New aqueous clean for aluminum interconnects: Part 1. Fundamentals

Two aqueous acid solutions are examined for cleaning DRAM devices built with Al-RIE technology. A mixture of chromic and phosphoric acids (C/P) successfully removed Al-RIE residue but did not prevent Al(Cu) galvanic corrosion. A novel clean formulated with a diluted mixture of sulfuric acid and hydrogen peroxide (dSP+) removed Al-RIE residue without damaging Al(Cu) irregardless of the galvanic environment. The dSP+ clean is demonstrated to be chemical in nature and to provide protective passivation on Al(Cu). The investigation utilizes SEM and electrochemical polarization techniques.