Plating bath and method
View Patent ↗Silver electroplating baths having certain sulfide compounds and methods of electrodepositing a silver-containing layer using these baths are disclosed. Such electroplating baths are useful to provide silver-containing solder deposits having reduced void formation and improved within-die uniformity.
1. An electroplating composition comprising: a bath-soluble source of silver ions; water; acid electrolyte; and a sulfide compound the formula:
Y 1 —(CR 1 R 2 ) m —S—(CR 3 R 4 ) x —S—(CR 5 R 6 ) n —Y 2
wherein Y 1 and Y 2 are independently chosen from CO 2 H, PO 3 H 2 , and CONR 7 R 8 ; each R 1 , R 2 , R 5 and R 6 is independently chosen from H, (C 1 -C 6 )alkyl, CO 2 H, and hydroxy-substituted (C 1 -C 6 )alkyl; each R 3 and R 4 is independently chosen from H and (C 1 -C 6 )alkyl; m=1-6; n=1-6; R 7 and R 8 are independently chosen from H and (C 1 -C 3 )alkyl; and x=1-6; provided that when any of R 1 , R 2 , R 5 and R 6 is hydroxy-substituted (C 1 -C 6 )alkyl, the hydroxy group is bonded to a carbon atom that is at least gamma to a sulfur atom.
2. The composition of claim 1 further comprising a bath-soluble source of tin ions.
3. The composition of claim 1 wherein each R 1 , R 2 , R 5 and R 6 is independently chosen from H, (C 1 -C 4 )alkyl, CO 2 H, and hydroxy-substituted (C 1 -C 4 )alkyl.
4. The composition of claim 1 wherein Y 1 and Y 2 are independently chosen from CO 2 H, and PO 3 H 2 .
5. The composition of claim 1 wherein m=1-4.
6. The composition of claim 1 wherein n=1-4.
7. The composition of claim 1 wherein Y 1 and Y 2 are the same.
8. The composition of claim 1 wherein Y 1 and Y 2 are CO 2 H; each R 1 , R 2 , R 5 and R 6 is independently chosen from H, (C 1 -C 3 )alkyl, and hydroxy-substituted (C 1 -C 3 )alkyl; each R 3 and R 4 is independently chosen from H and (C 1 -C 3 )alkyl; m=1-4; n=1-4; and x=1-4.
9. The composition of claim 1 further comprising an alkoxylated amine oxide surfactant of the formula:
wherein R a is selected from a (C 6 -C 22 )alkyl group and a substituted (C 7 -C 22 )aryl group; R b is an alkoxylated unit; m is 0 to 7 and represents the number of moles of R b ; n is 0 or 1; and R c and R d are each at least one alkoxylated unit and the total number of alkoxylated units present in R c and R d is from 3 to 30.
10. A method of depositing a silver layer comprising: contacting a substrate with the composition of claim 1 ; and applying a potential for a period of time to deposit a silver-containing layer on the substrate.