Plating bath and method

Abstract

Tin-containing electroplating baths having a combination of certain brightening agents provide tin-containing solder deposits having reduced void formation and smooth morphology.

What is claimed is: 
     
         1 . An electroplating composition comprising: a source of tin ions; an acid electrolyte; 0.0001 to 0.045 g/L of a first grain refiner; 0.005 to 0.75 g/L of an α,β-unsaturated aliphatic carbonyl compound as a second grain refiner; a nonionic surfactant; and water; wherein the first grain refiner is chosen from a compound 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. 
     
     
         2 . The composition of  claim 1  further comprising a source of alloying metal ions. 
     
     
         3 . The composition of  claim 1  wherein the α,β-unsaturated aliphatic carbonyl compound is chosen from α,β-unsaturated carboxylic acids, α,β-unsaturated carboxylic acid esters, α,β-unsaturated amides, and α,β-unsaturated aldehydes. 
     
     
         4 . The composition of  claim 3  wherein the α,β-unsaturated aliphatic carbonyl compound is chosen from (meth)acrylic acid, crotonic acid, (C 1-6 )alkyl (meth)acrylate, (meth)acrylamide, (C 1 -C 6 )alkyl crotonate, crotonamide, crotonaldehyde, or mixtures thereof. 
     
     
         5 . The composition of  claim 1  wherein the first grain refiner is chosen from cinnamic acid, cinnamaldehyde, benzylidene acetone, picolinic acid, pyridinedicarboxylic acid, pyridinecarboxaldehyde, pyridinedicarboxaldehyde, or mixtures thereof. 
     
     
         6 . The composition of  claim 1  wherein the first grain refiner is present in an amount of 0.001 to 0.04 g/L. 
     
     
         7 . The composition of  claim 1  wherein the nonionic surfactant comprises an alkoxylated amine moiety. 
     
     
         8 . A method of depositing a tin-containing layer on a semiconductor substrate 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. 
     
     
         9 . The method of  claim 8  wherein the bonding features comprise copper. 
     
     
         10 . The method of  claim 8  wherein the tin-containing layer on the bonding features is substantially free of voids as plated and after one reflow cycle.