Planarization of the Poly-Si gate for Non Volatile Memories

In order to achieve flat topography on Poly-Si films, effects of the slurry components and process parameters were studied using different ceria particles and additives. Abrasive particles size has a major effect on planarization efficiency. Also additives types and ratio are the key to achieve high selectivity to topography and self-stopping effect. However polishing pressure does not help to reduce wafer topography on Poly-Si films. A self-stopping Poly-Si CMP process is still required to achieve complete flatness without any poly consumption on bottom areas.