Manufacturing method of piezoelectric film element, piezoelectric film element and piezoelectric device

1. A manufacturing method of a piezoelectric film element, comprising:

forming a piezoelectric film comprising a lead-free alkali niobate based compound having a perovskite structure represented by a compositional formula of (K 1-x Na x )NbO 3 on a substrate;

forming a mask made of Cr, Ta, W, or Ti or a mask made of a laminated Cr, Ta, W or Ti body on the piezoelectric film; and

dry-etching the piezoelectric film formed with the mask thereon by using a low-pressure plasma in an atmosphere including a fluorine-based reactive gas,

wherein the forming of the piezoelectric film includes forming a lower electrode made of a metal including Pt on the substrate and forming the piezoelectric film on the lower electrode,

wherein the dry-etching of the piezoelectric film includes etching the piezoelectric film in conditions for the etch selectivity between the piezoelectric film and the lower electrode to be not less than 20,

wherein the conditions for the etch selectivity to be not less than 20 are that the pressure inside a chamber for the dry-etching is not lower than 0.5 Pa and not higher than 2.5 Pa, the bias power is not lower than 50 W and not higher than 100 W, and the antenna power is not lower than 600 W and not higher than 1000 W.

2. The manufacturing method according to claim 1 , wherein the dry-etching of the piezoelectric film comprises using a mixed gas of at least one fluorine system reactive gas selected from the group consisting of CHF 3 , C 2 F 6 , CF 4 , SF 6 , C 4 F 8 and C 3 F 7 I, and Ar, or a mixed gas of ones of the fluorine system reactive gas.

3. The manufacturing method according to claim 1 , wherein the dry-etching is conducted in a chamber at an internal pressure of not more than 2.5 Pa.