ECMP Enhances the Planarization Efficiency — a Phenomenon of Reverse Topography during Cu Removal

Planarization efficiency is a key parameter to evaluate the process effectiveness of CMP. When the Cu thickness was removed beyond the step height, under certain conditions, the recessed trenches become protruded, resulting in reverse topography. This reverse topography during bulk Cu removal can only be attributed to the low down force polishing, electrical driving Cu removal and Cu passivation mechanism in ECMP process. In this paper, the concept of reverse topography is introduced and the removal selectivity difference on the trench area and field area during bulk Cu removal is discussed. In ECMP, a “real” 100% planarization efficiency can be achieved when the Cu thickness removed is less than the trench step height. This new understanding in planarization efficiency sheds lights on ways to improve CMP productivity