Piezoelectric thin film resonator
A piezoelectric thin film includes a piezoelectric element and a substrate supporting the piezoelectric element. The piezoelectric element includes a piezoelectric thin film and first and second electrodes opposing each other with the piezoelectric thin film interposed therebetween. The piezoelectric thin film has a first-electrode-side content of each of aluminum and scandium higher than a second-electrode-side content thereof and a first-electrode-side content of nitrogen lower than a second-electrode-side content thereof.
1 . A piezoelectric thin film resonator comprising:
a piezoelectric thin film including aluminum nitride as a primary component and scandium;
a first electrode;
a second electrode opposing the first electrode with the piezoelectric thin film interposed therebetween; and
a substrate supporting a piezoelectric element including the first electrode, the second electrode, and the piezoelectric thin film; wherein
the piezoelectric thin film has a first-electrode-side content of each of scandium and aluminum higher than a second-electrode-side content of each of scandium and aluminum and a first-electrode-side content of nitrogen lower than a second-electrode-side content of nitrogen.
2 . The piezoelectric thin film resonator according to claim 1 , wherein a scandium content in an entirety of the piezoelectric thin film is about 5 atm % or more.
3 . The piezoelectric thin film resonator according to claim 1 , wherein scandium, aluminum, and nitrogen in the piezoelectric thin film having a concentration gradient in a thickness direction of the piezoelectric thin film.
4 . The piezoelectric thin film resonator according to claim 2 , wherein scandium, aluminum, and nitrogen in the piezoelectric thin film having a concentration gradient in a thickness direction of the piezoelectric thin film.
5 . The piezoelectric thin film resonator according to claim 1 , wherein
an absolute value of a difference between the content in the first-electrode-side end portion of the piezoelectric thin film and the content in the second-electrode-side end portion is:
about 1.3 atm % or more and about 5.0 atm % or less with respect to scandium;
about 8.8 atm % or more and about 11.3 atm % or less with respect to aluminum; and
about 10.0 atm % or more and about 15.0 atm % or less with respect to nitrogen.
6 . The piezoelectric thin film resonator according to claim 2 , wherein
an absolute value of a difference between the content in the first-electrode-side end portion of the piezoelectric thin film and the content in the second-electrode-side end portion is:
about 1.3 atm % or more and about 5.0 atm % or less with respect to scandium;
about 8.8 atm % or more and about 11.3 atm % or less with respect to aluminum; and
about 10.0 atm % or more and about 15.0 atm % or less with respect to nitrogen.
7 . The piezoelectric thin film resonator according to claim 3 , wherein
an absolute value of a difference between the content in the first-electrode-side end portion of the piezoelectric thin film and the content in the second-electrode-side end portion is:
about 1.3 atm % or more and about 5.0 atm % or less with respect to scandium;
about 8.8 atm % or more and about 11.3 atm % or less with respect to aluminum; and
about 10.0 atm % or more and about 15.0 atm % or less with respect to nitrogen.
8 . The piezoelectric thin film resonator according to claim 1 , further comprising:
an acoustic reflection layer between the piezoelectric element and the substrate; wherein
the acoustic reflection layer includes a plurality of layers that are stacked; and
the plurality of layers have respective acoustic impedances different from each other.
9 . The piezoelectric thin film resonator according to claim 2 , further comprising:
an acoustic reflection layer between the piezoelectric element and the substrate; wherein
the acoustic reflection layer includes a plurality of layers that are stacked; and
the plurality of layers have respective acoustic impedances different from each other.
10 . The piezoelectric thin film resonator according to claim 3 , further comprising:
an acoustic reflection layer between the piezoelectric element and the substrate; wherein
the acoustic reflection layer includes a plurality of layers that are stacked; and
the plurality of layers have respective acoustic impedances different from each other.
11 . The piezoelectric thin film resonator according to claim 5 , further comprising:
an acoustic reflection layer between the piezoelectric element and the substrate; wherein
the acoustic reflection layer includes a plurality of layers that are stacked; and
the plurality of layers have respective acoustic impedances different from each other.
12 . The piezoelectric thin film resonator according to claim 1 , wherein a cavity is included between the piezoelectric element and the substrate.
13 . The piezoelectric thin film resonator according to claim 2 , wherein a cavity is included between the piezoelectric element and the substrate.
14 . The piezoelectric thin film resonator according to claim 3 , wherein a cavity is included between the piezoelectric element and the substrate.
15 . The piezoelectric thin film resonator according to claim 5 , wherein a cavity is included between the piezoelectric element and the substrate.