Patent ID: 7544305
Filing Date: 2009-06-09
Classification: H01L

Abstract:
1. A multistage chemical mechanical polishing (CMP) method for planarizing a structure, the structure comprising a substrate having a dense region and an isolation region, a silicon nitride layer formed over the substrate, a plurality of trenches formed in the silicon nitride layer and the substrate, an oxide layer formed over the substrate, filling the trenches, wherein a width of the trenches in the dense region is smaller than that in the isolation region, the multistage CMP method comprising: performing a first polishing step having a first removal rate on the oxide layer with a non-FA pad until a thickness of a remaining portion of the oxide layer reaches a prescribed thickness that is at least 10 nm; and performing a second polishing step having a second removal rate on the remaining portion of the oxide layer with a high selectivity slurry (HSS) comprising CeO