Acoustic mirror for a bulk acoustic wave structure

Abstract

According to one embodiment of the invention, an acoustic mirror structure situated in a bulk acoustic wave structure includes a number of alternating low acoustic impedance and high acoustic impedance layers situated on a substrate. Each high acoustic impedance layer includes a first mole percent of a primary metal and a second mole percent of a secondary metal, where the first mole percent of the primary metal is greater than the second mole percent of the secondary metal, and where the secondary metal causes each high acoustic impedance layer to have increased resistivity. According to this exemplary embodiment, the second mole percent of the secondary metal can cause only a minimal decrease in density of each high acoustic impedance layer. The increased resistivity of each high acoustic impedance layer can cause a reduction in electrical loss in the bulk acoustic wave structure.

1 - 23 . (canceled) 
   
   
       24 . An acoustic mirror fabricated in a bulk acoustic wave structure utilizing a method comprising steps of:
 depositing a plurality of alternating low acoustic impedance and high acoustic impedance layers on a substrate;   wherein each of said high acoustic impedance layers comprises a first mole percent of a primary metal and a second mole percent of a secondary metal, wherein said secondary metal is selected to cause each of said high acoustic impedance layers to have an increase in resistivity.   
   
   
       25 . The acoustic mirror of  claim 24 , wherein said first mole percent of said primary metal is greater than said second mole percent of said secondary metal. 
   
   
       26 . The acoustic mirror of  claim 24 , wherein said second mole percent of said secondary metal does not cause a decrease in density of each of said high acoustic impedance layers. 
   
   
       27 . The acoustic mirror of  claim 24 , wherein said second mole percent of said secondary metal does not cause a substantial decrease in density of each of said high acoustic impedance layers. 
   
   
       28 . The acoustic mirror of  claim 24 , wherein said primary metal comprises tungsten. 
   
   
       29 . The acoustic mirror of  claim 24 , wherein said secondary metal comprises titanium. 
   
   
       30 . The acoustic mirror of  claim 24 , wherein said first mole percent is approximately 70 mole percent and said second mole percent is approximately 30 mole percent. 
   
   
       31 . The acoustic mirror of  claim 24 , wherein said secondary metal causes said resistivity of each of said high acoustic impedance layers to increase by a factor of approximately five. 
   
   
       32 . The acoustic mirror of  claim 24 , wherein said increase in said resistivity of each of said high acoustic impedance layers causes a reduction in electrical loss in said bulk acoustic wave structure. 
   
   
       33 . The acoustic mirror of  claim 24 , wherein said increase in said resistivity of each of said high acoustic impedance layers causes a reduction in electrical loss in said acoustic mirror. 
   
   
       34 . An acoustic mirror fabricated in a bulk acoustic wave structure utilizing a method comprising:
 depositing a plurality of low acoustic impedance and high acoustic impedance layers on a substrate of said bulk acoustic wave structure, wherein each of said high acoustic impedance layers is deposited so as to increase a resistivity thereof while preventing a decrease in a density thereof.   
   
   
       35 . The acoustic mirror of  claim 34 , wherein each of said high acoustic impedance layers is deposited by adding an impurity to a deposition process. 
   
   
       36 . The acoustic mirror of  claim 35 , wherein said impurity causes said resistivity of each of said high acoustic impedance layers to increase while preventing a decrease in said density thereof. 
   
   
       37 . The acoustic mirror of  claim 35 , wherein said impurity comprises oxygen. 
   
   
       38 . The acoustic mirror of  claim 36 , wherein said impurity comprises oxygen. 
   
   
       39 . The acoustic mirror of  claim 35 , wherein said impurity comprises nitrogen. 
   
   
       40 . The acoustic mirror of  claim 36 , wherein said impurity comprises nitrogen. 
   
   
       41 . The acoustic mirror of  claim 34 , wherein each of said high acoustic impedance layers is deposited by adjusting at least one process parameter in a deposition process so as to cause said resistivity of each of said high acoustic impedance layers to increase while preventing a substantial decrease in said density thereof. 
   
   
       42 . The acoustic mirror of  claim 41 , wherein said adjusting said at least one process parameter in said deposition process comprises increasing a deposition power. 
   
   
       43 . The acoustic mirror of  claim 34 , wherein said increase in said resistivity causes a reduction in electrical loss in said bulk acoustic wave structure.