Method to modulate the surface roughness of a plated deposit and create fine-grained flat bumps

Abstract

The present invention relates to a plating bath consisting of a plating solution, accelerating agent and a suppressing agent and a method of forming contact formations on a semiconductor substrate. In an embodiment, the deposition of contact formations occurs in a two step deposition process wherein the deposition process has different deposition rates. Furthermore, the present invention includes a method of forming smooth, flat contact formations for use in electronic packages.

1 . A plating bath consisting of: 
 a plating solution; and    an accelerating agent in said plating solution; and    a suppressing agent in said plating solution.    
   
   
       2 . The plating bath of  claim 1 , wherein said plating solution is selected from the group consisting of methane sulfonic, amidosulfuric, and aminoacetic.  
   
   
       3 . The plating bath of  claim 1 , wherein said accelerating agent is selected from the group consisting of SPS, 1-propane sulfonic acid, 3,3′-dithio-bis, di-sodium salt; 1-propanesulfonic acid, 3-[(ethoxy-thiomethyl_thio],-potassium salt; phosphonated disulfide; sulphonated monosulfide; phosphonated monsulfide.  
   
   
       4 . The plating bath of  claim 1 , wherein said suppressing agent is selected from the group consisting of polyoxyethylene lauryl ether; polyethylene glycol, polypropylene glycol; alkoxylated beta-naphtol; alkyl naphthalene sulphonate.  
   
   
       5 . The plating bath of  claim 1  further comprising copper.  
   
   
       6 . The plating bath of  claim 1  further comprising refractory metals, noble metals, transition metals, and halogens.  
   
   
       7 . A plating bath consisting of: 
 a methane sulfonic; and    a sulphonated monosulfide; and    polyethylene glycol; and    copper; and    bromine.    
   
   
       8 . The plating bath of  claim 7  further consists of metal deposit ions.  
   
   
       9 . The plating bath of  claim 7  further consists of mineral acids.  
   
   
       10 . A method consisting of: 
 forming an adhesion layer over the top surface of a semiconductor substrate;    forming a seed layer over the top surface of said adhesion layer;    patterning a first resist for a bump pattern over said seed layer;    exposing said semiconductor substrate to a plating bath, wherein said plating bath consists of a plating solution, accelerating agent, and a suppressing agent;    applying a current to said plating bath, wherein a first metal layer is deposited in said bump pattern;    removing said first resist;    etching a first portion of said adhesion layer and said seed layer, wherein the portion of said adhesion layer and said seed layer that remains is directly underneath said first metal layer.    
   
   
       11 . The method of  claim 10 , wherein said first metal layer deposition occurs in a first step and a second step.  
   
   
       12 . The method of  claim 11 , wherein said first step comprises applying a current to said plating bath, wherein said second metal layer is deposited at a rate approximately 69 microns/3600 seconds.  
   
   
       13 . The method of  claim 11 , wherein said second step comprises applying a current to said plating bath, wherein said second metal layer is deposited at a rate approximately 118 microns/3600 seconds.  
   
   
       14 . The method of  claim 10 , wherein said seed layer is a base metal layer.  
   
   
       15 . The method of  claim 14 , wherein said base metal layer comprises titanium copper.  
   
   
       16 . The method of  claim 10 , wherein said first metal layer comprises copper.  
   
   
       17 . A method consisting of: 
 forming an adhesion layer over the top surface of a semiconductor substrate;    forming a base metal layer over the top surface of said adhesion layer;    patterning a first resist for a bump pattern over said base metal layer;    exposing said semiconductor substrate to a plating bath, wherein said plating bath consists of a plating solution, accelerating agent, and a suppressing agent;    applying a current to said plating bath, wherein a copper layer is deposited in said bump pattern in a first step and a second step and wherein said first step deposits said copper layer at a rate of approximately 69 microns/3600 seconds and wherein said second step deposits said copper layer at a rate of approximately 118 microns/3600 seconds;    removing said first resist;    etching a first portion of said adhesion layer and said base metal layer, wherein the portion of said adhesion layer and said base metal layer that remains is directly underneath said copper layer.    
   
   
       18 . The method of  claim 17 , wherein said semiconductor substrate comprises a passivation layer, and wherein said passivation layer is on the top surface of said semiconductor substrate.  
   
   
       19 . The method of  claim 17 , wherein said adhesion layer comprises titanium.  
   
   
       20 . The method of  claim 17  further consisting of a pre-wet process prior to forming an adhesion layer over the top surface of said semiconductor substrate.