Plating bath and method
View Patent ↗Copper plating baths containing a leveling agent that is a reaction product of a certain benzimidazole 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 benzimidazole compounds with one or more epoxide-containing compounds; wherein at least one benzimidazole compound has the formula
wherein R 1 is selected from H, (C 1 -C 3 )alkyl, ar(C 1 -C 3 )alkyl, hydroxy(C 1 -C 3 )alkyl and hydroxy; each R 2 is independently selected from (C 6 -C 18 )aryl, (C 1 -C 3 )alkyl, ar(C 1 -C 3 )alkyl, hydroxy(C 1 -C 3 )alkyl and hydroxy; and a=0-4, provided that a >0 when R 1 ═H.
2. The copper electroplating bath of claim 1 wherein the epoxide-containing compound comprises from 1 to 3 epoxy groups.
3. The copper electroplating bath of claim 1 further comprising a second leveling agent.
4. 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.
5. The method of claim 4 wherein the substrate is a printed circuit board.
6. The copper electroplating bath of claim 1 wherein the source of copper ions is selected from copper sulfate, copper halides, copper acetate, copper nitrate, copper fluoroborate, copper alkylsulfonates, copper arylsulfonates, copper sulfamate, copper gluconate, and mixtures thereof.
7. The copper electroplating bath of claim 1 wherein the electrolyte is selected from sulfuric acid, acetic acid, fluoroboric acid, alkanesulfonic acids, arylsulfonic acids, sulfamic acid, hydrochloric acid, phosphoric acid and mixtures thereof.
8. 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 ; Al 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.
9. The copper electroplating bath of claim 8 wherein the epoxide-containing compound is chosen from epihalohydrins, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, di(ethylene glycol) diglycidyl ether, poly(ethylene glycol) diglycidyl ether compounds, glycerol diglycidyl ether, neopentyl glycol diglycidyl ether, propylene glycol diglycidyl ether, di(propylene glycol) diglycidyl ether, poly(propylene glycol) diglycidyl ether compounds, 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-cyclodecane and dicyclopentadiene dioxide.
10. The copper electroplating bath of claim 1 wherein R 1 is chosen from H, (C 1 -C 4 )alkyl, ar(C 1 -C 4 )alkyl, and hydroxy(C 1 -C 4 )alkyl.
11. The copper electroplating bath of claim 1 wherein R 2 is chosen from (C 6 -C 18 )aryl, (C 1 -C 4 )alkyl, ar(C 1 -C 4 )alkyl, and hydroxy(C 1 -C 4 )alkyl.