High-K Metal Gate Al-CMP Within Die Uniformity and Selectivity Study

High-K Metal Gate (HKMG) is one of the most significant steps in CMOS manufacturing for 28nm node process and beyond. For Metal Gate step to be accurately controlled the Chemical-mechanical planarization (CMP) method is required for surface planarization. In Al-CMP, the control of metal residue defect and thickness uniformity were crucial to influence the device and yield performance. In this work, different slurry was investigated to control different pattern selectivity and within die uniformity. We found that, different selectivity slurry combined with different polish pad and disk have different effect in within die uniformity. With the same pad disk, for Al/Poly selectivity, slurry A was the twice of slurry B, and Al/Oxide selectivity didn't change at the same time. As a result, poly thickness was improved by 7% when gate height meet target, and over polish risk can be reduced. With another Pad/disk, poly thickness can be improved by 10% when Al residue was all removed clear. Besides, chemical rinse treatment were also investigated to remove Al residue..