Plating bath and method

Abstract

Tin electroplating baths having certain brightening agents and nonionic surfactants provide tin-containing solder deposits having good morphology, reduced void formation and improved within-die uniformity.

What is claimed is: 
     
         1 . An electroplating composition comprising: a source of tin ions; an acid electrolyte; 0.0001 to 0.075 g/L of a grain refiner of formula (1) or (2) 
       
         
           
           
               
               
           
         
         wherein each R 1  is independently (C 1-6 )alkyl, (C 1-6 )alkoxy, hydroxy, or halo; R 2  and R 3  are independently chosen from H and (C 1-6 )alkyl; R 4  is H, OH, (C 1-6 )alkyl or O(C 1-6 )alkyl; m is an integer from 0 to 2; each R 5  is independently (C 1-6 )alkyl; each R 6  is independently chosen from H, OH, (C 1-6 )alkyl, or O(C 1-6 )alkyl; n is 1 or 2; and p is 0, 1 or 2; 
         a nonionic surfactant of formula (3) or (4): 
       
       
         
           
           
               
               
           
         
         wherein A and B represent different alkyleneoxide moieties, and x and y represent the number of repeat units of each alkyleneoxide, respectively; and water. 
       
     
     
         2 . The electroplating composition of  claim 1  wherein A and B are independently chosen from (C 2-4 )alkyleneoxides. 
     
     
         3 . The electroplating composition of  claim 1  wherein x and y are independently integers from 1 to 100. 
     
     
         4 . The electroplating composition of  claim 1  wherein the nonionic surfactant has an average of 1000 to 30000. 
     
     
         5 . The electroplating composition of  claim 1  further comprising a source of alloying metal ions. 
     
     
         6 . The electroplating composition of  claim 6  wherein the alloying metal ions are chosen from copper ions, silver ions, gold ions, bismuth ions, zinc ions, indium ions, or mixtures thereof. 
     
     
         7 . The electroplating composition of  claim 1  having a pH value of 0 to 6. 
     
     
         8 . The electroplating composition of  claim 1  wherein the grain refiner is chosen from cinnamic acid, cinnamaldehyde, benzylidene acetone, picolinic acid, pyridinedicarboxylic acid, pyridinecarboxaldehyde, pyridinedicarboxaldehyde, or mixtures thereof. 
     
     
         9 . A method of electroplating a tin-containing layer comprising: providing a semiconductor wafer comprising a plurality of conductive bonding features; contacting the semiconductor wafer with the composition of  claim 1 ; and applying sufficient current density to deposit a tin-containing layer on the conductive bonding features. 
     
     
         10 . The method of  claim 9  the tin-containing layer on the bonding features is substantially free of voids as plated and after reflow.