Plating bath and method
View Patent ↗Copper plating baths containing a leveling agent that is a reaction product of a certain imidazole with a certain epoxide-containing compound that deposit copper on the surface of a conductive layer are provided. Such plating baths deposit a copper layer that is substantially planar on a substrate surface across a range of electrolyte concentrations. Methods of depositing copper layers using such copper plating baths are also disclosed.
1. A copper electroplating bath comprising: a source of copper ions, an electrolyte, and a leveling agent, wherein the leveling agent is a reaction product of one or more imidazole compounds with one or more epoxide-containing compounds; wherein at least one imidazole compound has the formula
wherein R 1 , R 2 and R 3 are independently chosen from H, (C 1 -C 12 )alkyl, (C 2 -C 12 )alkenyl, and aryl and provided that R 1 and R 2 are not both H.
2. The copper electroplating bath of claim 1 wherein at least one of R 1 and R 2 is chosen from (C 1 -C 8 )alkyl, (C 3 -C 7 )alkenyl and aryl.
3. The copper electroplating bath of claim 2 wherein R 3 is H.
4. The copper electroplating bath of claim 1 wherein the epoxide-containing compound comprises from 1 to 3 epoxy groups.
5. The copper electroplating bath of claim 1 wherein the epoxide-containing compound is chosen from compounds of the formulae
where Y, Y 1 and Y 2 are independently chosen from H and (C 1 -C 4 )alkyl; X=halogen; A=OR 4 or R 5 ; R 4 =((CR 6 R 7 ) m O) n , (aryl-O) p , CR 6 R 7 -Z-CR 6 R 7 O or OZ 1 t O; R 5 =(CH 2 ) y ; A1 is (C 5 -C 12 )cycloalkyl; Z=a 5- or 6-membered ring; Z 1 is R 12 OArOR 12 , (R 13 O) a Ar(OR 13 ) a , or (R 13 O) a Cy(OR 13 ) a ; Cy=(C 5 -C 12 )cycloalkyl; each R 6 and R 7 are independently chosen from H, CH 3 and OH; each R 11 represents (C 1 -C 4 )alkyl or (C 1 -C 4 )alkoxy; each R 12 represents (C 1 -C 8 )alkyl; each R 13 represents a (C 2 -C 6 )alkyleneoxy; each a=1-10; m=1-6; n=1-20; p=1-6; q =1-6; r=0-4; t=1-4; and y=0-6; wherein Y and Y 1 may be taken together to form a (C 8 -C 12 )cyclic compound.
6. A method of depositing copper on a substrate comprising: contacting a substrate to be plated with copper into the copper electroplating bath of claim 1 ; and applying a current density for a period of time sufficient to deposit a copper layer on the substrate.
7. The method of claim 6 wherein the substrate is a printed circuit board.
8. The copper electroplating bath of claim 1 wherein R 1 , R 2 and R 3 are independently chosen from H, (C 1 -C 8 )alkyl, (C 2 -C 7 )alkenyl and aryl.
9. The copper electroplating bath of claim 1 wherein the electrolyte is chosen from sulfuric acid, acetic acid, fluoroboric acid, alkanesulfonic acids, arylsulfonic acids, sulfamic acid, hydrochloric acid, and phosphoric acid.
10. The copper electroplating bath of claim 1 wherein the at least one epoxide-containing compound is chosen from 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, di(ethylene glycol) diglycidyl ether, poly(ethylene glycol) diglycidyl ether compounds having a molecular weight of from 380 to 8000, glycerol diglycidyl ether, neopentyl glycol diglycidyl ether, propylene glycol diglycidyl ether, di(propylene glycol) diglycidyl ether, poly(propylene glycol) diglycidyl ether compounds having a molecular weight of from 380 to 8000, 1,2-cyclohexanedimethanol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, 1,5-diepoxyhexane, 1,7-diepoxyoctane, 1,9-diepoxydecane, 1,5-diepoxy-cyclooctane, 1,6-diepoxy-cyclooctane, and dicyclopentadiene dioxide.
11. The copper electroplating bath of claim 1 wherein the at least one imidazole compound is 2,4-dimethylimidazole and the one or more epoxide-containing compounds is 1,4-butanediol diglycidyl ether.
12. The coper eletroplating bath of claim 5 wherein Y 1 and Y 2 are each H.