Pattern density and deposition profile effects on oxide chemical-mechanical polishing and chip-level modeling

Abstract

Test masks for characterizing pattern-dependent variation of the remained thickness after chemical-mechanical polishing (CMP) were designed by taking the experimentally obtained interaction distance into consideration. Polishing behaviors were characterized by taking into consideration layout pattern density and pitch variations using these masks. Deposition profile effects were also compared between plasma-enhanced tetra ethyl ortho silicate (PETEOS) and high-density plasma (HDP) oxide. Both the measured post-CMP thickness and the expected oxide pattern density after the consideration of deposition profile effects showed a good correlation with respect to the pitch variation for a constant layout pattern density. Also, the relationship between remained thickness and true layout pattern density was deduced. Chip-level CMP modeling was investigated to obtain the post-CMP thickness distributions across a die from its design layout and a few oxide film and CMP parameters. The experimental CMP results agreed well with the modeling results. The effective dummy filling results were shown to achieve a smaller pattern density variation, which resulted in better post-CMP thickness uniformity. Whether the resulting oxide thickness could be predicted for any location on a die for an arbitrary layout, if the effective pattern density distributions are calculated, was discussed.