Piezoelectric element

Patent metadata

Field	Value
Publication number	US-11289642-B2
Application number	US-201816122392-A
Country	US
Kind code	B2
Filing date	Sep 5, 2018
Priority date	Sep 6, 2017
Publication date	Mar 29, 2022
Grant date	Mar 29, 2022

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: a lower electrode, disposed on a substrate; a seed layer, formed on the lower electrode and constituted 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 constituted of a laminated film of a Ti film at the substrate side and a Pt film laminated on the Ti film,
TiO is formed on the surface of the Pt film opposite to the Ti film,

and
the piezoelectric element being such that when a (111) orientation peak intensity of the Pt constituting the Pt film is represented as a Pt (111) peak intensity on an abscissa, a (100) orientation peak intensity of the PLT constituting the seed layer is represented as a PLT (100) peak intensity on an ordinate, and a peak characteristic curve is a curve joining points of the PLT (100) peak intensity with respect to the Pt (111) peak intensity according to substrate setting temperature during forming of the lower electrode, a relationship of the Pt (111) peak intensity and the PLT (100) peak intensity is within a range in the peak characteristic curve until the PLT (100) peak intensity decreases by 5% from a peak point, at which the PLT (100) peak intensity is the maximum, and a (100) orientation rate of the PLT constituting the seed layer is not less than 85%.

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 an insulating film, constituted of SiO 2 , is interposed between the substrate and the lower electrode.

7. The piezoelectric element according to claim 6 , wherein a lead barrier film, constituted of Al 2 O 3 , is interposed between the insulating film and the lower electrode.

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

• B41J2/1646

  thin film formation by sputtering · CPC title

• B41J2202/03

  Specific materials used · CPC title

• B41J2002/14241

  having a cover around the piezoelectric thin film element · CPC title

• B41J2002/14491

  Electrical connection · CPC title

• B41J2202/18

  Electrical connection established using vias · CPC title