PIEZOELECTRIC THIN FILM ELEMENT, METHOD FOR MANUFACTURING THE SAME, AND ELECTRONIC DEVICE INCLUDING PIEZOELECTRIC THIN FILM ELEMENT

1 . A method for manufacturing an alkali-niobate-based piezoelectric thin film element, comprising:

a lower-electrode-film forming step of forming a lower electrode film on a substrate;

a piezoelectric-thin-film forming step of forming a piezoelectric thin film on the lower electrode film, the piezoelectric thin film comprising an alkali-niobate-based piezoelectric material represented by the formula (Na x K y Li z )NbO 3 , where 0≦x≦1, 0≦y≦1, 0≦z≦0.2, and x+y+z=1;

an etching-mask-pattern forming step of forming a desired pattern of an etching mask on the piezoelectric thin film; and

a piezoelectric-thin-film etching step of dry-etching the piezoelectric thin film into a desired pattern,

wherein the etching mask comprises an oxide at least in a layer adjacent to the piezoelectric thin film.

2 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the oxide is silicon oxide.

3 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the etching mask has a multilayer structure including the layer comprising the oxide and a layer comprising an oxide different from the oxide.

4 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 3 , wherein the different oxide is aluminum oxide.

5 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the etching mask has a multilayer structure including the layer comprising the oxide and a layer comprising a metal.

6 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 5 , wherein the metal is chromium.

7 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the dry etching is reactive ion etching.

8 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the lower electrode film comprises platinum.

9 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the piezoelectric thin film has a pseudocubic crystal structure, is formed by sputtering, and has a main surface preferentially oriented in a (001) plane.

10 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein the substrate is a silicon substrate having a thermally oxidized film thereon.

11 . The method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , further comprising:

an upper-electrode-film forming step of forming an upper electrode film on the desired pattern of the piezoelectric thin film; and

a dicing step of dicing the substrate having thereon the piezoelectric thin film and the upper electrode film into a piezoelectric thin film element chip.

12 . An alkali-niobate-based piezoelectric thin film element manufactured by the method for manufacturing an alkali-niobate-based piezoelectric thin film element according to claim 1 , wherein

the dielectric loss tangent of the alkali-niobate-based piezoelectric thin film after the piezoelectric-thin-film etching step is 1.2 times or less the dielectric loss tangent of the alkali-niobate-based piezoelectric thin film before the piezoelectric-thin-film etching step, and

the leakage current density of the alkali-niobate-based piezoelectric thin film after the piezoelectric-thin-film etching step is 10 times or less the leakage current density of the alkali-niobate-based piezoelectric thin film before the piezoelectric-thin-film etching step.

13 . An electronic device comprising the alkali-niobate-based piezoelectric thin film element according to claim 12 .