A slurry for copper polishing has a pH between 7.5 and 12. In a particular embodiment
of the present invention, a slurry for polishing copper has a pH between 8 and
11.5, and includes a siO2 abrasive, a (NH4)2S2O8
oxidizer, a benzotriazole corrosion inhibitor, and a K3PO4/K2HPO4
buffer. A copper polish slurry, in accordance with the present invention,
operates with a high pH of greater than approximately 7.5. In this range the slurry
has a low static etch due to formation of a robust, protective layer. This slurry
may additionally have S2O8-;2 or Fe(CN)6
-;3 as an oxidizer and can thus offer a high polish rate on the
order of 7,000 to 10,000 angstroms per minute which does not decrease significantly
during polishing. Such an inventive slurry offers a wide CMP process window such
that the slurry and process parameters can be optimized to yield low recess, erosion,
and dishing on patterned wafers.
