MEMS Engineer Forum 2014

Eiji Fujii

Piezoelectric Thin Films

and their Applications

Advanced Technology Research Laboratories

Panasonic Corporation

1

April 25, 2014

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

2

1. Introduction

80 90 00 03 04 06 08 14

Panasonic R&D on Pb-based Ferroelectric Films

’04 Actuators for IJ heads (400 nozzle)

’03 Angular rate sensors

for a car navigation system

’83 c-axis oriented PbTiO3 films

’85 c-axis oriented PLT films

’87 c-axis oriented PZT films

’79 Start of study for ferroelectric films

’96 Piezoelectric (001)PZT films Materials

Devices & Applications

<001>

Pb-based Perovskite

● Ferroelectricity

● Nonlinear optical

property

● Pyroelectricity

● Piezoelectricity

● Dielectricity

with self-polarization

on MgO substrate

’06 Angular rate sensors

for image stabilization of DSC

’08 Actuators for IJ heads (800 nozzle)

PLT / MgO

PZT / Si

3

’97 Micro infrared sensors and ear thermometer

’93 Pyroelectric sensors applied to air conditioner

’01 Piezoelectric (001)PZT films on Si substrate

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

4

500.7

Target

Ar O2

RF power source

Substrate holder Temperature controller

RF magnetron sputtering

500.0

Vacuum pump

Preparation of PZT and PMN-PZT Films 5

Sputtering conditions

●Target: Pb(ZrxTi1-x)O3 + 0.2PbO

［x=0.5～0.6］

around morphotropic phase boundary (MPB)

●Substrate: Si(100)

●Temperature: 500 ~ 650 ˚C

●RF Power: ~2 W/cm2

●Gas Pressure: 0.2 ~ 0.5 Pa

●Deposition Rate: 10 ~ 100 nm/min

●Bottom electrode: (111)Pt, (111)Ir

Preparation of PZT Films

●Film Thickness : 3 μm

6

10 20 30 40 50 60 70

XRD pattern SEM image (cross section)

3m Si Substrate

Bottom electrode

PZT

Properties of PZT Films on Si

20 10 30 40 50 60 70

2Theta (degree)

Inte

ns

ity (

arb

. u

nit

)

Piezoelectric constant -d31=150 (pm/V) -e31=13.9 (C/m2)

Relative dielectric constant (εr ) 700

Dielectric loss factor (tanδ) 0.02

Pyroelectric coefficient (γ) 1.3 x 10-8 (C/cm2K)

PZ

T (

001)

PZ

T (

002)

Si

(400)

E. Fujii et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54, 2431 (2007)

Measured at 1kHz

Zr/Ti = 53/47

7

Piezoelectric constant -d31=225 (pm/V) -e31=20.8 (C/m2)

Relative dielectric constant (εr ) 1,400

Dielectric loss factor (tanδ) 0.03

Pyroelectric coefficient (γ) 1.9 x 10-8 (C/cm2K)

XRD pattern SEM images

15 20 25 30 35 40 45 50

２θ (deg.)

Inte

nsi

ty(a

rb.

unit

)

(001)

(002)

15 20 30 25 50 40 35 45

PM

N-P

ZT

(001)

Inte

ns

ity (

arb

. u

nit

)

2Theta (degree)

(002)

surface cross section

S. Fujii et al., Jpn. J. Appl. Phys. 48, 015502 (2009)

Properties of PMN-PZT Films on Si

Measured at 1kHz

0.125PMN–0.875PZT

Bottom electrode

8

Performance of PZT and PMN-PZT Films

"Recent Progress in Materials Issues for Piezoelectric MEMS“

Paul Muralt, J. Am. Ceram. Soc. 91, 1385 (2008)

PMN-PZT; 20.8 C/m2

PZT; 13.9 C/m2

9

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

10

Angular rate (w)

X Y

Z

Vibration

Driving Mode Sensing Mode

X Y

Z Coriolis Force

(Fc=2mVw)

Principle of Angular Rate Sensor 11

Conventional sensor PZT/Si tuning fork vibrator

Structure of Si Tuning Fork Vibrator

◆Piezoelectric materials (bulk PZT);

arranged for three dimensions

◆Piezoelectric materials and Electrodes;

arranged on identification plane

Structure: Complicated

Downsizing: Difficult

Structure: Simple

Downsizing: Easy

Electrode / PZT film

Si tuning fork

X

Z

Y

For sense

For drive

Electrode / PZT film

≤5 mm

12

Angular rate

25 mm

Electrode / PZT

For sense

Electrode / PZT

For drive

thin film forming patterning tuning fork forming

Si tuning fork forming process

casing

sensor assembly process

packaging

IC

tuning fork

Manufacturing the Angular Rate Sensor 13

● tuning fork prepared by Si deep etching

Si

150m

90±0.1°

Angular Rate Sensor for Car Navigation System

樹脂ベース

リッド

セラミックパッケージ

Resin

Control IC

Lid

Terminal Ceramic Package

Metal cap

Plate spring

vibration isolator

14

Vibrator

(Si tuning fork)

Angular Rate Sensor for DSC

Ceramic cap

Ceramic

package

Circuit

components

image stabilizing system

Control IC

Si tuning fork vibrator

for angular rate sensor

15

［1994～］

Panasonic Angular Rate Sensors

Metal tuning fork

Piezoelectric Bulk

Car Navigation

Volume Ratio

100

［1999～］

Quartz tuning fork

Car Navigation

18

［2003～］

PZT/Si tuning fork

Car Navigation

8

［2006～］

DSC

0.2

［2011～］

Smartphone

Gaming hard ware

PZT/Si motion sensor

16

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

17

Cross sectional illustration

Pressure chamber

Nozzle Water-repellent film

Ink canal

Actuator

Droplet

Accurate and stable drop control

Electrode films

PZT film

Vibration film

400 nozzles

42 m

m

42 m

m

Structure of Inkjet Head

15 mm

18

Manufacturing the Inkjet Head

《actuator element process》

Pressure chamber elements bonding

PZT film patterning

electrodes patterning

substrate etching

Estimation for displacement and resonance frequency

《 head assemble process》

《 ink chamber element 》

《 nozzle element 》

Water-repellent film

Nozzle forming

Estimation for ink discharge

properties

《film forming process》

Vibration film (common electrode)

Electrode film

PZT film

Substrate

19

Multi-Volume: 1.5 / 3.0 / 13 (pl)

Accurate and stable drop control

State of the Ejected Ink Droplets 20

29 heads (474 mm)

600 dpi pitch

( ’04～)

400 nozzles each

(’04～)

Single head

●High resolution

●High speed

60 m/min

( ’04～)

Line head

device

Sending direction

of the printed matter

Structure of Line Lead Device

1200 dpi pitch

( ’08～)

800 nozzles each

( ’08～)

150 m/min

( ’08～)

21

● Industrial-scale printed matter (Bills, DMs, Education texts)

Single head Line head device

22

・High printing speed

・Large printing width

On-demand printer

800

nozzles

29 heads

On-demand Printer and Line Head Device

◆High resolution

◆High speed

◆Large width

State of Printing by On-demand Printer

Miyakoshi (2004) Impika (2010)

600 dpi, 60 m/min 1,200 dpi, 152 m/min

23

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

24

Future Applications

PZT/Si Film

AVC

Navigation

Game

DSC CAR Phone

Printer

Control Ink Jet Head Display

Power Source for Sensors

Mirror Device

Robot

MicroTAS

Hearing Aid

Energy Harvesting

Combine Sensor

Pump

Speaker

Health Care Energy Lead-Free Device

RoHS Directive

Motion Sennsor

Angular Rate Sensor

25

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

26

Lead-Free Piezoelectric Material

PZT

Lead-free piezoelectric material

Enviroment pollution, RoHS / ELV directives

27

Material -d31(pm/V) Temp. properties Material stability

PZT（Ref.） 170

(Ceramic, PZT-5A)

Stable until

TC=365℃ Stable in air

BaTiO3

80

(Ceramic)

Stable until

TC=120℃ Stable in air

(K,Na)NbO3 150

(Ceramic, LF4)

Unstable around R.T.

Deliquescence of K

(Na,Bi)TiO3-BaTiO3

(NBT-BT)

40

(Ceramic)

Stable until

Td=150℃ Stable in air

◆(Na,Bi)TiO3-BaTiO3 (NBT-BT) was selected as a R&D target

due to good material stability and stable temperature property

T. Takenaka et al., Jpn. J. Appl. Phys. 30 (1991) 2236.

◆MPB* is formed between

Rhomb. NBT and Tetra. BT ◆Piezoelectric constant is strongly

dependent on crystal orientation

・d33= 125 pm/V (Ceramic)

H. Yilmaz et al., J. Electroceram. 11, 217 (2003).

・d33= 520 pm/V (<001> Ceramic)

d33; 520 pC/N

0

100

200

300

400

0 5 10 15 20 25 30

BT (mol%)

Tem

peratu

re (

deg.)

NBT

400

300

200

100

0 0 5 10 15 20 25 30

BT (mol%) NBT

Te

mp

era

ture

(℃

)

Rhomb.

Tetra.

P

AF

F

F

MPB:x=6-7%

<Phase diagram of (1-x)NBT-xBT>

*Morphotropic phase boundary

Characteristics of NBT-BT Ceramics 28

We fabricated NBT-BT films around MPB composition,

and investigated into crystal structure, piezoelectric properties.

Sputtering conditions

●Target: (1-x)(Na,Bi)TiO3 + xBaTiO3

［x=0.00～0.15］

●Substrate: MgO(100), (110), (111)

●Temperature: 600 ~ 700 ˚C

●RF Power: 1.5 ~ 2.0 W/cm2

●Gas Pressure: 0.6 ~ 0.8 Pa

●Deposition Rate: 5 ~ 10 nm/min

●Bottom electrode: Pt

Preparation of NBT-BT Films

●Film Thickness : 3 μm

29

Epitaxial Growth of NBT-BT Films on MgO 30

(001) Orientation (111) orientation

500 nm

(b)

MgO(111)500 nm

(b)

MgO(111)500 nm

MgO(100)

PtNBT–BT

(a)

500 nm

MgO(100)

PtNBT–BT

(a)

500 nm

(c)

MgO(110)500 nm

(c)

MgO(110)

(110) orientation

Properties of NBT-BT Films on MgO

NBT-BT thin films are promising lead-free replacement

for PZT-based applications.

0

50

100

150

200

250

-d

31

(p

m/V

)

(001) (110) (111)

Crystal orientation of NBT- BT thin film

(001)PZT/Si

(001)PMN-PZT/Si

31

Y. Tanaka, et al., J. Am. Ceram. Soc., 95, 3547 (2012)

Epitaxial Growth of NBT-BT Film on Si 32

TEM images

10 30 50

Lo

g I

nte

ns

ity (

a.u

.)

2θ (deg.)

(00

2)

(00

1)

YS

Z (

20

0) CeO

2 (20

0)

-d31 97 (pm/V)

εr 493

tanδ 0.06

1. Introduction

2. Lead-based piezoelectric films

3. Piezoelectric applications of PZT films

3-1. Angular rate sensor

3-2. Inkjet head

3-3. Future applications

5. Summary

Table of Contents

4. Lead-free piezoelectric films

33

1. (001)-PZT films were deposited on Si by RF magnetron sputtering

-d31 = 150pm/V(PZT), 225pm/V(PMN-PZT)

Summary

2. PZT films on Si were applied to

a. Angular rate sensors for car navigation systems and DSC

b. Actuators for inkjet printer heads

3. Lead-free NBT-BT epitaxial films were fabricated on MgO and Si

MgO: -d31 = 195pm/V(001), 221pm/V(110), 162pm/V(111)

Si: -d31 = 97pm/V(001)

PZT and PMN-PZT films on Si are suitable for sensors and actuators

in micro-electro-mechanical systems (MEMS)

34

Thank you very much

for your attention.

35