Model slurries for chemical mechanical planarization of copper

Chemical-Mechanical Planarization (CMP) is the most widely accepted method to achieve global planarization for fabrication of integrated circuits. A major drawback of CMP is that post-CMP wafers may have various contaminants. Since removal of particles from a dried surface is much more difficult, reduction of particulate contamination during the CMP process is desirable to alleviate post-CMP cleaning requirements.; Model slurries containing different alumina abrasives, oxidizers and surfactants for the CMP of copper are investigated, using various slurry characteristics, CMP removal rate, and surface contamination as metrics. Surface tension of slurries and zeta potential of abrasive and abraded materials (CuO and Cu ₂O) are measured.; Alumina abrasives with the same nominal size, from different manufactures, showed appreciably different removal rates, attributed to differences in phase, size, and shape of the abrasives. CMP of Cu films with alumina, but without any chemical in the slurry, always results in a high density of particulate defects, because of the attraction between abrasive and the surface of Cu film.; The influence of different oxidizers was studied by using electrochemical measurements together with CMP removal rates and static etch rates. An effective passivation layer on the surface of copper was formed with potassium dichromate. The use of potassium dichromate not only increases removal rate of copper but also decreases particulate defect density, due to the like charge developed on the surfaces of the abrasive, Cu film, and abraded material.; The CMP removal rate of Cu film decreases with either nonionic or anionic surfactant in the slurry, due to the adsorbed surfactant layer which reduces the efficiency of abrasion by cushioning effect. A nonionic surfactant, Triton X, does not reduce the particulate defect density on the post-CMP copper film, even with appreciably decreased surface tension of the slurry. However, the use of an anionic surfactants, DOWFAX, not only decrease the surface tension of the slurry but also greatly decrease particulate contamination on the post-CMP copper surface by developing repulsive forces between abrasive, Cu film, and abraded material. The post-CMP surfaces of damascene patterned copper lines are in agreement with the copper CMP process concepts developed in this research.