US-12622177-B2 - Piezoelectric laminate and piezoelectric element

US12622177B2US 12622177 B2US12622177 B2US 12622177B2US-12622177-B2

Abstract

The piezoelectric laminate and the piezoelectric element have, on a substrate in the following order, a lower electrode layer and a piezoelectric film containing a perovskite-type oxide, in which the lower electrode layer includes the metal layer containing Ni and a surface layer containing a Ni oxide or a Ni oxynitride, and in the lower electrode layer, the surface layer is arranged on the side closest to the piezoelectric film.

Inventors

Tsutomu Sasaki
Fumihiko Mochizuki

Assignees

FUJIFILM CORPORATION

Dates

Publication Date: 20260505
Application Date: 20220819
Priority Date: 20210831

Claims (8)

1 . A piezoelectric laminate comprising, on a substrate in the following order: a lower electrode layer; and a piezoelectric film containing a perovskite-type oxide, wherein the lower electrode layer includes a metal layer containing Ni and a surface layer containing a Ni oxide or a Ni oxynitride, and the surface layer in the lower electrode layer is arranged a side closest to the piezoelectric film, wherein in a thickness direction of the surface layer, a content of Ni in the lower electrode layer, which includes the Ni oxide or the Ni oxynitride, gradually increases from the side closest to the piezoelectric film toward the metal layer, and a change of the content of the Ni is continuous in the thickness direction from the surface layer to the metal layer without discontinuity.
2 . The piezoelectric laminate according to claim 1 , wherein a thickness of the surface layer is 20 nm to 60 nm.
3 . The piezoelectric laminate according to claim 1 , further comprising: an alignment control layer containing a metal oxide different from the Ni oxide, between the lower electrode layer and the piezoelectric film.
4 . The piezoelectric laminate according to claim 3 , wherein the metal oxide contains at least one of Sr or Ba.
5 . The piezoelectric laminate according to claim 1 , wherein the perovskite-type oxide contains Pb, Zr, Ti, and O.
6 . The piezoelectric laminate according to claim 5 , wherein the perovskite-type oxide contains at least one of Nb, Sc, or Ni.
7 . The piezoelectric laminate according to claim 6 , wherein the perovskite-type oxide is a compound represented by General Formula (1), Pb{(Zr x Ti 1-x ) 1-y Nb y }O 3 (1) 0< x< 1,0.1≤ y≤ 0.4.
8 . A piezoelectric element comprising: the piezoelectric laminate according to claim 1 ; and an upper electrode layer provided on the piezoelectric film of the piezoelectric laminate.

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-141806 filed on Aug. 31, 2021. The above application is hereby expressly incorporated by reference, in its entirety, into the present application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present disclosure relates to a piezoelectric laminate and a piezoelectric element. 2. Description of the Related Art As a material having excellent piezoelectricity and excellent ferroelectricity, there is known a perovskite-type oxide such as lead zirconate titanate (Pb(Zr,Ti)O3, hereinafter referred to as PZT). A piezoelectric body consisting of a perovskite-type oxide is applied as a piezoelectric film in a piezoelectric element having a lower electrode, a piezoelectric film, and an upper electrode on a substrate. This piezoelectric element has been developed into various devices such as a memory, an inkjet head (an actuator), a micromirror device, an angular velocity sensor, a gyro sensor, a piezoelectric micromachined ultrasonic transducer (PMUT), and an oscillation power generation device. The piezoelectric characteristics greatly change due to the excess or deficiency of oxygen in the perovskite structure of the perovskite-type oxide. In particular, in a perovskite-type oxide containing Pb such as a PZT film, oxygen is easily eliminated, and the oxygen defect in the piezoelectric film easily causes the deterioration of piezoelectric characteristics and the deterioration of durability. In order to suppress the oxygen elimination in the perovskite-type oxide, it is effective to use a conductive oxide such as SRO (SrRuO3) or IrO2 in regions of the lower electrode and the upper electrode, where these regions are in contact with the piezoelectric film. Further, in a case where a conductive oxide is used in the region in contact with the piezoelectric film, an electrode layer consisting of a layer of a noble metal such as Pt or Ir is generally laminated on the conductive oxide layer in order to ensure good conductivity (see, for example, JP2018-085478A). JP2007-300071A proposes a piezoelectric element having a PZT film, in which a lower electrode has a configuration such that an amount of a conductive oxide is large on a side of a substrate and an amount of a conductive metal is large on a side of a piezoelectric film in order to improve the adhesiveness at each interface between the substrate and the lower electrode and between the lower electrode and the piezoelectric film. Further, it describes that a Pt group is preferable as the conductive metal contained in the lower electrode. SUMMARY OF THE INVENTION As described in JP2018-085478A, in a piezoelectric element having a piezoelectric film of perovskite-type oxide, deterioration of piezoelectric characteristics can be suppressed by providing a conductive oxide layer on the side of the piezoelectric film of the electrode layer. Further, as described in JP2018-085478A and JP2007-300071A, a noble metal which is a Pt group is generally used in the lower electrode. However, since a metal of the platinum group is very expensive, there is a problem that it is not possible to sufficiently suppress the manufacturing cost of a piezoelectric element having an electrode containing the platinum group. The present disclosed technology has been made in consideration of the above circumstances, and an object of the present disclosed technology is to provide a piezoelectric laminate and a piezoelectric element, which makes it possible to suppress the deterioration of piezoelectric characteristics and suppress the manufacturing cost. The piezoelectric laminate of the present disclosure is a piezoelectric laminate comprising, on a substrate in the following order: a lower electrode layer; anda piezoelectric film containing a perovskite-type oxide,in which the lower electrode layer includes a metal layer containing Ni and a surface layer containing a Ni oxide or a Ni oxynitride, andin the lower electrode layer, the surface layer is arranged on the side closest to the piezoelectric film. In the piezoelectric laminate of the present disclosure, it is preferable that in a thickness direction of the surface layer, a content of a Ni element changes in an increasing trend from the side closest to the piezoelectric film to the metal layer, the change in the content of the Ni element is continuous, and the change in the content of the Ni element from the surface layer to the metal layer is continuous. In the piezoelectric laminate of the present disclosure, it is preferable that the thickness of the surface layer is 20 nm to 60 nm. In the piezoelectric laminate of the present disclosure, it is preferable that an alignment control layer containing a metal oxide different from the Ni oxide is provided between the lower electrode layer and the piezoelectric film. Here, the metal oxide preferably contains at least one of Sr or Ba. In the piez