Aluminum Gap Fill Improvement For 28 HKMG Process

Aluminum (Al) is used as the top fill-in metal layer for forming replacement metal gate (RMG) device at 28nm node. Gap fill and Al diffusion are the main concern of this process. A serials experiments, including top opening CD, Al reflow effect, TBM (Top Barrier Metal) profile, Al process was well studied in this paper to improve gap fill capacity. Results show 50% TiN thickness thin down combine with AC bias power /E-magnet current optimization, Al process temperature 7.5% higher and reflow time 25% longer will significantly improve gap filling. And at the same time, Al diffusion block was well considered.