Method for producing a piezoelectric resonator element and method for producing a piezoelectric device using the piezoelectric resonator element

Abstract

A crystal resonator element 2 has excitation electrodes 23 a, 23 b formed on front and back main surfaces of a crystal resonator plate. Each of the excitation electrodes is made of a ternary alloy containing silver as a major component, a first additive, and a second additive. The first additive is a metal element having a lower sputtering yield than silver and being resistant to corrosion in an etching liquid. The second additive is an element for forming a solid solution with silver. Outer peripheries of the excitation electrodes are first additive-rich regions 9 in which the first additive is rich.

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         4 . A method for producing a piezoelectric resonator element having a pair of excitation electrodes for driving a piezoelectric resonator plate,
 the method comprising the steps of:   forming metal films, one each, on a front surface and a back surface of the piezoelectric resonator plate, as a metal film formation step, wherein each of the metal films comprises a ternary alloy containing silver as a major component, a first additive, and a second additive, the first additive being a metal element which has a lower sputtering yield than silver and which is resistant to corrosion in an etching liquid, and a second additive being an element for forming a solid solution with silver;   forming a resist on a top surface of each of the metal films; and   etching the metal films with use of an etching liquid which is corrosive to silver, as a metal etching step, and thereby making an outer periphery of each of the excitation electrodes rich in the first additive.   
     
     
         5 . The method for producing a piezoelectric resonator element according to  claim 4 , wherein the alloy contains palladium as the first additive and copper as the second additive. 
     
     
         6 . A method for producing a piezoelectric device, comprising the steps of:
 bonding a piezoelectric resonator element obtained by the production method according to  claim 4  to an inside of a holder;   conducting fine adjustment of a frequency of the piezoelectric resonator element by irradiating the excitation electrodes by an ion beam and reducing a mass of the excitation electrodes, and   sealing the piezoelectric resonator element hermetically by bonding a lid on the holder.