US Patent 7575666 Process for electrolytically plating copper

An electrolytic copper plating process comprising two steps is proposed. The process is particularly suited to plating in very confined spaces. The first step comprises a pre-treatment solution comprising an anti-suppressor that comprises a sulfur containing organic compound, preferably incorporating an alkane sulfonate group or groups and/or an alkane sulfonic acid. The second step comprises an electrolytic copper plating solution based on an alkane sulfonic acid.