Piezoelectric film, method of manufacturing same, piezoelectric film laminated body, and method of manufacturing same

Patent metadata

Field	Value
Publication number	US-2020357976-A1
Application number	US-202016937966-A
Country	US
Kind code	A1
Filing date	Jul 24, 2020
Priority date	Feb 21, 2018
Publication date	Nov 12, 2020
Grant date	—

Abstract

Provided is a piezoelectric film including an AlN crystal, and a first element and a second element doped to the AlN crystal. The first element is an element having an ionic radius larger than an ionic radius of Al. The second element is an element having an ionic radius smaller than the ionic radius of Al. Also provided are piezoelectric film laminated body including an underlayer and a piezoelectric film including ScAlN, and a method of manufacturing the same. The underlayer has a crystal lattice having six-fold symmetry or three-fold symmetry. Also provided are a piezoelectric film including ScAlN having a laminated structure of a hexagonal crystal and a cubic crystal, and a method of manufacturing the same. The cubic crystal is doped with an element other than trivalent element.

First claim

What is claimed is:

1 . A piezoelectric film comprising:
an AlN crystal; a first element doped to the AlN crystal, and having an ionic radius in tetracoordination larger than an ionic radius of Al in tetracoordination; and a second element doped to the AlN crystal, and having an ionic radius in tetracoordination smaller than the ionic radius of Al in tetracoordination, wherein a ratio of the number of atoms of the first element to 100 at % of a total amount of the number of atoms of the first element and the number of atoms of Al exceeds 43 at %.

2 . The piezoelectric film according to claim 1 ,
wherein the first element is at least one selected from rare earth elements.

3 . The piezoelectric film according to claim 1 ,
wherein the first element is Sc.

4 . The piezoelectric film according to claim 1 ,
wherein the second element is a trivalent element.

5 . The piezoelectric film according to claim 1 ,
wherein the second element is B.

6 . The piezoelectric film according to claim 1 ,
wherein the second element includes a divalent element and a tetravalent element, and the number of atoms of the divalent element and the number of atoms of the tetravalent element are substantially equivalent.

7 . The piezoelectric film according to claim 1 , further comprising a third element doped to the AlN crystal, having an ionic radius in tetracoordination equal to or larger than the ionic radius of Al in tetracoordination, being a univalent element, and including an element different from the first element,
wherein the second element is a pentavalent element, and the number of atoms of the pentavalent element and the number of atoms of the univalent element are substantially equivalent.

8 . The piezoelectric film according to claim 1 , further comprising a fourth element doped to the AlN crystal, having an ionic radius in tetracoordination equal to or larger than the ionic radius of Al in tetracoordination, being a tetravalent element, and including an element different from the first element,
wherein the second element is a divalent element, and the number of atoms of the divalent element and the number of atoms of the tetravalent element are substantially equivalent.

9 . The piezoelectric film according to claim 1 , further comprising a fifth element doped to the AlN crystal, having an ionic radius in tetracoordination equal to or larger than the ionic radius of Al in tetracoordination, being a divalent element, and including an element different from the first element,
wherein the second element is a tetravalent element, and the number of atoms of the tetravalent element and the number of atoms of the divalent element are substantially equivalent.

10 . A piezoelectric film laminated body comprising:
an underlayer; and a piezoelectric film including ScAlN and formed on a surface of the underlayer, wherein the underlayer has a six-fold symmetric crystal lattice when a crystal structure of the underlayer is observed from a direction in parallel with a c-axis of a crystal of the ScAlN, and includes an underlayer material having an a-axis length in the six-fold symmetric crystal lattice longer than an a-axis length of the ScAlN.

11 . The piezoelectric film laminated body according to claim 10 ,
wherein the underlayer material has a c-axis oriented hexagonal crystal lattice.

12 . The piezoelectric film laminated body according to claim 10 ,
wherein the underlayer material includes ZnO doped with a divalent element having an ionic radius in tetracoordination larger an ionic radius of Zn in tetracoordination, GaN doped with a trivalent element having an ionic radius in tetracoordination larger than an ionic radius of Ga in tetracoordination, InN doped with a trivalent element having an ionic radius in tetracoordination larger than an ionic radius of In in tetracoordination, InN, or Ti.

13 . The piezoelectric film laminated body according to claim 10 ,
wherein the underlayer material includes ZnO doped with at least one element selected from the group consisting of Ca, Sr, and Ba, or GaN doped with at least one element selected from the group consisting of Sc, Y, and La.

14 . The piezoelectric film laminated body according to claim 10 ,
wherein the underlayer material includes ZnO doped with an element other than a divalent element and having an ionic radius in tetracoordination larger than an ionic radius of Zn in tetracoordination, GaN doped with an element other than a trivalent element and having an ionic radius in tetracoordination larger than an ionic radius of Ga in tetracoordination, or InN doped with an element other than a trivalent element and having an ionic radius in tetracoordination larger than an ionic radius of In in tetracoordination.

15 . A piezoelectric film laminated body comprising:
an underlayer; and a piezoelectric film including ScAlN and formed on a surface of the underlayer, wherein the underlayer has a three-fold symmetric crystal lattice when a crystal structure of the underlayer is observed from a direction in parallel with a c-axis of a crystal of the ScAlN, and includes an underlayer material having a nearest neighbor interatomic distance in a lattice plane in parallel with the surface of the underlayer longer than an a-axis length of the ScAlN.

16 . The piezoelectric film laminated body according to claim 15 ,
wherein the underlayer material has a (111)-oriented cubic crystal lattice.

17 . The piezoelectric film laminated body according to claim 15 ,
wherein the underlayer material includes a diamond structural material, a sphalerite structural material, Ta, or Cr.

18 . The piezoelectric film laminated body according to claim 15 ,
wherein, in the ScAlN of the piezoelectric film, a ratio of the number of atoms of Sc to 100 at % of a total amount of the number of atoms of Sc and the number of atoms of Al exceeds 43 at %.

19 . A method of manufacturing a piezoelectric film laminated body having an underlayer, and a piezoelectric film including ScAlN and formed on a surface of the underlayer, the method comprising:
preparing the underlayer including an underlayer material having a six-fold symmetric crystal lattice when a crystal structure of the underlayer is observed from a thickness direction of the underlayer, and having an a-axis length in the six-fold symmetric crystal lattice longer than an a-axis length of the ScAlN; and epitaxially growing the piezoelectric film including the ScAlN on the underlayer.

20 . The method of manufacturing the piezoelectric film laminated body according to claim 19 ,
wherein the underlayer material has a c-axis oriented hexagonal crystal lattice.

21 . The method of manufacturing the piezoelectric film laminated body according to claim 19 ,
wherein the underlayer material includes ZnO doped with a divalent element having an ionic radius in tetracoordination larger than an ionic radius of Zn in tetracoordination, GaN doped with a trivalent element having an ionic radius in tetracoordination larger than an ionic radius of Ga in tetracoordination, InN doped with a tivalent element having an ionic radius in tetracoordination larger than an ionic radius of In in tetracoordination, InN, or Ti.

22 . The method of manufacturing the piezoelectric film laminated body according to claim 19 ,
wherein the underlayer material includes ZnO doped with at least one element selected from the group consisting of Ca, Sr, and Ba, or GaN doped with at least one e

Assignees

• Denso Corp

Inventors

• Teshigahara Akihiko
• Kano Kazuhiko
• Sakai Kenichi

Classifications

• H10N30/079

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

• H10N30/30

  with mechanical input and electrical output, e.g. functioning as generators or sensors · CPC title

• H10N30/20

  with electrical input and mechanical output, e.g. functioning as actuators or vibrators · CPC title

• H10N30/853 Primary

  Ceramic compositions · CPC title

• H10N30/50

  having a stacked or multilayer structure · CPC title