Piezoelectric materials for MEMS applications · Piezoelectric materials for MEMS applications...

MEMS Engineer Forum2016/5/11

11：50-12：15

Piezoelectric materials for MEMS applications

Hiroshi FunakuboTokyo Institute of Technology

Content

1. Introduction2. Processing3. Materials Matter

Content

1. Introduction2. Processing3. Materials Matter

4

Piezoelectric Materials

Stress-induced Electricity

+ + + +

- - - -

1880 P. Curie & J. Curie

Electric Field-induced Displacement

1881 Lippman

Direct Piezoelectric Effect

Inverse Piezoelectric Effect

Dielectric Materials

Piezoelectricity

Ferroelectricity

Energy Conversion Materials Between Electrical Energy and Mechanical Energy

Pyroelectricity

Spontaneous Polarization

Reversibility of Spontaneous Polarization

Nonsymmetrical Crystal Having Ionic Displacement

Application of Piezoelectric PropertySensor Gyro Ink Jet Printer Head

Sonogram

Fuel Injector

+ + + +

- - - -

Piezoelectric Materials

8

Piezoelectric MaterialsDielectric Materials

Piezoelectricity

Ferroelectricity

Pyroelectricity

Spontaneous Polarization

Reversibility of Spontaneous Polarization

Nonsymmetrical Crystal Having Ionic Displacement

QuartsZnO, AlN, GaN, GaAs

Polarization DirectionDepend on Stack Direction of Charged Layer

http://phys.sci.hokudai.ac.jp/newHP/topics/ferro‐electro.htm

Pola

riza

tion

Dir

ectio

n

Polarization Direction is Determined by Deposition Condition.

9

Piezoelectric Property

（following Devonshire[1] and Kay[2] ）

[1] A. F. Devonshire, Adv. Phys. 3, 85 (1954). [2] H. F. Kay, Rep. Prog. Phys. 43, 230 (1955).

x : StrainQ : Electrostrictive CoefficientP : PolarizationPs : Spontaneous Polarization0 : Dielectric Constant in Vacuumr : Relative Dielectric ConstantE : Electric Fields

Piezoelectric Effect

Electrostrictive Effect

E = 0

Ps

Ps+Ps

E

180º Domain Contribution

Field Induced Strain （Dx） from E=0 to E222

002 EQEPQx rsr

Intrinsic contribution

22200

2

0

2

2 EQEPQQPx

EPPQPx

rsrs

rs

10

Piezoelectric MaterialsDielectric Materials

Piezoelectricity

Ferroelectricity

Pyroelectricity

Spontaneous Polarization

Reversibility of Spontaneous Polarization

Nonsymmetrical Crystal Having Ionic Displacement

LiNbO3, LiTaO3BaTiO3, Pb(Zr, Ti)O3

11

Various Sensor ApplicationsDielectric Materials

Piezoelectricity

Ferroelectricity

Pyroelectricity

Spontaneous Polarization

Reversibility of Spontaneous Polarization

Nonsymmetrical Crystal Having Ionic Displacement

Cooling System

PyrometerBolometer

Tunable Devices

12

Spontaneous Polarization (Ps)Origin of spontaneous polarization (Ps)

← Displacement of Ions Along Polar-axis Direction. x = (c-a)/a = (c/a)-1

a

Pb

O

Ti (Zr)c

x

The projection of the PZTtetragonal perovskite unit cell

13

Feature of Ferroelectric Materials• Ferroelectric materials have Critical Temperature (Tc : Curie

Temperature)by Phase Transition from Ferroelectric Phase to Paraelectric Phase

Curie – Wise Law

Low Temperature Ferroelectric Phase

High Temperature Paraelectric Phase

14

Domain Formation by Phase Change

15

Piezoelectric MaterialsDielectric Materials

Piezoelectricity

Ferroelectricity

Pyroelectricity

Spontaneous polarization

Reversibility of spontaneous polarization

Nonsymmetrical crystal Having Ionic displacement

LiNbO3, LiTaO3, PVDFBaTiO3, Pb(Zr, Ti)O3

(Poling Treatment)

16

⑤

＋E －E

① ② ③ ④ ⑥

Bipolar MeasurementBipolar Measurement

Polarization Direction

Unipolar MeasurementUnipolar Measurement

S

P

E

E

①

②

③

④

⑥

①

②

③⑥

⑤

④

⑤

S

P

E

E

①

①

②

②

Ｘ０

①②

Electric field ( kV/cm)

Stra

in(%

)

Electric field ( kV/cm)

Stra

in(%

)

Bipolar and Unipolar Response

17

Piezoelectric MaterialsDielectric Materials

Piezoelectricity

Ferroelectricity

Pyroelectricity

Spontaneous polarization

Reversibility of spontaneous polarization

Nonsymmetrical crystal Having Ionic displacement

LiNbO3, LiTaO3BaTiO3, Pb(Zr, Ti)O3

18

Linear and Small Response with Electric Field (Voltage)

Non Linear and Large Response with Electric Field (Voltage)

Piezoelectric MaterialsPb(Zr, Ti)O3, Pb(Mg1/3Nb2/3)TiO3-PbTiO3BaTiO3, (K, Na)NbO3, BaTiO3-(Bi1/2Na1/2)TiO3

Content

1. Introduction2. Processing3. Materials Matter

20

Sputtering Method

Solution Based Process• Good Compatibility for

Multi Composition System to Increase Reliability.

• Low Density Strain Introduction by Sintering (Shrinkage).

Content

1. Introduction2. Processing3. Materials Matter

Pb(ZrxTi1-x)O3 (PZT)

B. Jaffe et al., J. Res. Nat. Bur. Stand. 55, 239 (1955).

Tetragonal RhombohedralMPB

There is Morphotropic Phase Boundary (MPB) at x = 0.52 at Room Temperature.

Dielectric Constant and Electromechanical Coupling Factor Show the Maximum around MPB.

Origin of Large Piezoelectricity at MPB in Pb(Zr, Ti)O3

Polarization Rotation Model

Phase Change Under Electric Filed

111 001101

RhombohedralMonoclinic

Tetragonal

Electric Filed

B. Noheda et al., Phys. Rev. Lett. (2001)D. J. Kim , J. Appl. Phys. 93, 5568 (2003).

Bulk PZT

Potential Map Near MPB

B. Noheda et al., Phys. Rev. Lett. (2001)

Depression of Piezoelectricity in Pb(Zr, Ti)O3 Films

Polarization Rotation Model

Phase Change Under Electric Filed

Thin Films• Depression of Piezoelectric Responseby Substrate Clamping

D. J. Kim , J. Appl. Phys. 93, 5568 (2003).

111 001101

-200 -100 0 100 200

-0.2

0

0.2

0.4

0.6

0.8

Electric field (kV/cm)

Fiel

d-in

duce

d-St

rain

(%)

Pb(Zr,Ti)O3

Problem ： Smaller Piezoelectricity in Films Form

Free standing

Film is In-plane Clamped by Substrate

3133,33 ddd film

E

E

Inverse Piezoelectricity

Bulk

Film

V. Nagarajan et al, Appl. Phys. Lett., 81, 4215 (2002).

E

Clamping Effect in Piezoelectric Film

Clamping Effect of Single Crystalline Pb(Zr, Ti)O3 Films

SubstratePZT

PZT

※Nagarajan, et al., Appl. Phys. Lett. 81, 4215 (2002).

d33(obs.) = 75pm/V

d33(expect.) = 150pm/V

0 0.1 0.2 0.3 0.4 0.5Zr/(Zr+Ti) ratio

EE

E

ectobs sssddd

1211

1331.)(exp,33.)(,33 2

d33、(expect.)d33、(obs.)

d31: Real in plain in-plane d31d33: Real out-of-plane d33sij

E: elastic compliance under constant E

<For Single Crystal

0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.1

0.2

0.3

0.4

Fiel

d-in

duce

d st

rain

(%)

PT content

{100}

{110}

{111}

5Hz

Mixture Tetra.Rhombo.{100}{110}{111}

{111}PZT films consisting of mixed phase showed larger field-induced strain than others.

Piezoresponse property was enhanced for the film with mixed phase anddepended on crystal orientation.

Orientation DependencyPolarization-electric field (P-E) & Strain-electric field (S-E) properties

-100 -50 0 50 100Electric field (kV/cm)

-100 -50 0 50 100Electric field (kV/cm)

-150

-100

-50

0

50

100

150

Pola

riza

tion

(µC

/cm

2 )

-100 -50 0 50 100

-0.1

0

0.1

0.2

0.3

0.4

Electric field (kV/cm)

Fiel

d-in

duce

d st

rain

(%)

5Hz

Rhombo. Mixture Tetra.

{111}{110}

{100}

J. Applied Physics 98, 094106 2005

MOCVD Samples

Rhombo. Tet.Mix.[Epi. film]

PC(Rhombo.)

1) H. Jaffe et al., Proc. IEEE 53, 1372 (1965). 2) H. Cao et al., J. Appl. Phys. 96, 3471 (2004).

Pb(Zr, Ti)O3 vs Pb(Mg1/3Nb2/3)TiO3-PbTiO3

Tet.

Similar to “Engineered domain” concept

Ref. 2 [Single crystal]

Mix.[Single crystal]

Mix.[Sintered body]

Ref. 1 [Sintered body]

Mix.[Epi. film]

AFM cantilever

Laser Doppler0

0.05

0.1

0.15Fi

eld-

indu

ced

stra

in,

x 3

3 (%

)

0 0.2 0.4 0.6 0.8 10

5

10

15

PT content, x

|e31

| (C

/m2 )

0 0.2 0.4 0.6 0.8 1PT content, x

{100} Pb(Mg1/3Nb2/3)TiO3-PbTiO3

{100}Pb（Zr, Ti)O3

MOCVD Samples

Green Piezoelectric Films -Lead Free-

Pb‐based Materials

Strategy for Materials SurveyPbTiO3-Based

Pb(Mg1/3Nb2/3)O3 - PbTiO3

Pb(Zn1/3Nb2/3)O3-PbTiO3

TR

T

PC

BaTiO3-Based

(Bi1/2K1/2)TiO3-(Bi1/2Na1/2)TiO3-BaTiO3

T R

BaTiO3-Bi(Mg1/2T1/2)O3

TR

J. Kuwata et al., Ferrorlrctrics 37, 579 (1981). J. Zhao et al., Jpn. J. Appl. Phys. 34, 5658 (1995).

Y. Hiruma et al., Jpn. J. Appl. Phys. 45, 7409 (2006). S. Wada, J. Appl. Phys. 108, 194114 (2010).

(Bi1/2K1/2)TiO3-Based

• End Member of MPB Composition is Ferroelectric Materials with Tetragonal Symmetry.

Tetragonality(c/a)＞1.2

*BiCoO3**Bi(Zn1/2Ti1/2)O3

(2006)

PbVO3(2004)

New area after 2000

Tetragonal Ferroelectric CompoundConventional materials

1.00 1.01

BaTiO3(1940s)

1.02

(Bi, K)TiO3(1960s)

1.07

PbTiO3(1950s)

Research area up to now

* A. A. Belik et al.,Chem. Mater., 18, (2006) 798 ** M. Suchomel et al., Chem. Mater. 18 (2006) 4987

Tetragonality(c/a)

PbTiO3

Pb2+O2-

Ti4+

Pb2+O2-

Ti4+

c/a = 1.06

Growth: Ambient pressure

BiCoO3Bi(Zn1/2Ti1/2)O3

c/a > 1.2

Bi3+

O2-

Co3+(Zn2+Ti4+)Growth:High pressure

Poling ImpossiblePoling Possible

(Bi1/2Na1/2)TiO3-BaTiO3 System

KNbO3-NaNbO3 System

State of Art of Piezoelectric Films

(K0.5Na0.5)NbO3

(Bi1/2Na1/2)TiO3-BaTiO3

Remarks• Selection of Best Piezoelectric Materials

Depend on Required Properties (Application).

• Novel Materials are Under Developed for Thin Films Applications.

• Piezo MEMs Design Must Think About Origin of Piezoelectricity.

• Reliability Matters also Need to Understand Origin of Piezoelectricity.