Tunable Low-Shear Copper CMP Pads: Purpose-Built Pad Engineering Solutions

摘要

Novel design concepts for fabrication of low-shear surface-engineered polymeric pads for Copper (Cu) Chemical Mechanical Planarization (CMP) are presented. Purpose built planarization solutions are realized through systematic applications of these design concepts. It is demonstrated that pad polymeric nano-structure containing small (1-2) hard segments in a soft urethane with molecular regularity results in significantly improved polishing performance. Furthermore, such purpose built pad engineering solutions allow for minimal stress incorporation during the bulk copper removal step. Tribological studies are carried out on blanket and patterned Copper films using these novel pads and comparison is made with state of the art commercial pads (IC 1000, JSR and Politex). Results indicate ⅰ) significant reduction in coefficient of friction (40%) ⅱ) low temperature transients (～1-2℃) ⅲ) large reduction in dishing and erosion (40-60%), ⅳ) significant improvement in topography (60%), ⅴ) reduction in Cu overpolish burden (50%), ⅵ) excellent defect performance, ⅶ) a 10x reduction in process-induced stress thus minimizing stress voids and stress induced electromigration and maintaining low-k integrity. These results indicate that it is possible to extend conventional CMP all the way to the 32 nm technology node by using novel pad engineering concepts.