Piezoelectric element and method for manufacturing piezoelectric element

Abstract

Provided are a piezoelectric element having high stability, which operates with high efficiency, and a method for manufacturing the piezoelectric element. The piezoelectric element ( 10 ) has a laminate structure in which a first electrode ( 14 ), a first piezoelectric film ( 16 ), a second electrode ( 18 ), an adhesion layer ( 20 ), an interlayer ( 22 ), a third electrode ( 24 ), a second piezoelectric film ( 26 ), and a fourth electrode ( 28 ) are laminated in this order on a silicon substrate ( 12 ). The interlayer ( 22 ) is formed of a material different from that of the second electrode ( 18 ) and has a thickness of 0.4 μm to 10 μm. A device having a diaphragm structure or a cantilever structure is formed by removing a part of the silicon substrate ( 12 ). The respective layers ( 14 to 28 ) laminated on the silicon substrate ( 12 ) can be formed using a thin film formation method represented by a vapor phase epitaxial method.

What is claimed is: 
     
         1 . A piezoelectric element comprising:
 a silicon substrate;   a first electrode that is laminated on the silicon substrate;   a first piezoelectric film that is laminated on the first electrode;   a second electrode that is laminated on the first piezoelectric film;   an adhesion layer that is laminated on the second electrode;   an interlayer that is laminated on the adhesion layer, is formed of a material different from that of the second electrode, and has a thickness of 0.4 μm to 10 μm;   a third electrode that is laminated on the interlayer;   a second piezoelectric film that is laminated on the third electrode; and   a fourth electrode that is laminated on the second piezoelectric film.   
     
     
         2 . The piezoelectric element according to  claim 1 ,
 wherein in a bending mode of being bent in a film thickness direction, the interlayer is used as a vibration plate and operates using displacements of the first piezoelectric film and the second piezoelectric film in a piezoelectric constant d31 direction.   
     
     
         3 . The piezoelectric element according to  claim 2 ,
 wherein a stress neutral surface during the bending is present in the interlayer.   
     
     
         4 . The piezoelectric element according to  claim 1 ,
 wherein a material of the adhesion layer is a transition metal element.   
     
     
         5 . The piezoelectric element according to  claim 1 ,
 wherein a material of the adhesion layer is a transition metal element oxide.   
     
     
         6 . The piezoelectric element according to  claim 1 ,
 wherein a material of the adhesion layer is a combination of a transition metal element and a transition metal element oxide.   
     
     
         7 . The piezoelectric element according to  claim 1 ,
 wherein a material of the interlayer contains silicon.   
     
     
         8 . The piezoelectric element according to  claim 1 ,
 wherein each of the first piezoelectric film and the second piezoelectric film has a thickness of 0.3 μm to 10 μm.   
     
     
         9 . The piezoelectric element according to  claim 1 ,
 wherein the first piezoelectric film and the second piezoelectric film have the same crystal orientation.   
     
     
         10 . The piezoelectric element according to  claim 9 ,
 wherein the first piezoelectric film and the second piezoelectric film have a (100) orientation.   
     
     
         11 . The piezoelectric element according to  claim 9 ,
 wherein the first piezoelectric film and the second piezoelectric film have a (001) orientation.   
     
     
         12 . The piezoelectric element according to  claim 1 ,
 wherein a polarization direction of the first piezoelectric film and a polarization direction of the second piezoelectric film are the same.   
     
     
         13 . The piezoelectric element according to  claim 1 ,
 wherein each of a residual stress of the first piezoelectric film and a residual stress of the second piezoelectric film is 200 MPa or lower in terms of an absolute value.   
     
     
         14 . The piezoelectric element according to  claim 1 ,
 wherein a thermal expansion coefficient of the interlayer is two times or less thermal expansion coefficients of the first piezoelectric film and the second piezoelectric film.   
     
     
         15 . The piezoelectric element according to  claim 1 ,
 wherein a thickness of the second piezoelectric film is 0.5 times to 2 times a thickness of the first piezoelectric film.   
     
     
         16 . The piezoelectric element according to  claim 1 ,
 wherein each of the first electrode, the first piezoelectric film, the second electrode, the interlayer, the adhesion layer, the third electrode, the second piezoelectric film, and the fourth electrode is formed using a thin film formation method.   
     
     
         17 . The piezoelectric element according to  claim 16 ,
 wherein the thin film formation method is a vapor phase epitaxial method.   
     
     
         18 . A method for manufacturing a piezoelectric element, the method comprising:
 a first electrode formation step of forming a first electrode on a silicon substrate;   a first piezoelectric film formation step of forming a first piezoelectric film on the first electrode;   a second electrode formation step of forming a second electrode on the first piezoelectric film;   an adhesion layer formation step of forming an adhesion layer on the second electrode;   an interlayer formation step of forming an interlayer on the adhesion layer the interlayer being formed of a material different from that of the second electrode and having a thickness of 0.4 μm to 10 μm;   a third electrode formation step of forming a third electrode on the interlayer;   a second piezoelectric film formation step of forming a second piezoelectric film on the third electrode;   a fourth electrode formation step of forming a fourth electrode on the second piezoelectric film; and   a removal step of removing a part of the silicon substrate by etching,   wherein each of the first electrode, the first piezoelectric film, the second electrode, the interlayer, the adhesion layer, the third electrode, the second piezoelectric film, and the fourth electrode is formed using a thin film formation method.