Piezoelectric materials for MEMS applications Hiroshi Funakubo Tokyo Institute of Technology

Transcription

1 Piezoelectric materials for MEMS applications Hiroshi Funakubo Tokyo Institute of Technology MEMS Engineer Forum 2016/5/11 11:50-12:15

2 Content 1. Introduction 2. Processing 3. Materials Matter

3 Content 1. Introduction 2. Processing 3. Materials Matter

4 Piezoelectric Materials Dielectric Materials Piezoelectricity Pyroelectricity Ferroelectricity Direct Piezoelectric Effect Stress-induced Electricity P. Curie & J. Curie Inverse Piezoelectric Effect Nonsymmetrical Crystal Having Ionic Displacement Electric Field-induced Displacement Spontaneous Polarization Reversibility of Spontaneous Polarization 1881 Lippman Energy Conversion Materials Between Electrical Energy and Mechanical Energy 4

5 Application of Piezoelectric Property Sensor Gyro Ink Jet Printer Head Fuel Injector Sonogram

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7 Piezoelectric Materials

8 Piezoelectric Materials Dielectric Materials Piezoelectricity Pyroelectricity Quarts ZnO, AlN, GaN, GaAs Polarization Direction Depend on Stack Direction of Charged Layer Ferroelectricity Nonsymmetrical Crystal Having Ionic Displacement Polarization Direction Spontaneous Polarization electro.htm Reversibility of Spontaneous Polarization Polarization Direction is Determined by Deposition Condition. 8

9 Piezoelectric Property 2 x QP P P E s x QP 2 s 0 r x : Strain Q : Electrostrictive Coefficient P : Polarization P s : Spontaneous Polarization 0 : Dielectric Constant in Vacuum r : Relative Dielectric Constant E : Electric Fields Piezoelectric Effect Intrinsic contribution Q 0 rps E Q 0 r E Electrostrictive Effect P s (following Devonshire [1] and Kay [2] ) E = 0 P s + P s E 180º Domain Contribution Field Induced Strain (Dx) from E=0 to E x Q 0 rps E Q 0 r E [1] A. F. Devonshire, Adv. Phys. 3, 85 (1954). [2] H. F. Kay, Rep. Prog. Phys. 43, 230 9(1955).

10 Piezoelectric Materials Dielectric Materials Piezoelectricity LiNbO 3, LiTaO 3 BaTiO 3, Pb(Zr, Ti)O 3 Pyroelectricity Ferroelectricity Nonsymmetrical Crystal Having Ionic Displacement Spontaneous Polarization Reversibility of Spontaneous Polarization 10

11 Various Sensor Applications Dielectric Materials Piezoelectricity Pyroelectricity Tunable Devices Ferroelectricity Cooling System Nonsymmetrical Crystal Having Ionic Displacement Spontaneous Polarization Pyrometer Bolometer Reversibility of Spontaneous Polarization 11

12 Spontaneous Polarization (P s ) Origin of spontaneous polarization (Ps) Displacement of Ions Along Polar-axis Direction. x = (c-a)/a = (c/a)-1 Pb x O c Ti (Zr) a The projection of the PZT tetragonal perovskite unit cell 12

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 13

14 Domain Formation by Phase Change 14

15 Piezoelectric Materials Dielectric Materials Piezoelectricity LiNbO 3, LiTaO 3, PVDF BaTiO 3, Pb(Zr, Ti)O 3 Pyroelectricity Ferroelectricity Nonsymmetrical crystal Having Ionic displacement Spontaneous polarization (Poling Treatment) Reversibility of spontaneous polarization 15

16 Bipolar and Unipolar Response +E -E Polarization Direction X Bipolar Measurement P E 5 Unipolar Measurement P 2 1 E 6 1 S Strain(%) Strain(%) S E Electric field ( kv/cm) Electric field ( kv/cm) 2 1 E 1 16

17 Piezoelectric Materials Dielectric Materials Piezoelectricity LiNbO 3, LiTaO 3 BaTiO 3, Pb(Zr, Ti)O 3 Pyroelectricity Ferroelectricity Nonsymmetrical crystal Having Ionic displacement Spontaneous polarization Reversibility of spontaneous polarization 17

18 Piezoelectric Materials Pb(Zr, Ti)O 3, Pb(Mg 1/3 Nb 2/3 )TiO 3 -PbTiO 3 BaTiO 3, (K, Na)NbO 3, BaTiO 3 -(Bi 1/2 Na 1/2 )TiO 3 Linear and Small Response with Electric Field (Voltage) Non Linear and Large Response with Electric Field (Voltage) 18

19 Content 1. Introduction 2. Processing 3. Materials Matter

20 Sputtering Method 20

21 Solution Based Process Good Compatibility for Multi Composition System to Increase Reliability. Low Density Strain Introduction by Sintering (Shrinkage).

22 Content 1. Introduction 2. Processing 3. Materials Matter

23 Pb(Zr x Ti 1-x )O 3 (PZT) There is Morphotropic Phase Boundary (MPB) at x = 0.52 at Room Temperature. Dielectric Constant and Electromechanical Coupling Factor Show the Maximum around MPB. Tetragonal MPB Rhombohedral B. Jaffe et al., J. Res. Nat. Bur. Stand. 55, 239 (1955).

24 Origin of Large Piezoelectricity at MPB in Pb(Zr, Ti)O 3 Phase Change Under Electric Filed Polarization Rotation Model B. Noheda et al., Phys. Rev. Lett. (2001) Electric Filed Bulk PZT Tetragonal Monoclinic Rhombohedral Potential Map Near MPB D. J. Kim, J. B. Appl. Noheda Phys. et 93, al., 5568 Phys. (2003). Rev. Lett. (2001)

25 Depression of Piezoelectricity in Pb(Zr, Ti)O 3 Films Phase Change Under Electric Filed Polarization Rotation Model Depression of Piezoelectric Response by Substrate Clamping Thin Films D. J. Kim, J. Appl. Phys. 93, 5568 (2003).

26 Clamping Effect in Piezoelectric Film Problem : Smaller Piezoelectricity in Films Form Field-induced-Strain (%) E Inverse Piezoelectricity Bulk Film -0.2 Pb(Zr,Ti)O Electric field (kv/cm) E Free standing E Film is In-plane Clamped by Substrate d film 33, d33 d31 V. Nagarajan et al, Appl. Phys. Lett., 81, 4215 (2002).

27 Clamping Effect of Single Crystalline Pb(Zr, Ti)O 3 Films d 33(expect.) = 150pm/V d 33(obs.) = 75pm/V PZT d Zr/(Zr+Ti) ratio 33,( obs.) d33,(expect.) 2 d 31 s E 11 E s13 s d 31 : Real in plain in-plane d 31 d 33 : Real out-of-plane d 33 s ije : elastic compliance under constant E E 12 d 33 (obs.) PZT Substrate d 33 (expect.) < For Single Crystal Nagarajan, et al., Appl. Phys. Lett. 81, 4215 (2002).

28 Orientation Dependency Polarization-electric field (P-E) & Strain-electric field (S-E) properties MOCVD Samples Polarization (µc/cm 2 ) Field-induced strain (%) Hz Rhombo. Mixture Tetra Electric field (kv/cm) {111} {110} {100} Electric field (kv/cm) Electric field (kv/cm) {100} {110} {111} Field-induced strain (%) Rhombo. {110} {100} Mixture PT content {111}PZT films consisting of mixed phase showed larger field-induced strain than others. Piezoresponse property was enhanced for the film with mixed phase and depended on crystal orientation. J. Applied Physics 98, Tetra. {111} 5Hz

29 Pb(Zr, Ti)O 3 vs Pb(Mg 1/3 Nb 2/3 )TiO 3 -PbTiO 3 AFM cantilever Laser Doppler Field-induced strain, x 33 (%) e 31 (C/m 2 ) {100}Pb(Zr, Ti)O Rhombo. Tet. Mix. [Epi. film] Mix. [Sintered body] Ref. 1 [Sintered body] PT content, x {100} Pb(Mg 1/3 Nb 2/3 )TiO 3 - PbTiO 3 PC (Rhombo.) Tet. Mix. [Epi. film] Mix. [Single crystal] Ref. 2 [Single crystal] PT content, x MOCVD Samples Similar to Engineered domain concept 1) H. Jaffe et al., Proc. IEEE 53, 1372 (1965). 2) H. Cao et al., J. Appl. Phys. 96, 3471 (2004).

30 Green Piezoelectric Films -Lead Free- Pb based Materials

31 Strategy for Materials Survey PbTiO 3 -Based (Bi 1/2 K 1/2 )TiO 3 -Based BaTiO 3 - Based PC T T R T R Pb(Mg 1/3 Nb 2/3 )O 3 - PbTiO 3 (Bi 1/2 K 1/2 )TiO 3 -(Bi 1/2 Na 1/2 )TiO 3 -BaTiO 3 BaTiO 3 -Bi(Mg 1/2 T 1/2 )O 3 Y. Hiruma et al., Jpn. J. Appl. Phys. 45, 7409 (2006). S. Wada, J. Appl. Phys. 108, (2010). R T Pb(Zn 1/3 Nb 2/3 )O 3 -PbTiO 3 J. Zhao et al., Jpn. J. Appl. Phys. 34, 5658 (1995). J. Kuwata et al., Ferrorlrctrics 37, 579 (1981). End Member of MPB Composition is Ferroelectric Materials with Tetragonal Symmetry.

32 Tetragonal Ferroelectric Compound Conventional materials Tetragonality (c/a) 1.07 >1.2 Tetragonality (c/a) BaTiO 3 (Bi, K)TiO 3 (1940s)(1960s) PbTiO 3 (1950s) PbVO 3 (2004) *BiCoO 3 **Bi(Zn 1/2 Ti 1/2 )O 3 (2006) Research area up to now Poling Possible New area after 2000 Poling Impossible O 2- PbTiO 3 Pb 2+ Growth: Ambient Ti 4+ pressure c/a = 1.06 (Zn 2+ Ti 4+ ) O 2- Co 3+ Bi 3+ BiCoO 3 Bi(Zn 1/2 Ti 1/2 )O 3 Growth: High pressure c/a > 1.2 * A. A. Belik et al.,chem. Mater., 18, (2006) 798 ** M. Suchomel et al., Chem. Mater. 18 (2006) 4987

33 (Bi 1/2 Na 1/2 )TiO 3 -BaTiO 3 System

34 KNbO 3 -NaNbO 3 System

35 State of Art of Piezoelectric Films (Bi 1/2 Na 1/2 )TiO 3 -BaTiO 3 (K 0.5 Na 0.5 )NbO 3

36 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.