Piezoelectric element

Patent metadata

Field	Value
Publication number	US-11744155-B2
Application number	US-202217672283-A
Country	US
Kind code	B2
Filing date	Feb 15, 2022
Priority date	Sep 6, 2017
Publication date	Aug 29, 2023
Grant date	Aug 29, 2023

Abstract

A piezoelectric element 10 includes a lower electrode, constituted of a Pt/Ti laminated film, a PLT seed layer, formed on the lower electrode, a PZT piezoelectric film, formed on the PLT seed layer, and an upper electrode, formed on the PZT piezoelectric film. A curve Q1 is a curve drawn such as to pass through a plurality of plotted points, each expressing a PLT (100) peak intensity with respect to a Pt (111) peak intensity according to a substrate setting temperature during forming of the Pt/Ti laminated film. A relationship of the PLT (100) peak intensity with respect to the Pt (111) peak intensity is within a range in the curve Q1 until the PLT (100) peak intensity decreases by 5% from a peak point P, at which the PLT (100) peak intensity is the maximum, and a (100) orientation rate of PLT constituting the seed layer is not less than 85%.

First claim

What is claimed is:

1. A piezoelectric element comprising: an insulating film, formed on a substrate; a lead barrier film, formed on the insulating film; a lower electrode, formed on the lead barrier film; a seed layer, formed on the lower electrode and comprised of a sputtered film having lead lanthanum titanate (PLT) as a main component; and a piezoelectric film, formed on the seed layer and having lead zirconate titanate (PZT) or lead lanthanum zirconate titanate (PLZT) as a main component; and wherein the lower electrode is comprised of a laminated film of a Ti film at the substrate side and a Pt film laminated on the Ti film,
the piezoelectric element being such that a ( 111 ) orientation peak intensity of the Pt constituting the Pt film is 17×10000 counts to 35×10000 counts and a ( 100 ) orientation peak intensity of the PLT constituting the seed layer is not less than 70×1000 counts, and
a film thickness of the lead barrier film is thinner than a film thickness of the insulating film.

2. The piezoelectric element according to claim 1 , wherein a film thickness of the seed layer is 20 nm to 100 nm,
a film thickness of the Pt film is 50 nm to 200 mm, and
a film thickness of the Ti film is not more than 10 nm.

3. The piezoelectric element according to claim 1 , wherein the piezoelectric film is a piezoelectric film formed by a sol-gel method.

4. The piezoelectric element according to claim 1 , wherein the seed layer has, near the lower electrode side, a Pb-rich layer high in Pb concentration.

5. The piezoelectric element according to claim 1 , further comprising: an upper electrode formed on the piezoelectric film.

6. The piezoelectric element according to claim 1 , wherein the insulating film comprises SiO 2 .

7. The piezoelectric element according to claim 6 , wherein the lead barrier film comprises Al 2 O 3 .

8. The piezoelectric element according to claim 6 , wherein a film thickness of the insulating film is 300 nm to 2000 nm.

9. The piezoelectric element according to claim 7 , wherein a film thickness of the insulating film is 300 nm to 2000 nm and a film thickness of the lead barrier film is 50 nm to 100 nm.

Assignees

• Rohm Co Ltd

Inventors

• Nomura Koji
• Matsuo Nobufumi
• Date Tomohiro

Classifications

• H10N30/708 Primary

  Intermediate layers, e.g. barrier, adhesion or growth control buffer layers · CPC title

• H10N30/10516 Primary

  Electricity · mapped topic

• H10N30/079

  using intermediate layers, e.g. for growth control · CPC title

• H10N30/8554

  Lead-zirconium titanate [PZT] based · CPC title

• H10N30/871

  Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes · CPC title