Thin film piezoelectric element and manufacturing method thereof, micro-actuator, head gimbal assembly and disk drive unit with the same

Patent metadata

Field	Value
Publication number	US-9450171-B2
Application number	US-201313853403-A
Country	US
Kind code	B2
Filing date	Mar 29, 2013
Priority date	Apr 19, 2012
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A thin film piezoelectric element of the present invention includes a substrate and a piezoelectric thin film stack formed on the substrate. The piezoelectric thin film stack includes a top electrode layer, a bottom electrode layer and a piezoelectric layer sandwiched between the top electrode layer and the bottom electrode layer, wherein the piezoelectric layer includes a first piezoelectric layer and a second piezoelectric layer whose compositions have different phase structures. The present invention can obtain high piezoelectric constants, enhanced coercive field strength and good thermal stability, thereby enabling larger applied field strength without depolarization and achieving a large stroke for its applied device.

First claim

What is claimed is:

1. A thin film piezoelectric element comprising:
a substrate; and
a piezoelectric thin film stack formed on the substrate, and the piezoelectric thin film stack comprising a top electrode layer, a bottom electrode layer and a piezoelectric layer sandwiched between the top electrode layer and the bottom electrode layer, wherein the piezoelectric layer comprises a first piezoelectric layer and a second piezoelectric layer whose compositions have different phase structures, the second piezoelectric layer is formed directly on top of the first piezoelectric layer, the top electrode layer is formed directly on top of the second piezoelectric layer, and the bottom electrode layer is formed directly below the first piezoelectric layer,
wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that (a) stroke of the thin film piezoelectric element is progressively increasable by increasing AC voltage provided to the thin film piezoelectric element up to about 50 volts, at which point depolarization occurs, and (b) in use, the thin film piezoelectric element has a depoling voltage change and a polarization change of no more than +/−10% over a temperature range of −40° C. to 125° C.

2. The thin film piezoelectric element according to claim 1 , wherein one of the first piezoelectric layer and the second piezoelectric layer has a rhombohedra phase structure, and the other has a tetragonal phase structure.

3. The thin film piezoelectric element according to claim 1 , wherein one of the first piezoelectric layer and the second piezoelectric layer has composition at a morphotropic phase boundary, and the other has a rhombohedra phase structure or a tetragonal phase structure.

4. The thin film piezoelectric element according to claim 1 , wherein the piezoelectric layer is made of Pb(Zr x Ti 1-x )O 3 .

5. The thin film piezoelectric element according to claim 4 , wherein the piezoelectric layer comprises two layers with different Ti compositions respectively.

6. The thin film piezoelectric element according to claim 5 , wherein the compositions of the piezoelectric layer comprise step differences in Ti composition which are made by two-layer or multi-layer deposition, or comprise smooth gradient in Ti composition by special deposition arrangement or post annealing treatment.

7. The thin film piezoelectric element according to claim 1 , wherein the first piezoelectric layer and the second piezoelectric layer have a thickness in the range of 0.1 μm˜1.5 μm.

8. The thin film piezoelectric element according to claim 1 , wherein the piezoelectric layer comprises KNaNbO 3 , LiNbO 3 , LiTaO 3 , BaTiO 3 , PbTiO 3 or BaSrTiO 3 .

9. The thin film piezoelectric element according to claim 1 , wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that in use, the thin film piezoelectric element has a depoling voltage change of about 0% to less than 10%, and a polarization change of −5% to 10%, over a temperature range of −40° C. to 125° C.

10. The thin film piezoelectric element according to claim 1 , wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that stroke of the thin film piezoelectric element, as measured in nm, generally linearly increases by increasing AC voltage provided to the thin film piezoelectric element, over a range of 5-50 volts.

11. The thin film piezoelectric element according to claim 1 , wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that stroke of the thin film piezoelectric element progressively increases from about 8 nm to about 60 nm, by increasing AC voltage provided to the thin film piezoelectric element, over a range of 5-50 volts.

12. The thin film piezoelectric element according to claim 11 , wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that in use, the thin film piezoelectric element has a depoling voltage change of about 0% to less than 10%, and a polarization change of −5% to 10%, over a temperature range of −40° C. to 125° C.

13. A manufacturing method of a thin film piezoelectric element, the method comprising:
providing a substrate;
depositing a bottom electrode layer on the substrate; and
depositing a piezoelectric layer comprising a first piezoelectric layer and a second piezoelectric layer on the bottom electrode layer, and a top electrode layer on the piezoelectric layer; wherein the first piezoelectric layer and the second piezoelectric layer have different phase structures, the second piezoelectric layer is formed directly on top of the first piezoelectric layer, the top electrode layer is formed directly on top of the second piezoelectric layer, and the bottom electrode layer is formed directly below the first piezoelectric layer,
wherein the piezoelectric layer comprising the first and second piezoelectric layers is formed to have a compositional constitution and physical structure that ensures that (a) stroke of the thin film piezoelectric element is progressively increasable by increasing AC voltage provided to the thin film piezoelectric element up to about 50 volts, at which point depolarization occurs, and (b) in use, the thin film piezoelectric element has a depoling voltage change and a polarization change of no more than +/−10% over a temperature range of −40° C. to 125° C.

14. The manufacturing method according to claim 13 , wherein one of the first piezoelectric layer and the second piezoelectric layer has a rhombohedra phase structure, and the other has a tetragonal phase structure.

15. The manufacturing method according to claim 13 , wherein one of the first piezoelectric layer and the second piezoelectric layer has composition at a morphotropic phase boundary, and the other has a rhombohedra phase structure or a tetragonal phase structure.

16. The manufacturing method according to claim 15 , wherein the piezoelectric layer is made of Pb(Zr x Ti 1-x )O 3 .

17. The manufacturing method according to claim 16 , wherein the piezoelectric layer comprises two layers with different Ti compositions respectively.

18. The manufacturing method according to claim 17 , wherein the compositions of the piezoelectric layer comprise step differences in Ti composition which are made by two-layer or multi-layer deposition, or comprise smooth gradient in Ti composition by special deposition arrangement or post annealing treatment.

19. A micro-actuator comprising a thin film piezoelectric element which comprises:
a substrate; and
a piezoelectric thin film stack formed on the substrate, and the piezoelectric thin film stack comprising a top electrode layer, a bottom electrode layer and a piezoelectric layer sandwiched between the top electrode layer and the bottom electrode layer, wherein the piezoelectric layer comprises a first piezoelectric layer and a second piezoelectric layer whose compositions have different phase structures, the second piezoelectric layer is formed directly on top of the first piezoelectric layer, the top electrode layer is formed directly on top of the second piezoelectric layer, and the bottom electrode layer is formed d

Assignees

• Sae Magnetics Hk Ltd

Inventors

• Xiong Wei
• Rokrakthong Panjalak
• Hata Kenjiro
• Nishiyama Kazushi
• Iitsuka Daisuke
• Iijima Atsushi

Classifications

• G11B21/16

  Supporting the heads; Supporting the sockets for plug-in heads · CPC title

• G11B5/483

  Piezoelectric devices between head and arm, e.g. for fine adjustment · CPC title

• H01L41/0805

  Electricity · mapped topic

• H01L41/316

  Electricity · mapped topic

• H01L41/297

  Electricity · mapped topic