Semiconductor device and method of fabricating the same

Abstract

There is provided a semiconductor device including (a) a semiconductor chip, (b) a wiring making electrical connection with the semiconductor chip and containing copper (Cu) therein, (c) a solder ball making contact with the wiring and containing tin (Sn) therein, and (d) a layer made of copper-tin (Cu—Sn) alloy, sandwiched between the wiring and the solder ball, and having a thickness equal to or greater than about 1.87 micrometers. The copper-tin alloy layer strengthens connection between the wiring and the solder ball, and hence, ensures reduction in occurrence of breakage and/or cracking in the wiring and the solder ball. As a result, it would be possible to avoid the solder ball from being separated from the wiring due to the breakage and cracking. Accordingly, a fabrication yield of the semiconductor device can be enhanced.

What is claimed is:  
     
         1 . A semiconductor device comprising: 
 (a) a semiconductor chip;    (b) a wiring making electrical connection with said semiconductor chip and containing copper (Cu) therein;    (c) a solder ball making contact with said wiring and containing tin (Sn) therein; and    (d) a layer made of copper-tin (Cu—Sn) alloy, sandwiched between said wiring and said solder ball, and having a thickness equal to or greater than about 1.87 micrometers.    
     
     
         2 . The semiconductor device as set forth in  claim 1 , wherein said copper-tin (Cu—Sn) alloy layer has a thickness equal to or greater than 2 micrometers.  
     
     
         3 . The semiconductor device as set forth in  claim 2 , wherein said copper-tin (Cu—Sn) alloy layer has a thickness equal to or greater than 3 micrometers.  
     
     
         4 . The semiconductor device as set forth in  claim 1 , wherein said solder ball contains agglomerates scattering therein, said agglomerates being composed of material other than tin.  
     
     
         5 . The semiconductor device as set forth in  claim 4 , wherein said agglomerates are composed of lead (Pb), and wherein said lead agglomerates are scattered at a density of 20×10 4  mm −3  or greater.  
     
     
         6 . The semiconductor device as set forth in  claim 4 , wherein said agglomerates are composed of lead (Pb), and wherein said lead agglomerates have a cross-sectional area of 10 square micrometer or smaller in average.  
     
     
         7 . The semiconductor device as set forth in  claim 1 , further comprising a printed wiring board making electrical connection with said solder ball.  
     
     
         8 . A semiconductor device comprising: 
 (a) a semiconductor chip;    (b) a wiring making electrical connection with said semiconductor chip, having first and second surfaces, and containing copper (Cu) therein;    (c) a solder ball making contact with said wiring at said first surface and containing tin (Sn) therein;    (d) a film substrate making contact with said wiring at said second surface, said film substrate being formed with a through-hole reaching said wiring;    (e) an electrical conductor filling said through-hole therewith;    (f) a first layer covering said electrical conductor therewith at the opposite side of said wiring, and made of gold; and    (g) a second layer made of copper-tin alloy, sandwiched between said wiring and said solder ball, and having a thickness equal to or greater than about 1.87 micrometers.    
     
     
         9 . The semiconductor device as set forth in  claim 8 , wherein said second layer has a thickness equal to or greater than 2 micrometers.  
     
     
         10 . The semiconductor device as set forth in  claim 9 , wherein said second layer has a thickness equal to or greater than 3 micrometers.  
     
     
         11 . The semiconductor device as set forth in  claim 8 , wherein said solder ball contains agglomerates scattering therein, said agglomerates being composed of material other than tin.  
     
     
         12 . The semiconductor device as set forth in  claim 11 , wherein said agglomerates are composed of lead (Pb), and wherein said lead agglomerates are scattered at a density of 20×10 4  mm −3  or greater.  
     
     
         13 . The semiconductor device as set forth in  claim 11 , wherein said agglomerates are composed of lead (Pb), and wherein said lead agglomerates have a cross-sectional area of 10 square micrometer or smaller in average.  
     
     
         14 . The semiconductor device as set forth in  claim 8 , further comprising a printed wiring board making electrical connection with said solder ball.  
     
     
         15 . A method of fabricating a semiconductor device, comprising the steps of: 
 (a) forming a wiring containing copper (Cu), on a substrate;    (b) mounting a solder ball containing tin (Sn), on said wiring; and    (c) keeping a product resulted from said step (b), in inactive gas atmosphere or in reducing gas atmosphere at a temperature equal to or greater than a melting point of said solder ball.    
     
     
         16 . The method as set forth in  claim 15 , wherein said product resulted from said step (b) is kept in said inactive gas atmosphere or in said reducing gas atmosphere for an hour or longer.  
     
     
         17 . The method as set forth in  claim 15 , further comprising the step of forming a gold layer on said wiring in advance of mounting said solder ball on said wiring.  
     
     
         18 . A method of fabricating a semiconductor device, comprising the steps of: 
 (a) forming a wiring containing copper (Cu), on a substrate;    (b) covering said wiring with a resist having a recess through which said wiring appears;    (c) forming a through-hole through said substrate so that said through-hole reaches said wiring;    (d) filling electrical conductor in said through-hole;    (e) covering said electrical conductor with a gold layer;    (f) connecting said substrate to a semiconductor chip.    (g) mounting a solder ball containing tin (Sn), in said recess; and    (h) keeping a product resulted from said step (g), in inactive gas atmosphere or in reducing gas atmosphere at a temperature equal to or greater than a melting point of said solder ball.    
     
     
         19 . The method as set forth in  claim 18 , wherein said product resulted from said step (g) is kept in said inactive gas atmosphere or in said reducing gas atmosphere for an hour or longer.  
     
     
         20 . The method as set forth in  claim 18 , further comprising the step of forming a gold layer on said wiring in advance of mounting said solder ball on said wiring.  
     
     
         21 . A semiconductor device comprising: 
 (a) a semiconductor chip;    (b) a wiring making electrical connection with said semiconductor chip and containing copper (Cu) therein;    (c) a solder ball making contact with said wiring and containing tin (Sn) therein; and    (d) a layer made of copper-tin (Cu—Sn) alloy, sandwiched between said wiring and said solder ball, and having a thickness equal to or greater than about 1.87 micrometers,    said semiconductor device being resulted from the steps of: 
 (a) forming said wiring on a substrate;  
 (b) mounting said solder ball on said wiring; and  
 (c) keeping a product resulted from said step (b), in inactive gas atmosphere or in reducing gas atmosphere at a temperature equal to or greater than a melting point of said solder ball.  
   
     
     
         22 . The semiconductor device as set forth in  claim 21 , wherein said product resulted from said step (b) is kept in said inactive gas atmosphere or in said reducing gas atmosphere for an hour or longer.  
     
     
         23 . The semiconductor device as set forth in  claim 21 , wherein said copper-tin (Cu—Sn) alloy layer has a thickness equal to or greater than 2 micrometers.  
     
     
         24 . The semiconductor device as set forth in  claim 21 , wherein said copper-tin (Cu—Sn) alloy layer has a thickness equal to or greater than 3 micrometers.  
     
     
         25 . A semiconductor device comprising: 
 (a) a semiconductor chip;    (b) a wiring making electrical connection with said semiconductor chip and containing copper (Cu) therein; and    (c) a solder ball making contact with said wiring and containing tin (Sn) therein, said solder ball containing lead (Pb) agglomerates scattering therein at a density of 20×10 4  mm −3  or greater,    said semiconductor device being resulted from the steps of: 
 (a) forming said wiring on a substrate;  
 (b) mounting said solder ball on said wiring; and  
 (c) keeping a product resulted from said step (b), in inactive gas atmosphere or in reducing gas atmosphere at a temperature equal to or greater than a melting point of said solder ball.  
   
     
     
         26 . A semiconductor device comprising: 
 (a) a semiconductor chip;    (b) a wiring making electrical connection with said semiconductor chip and containing copper (Cu) therein; and    (c) a solder ball making contact with said wiring and containing tin (Sn) therein, said solder ball containing lead (Pb) agglomerates scattering therein, said lead agglomerates having a cross-sectional area of 10 square micrometer or smaller in average,    said semiconductor device being resulted from the steps of: 
 (a) forming said wiring on a substrate;  
 (b) mounting said solder ball on said wiring; and  
 (c) keeping a product resulted from said step (b), in inactive gas atmosphere or in reducing gas atmosphere at a temperature equal to or greater than a melting point of said solder ball.