Copper Plating Solutions and Method of Making and Using Such Solutions
The present technology generally relates to copper plating solutions. Specifically, the present technology includes a copper plating solution comprising a source of copper ions and a conductivity salt wherein the copper plating solution has a pH between 1.7 and 3.5 as is essentially free of chloride ions. The present technology also relates to a method of using such copper plating solutions.
1 . A method of plating copper onto a substrate comprising:
providing a substrate; and
contacting said substrate with a copper plating solution comprising a source of copper ions and a conductivity salt wherein said copper plating solution has a pH between about 1.7 and about 3.5 as is essentially free of chloride ions.
2 . The method of claim 1 wherein said substrate is a metal seed layer on a silicon solar cell wafer.
3 . The method of claim 1 wherein said source of copper ions is copper sulfate.
4 . The method of claim 1 wherein said conductivity salt is lithium sulfate.
5 . The method of claim 1 wherein said pH is between about 2.3 and about 3.0.
6 . The method of claim 1 further comprising an additive selected from the group of imidazoles and imidazole derivatives, thiazoles and thiazole derivatives, compounds that contain a quaternary nitrogen atom such as thiazolium compounds and polymeric quaternary compounds.
7 . The method of claim 6 wherein said additive is selected from the group of 2 mercaptoimidazole, 2 mercaptothiazole, 3-(carboxymethyl)benzothiazolium bromide, 2 mercapto-1-methylimidazole, 2 aminothiazole and Cyastat SN.
8 . A copper plating solution comprising:
a source of copper ions; and
a conductivity salt
wherein said copper plating solution has a pH between about 1.7 and about 3.5 as is essentially free of chloride ions.
9 . The solution of claim 8 wherein said source of copper ions is copper sulfate.
10 . The solution of claim 8 wherein said conductivity salt is lithium sulfate.
11 . The solution of claim 8 wherein said conductivity salt is sodium sulfate.
12 . The solution of claim 8 wherein said pH is between about 2.3 and about 3.0.
13 . The solution of claim 8 further comprising an additive selected from the group of imidazoles and imidazole derivatives, thiazoles and thiazole derivatives, compounds that contain a quaternary nitrogen atom such as thiazolium compounds and polymeric quaternary compounds.
14 . The solution of claim 13 wherein said additive is selected from the group of 2 mercaptoimidazole, 2 mercaptothiazole, 3-(carboxymethyl)benzothiazolium bromide, 2 mercapto-1-methylimidazole, 2 aminothiazole and Cyastat SN.