Origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid

We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid.The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing.By using zeta potential analyzer,particle size analyzer,horizon profilometer,thermogravimetric analysis and Fourier transform infrared spectroscopy,the pre-and the post-polished wafer surfaces as well as the pre-and the post-used ceria-based slurries are compared.Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed.     

Effect of Chemicals on Chemical Mechanical Polishing of Glass Substrates

We investigate the effect of chemicals on chemical mechanical polishing （CMP） of glass substrates. Ceria slurry in an ultra-low concentration of 0.25 wt. % is used and characterized by scanning electron microscopy. Three typical molecules, i.e. acetic acid, citric acid and sodium acrylic polymer, are adopted to investigate the effect on CMP performance in terms of material removal rate （MRR） and surface quality. The addition of sodium acrylic polymer shows the highest MRR as well as the best surface by atomic force microscopy after CMP, while the addition of citric acid shows the worst performance. These results reveal a mechanism that a long-chain molecule without any branches rather than small molecules and common molecules with ramose abundant-electron groups is better for the dispersion of the slurry and thus better for the CMP process.     

Cation Effect on Copper Chemical Mechanical Polishing

We examine the effect of cations in solutions containing benzotriazole （BTA） and H202 on copper chemical mechanical polishing （CMP）. On the base of atomic force microscopy （AFM） and material removal rate （MRR） results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demonstrates the worst performance. These results reveal a mechanism that small molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential （OCP）.