Piezoelectric resonator, piezoelectric filter, duplexer, communication apparatus, and method for manufacturing piezoelectric resonator

Abstract

A piezoelectric thin film resonator having a stabilized temperature characteristic of resonant frequency, a method for manufacturing the same, and a communication apparatus using the piezoelectric thin film resonator are provided. The piezoelectric thin film resonator is provided with a substrate having an opening, first and second insulation films which are provided on one surface of the substrate while covering the opening and which primarily include SiO 2 and Al 2 O 3 , respectively, Al 2 O 3 having oxygen defect and being in an amorphous state, and a piezoelectric thin film which is provided on the second insulation film and is sandwiched between electrodes and which primarily includes ZnO.

1 . A method for manufacturing a piezoelectric resonator comprising a substrate, first and second insulation films provided on the substrate, wherein the first and second insulation films and top and bottom surfaces of a thin film portion including at least one layer of piezoelectric thin film are sandwiched between at least a pair of upper and lower electrodes which face each other in the thickness direction of the thin film, the method comprising the step of: 
 forming an insulation film primarily including SiO 2  by an RF magnetron sputtering method while the power density is set to about 2.0 W/cm 2  to about 8.5 W/cm 2 , wherein the insulation film primarily including SiO 2  is an upper layer of the first and second insulation films.    
   
   
       2 . The method for manufacturing a piezoelectric resonator according to  claim 1 , wherein the gas pressure during film formation by the RF magnetron sputtering method is about 0.6 Pa or less.  
   
   
       3 . A method for manufacturing a piezoelectric resonator comprising a substrate, an insulation film provided on the substrate, and a vibration portion provided on the insulation film, the vibration portion including a thin film portion having top and bottom surfaces including at least one layer of piezoelectric thin film sandwiched between at least a pair of upper lower electrodes which face each other in the thickness direction of the thin film, the method comprising: 
 a first step of forming the insulation film from silicon oxide as a primary component by an RF magnetron sputtering method while the power density is within a range of about 2.0 W/cm 2  to about 8.5 W/cm 2 ; and    a second step of forming the piezoelectric thin film from zinc oxide as a primary component.    
   
   
       4 . The method for manufacturing a piezoelectric resonator according to  claim 3 , wherein the gas pressure during film formation by the RF magnetron sputtering method is about 0.6 Pa or less.