Elimination of Post Cu-CMP Watermark by Optimizing Post CMP Clean to Control Cu Dissolution

No watermarks are detected for 1000A of initial cap thickness. Between 400 and 600 A, the density of watermark is multiplied by a factor 10. The increase in watermark with the decrease of the initial cap thickness is explained by a larger low-k film area exposure. In particular, patterned structures with higher metal density will be more eroded because of the increased amount of in-between metal lines dielectric consumption. Auger analysis of the watermark indicates that defects consist of Cu precipitate likely originating from the post-CMP clean step.