelectric layers comprise PZT of 2-8 μm in thickness.

### Claim 6 (depends on 1)

The device of claim 1, wherein the first and second piezoelectric layers comprise PZT of 2-4 μm in thickness.

### Claim 7 (depends on 1)

The device of claim 1, wherein the intervening layer is one of a plurality of intervening layers separated by an intervening piezoelectric layer.

### Claim 8 (depends on 1)

The device of claim 1, wherein the intervening layer spans a smaller area than does at least one of the upper and lower electrodes, and wherein the second piezoelectric layer is disposed directly on the first piezoelectric layer in a portion of the first region where the intervening layer is absent.

### Claim 9

A piezoelectric apparatus, comprising
a substrate;
an array of piezoelectric elements disposed over the substrate, wherein each piezoelectric element comprises:
a first electrode disposed over a first region of a substrate;
a first piezoelectric layer having a first polarization disposed over the first electrode;
a second piezoelectric layer having the first polarization disposed over the first piezoelectric layer; and
an intervening layer disposed between the first and second piezoelectric layers in at least a portion of the first region, wherein the intervening layer is of a different composition than that of the first and second piezoelectric layers; and
a second electrode disposed over the second piezoelectric layer;
wherein each piezoelectric element is in fluid communication with a pumping chamber of a respective microfluidic device, or each piezoelectric element is disposed over a sealed cavity of a respective ultrasonic transducer.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein the intervening layer spans a smaller area than does the first electrode, and wherein the second piezoelectric layer is disposed directly on the first piezoelectric layer in a portion of the first region where the intervening layer is absent.

### Claim 11 (depends on 10)

The apparatus of claim 10, wherein at least one of the first and second electrode is patterned to be disposed in an area where the intervening layer is absent.

### Claim 12

A method comprising:
operating a piezoelectric element of a thin film piezoelectric device, the piezoelectric element including:
a lower electrode disposed over a first region of a substrate;
a first piezoelectric layer having a first polarization disposed over the lower electrode;
a second piezoelectric layer having the first polarization disposed over the first piezoelectric layer;
an intervening layer disposed between the first and second piezoelectric layers in at least a portion of the first region, wherein the intervening layer is of a different composition than that of the first and second piezoelectric layers; and
an upper electrode disposed over the second piezoelectric layer;
wherein operating the piezoelectric element includes:
driving a time varying voltage across the upper electrode and the lower electrode to place an electric field across the first piezoelectric layer and the second piezoelectric layer; and
biasing the inner electrode;
wherein the piezoelectric element is in fluid communication with a pumping chamber, or wherein the piezoelectric element is disposed over a sealed cavity of an ultrasonic transducer.

### Claim 13 (depends on 12)

The device of claim 12, wherein the lower, inner, and upper electrodes are driven to place substantially equal electric fields oriented in a same direction across each of the first and second piezoelectric layers.

### Claim 14 (depends on 12)

The device of claim 12, wherein each of the upper and lower electrodes are driven with a time varying voltage source having a peak-to-peak voltage, and wherein the inner electrode is maintained at a voltage intermediate of the time varying voltage over an entire phase of the time varying voltage.