Barrier and low k polish with a novel alkaline barrier slurry combining with FA/O chelating agent

In this work, a novel alkaline barrier slurry without the addition of H₂O₂ is used to polish TaN and ULK. A FA/O chelating agent (abbreviated as FA/O) is used to further remove the particles from the TaN and low k surface. The direct chemical mechanical polishing CMP process of a ULK (K=2.35) is compared by using commercial acidic, commercial alkaline and the novel slurry. It is found that the colloidal silica particles of the commercial alkaline are severely adsorbed onto the TaN surface after polishing. By adding the FA/O into this commercial slurry or adding another 10s polishing using the FA/O, the TaN surface becomes quite smooth and clean. Results show that the novel slurry has the lowest k value increment, best surface quality when combining with FA/O. High selectivity among TEOS, barrier and low-k can be achieved by using this process. All the results show the advanced properties of this FA/O CMP slurry.