Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres
Xiangdong Feng,1*
Dean C. Sayle,2
Zhong Lin Wang,3,4,5*
M. Sharon Paras,6
Brian Santora,1
Anthony C. Sutorik,6
Thi X. T. Sayle,2
Yi Yang,1
Yong Ding,3
Xudong Wang,3
Yie-Shein Her1
Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal rate by 50%, facilitating precise and reliable mass-manufacturing of chips for nanoelectronics. We doped the ceria system with titanium, using flame temperatures that facilitate crystallization of the ceria yet retain the titania in a molten state. In conjunction with molecular dynamics simulation, we show that under these conditions, the inner ceria core evolves in a single-crystal spherical shape without faceting, because throughout the crystallization it is completely encapsulated by a molten 1- to 2-nanometer shell of titania that, in liquid state, minimizes the surface energy. The principle demonstrated here could be applied to other oxide systems.
1 Ferro Corporation, 7500 East Pleasant Vally Road, Independence, OH 44131, USA.
2 Cranfield University, Defense Academy of the United Kingdom, Shrivenham, Swindon SN6 8LA, UK.
3 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332–0245, USA.
4 Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, 100871 Beijing, China.
5 National Center for Nanoscience and Technology, Beijing 100080, China.
6 Nanocerox, Inc., 712 State Circle, Ann Arbor, MI 48108, USA.
Present address: James Hardie Building Products, 10901 Elm Avenue, Fontana, CA 92337, USA.
* To whom correspondence should be addressed. E-mail: shawn.feng{at}jhresearchusa.com (X.D.F.); zhong.wang{at}mse.gatech.edu (Z.L.W.)
