Development of Zr- and Gd-doped porous ceria (pCeO2) abrasives for achieving high-quality and high-efficiency oxide chemical mechanical polishing

Abstract

Porous ceria (pCeO2), Zr-doped pCeO2 (pCeZrO2), and Gd-doped pCeO2 (pCeGdO2) abrasives for both surface quality and removal rate improvements were developed using a facile one-pot solvothermal approach. The resulting products were characterized via XRD, SEM, TEM, HRTEM, Raman spectroscopy, UV–visible spectroscopy, and N2 adsorption-desorption measurements. Raman spectra revealed that oxygen vacancies were the dominant defects in pCeO2 nanospheres. Zr- and Gd-doping treatments contributed to oxygen vacancy enrichment, thus leading to an increased content of trivalent cerium (Ce3+) formed on the pCeO2 surfaces. Oxide-CMP capability of pure pCeO2, pCeZrO2, and pCeGdO2 abrasives were compared in terms of surface morphology/roughness/defect, topographical variation, as well as material removal rate (MRR). Atomic force microscopy and interferometric microscopy investigations showed that both pCeO2, pCeZrO2, and pCeGdO2 abrasives achieved high-quality surfaces with ultra-low roughness (0.11–0.14 nm Ra, 0.13–0.17 nm RMS). As expected, the MRR was accelerated by 78.7% in alkaline slurries containing pCeGdO2 abrasives compared to the undoped pCeO2. The improved CMP performance might be attributed to the reduced modulus, the expend pore size, as well as the enriched Ce3+ and oxygen vacancy. Furthermore, the interfacial action and removal mechanism of the pCeO2 abrasives were discussed on the basis of their structure feature and surface chemistry.