CMP process development for Cu/low-k with Ru liner

As the design rule of BEOL of the device decreases, it becomes difficult to obtain void-free Cu fill with the conventional PVD barrier metal (TaN/Ta). To increase Cu gap-fill performance, CVD liners such as Co and Ru have been extensively developed. Among them, Ru liner has a great potential for the next generation Cu interconnect technology because it can provide Cu reflow process. However, Ru is one of the famous noble metals, which means that Ru CMP becomes a very challenging and key technology in BEOL technology. In this presentation, the characteristics of Cu/low-k CMP with Ru liner will be discussed in terms of planarity, uniformity and defects. Especially, dishing and erosion behavior including the pattern density and pitch dependency on CMP slurry and conditions will be focused. Electric results from successfully integrated Cu interconnects with Ru will be also presented.