Piezoelectric element
View Patent ↗A piezoelectric film formed above a Si substrate. The piezoelectric film is formed of a potassium sodium niobate expressed by a general formula (K,Na)NbO 3 with perovskite structure. A film thickness of the piezoelectric film is within a range from 0.3 μm to 10 μm. An intermediate film is formed between the Si substrate and the piezoelectric film. The intermediate film generates a stress in a compressive direction in the piezoelectric film.
1. A piezoelectric element comprising:
a Si substrate;
a piezoelectric film formed above the Si substrate and comprising a potassium sodium niobate expressed by a general formula (K,Na)NbO 3 with perovskite structure with a film thickness within a range of 0.3 μm to 10 μm; and
an intermediate layer formed between the Si substrate and the piezoelectric film for generating a stress in a compressive direction in the piezoelectric film,
wherein the piezoelectric film further comprises piezoelectric material having an average grain size within a range 0.1 μm to 1.0 μm,
wherein the intermediate layer further comprises additives of 10% or less of other elements and has the perovskite structure, and
wherein the additives in the intermediate layer are in a range of greater than 0% and 10% or less of the other element; and
wherein the intermediate layer comprises at least one compound selected from the group consisting of LaAlO 3 and YAlO 3 .
2. The piezoelectric element according to claim 1 , wherein the piezoelectric film is formed above the Si substrate by RF magnetron.
3. The piezoelectric element according to claim 1 , wherein the intermediate layer is predominantly oriented in one of plane orientations (100), (110), (010), and (111).
4. The piezoelectric element according to claim 1 , wherein the piezoelectric film is predominantly oriented in one of plane orientations (100), (110), (010), and (111).
5. The piezoelectric element according to claim 1 , further comprising a thermally-oxidized film on the Si substrate.
6. The piezoelectric element according to claim 1 , further comprising a metallic layer comprising Pt or Pt and Ti between the intermediate layer and the Si substrate.
7. The piezoelectric element according to claim 6 , wherein the Pt in the metallic layer is predominantly oriented in a plane orientation (111).
8. The piezoelectric element according to claim 1 , wherein the piezoelectric film further comprises additives 10 at. % or less in total of at least one of Li and Ta.
9. The piezoelectric element according to claim 1 , wherein a value of Na/(K+Na) in the (K,Na)NbO 3 of the piezoelectric film is in a range from 0.4 to 0.75.
10. The piezoelectric element according to claim 1 , wherein the intermediate layer comprises:
a first partial intermediate film; and
a second partial intermediate film adjacent to the piezoelectric film, and
wherein the second partial intermediate film comprises a compound having a pseudo-cubic or cubic crystal with perovskite structure and a lattice constant of 0.391 nm or less.
11. The piezoelectric element according to claim 1 , wherein the intermediate layer is oriented in plane orientation (100).
12. The piezoelectric element according to claim 1 , wherein a thickness of said intermediate layer is 0.2 μm.
13. The piezoelectric element according to claim 1 , wherein said intermediate film is formed by RF magnetron on a lower electrode grown above said Si substrate, and
wherein said piezoelectric film is formed on said intermediate film.