A study on the comparison of CMP performance between a novel alkaline slurry and a commercial slurry for barrier removal

Abstract

Chemical mechanical planarization (CMP) is a vital process for the fabrication of advanced copper multilevel interconnects schemes. The formidable challenge in barrier CMP is that the copper lines suffer from dishing and erosion. There have been several efforts to reduce both dishing and erosion by extensive experimental investigations. However, most of the slurries applied in CMP processes are acidic and containing some kinds of inhibitors. In this paper, we have proposed a novel alkaline slurry without any inhibitors (namely slurry A) for barrier CMP and investigated its CMP performance by comparison with a commercial slurry (namely slurry B). The CMP performance is evaluated in terms of surface roughness, dishing and erosion values. The CMP results obtained from the roughness maps of copper blanket wafers show that the Cu films polished by slurry A has lower surface roughness values and good surface quality than that polished by slurry B. CMP data obtained from patterned wafers show that the amounts of dishing increases with the increment of line width, while the erosion has a slight decrease with increasing line width, the tendency is apparently the same by using the two different slurries, but slurry A provides a lower dishing and erosion values. The root mean square (RMS) roughness within 10 × 10 μm2 area of copper lines after being polished by slurry A and slurry B is 0.125 and 0.225 nm, respectively. By comparison, the alkaline barrier slurry has a good planarization performance and can be useful for barrier CMP.