Surface acoustic wave device and production process thereof

Abstract

This invention relates to a surface acoustic wave device and a production process thereof. An electrode is formed by alternately laminating a film of an aluminum alloy containing at least copper added thereto and a copper film on a piezoelectric substrate. While the particle size of the multi-layered electrode materials in kept small, the occurrence of voids in the film is prevented and life time of the surface acoustic wave device is elongated.

We claim:  
     
       1. A surface acoustic wave device comprising: 
       a piezoelectric substrate; and  
       an electrode formed on said substrate by alternately laminating  of an aluminum copper alloy film and a copper film such that said electrode has a three-layered laminate structure with two  with CuAl 2    formed at an interface between said  aluminum-copper alloy films sandwiching one  film and said copper film.  
     
     
       2. A surface acoustic wave device according to  claim 1 , wherein 
       the aluminum-copper alloy films have  film has one of a tensile internal stress and a compressive internal stress,  
       the copper film has the other of a tensile internal stress and a compressive internal stress such that the internal stresses of said aluminum-copper alloy films  film and said copper film have mutually opposite directions, and  
       the sum of said internal stresses is either zero or compressive.  
     
     
       3. A surface acoustic wave device according to  claim 1 , wherein the amount of copper in the aluminum-copper alloy film is from 0.5 to 4 wt % on the basis of the total weight of said alloy film. 
     
     
       4. A surface acoustic wave device according to  claim 1 , wherein said piezoelectric substrate is made of one of LiTaO 3  and LiNbO 3 . 
     
     
       5. A surface acoustic wave device according to  claim 1 , wherein the piezoelectric substrate and the electrode are in the form of a surface acoustic wave filter. 
     
     
       6. A surface acoustic wave device according to  claim 1 , wherein the electrode has two aluminum- copper alloy films, one copper film and two CuAl   2    films between the copper film and the respective aluminum - copper alloy films.   
     
     
       7. A surface acoustic wave device according to  claim 1 , wherein the electrode forms a comb- tooth interdigital transducer on the piezoelectric substrate.   
     
     
       8. A surface acoustic wave device comprising: 
       
         a piezoelectric substrate; and  
       
         an electrode formed on said substrate, the electrode having aluminum - copper alloy films and a CuAl   2    layer formed between the aluminum - copper alloy films, wherein    
         the electrode is produced by a process of laminating aluminum - copper alloy films and a copper film, and    
         said CuAl   2    layer is formed from aluminum of the aluminum - copper alloy films and from copper of the copper film.   
     
     
       9. A surface acoustic wave device according to  claim 8 , wherein the electrode has a plurality of aluminum- copper alloy films and a plurality of CuAl   2    layers formed between the aluminum - copper alloy films.   
     
     
       10. A surface acoustic wave device according to  claim 8 , wherein the amount of copper in the aluminum- copper alloy films is from  0 . 5  to  4  wt  %  on the basis of the total weight of said alloy films.   
     
     
       11. A surface acoustic wave device according to  claim 8 , wherein said piezoelectric substrate is made of one of LiTaO 3    and LiNbO   3 . 
     
     
       12. A surface acoustic wave device according to  claim 8 , wherein the piezoelectric substrate and the electrode are in the form of a surface acoustic wave filter. 
     
     
       13. A surface acoustic wave device according to  claim 8 , wherein the CuAl 2    formed between the aluminum - copper alloy films and a CuAl   2    formed in a grain boundary of the aluminum - copper alloy films are mutually bonded.   
     
     
       14. A surface acoustic wave filter comprising: 
       
         a piezoelectric substrate;  
       
       
         an input terminal;  
       
       
         an output terminal;  
       
       
         a series resonator connected to said input terminal and said output terminal; and  
       
       
         a parallel resonator connected between said series resonator and a ground, said series and said parallel resonators including an electrode formed on said substrate of an aluminum copper alloy film and a copper film with CuAl 
         2  
         formed at an interface between said aluminum copper alloy film and said copper film. 
       
     
     
       15. A surface acoustic wave device according to  claim 14 , wherein 
         the aluminum - copper alloy film has one of a tensile internal stress and a compressive internal stress,    
         the copper film has the other of a tensile internal stress and a compressive internal stress such that the internal stresses of said aluminum - copper alloy film and said copper film have mutually opposite directions, and    
       
         the sum of said internal stresses is either zero or compressive. 
       
     
     
       16. A surface acoustic wave device according to  claim 14 , wherein the amount of copper in the aluminum- copper alloy film is from  0 . 5  to  4  wt  %  on the basis of the total weight of said alloy film.   
     
     
       17. A surface acoustic wave device according to  claim 14 , wherein said piezoelectric substrate is made of one of LiTaO 3    and LiNbO   3 . 
     
     
       18. A surface acoustic wave device according to  claim 14 , wherein the piezoelectric substrate and the electrode are in the form of a surface acoustic wave filter. 
     
     
       19. A surface acoustic wave device according to  claim 14 , wherein the electrode has two aluminum- copper alloy films, one copper film and two CuAl   2    films between the copper film and the respective aluminum - copper alloy films.   
     
     
       20. A surface acoustic wave filter comprising: 
       
         a piezoelectric substrate;  
       
       
         an input terminal;  
       
       
         an output terminal;  
       
       
         a series resonator connected to said input terminal and said output terminal; and  
       
         a parallel resonator connected between said series resonator and a ground, said series and said parallel resonators including an electrode formed on said substrate, the electrode having aluminum - copper alloy films and a CuAl   2    layer formed between the aluminum - copper alloy films, wherein    
         the electrode is produced by a process of alternately laminating aluminum - copper alloy films and a copper film, and    
         said CuAl   2    layer is formed from aluminum of the aluminum - copper alloy films and from copper of the copper film.   
     
     
       21. A surface acoustic wave filter according to  claim 20 , wherein the electrode has a plurality of aluminum- copper alloy films and a plurality of CuAl   2    films formed between the aluminum - copper alloy films.   
     
     
       22. A surface acoustic wave filter according to  claim 20 , wherein the amount of copper in the aluminum- copper alloy films is from  0 . 5  to  4  wt  %  on the basis of the total weight of said alloy films.   
     
     
       23. A surface acoustic wave filter according to  claim 20 , wherein said piezoelectric substrate is made of one of LiTaO 3    and LiNbO   3 . 
     
     
       24. A surface acoustic wave filter according to  claim 20 , wherein the piezoelectric substrate and the electrode are in the form of a surface acoustic wave filter. 
     
     
       25. A surface acoustic wave filter according to  claim 20 , wherein the piezoelectric substrate, input terminal, output terminal, series resonator and parallel resonator form an antenna duplexer. 
     
     
       26. A surface acoustic wave filter according to  claim 22 , wherein the piezoelectric substrate, input terminal, output terminal, series resonator and parallel resonator form an antenna duplexer. 
     
     
       27. A surface acoustic wave filter according to  claim 23 , wherein the piezoelectric substrate, input terminal, output terminal, series resonator and parallel resonator form an antenna duplexer. 
     
     
       28. A surface acoustic wave filter according to  claim 24 , wherein the piezoelectric substrate, input terminal, output terminal, series resonator and parallel resonator form an antenna duplexer. 
     
     
       29. A surface acoustic wave device comprising: 
       
         a piezoelectric substrate; and  
       
       
         an electrode formed on said substrate by a process comprising the steps of:  
       
         laminating an aluminum - copper alloy film and a copper film thereby forming a laminated structure; and    
       
         heating the laminated structure. 
       
     
     
       30. A surface acoustic wave device according to  claim 29 , wherein the amount of copper in the aluminum- copper alloy film is from  0 . 5  to  4  wt  %  on the basis of the total weight of said alloy film.   
     
     
       31. A surface acoustic wave device according to  claim 29 , wherein said piezoelectric substrate is made of one of LiTaO 3    and LiNbO   3 . 
     
     
       32. A surface acoustic wave filter comprising: 
       
         a piezoelectric substrate;  
       
       
         an input terminal;  
       
       
         an output terminal;  
       
       
         a series resonator connected to said input terminal and said output terminal; and  
       
         a parallel resonator connected between said series resonator and a ground, said series and said parallel resonators including an electrode having an aluminum - copper alloy film and a CuAl   2    layer, the electrode being formed on said substrate by a process comprising the steps of:    
         laminating the aluminum - copper alloy film and a copper film thereby forming a laminated structure; and    
       
         heating the laminated structure. 
       
     
     
       33. A surface acoustic wave filter according to  claim 32 , wherein the amount of copper in the aluminum- copper alloy film is from  0 . 5  to  4  wt  %  on the basis of the total weight of said alloy film.   
     
     
       34. A surface acoustic wave filter according to  claim 32 , wherein said piezoelectric substrate is made of one of LiTaO 3    and LiNbO   3 . 
     
     
       35. A surface acoustic wave device comprising: 
       
         a piezoelectric substrate; and  
       
       
         an electrode formed on said substrate by a process comprising the steps of:  
       
         laminating an aluminum - copper alloy film and a copper film thereby forming a laminated structure with the aluminum - copper alloy film facing said substrate; and    
       
         heating the laminated structure. 
       
     
     
       36. A surface acoustic wave device comprising: 
       
         a piezoelectric substrate; and  
       
       
         an electrode formed on said substrate by a process comprising the steps of:  
       
         alternately laminating aluminum - copper alloy films and a copper film thereby forming a laminated structure; and    
       
         heating the laminated structure. 
       
     
     
       37. A surface acoustic wave device comprising: 
       
         a piezoelectric substrate; and  
       
       
         an electrode formed on said substrate by a process comprising the steps of:  
       
         alternately laminating aluminum - copper alloy films and a copper film thereby forming a laminated structure with one of the aluminum - copper alloy films facing said substrate; and    
       
         heating the laminated structure.