Method of forming an electrical contact

Abstract

In a test system, a silicon interconnect is provided that can accommodate a packaged part, such as a Land Grid Array (LGA) package. The interconnect can be made by etching a silicon substrate to form projections therefrom; forming an insulation or passivation layer through deposition or growth; depositing a seed layer over the insulation layer; depositing a metal layer over the seed layer; and etching contact members from the seed and metal layers using a single mask step. In a preferred embodiment, the metal layer is coated with another metal layer that matches the metal of the packaged part's electrical communication nodes. In one embodiment, the contact surfaces of the silicon contact are plated in gold and are planar. Included within the scope of the current invention are at least one method of testing an LGA package and at least one method of allowing electrical communication with a packaged part.

1 . A method of coating an interconnect projection on a substrate comprising: 
 forming a seed layer over the interconnect projection on the substrate;    forming a copper layer over the seed layer; and    forming a gold layer directly over the copper layer, the gold layer including a flat top.    
   
   
       2 . The method in  claim 1 , wherein the forming a copper layer comprises electroplating copper onto the seed layer.  
   
   
       3 . The method in  claim 1 , wherein the forming a copper layer comprises sputtering copper onto the seed layer.  
   
   
       4 . The method in  claim 3 , wherein the forming a seed layer further comprises sputtering tungsten over the interconnect projection.  
   
   
       5 . A method of coating a projection on a substrate comprising: 
 forming a seed layer over the projection on the substrate;    forming a copper layer over the seed layer; and    forming a gold layer directly over the copper layer, the gold layer including a flat top.    
   
   
       6 . The method in  claim 5 , wherein the forming a copper layer comprises electroplating copper onto the seed layer.  
   
   
       7 . The method in  claim 5 , wherein the forming a copper layer comprises sputtering copper onto the seed layer.  
   
   
       8 . The method in  claim 7 , wherein the forming a seed layer further comprises sputtering tungsten over the projection.  
   
   
       9 . A method of coating an interconnect layer on a substrate comprising: 
 forming a seed layer over the layer on the substrate;    forming a copper layer over the seed layer; and    forming a gold layer directly over the copper layer, the gold layer including a flat top.    
   
   
       10 . The method in  claim 9 , wherein the forming a copper layer comprises electroplating copper onto the seed layer.  
   
   
       11 . The method in  claim 9 , wherein the forming a copper layer comprises sputtering copper onto the seed layer.  
   
   
       12 . The method in  claim 11 , wherein the forming a seed layer further comprises sputtering tungsten over the layer.  
   
   
       13 . A method of coating an interconnect layer on a substrate comprising: 
 forming a seed layer over the interconnect layer on the substrate;    forming a copper layer over the seed layer; and    forming a gold layer directly over the copper layer, the gold layer including a flat top.    
   
   
       14 . The method in  claim 13 , wherein the forming a copper layer comprises electroplating copper onto the seed layer.  
   
   
       15 . The method in  claim 13 , wherein the forming a copper layer comprises sputtering copper onto the seed layer.  
   
   
       16 . The method in  claim 15 , wherein the forming a seed layer further comprises sputtering tungsten over the interconnect layer.  
   
   
       17 . A method of coating an interconnect projection layer on a substrate comprising: 
 forming a seed layer over the interconnect projection on the substrate;    forming a copper layer over the seed layer; and    forming a gold layer directly over the copper layer, the gold layer including a flat top.    
   
   
       18 . The method in  claim 17  wherein the forming a copper layer comprises electroplating copper onto the seed layer.  
   
   
       19 . The method in  claim 17  wherein the forming a copper layer comprises sputtering copper onto the seed layer.  
   
   
       20 . The method in  claim 19 , wherein the forming a seed layer further comprises sputtering tungsten over the interconnect projection layer.