Aluminum-germanium-copper multilevel damascene process using low-temperature reflow sputtering and chemical mechanical polishing

A low-temperature multilevel aluminum-germanium-copper (Al-Ge-Cu) damascene technology was developed using reflow sputtering and chemical mechanical polishing (CMP). The maximum processing temperature for the fabrication of multilevel interconnections could be reduced to 420°C using Al-1%Ge-0.5%Cu, whereas the conventional reflow temperature was not less than 500°C. No degradation due to reflow heat cycles was observed in terms of Al-Ge-Cu wiring resistance. Electromigration test results indicated that the mean time to failure (MTTF) of Al-1%Ge-0.5%Cu was longer than 10 years at the operating condition, which was equivalent to that of Al-1%Si-0.5%Cu. The Al-1%Ge-0.5%Cu triple-level interconnection was fabricated using reflow sputtering to fill vias and wiring trenches and subsequent CMP for Al-Ge-Cu films