Semiconductor device and method of fabricating the same

Abstract

After a copper diffusion preventing film 4 is formed on a copper pad 1, a barrier metal including a titanium film 5, a nickel film 6, and a palladium film 7 is formed on the copper diffusion preventing film 4. The copper diffusion preventing film formed on the copper pad suppresses diffusion of copper. Even when a solder bump is formed on the copper pad, diffusion of tin in the solder and copper is suppressed. This prevents formation of an intermetallic compound between copper and tin, so no interface de-adhesion or delamination occurs and a highly reliable connection is obtained. This structure can be realized by a simple fabrication process unlike a method of forming a thick barrier metal by electroplating. In this invention, high shear strength can be ensured by connecting a solder bump, gold wire, or gold bump to a copper pad without increasing the number of fabrication steps.

1 .- 11 . (Canceled).  
     
     
         12 . A method of fabricating a semiconductor device in which a semiconductor element having a copper pad is mounted on a wiring substrate, comprising the steps of: 
 forming a copper diffusion preventing film for preventing diffusion of copper on the surface of said copper pad;    forming a metal bump to be electrically connected to said copper pad with said copper diffusion preventing film interposed therebetween; and    mounting said semiconductor element on said wiring substrate via said metal bump.    
     
     
         13 . A semiconductor device fabrication method of mounting a semiconductor element having a copper pad on a wiring substrate by flip chip mounting by using a solder bump, comprising the steps of: 
 forming a copper diffusion preventing film for preventing diffusion of copper on the surface of said copper pad;    forming a metal stacked film for suppressing diffusion of tin contained in a solder bump on said copper diffusion preventing film;    forming said solder bump on said metal stacked film; and    mounting said semiconductor element on said wiring substrate via said solder bump.    
     
     
         14 . A method according to  claim 13 , wherein said metal stacked film is one of a stacked film of Ti and Ni, a stacked film of Ti, Ni, and Pd, a stacked film of Ti, Ni, and Au, a stacked film of Cr and Ni, a stacked film of Cr and Au, a stacked film of Cr, Ni, and Au, a stacked film of Cr, Ni, and Pd, a stacked film of Ti and Cu, a stacked film of Ti, Cu, and Au, a stacked film of Cr and Cu, and a stacked film of Cr, Cu, and Au.  
     
     
         15 . A method of fabricating a semiconductor device in which a semiconductor element having a copper pad is mounted on a wiring substrate, comprising the steps of: 
 forming a copper diffusion preventing film for preventing diffusion of copper on the surface of said copper pad;    forming a metal film for improving adhesion to a metal wire on said copper diffusion preventing film;    electrically connecting said metal wire to said copper pad with said copper diffusion preventing film and said metal film interposed therebetween; and    mounting said semiconductor element on said wiring substrate via said metal wire.    
     
     
         16 . A method of fabricating a semiconductor device in which a semiconductor element having a copper pad is mounted on a wiring substrate, comprising the steps of: 
 forming a copper diffusion preventing film for preventing diffusion of copper on the surface of said copper pad;    forming a metal stacked film for preventing diffusion of gold on said copper diffusion preventing film;    forming a gold bump to be electrically connected to said copper pad with said copper diffusion preventing film and said metal stacked film interposed therebetween; and mounting said semiconductor element on said wiring substrate via said gold bump.    
     
     
         17 . A method of fabricating a semiconductor device in which a semiconductor element having a copper pad is mounted on a wiring substrate, comprising the steps of: 
 forming a copper diffusion preventing film for preventing diffusion of copper on the surface of said copper pad;    forming an aluminum film on said copper diffusion preventing film;    electrically connecting a metal wire to said copper pad with said copper diffusion preventing film and said aluminum film interposed therebetween; and    mounting said semiconductor element on said wiring substrate via said metal wire.    
     
     
         18 . A method according to  claim 17 , further comprising the step of forming a metal film for improving adhesion between said copper diffusion preventing film and said aluminum film.