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.
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