Investigation of novel alumina nanoabrasive and the interactions with basic chemical components in copper chemical mechanical planarization (CMP) slurries

Chemical mechanical planarization (CMP) is an enabling process technology for IC fabrication to maintain global planarity across the wafer to satisfy lithographic depth of focus constraints. It also enables integration of materials that cannot be anisotropically etched, such as Cu. CMP utilizes nanoparticle abrasives in aqueous slurry to aid in planarization. Commercially available copper CMP slurries contain four basic components, in addition to propriety chemical compounds which aid in the removal process. But, reduction of on-chip feature sizes demands high planarity performance with reduced levels of defectivity. This calls for more understanding of the role of each basic component as well as less chemically aggressive slurries. Also, the utilization of smaller nanoabrasive particles in slurries is being investigated as a pathway for extendability of CMP processing to smaller integrated feature sizes. In this work, the use of novel nanoabrasives for the development of copper CMP slurries for 300mm wafer processing is investigated by engineering and developing copper CMP slurries based on novel single component nanoabrasives. Abrasives are alumina nanoabrasives substantially smaller than used in conventional commercial slurries (approximately 40–50nm in size) that have been manufactured using a novel propriety process that promotes their suspension in solution without the use of additional chemical components. The experimental slurry formulations were comprised of the four basic components—abrasives, oxidizer, passivating agent, complexing agent. In this work, 200mm Cu blanket wafers, 300mm Cu blanket wafers, and 300mm M1-patterned, Cu wafers were used to develop and evaluate slurry formulations for optimal performance. The absence of additional chemical components in the experimental slurries enables a direct correlation between the individual slurry components and their effects on the Cu polishing performance. Investigation of the interplay between the nanoabrasives, the slurry chemical components and the efficacy of the CMP process are discussed in terms of the physical effects of slurry composition on 300mm Cu CMP performance and in relationship to post-CMP electrical characterization of patterned interconnect test structures. In addition, initial processing work on 200m blanket Cu wafers is discussed with respect to developing initial slurry formulations with the novel nanoabrasive particles