Oxide-chemical mechanical polishing characteristics using silica slurry retreated by mixing of original and used slurry

Chemical mechanical polishing (CMP) technology has been widely used for global planarization of multi-level interconnection for ULSI applications. However, the cost of ownership and cost of consumables are relatively high because of expensive slurry. In this work, we have studied the possibility of recycling silica slurry in order to reduce the costs of CMP slurry. Also, we have investigated the CMP characteristics of silica slurry retreated by mixing of original slurry and used slurry. The removal rate and within-wafer non-uniformity were measured as a function of different slurry composition. As an experimental result, the retreated slurry with annealed silica abrasive of 2 weight percent (wt%) contents was showed to exhibit high removal rate and low non-uniformity. Therefore, we propose a two-step CMP process as follows: in the first-step CMP, we can polish the thick and rough film surface using retreated slurry, and then, in the second-step CMP, we can polish the thin film and fine pattern using original slurry. Consequently, we can expect to save high costs of slurry.